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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I
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AXIOM 5 (2) LIFE SYSTEMS of PLANT PESTS
SPECIES POTENTIAL of HERBIVORES
The species potential (SP) of a taxon of PPs is a set of traits, which are used by this taxon to
counteract to a composition of CESPPs in its EE, to compete with other taxa, and to disperse.
Every of the traits is considered as a strategy of survivorship (SS). The subject matter of (SP)
becomes clear if to compare peculiarities of SSes herbivores, which differ each other as to their
density in space and time.
It is relevant to quote J. Kranz (1980, p. 18), who has put forward such an idea: "Cognition
starts with comparison. But comparison is also a major technique of research. It helps to derive
principles and models from discrete data…"
Cognition should give benefit for mankind resulting in management implications. Therefore,
suggestions as to SPs of PPs will be accompanied by propositions of measures to overcome their
SPs, i.e. how to protect ecosystems against PPs.
It will be considered a diversity of traits of groups of herbivores or separate taxa with the aim
to characterize these traits as to either category of SS, and to evaluate the level of its expression
in a given subject of the consideration. This discourse will be done with the aim to understand
the causes, which determine diversity in abundance, which a taxon or group of taxa of herbivores
can reach. The choice of herbivores’ taxa is determined by the data available for the author.
Knowledge of composition of EE of herbivores allows offering the list of counteracting parts
- CESPPs and SSes characteristic for a group of herbivores, which is given in the Table 33. Here,
also it is shown competitors for foodstuff and restrictions of the current range. A list of SPs for a
number of insect herbivore taxa is given in the Table 35.
Table 33. A list of the counteracting parts - components of ecosystem stability to plant pests
(CESPPs), competitors for foodstuff, restrictions of the current range, and strategies of
survivorship characteristic for certain groups invertebrate herbivores. Within the groups, some
taxa are shown, and expression of their strategies is given
Subjects of Groups of
Strategies of survivorship Expressi
The taxa
withstand
characteristic for the taxa on of the
herbivores
representing the
– CESPPs
strategie
strategies under
and other
s in the
consideration in
factors
taxa
some
circumstances
1
2.1.1.1.1.3.
2.1.1.2.1.2.
2.1.2.4.1.
2
5.1.2.a. Bark
beetles with
increased
aggressiness
(three species)
3
4
5.1.2.a. (I) Scolytus
scolytus and S.
multistriatis in
symbiosis with the 5.1.2.a.(1.) To overcome
Dutch elm disease, resistance of host-plants in
Cerastocystis ulmi the wide range of genotypes
and physiological state
5.1.2.a. (II)
Dendroctonus
micans on Picea
orientalis in the
Borzhomi Valley
5
Very
High,
High
High
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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I
Table 33 (continuation)
1
2
2.1.1.1.1.3.
2.1.1.2.1.2.
2.1.1.2.1.2.
2.1.1.2.1.2.1.
2.1.2.1.1.
3
5.1.2.b. (I) Primary
(Dendroctonus
frontalis, Ips
typographus)
4
5.1.2.b.(2.) To suppress
host-tree antibiosis by mass
attack responding on
aggregational pheromones
or stimuli of primary
attraction
5.1.2.b. (II) Secondary 5.1.2.b.(3.) To restrict
5.1.2.b.
(Polygraphus spp.)
colonization by D-III due to
Bark beetles
developed ability to percept
species
stimuli of primary attraction
with
of foodstuff
normal
5.1.2.b. (III) Tertiary
5.1.2.b.(4.) To restrict
aggressive- (Scolytus kirshi)
colonization by small
ness
portions of host-trees with
weakened antibiosis due to
developed ability to find
foodstuff with decreased
nonpreference and antibiosis
5.1.1.3.1. All the
5.1.1.3.1.(5.) To avoid selfspecies of this group
protection of host-trees by
feeding in early larval
instars by needles with
absent or residual antibiosis
5.1.1.3.1.
5.1.1.3.1.5..
5.1.1.3.1.(5.1.) To suppress
OpenlyNeodiprion sertifer
residual oleoresin exudation in
feeding
and Diprion pini
pine needles by wounding for
defoliators
protection of neonate larvae
of
5.1.1.3.1.(5.2.), To tolerate
5.1.1.3.1.1.
evergreen
Dendrolimus
residual antibiosis in needles
coniferous
sibiricus, 5.1.1.3.1.2. even in young larval instars
trees
Dendrolimus pini
5.1.1.3.1.3. Panolis 5.1.1.3.1.(5.3.) To limit
flammea,
feeding by needles with
5.1.1.3.1.4. Bupalus insignificant antibiosis in all
piniarius
the larval instars
5.1.1.3.2.1.
5.1.1.3.2.1.(5.4.), and
Defoliators Choristoneura
5.1.3.1.6.(5.4.) To feed by
of
fumiferana and
plant parts with a lack of
coniferous
5.1.3.1.6. Porthetria antibiosis- staminate
tree species monacha
"flowers" and newly-flushed
consuming
needles with absence of
also
antibiosis
staminate
“flowers”
5
High
High
High
High
High
High
High
High
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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I
Table 33 (Continuation)
1
2
2.1.1.3.1.2.
2.1.2.1.1.
2.2.1.
5.1.1.1.
Defoliators
deciduous
trees and
5.1.1.2.
Defoliators of
larch
5.1.1.1.
Defoliators of
deciduous
trees, and the
larch
5.1.
Herbivores
of diverse
groups
3
5.1.1.1.2.1.
Tortrix
viridana, and
5.1.1.1.2.2.
Operophthera
brumata
5.1.1.1.1.1. The
Bashkirian
ecotype of
Porthetria dispar
5.1.1.1.1.1.
Porthetria dispar
and 5.1.1.2.1.1.
Zeiraphera
diniana
5.1.1.1.2.1.
Tortrix viridana,
5.1.1.1.2.2.
Operophthera
brumata, and
5.1.1.2.1.1.
Zeiraphera
diniana
5.1.1.1.2.1.
Tortrix viridana
5.1.2. Bark
beetles
5.1.1.2.1.1.
Zeiraphera
diniana, 5.1.2.
Bark beetles
4
5.1.1.1.(6.), and 5.1.1.2.(6)
To exert the least negative
impact on vitality of hostplants by means of
reduction of development
5
High
5.1.1.1.(7.) and 5.1.1.2.(7.)
To minimize negative
impact on host-plants by
leaving of infestation spots
as early as possible, when
density reaches high level
5.1.1.1.(8.) and 5.1.1.2.(8.)
To expand the range of
host-plants, when density of
defoliators reaches the high
level
5.1.1.1.(9.) and 5.1.1.2.(9.) To
develop the traits directed on
affection of host-plants in
vulnerable stages of their life
cycle
High
High
High
5.1.(10.) To develop selfprotection against natural
enemies by behavior traits
5.1.(10.1.) Avian predators
Diverse
5.1.(10.1.) Avian predators
Moderate,
in S.
ratseburgi Weak
High, in
5.1.2.b
(III)
Moderate
5.1.(10.2.) Invertebrate
predators and parasites
High
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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I
Table 33 (Continuation)
1
2
2.2.1.
2.3. Routine
weather
suppression
5.1. Herbivores
of diverse
groups
5.1.1.
Defoliators of
diverse groups
3
5.1.1.3.1.2.
Dendrolimus pini
4
5.1.(10.3.) Mammal
predators
5
High
5.1.1.1.1.1.
Porthetria dispar
(some
populations),
5.1.2. Bark
beetles
5.1.1.1.2.1.
Tortrix viridana
5.1.(10.4.) Pathogens
High
5.1.(11.) To avoid impact of
pathogens by means of
shortage of a life cycle
High
5.1.1.1.1.1.
Porthetria dispar
(some
populations)
5.1.1.1.1.1.
Porthetria dispar
(the Bashkirian
ecotype)
5.1.(12.) To enhance
resistance to pathogens
High
High
5.1.1.1.1.1.
Porthetria
dispar asiatica
5.1.(13.) To leave
infestation spots as early as
possible, when virulence of
pathogens and activity on
other natural enemies begin
to grow
5.1.1.(14.) To tolerate well low
temperatures at hibernation in
the egg stage
5.1.1.3.1.1.
Dendrolimus
sibiricus
5.1.1.(15.) To tolerate weather
stresses in the stages from
larvae to adults
5.1.1.(15.1.) Cool and rainy
weather in the larval and
adult stages
High
High
5.1.1.(15.1.) Cool and rainy
weather in the larval stage
5. 1.1.(15.2.) High moisture of
media at hibernation in the
larval stage
Weak
5.1.1.3.1.1.
Dendrolimus
sibiricus
5. 1.1.(15.3.) The late frost
High
5.1.1.3.1.1.
Dendrolimus
sibiricus
5. 1.1.(15.4.) Low
temperatures at hibernation in
the larval stage
High
5.1.1.1.1.1.
Porthetria dispar
5.1.1.3.1.1.
Dendrolimus
sibiricus
Weak
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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I
Table 33 (Continuation)
1
2
3
5.1.1.1.1.1.
Porthetria dispar
4
5. 1.1.(15.5.) Low
temperatures in the pupal stage
5
Zero
5.1.1.1.1.2.2.
Euproctis
chrysorrhoea
5. 1.1.(15.6.) Weather situation
precluding imaginal feeding
Moderate
2.3. Routine
weather
suppression
5.1.1.
Defoliators of
diverse groups
Competitors
for food
5.1.1.3.1.1.
Dendrolimus
sibiricus
5.1.1.1.1.1.
Porthetria
dispar asiatica
5.1. Herbivores of 5.1.1.3.1.1.
diverse groups
Dendrolimus
sibiricus
5.4.5. Porthetria
5.4.5. Porthetria
dispar in North
dispar in North
America and
America
other exotic
species
Restrictions
of the
current
range
5. 1.1.(16.) To develop
behavior traits to overcome
limitations of short season
High
5.1.(17.) To forestall
competitors or evade from
competition
High
5.4.5.(18.) To spread on
unlimited distance by means of
usage of moving objects
High
5.1.2. Bark beetles
5.1.2.a. Species of bark beetles with increased aggressiveness
The species of the type 5.1.2.a. have SS 5.1.2.a.(1.) "To colonize host-trees in the wide range
of genotypes and physiological state." This SS is the component of most advanced SP, which
endangers mortality of host-trees with a little weakening of physiological state or quite healthy.
The latter is able to lead to extinction of host-trees on the level of a taxon. An operation of SS
5.1.2.a.(1.) takes place in two types of bark beetle outbreaks.
The subtype 5.1.2.a.(I.)
This subtype concerns the elm engraver bark beetles Scolytus multistriatus Marsh., and S.
scolytus F. These species did not differ from others bark beetles in elm species as to
aggressiveness until 1920-ies. Since then, when the Dutch elm disease, Cerastocystis ulmi
(Buismen) C. Moreau. invaded into their range, they suddenly occurred to be very aggressive
being in the symbiosis with this phytopathogen. The beetles inoculate spores of the
phytopathogen at imaginal feeding on twigs in crowns of diverse elm species.
In Europe and America, this phytopathogen is highly virulent for all the native elm species,
but not for an exotic species – the Siberian elm, Ulmus pumila L. Unsusceptibility of the latter
species is explained by the fact that the natural ranges of the elm and the phytopathogen
coincide. Among other elm species, most susceptible is the English elm, Ulmus campestris L.
(synonyms: U. foliacea Gilbert, U. glabra Mill., U. suberosa Moench.). It is supposed to be that
this species abundant till recently in the Forest-Steppe biome in East Europe now has become
extinct. Trees of this species have been affected by the pests indiscriminately as to their
physiological state.
In such a situation, salvage of host-trees species consists in operation of CESPPs 2.1.2.4.1.
"Hereditary heterogeneity of a stock of host-plants." Some trees within a species would be
resistant to the phytopathogen on the hereditary level.
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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I
The resistant to the phytopathogen Ulmus pumila is colonized by the beetles on condition that
the trees are significantly weakened, whereas other species, except Ulmus campestris, are
colonized at a little level of weakening. As to U. campestris, weakening of its trees is
unnecessary.
Expression of SS 5.1.2.a.(1.) "To colonize host-trees in the wide range of genotypes and
physiological state" in the Scolytus species cooperating the Dutch elm disease is "Weak" in the
case of Ulmus pumila, and "Very High" in the case of U. campestris. In the rest of host-plant
species, the expression is "High."
Avian predators (mainly the woodpeckers) chase these bark beetles actively. In forest plots,
where conditions of existence of these birds are favorable, they are able to suppress the pests.
However, in the most cases, avian predators are unable to do this, although they kill high
percentage of the pests. Therefore, expression of SS 5.1.(10.) "To develop self-protection against
natural enemies by behavior traits", 5.(10.1.) Avian predators" is "Moderate or Low." As to
subcortial associates - 5.1.(10.2.) "Invertebrate predators and parasites", 5.1.(10.3.) "Mammal
predators" and 5.1.(10.4.) "Pathogens", expression of these SSes is "High."
SP of the type 5.1.2.a. Species of bark beetles with increased aggressiveness, the subgroup
5.1.2.a.(I) Scolytus scolytus and S. multistriatus in symbiosis with Cerastocystis ulmi is as
follows:
SP(5.1.2.a.(I) = 5.1.2.a.(1.) – Weak (on Ulmus pumila), Very High (on U. campestris), and
High (on the rest Ulmus species ); 5.1.(10.1.) – Moderate or Low; 5.1.(10.2.) – High; 5.1.(10.3.)
– High; 5.1.(10.4.) – High.
The subtype 5.1.2.a. (II)
This subtype concerns the outbreak of Dendroctonus micans in the Borzhomi Valley
(Transcaucasus area, Georgia, the Former Soviet Union) on the East spruce, Picea orientalis (L.)
Link. It was supposed to be that Dendroctonus micans was brought into the Borzhomi Valley
with mass transportation of unbarked spruce logs from northern areas of Soviet Union. The
species was firstly found out in the Borzhomi in 1956, and during ten years spread on the area of
120 thousand hectares (Supataschvili et al., 1968). This species became much more dangerous
for the East spruce, Picea orientalis than did its main resident pest – Ips sexdentatus Boern.
Thousands of spruce trees were killed by Denroctonus micans in the Borzhomi. Nevertheless,
Dendroctonus micans demonstrated the selectivity at the colonization. The killed trees had been
weakened by human activity, they were of old age, or grew near by borders of the spruce range.
Ips typographus is also a newcomer in the Borzhomi Valley. Here, it was recorded firstly as
early as in 1952 (Ibid.). Nevertheless, in the Borzhomi, this species occurred to be a secondary
pest. This is rather strange, because in their natural range, the pest statuses of these species are
opposite. Ips typographus is the main pest of the Norway spruce, Picea excelsa (abies), whereas
outbreaks of Dendroctonus micans have been recorded on very limited areas – in an island in the
Baltic Sea and in pine plantations in the Novosibirsk Region, Russia. These outbreaks took place
in obviously weakened forest stands.
Let’s explain the differences in pest statuses of the species in their natural and new ranges
taking into account inequality of climatic conditions in the regions. Values of precipitation in the
Borzhomi are 2-2.5 times less than those in the Carpathians Mountains (Vasetchko, 1968). In
stands of Picea orientalis, forest litter and a soil surface stay dry over a significant part of fall
and winter. Just in these sites, Ips typorgaphus hibernates. It is probable that the beetles die due
to desiccation. A part of Ips typographus population hibernates under a bark in sites of
development above a butt area of spruce stems. Here, they are killed by woodpeckers. Contrary,
most part of Dendroctonus micans population hibernates under thick bark in a base of stems or
in roots often penetrating into the soil. Here, the beetles are well protected against desiccation
and avian predators.
Thus, SP of Ips typographus is advanced in the conditions of its natural range, but it occurred
to be inadequate in the conditions of the Borzhomi Valley. In the case of Dendroctonus micans,
the situation is opposite one. In its natural range, the outbreaks arise in the special conditions of
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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I
slow weakening of host-trees and a deficiency of competitors.
Notably, Ips typographus in its optimum is an effective competitor as to Dendroctonus
micans because the former at mass attack kill trees over short time, whereas the latter develops
much slowly and needs in fresh and thick phloem. So, probably due to climatic conditions and
activity of woodpeckers Ips typographus and Ips sexdentatus in the Borzhomy Valley, occurred
to be out of competition with Dendroctonus micans. Therefore, SS 5.(17) does not participate in
its SP.
Avian predators kill significant part of the population, although they are impossible to
suppress the outbreak. Therefore, expression of SS 5.1.(10.1.) is "Moderate." The role of other
natural enemies is insignificant. Therefore, expression of SS 5.1.(10.2.) and 5.1.(10.3.) and
5.1.(10.4) is "High."
Thus, SP of the type 5.1.2.a (II) Dendroctonus micans on Picea orientalis in the Borzhomi
Valley is as follows:
SP(5.1.2.a. (II) = 5.1.2.(1.) – High; 5.1.(10.1.) – Moderate; 5.1.(10.2.) – High; 5.1.(10.3.) –
High; 5.1.(10.4.) – High.
The above discourse gives the ground to conclude that SS 5.1.2.a.(1.) "To overcome
resistance of host-plants in the wide range of genotypes and physiological state" operates on
condition, where a herbivore species gets a possibility to overcome in host-trees CESPPs
2.1.1.1.1.3. "Nonpreference to herbivores, Of unknown nature" and CESPPs 2.1.1.2.1.2.1.
"Antibiosis to herbivores, Physiological (biochemical), Permanent."
These conditions take place at two circumstances: appearing of a symbiotic phytopathogen
or penetrating of this species into a new area, where host-trees are not adapted to resist it. In the
latter case, the adequacy of SPs of species to local environmental conditions is a prerequisite of
success of the invader.
Management implications as to the type 5.1.2.a.:
i) Breeding of elm varieties resistant to Cerastocystis ulmi.
ii) Suppression of populations of bark beetles vectoring this phytopathogen by any means,
including:
To pare branches of elm trees at the first signs of fading of leaves that is a result of affection
by Ceratocystis ulmi at imaginal feeding of the vectors,
To spray these trees with fungicides of a systemic action,
To salvage of moribund elm trees spraying of them with insecticides before emergence of
the vectors,
To expose pheromonal traps with the aim to catch the vectors.
iii) Because colonization of trees by Dendroctonus micans causes their mortality after a
number of years, they can be saved by means of spraying with insecticides at beginning of the
attacks. For this aim, in Germany, it was developed the preparation Mobe-T, which kills the pest
being non-toxic for the trees. A number of preparations were tested by D.F. Rudnev and
G.I. Vasechko (1969). The usage of special nozzles gives a possibility to treat stems with a
knapsack sprayer up to height 10 meters.
5.1.2.b Species of bark beetles with normal aggressiveness
The species of the type 5.1.2.b. have SSes 5.1.2.b.(2.) "To antibiosis of host-trees by mass
attack responding on aggregational pheromones or stimuli of primary attraction", 5.1.2.b.(3.) "To
restrict colonization by D-III due to developed capacity to percept stimuli of primary attraction
of host objects", and 5.1.2.b.(4.) "To restrict colonization by small portions of host-trees due to
developed capacity to find foodstuff with weakened antibiosis."
These SSes participate in SPs of numerous species of the family Scolytidae. On the base of
participation of the above SSes, the family might be classified by three groups as follows:
5.1.2.b.(I) Primary – the species, which are able in condition of increased amount of their
populations to colonize healthy host-trees. The beetles of the genus Dendroctonus do it by means
of producing of aggregational (contact) pheromones, which excite mass attacks of both sexes.
Aggregation of attacking beetles allows them to suppress Nonpreference and Antibiosis of
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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
PART II. SUBSTANTIATION OF THE AXIOMS PROPOSED IN THE PART I
healthy trees. In Ips typographus, mass attack is possible on stimuli of primary attraction even at
initial weakening. These species use SS 5.1.2.b.(2.) "To colonize of host-trees by mass attack
responding on pheromones or stimuli of primary attraction."
5.1.2.b.(II) Secondary – the species, which are limited at colonization by D-III biomass of
dominants. They possess developed capacity to detect weakened physiological state of hosttrees. Their pheromones play the role mainly of sex attractant. These species use SS 5.1.2.b.(3.)
"To restrict colonization by D-III due to developed capacity to percept stimuli of primary
attraction of host objects."
5.1.2.b.(III) Tertiary – the species, which are able to colonize limited areas within their hosttrees. This is possible, because they possess well developed capacity to detect weakened state of
tissues in these areas. This trait allows them to provide favorable environment for their brood,
and do not exhaust a stock of their host-trees. These species use SS 5.1.2.b.(4.) "To restrict
colonization by small portions of host-trees of diverse categories of biomass due to developed
capacity to find foodstuff with weakened antibiosis."
5.1.2.b (I) Primary species of bark beetles with normal aggressiveness
The primary group: Dendroctonus frontalis, D. ponderosae, D. brevicomis, Ips typographus,
and Blastophagus (Tomicus) piniperda. These species differ from all other herbivores
fundamentally being able to colonize and kill healthy host-trees. They demonstrate two patterns
of a behavior at the colonization depending on amount of their population.
The first pattern is pertinent to an innumerous population of them existing on the level ESPPs
3.1. "Proper control" corresponding to foodstuff resource, which offered by the annual stem fall.
In so doing, they are forced to choice for colonization weakened trees or other weakened
foodstuff by using stimuli of primary attraction. Then their pheromones play the role mainly of a
sex attractant.
The second pattern is pertinent of to a large population rising in a result of appearing
abundant weakened foodstuff. When the abundance is exhausted, an enlarged population is
unable to provide its brood by foodstuff on the annual stem fall. Therefore, the population is
forced to colonize the main stock of dominants – healthy host-trees. In so doing, the pheromones
play the role of aggregational attractants. The protective response of healthy host-trees is
overcome by mass attack.
SS 5.1.2.b.(2.) " To suppress host-trees antibiosis by mass attack responding on aggregational
pheromones or stimuli of primary attraction" is a consequence of evolutionary history of a PPs.
Consider the circumstances, which caused a development of the SS 5.1.2.b.(2.). These
species have evolved in the ecosystems, which have been undergone by recurrent catastrophic
stresses. They lead to growth of bark beetle population to enormous amounts. To survive, this
population must develop a capacity to colonize healthy host-trees, when a stock of weakened
foodstuff occurred to be exhausted. Thus, SS 5.1.2.b.(2.) is a diversity of traits developed under
impact of an obvious selective pressure.
The stresses are well known. F.C. Craighead (1942, p. 385) has reported.that "The southern
pines (shortleaf, loblolly, and longleaf) have from time to time been subjected to sharp local
droughts which have killed large volumes of timber. Outstending among these was the summer
drought of 1924 in Texas and Louisiana, when a deficiency in precipitation of some 15 inches,
occurring from June to January, resulted in the destruction of over 100,000,000 board feet of
timber…
A few years later Cary (1932) reported a similar drought in Florida and Georgia extending
through 7 months, which destroyed nearly as much pine timber…
Blackman (1924) showed that the attack of the hickory bark beetle was dependent on a
moisture deficiency and that the attacking insects were destroyed when normal rainfall was
resumed. Craighead (1925b) analyzed a series of outbreaks of the southern pine beetle in
shortleaf pine and found that the same conditions held."
Fires spreading on vast areas endanger forest for a long time. Recently, they became even
more destructive.
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In mountain spruce and pine ecosystems, it is common the aged crash of forest, when nearly
all the stock dominants occurred to be suddenly weakened. In the Carpathians Mountains, in
forests with dominance of spruce and fir, areas of such plots destroys by mighty winds, and
windfall nearly annually reaches hundreds hectares. Approximately, once time upon in decade,
areas of destroyed by the wind forest plots increase to thousands hectares. So that, Ips
typographus has had a possibility to develop its traits concerned SS 5.1.2.b.(2.) "To colonize of
host-trees by mass attack responding on pheromones or stimuli of primary attraction" for
millennia.
Expression of SS 5.1.(10.) "To develop self-protection against natural enemies by behavior
traits on the levels of low and intermediate densities", 5.1.(10.1.) Avian predators" is
"Moderate", whereas the expression is "High" as to other natural enemies - 5.1.(10.2.),
5.1.(10.3.) and 5.1. (10.4.).
Because the above species are able to colonize host-trees in a good physiological state, they
compete effectively with other species of their guilds – expression of SS 5.1.(17.) "To forestall
competitors or evade from competition" is "High."
Thus, the composition of SP in the type 5.2.1.b.(I) is as follows:
SP(5.1.2.b.(I) = 5.1.2.b.(2.) – High; 5.1.(10.1.) – Moderate; 5.1.(10.2.) – High; 5.1.(10.3.) –
High; 5.1.(10.3.) - High; 5.1.(17.) – High.
5.1.2.b. (II) Secondary species of bark beetles with normal aggressiveness
This group unites species of bark beetles, which use SS 5.1.2.b.(3.) "To restrict colonization
by D-III due to developed capacity to percept stimuli of primary attraction of foodstuff" with
expression "High." As to other SSes, expression of them within the group is unequal. This
concerns, in particular to demands as to weakening of foodstuff, its freshness, and capacity to
protect themselves against natural enemies. Therefore, there exists the wide range within the
group as to their abundance, and a number of subgroups might be found out.
The subtype 5.1.2.b.(IIa)
This subgroup unites species of bark beetles, which hardly are able to colonize healthy trees
at any increase of amount of their populations. But their demands to freshness of phloem are
high. They often attack the trees with perceptible residual antibiotic factor, in particular oleoresin
exudation, so that boring dust dragging out of their entrance holes contain oleoresin.
They belong to the genera Ips, and Blastophagus except those сoncerning to the subtype
5.1.2.b.(I.), Polygraphus, and some others. In them, expression of SS 5.1.(10.) "To develop selfprotection against natural enemies by behavior traits" 5.1.(10.1.) is "Moderate" 5.1.(10.2.)
"High", 5.1.(10.3.), and 5.1.(10.4) is "High", 5.1.(17.) is "Moderate."
In Dendroctonus rufipennis Kir. on the spruce, and on the fir – Scolytus ventralis Lec. in
North America, the pheromonal communication is less developed comparing with the species of
the group 5.2.1.b.(I). SSes in their SPs are close to the category 5.1.2.b.(3.) "To restrict
colonization by D-III due to developed capacity to percept stimuli of primary attraction of
foodstuff."
In this context, some remarks might be put forward. Comparing their traits with those in
more aggressive species of the type 5.1.2.b.(I), it seems that in their evolutionary history, there
were no situations, when vast areas of their host-trees had been weakened. Therefore, it was no
need in a developing of the SS 5.1.2.b.(2.) “To suppress host-trees antibiosis by mass attack
responding on aggregational pheromones or stimuli of primary attraction" This suggests that the
heavy damage at outbreaks of Choristoneura fumiferana is a phenomenon appearing in several
recent centuries due to human activity.
The subtype 5.1.2.b (IIb)
The bark beetles of this subgroup evade residual antibiotic response of host-trees. In
particular, the ambrosia beetles (Trypodendron spp., Xyleborus spp., and Anisandrus spp.). The
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stripped ambrosia beetle, Trypodendron lineatum Oliv. should be considered as a typical
example of this subgroup as to its SP.
These beetles are especially sensitive to oleoresin exudation. Therefore, they need in very
weakened foodstuff. On the other hand, they need in rather fresh wood. This task is achieved on
condition that pioneer beetles are able to perceive exactly stimuli of primary attraction. Also, this
species produces very active pheromone, which attracts beetles of both sexes. Mass aggregation
of the beetles in a response to the pheromone is not directed on suppression of host Antibiosis.
Destination of the aggregation is a conditioning of hosts as to optimal moisture in sapwood for
development of the brood, as well as facilitation to find out foodstuff for the species. This SS
occurred to be effective. Tripodendron lineatum is abundant on diverse species of pines and
spruces, and it has the Holoarctic range.
Other species of the ambrosia beetles, which probably also possess by a well-developed
capacity to percept stimuli of primary attraction, but they are not abundant. V.N. Stark (1926)
reported about colonization by Xyleborus signatus Oliv. and Anisandrus dispar Fabr. of
"absolutely healthy" (Ibid., pp. 103-104) trees, especially the aspen, the birch, the alder. The
beetles attacked weakened boughs in a lower part of a tree crown. Since then, they penetrated in
stems that resulted into full mortality of a tree or its dieback. Probably, these trees were healthy
only in outward appearance, and the species colonized them in the period of stressed state.
In the area, where V.N. Stark conducted his studies, the cases of tree mortality or dieback
were common, but in all the other situations these species of the ambrosia beetles are
innumerous greatly coming behind Tripodendron lineatum. This is an example of a combination
of well-developed perception of stimuli of primary attraction and high demands to condition of
feeding media.
The ambrosia beetles, which inhabit sapwood, are protected against natural enemies much
better than other genera of bark beetles do. Expression of SS 5.1.(10.) "To develop selfprotection against natural enemies by behavior traits." Expression of its subcategories 5.1.(10.1.), 5.1.(10.2.), 5.1.(10.3.), and 5.1.(10.4.) in the ambrosia beetles is "High."
All the ambrosia beetles demonstrate well developed traits of the SS 5.1.(17.) "To forestall
competitors or evade competition." This is so because they inhabit in sapwood of host-trees.
These tissues are consumed by stem borers of the families Cerambycidae, Buprestidae,
Syricidae, and Curculionidae. These insects develop more slowly than the ambrosia beetles do,
and used sapwood to limited extends, so that the ambrosia beetles do not meet with serious
competitors. Expression of SS 5.1.(17.) in them is "High."
The subtype 5.1.2.b. (IIc)
Scolytus ratzeburgi Jans. represents a special subgroup. Because the content of nutrients in
phloem of its host-trees (the birch) is low, the brood matures on the next year after colonization.
It spends winter period under bark suffering heavily due to predation on the part of the
woodpeckers.
That is why expression of SS 5.1.(10.) To develop self-protection against natural enemies by
behavior traits, 5.1.(10.1.) Avian predators" is "Weak." This species is innumerous everywhere,
although expression of SS 5.1.(10.2.), 5.1.(10.3.), and 5.1.(10.4.) is "High." Because this species
actually has no competitors, expression of SS 5.1.(17.) is "High."
Thus, the composition of SP of subgroups in the subtype 5.1.2.b (II) is as follows:
SP(5.1.2.b.(IIa)= 5.1.2.(3.) – High; 5.(10.1.) - Moderate; 5.1.(10.2.) – High; 5.1.(10.3.) – High;
5.1.(10.4.) – High; 5.1.(17.) – Moderate.
SP(5.1.2.b.(IIb)= 5.1.2.b.(3.) – High; 5.1.(10.1.) – High; 5.1.(10.2), - High; 5.1.(10.3.) - High;
5.1.(10.4.) – High; 5.1.(17.) – High.
SP((5.1.2.b.(IIc)= 5.1.2.b(3.) - High; 5.1.(10.1.)– Weak; 5.1.(10.2.) – High; 5.1.(10.3.) – High;
5.1. (10.4.) – High; 5.1.(17.) – High.
5.1.2.b (III) Tertiary species of bark beetles with normal aggressiveness
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The tertiary group might be characterized by a number of species, whose traits were studied
by G.V. Lindeman (1978) in areas of unstable moistening (the Steppe and Dry Steppe biomes
from the southeastern Europe, to the Sea of Japan). Here, it is common temporal weakening of
small portions of trees ("stains" on a stem or branches), which are able to revive at onset wet
weather. A number of species of the engravers (Scolytus spp.) are able to find such sites and
colonize them. A size of the “stains” is sometimes so small that the female cannot oviposite all
its eggs in one of them. Then, they are forced to lay eggs in several divers portions of host-trees.
These species do not suppress vitality of a host-tree as a whole that would be lethal for their
brood. Indeed, in dry climate, quick mortality of host-trees results in desiccation of phloem
before the brood would finish its development. Therefore, they need not aggregation
pheromones, but only sex pheromones. Such strict circumstances determine a necessity to
possess a developed capacity to detect weakened sites within host-trees. The difficulties are
obvious, because nearly a half of such colonies occurred to be failed due to restoration of a host
protective response.
This group includes Scolytus kirshi Scal., S. saitzevi But. S. rugulosus Ratz., S. japonicus
Chap., S. moravitzi Sem. "Their traits at host colonization, probably, favor prosperity of these
species. They are numerous in most parts of their ranges, and S. kirshi spreads on a huge area
with its elm host-trees over the low part of the River Volga Basin, Kazakhstan and Middle Asia"
(Lindeman, 1978, p. 66).
These species demonstrate traits of the category SS 5.1.(4.) "To restrict colonization by small
portions of host-trees with weakened antibiosis due to developed ability to find objects with
decreased nonpreference", which provides them with a possibility to reach relatively high
abundance and the wide range, but does not lead to exhaust of their host-trees. This is a case of a
to certain degree peaceful co-existence of the counteracting parts that it is not characteristic for
interrelations of bark beetles and trees.
Colonies of these species attract woodpeckers, which produce holes in boles and boughs. The
holes are used by diverse bird species for nestling. Presence of birds promotes enrichment of the
soil within tree crowns with bird excrements.
Expression of SS 5.1.2.b.(4.) is "High." G.V.Lindeman did not reported about presence of
more than one species of bark beetles per “stain.” Probably, in the conditions of deficiency of the
foodstuff, the parent beetles mark a “stain”at oviposition with a pheromon-repellent. Therefore,
interspecific competition in their colonies is little of probable. Therefore, expression of SS
5.1.(17.)"To forestall competitors or evade competition" is "High."
These species usually colonize branches and twigs in tree crowns, which often suffer due to
moisture deficiency. Because outer bark here is thin, affection of the brood by parasites is
significant. However, mortality due to parasitization, which decreases competition within the
brood, is even beneficial. Survivorship of the brood is sufficient to maintain population density,
which provides abundance of the species.
Let us evaluate expression of all the SS 5.(10.2.) as "Moderate." These species suffer due to
woodpecker’s predation. Therefore, expression of SS 5.1.(10.1.) is "Moderate." Thus, the
composition of SP in the subtype 5.1.2.b.(III.) is as follows:
SP( 5.1.2.b.(III)= 5.1.2.b.(4.) – High; 5.1.(10.1.) – Moderate; 5.1.(10.2.) – Moderate; 5.1.(17.) –
High.
Management implications as to bark beetles of the group 5.1.2.b.(III):
To keep proper physiological state of host-trees in an ecosystem:
i) Do not allow accumulation of weakened trees above values of the annual stem fall by
sanitary measures,
ii) Salvage in time colonized by bark beetles trees if their number exceeds the annual stem
fall,
iii) Timber production should be transferred from forest or be protected from colonization by
bark beetles before beginning their flight period,
At arising of outbreaks of bark beetles, it should decrease their abundance by pheromonal
traps.
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5.1.1. Defoliators
5.1.1.3. Defoliators of evergreen coniferous tree species
5.1.1.3.1. Openly-feeding species of needle-eating defoliators
For all these defoliators, it is characteristic SS 5.1.1.3.1.(5.) “To avoid self-protection of hosttrees by feeding in early larval instars by needles with absent or residual antibiosis." This
avoiding is fulfilled by a number of traits. The efficacy of this SS is obvious. Among the species
having such a SS, there are very destructive defoliators. Areas of their infestation spots per year
reach millions hectares that accompanied by heavy mortality of host-trees. The expression of SS
5.1.1.3.1.(5.) in all the species of this group (5.1.1.3.1.) is “High.”
On the level ESPPs 3.1."Proper control", caterpillars in the group 5.1.1.3.1. feed by needles
with weak Antibiosis, in particular growing in shade. Because this foodstuff source is very
limited, their density is unable to exceed the Insignificant level, and a population stays at the
innocuous phase of population dynamics. To turn it into the outbreak phase, it is necessary to
disturb physiological state of the main stock of dominants under an effect of any stressor. Such a
disturbance leads to a great increase of the foodstuff resource – host tissues with a lack of
CESPPs 2.1.1.2.1.2.1. "Antibiosis to herbivores, Physiological (biochemical), Permanent."
Although this CESPPs is decreased, the defoliators need to overcome residual Antibiosis in hosttrees. Consider how diverse species of the defoliators do it.
An operation of SS 5.1.1.3.1.(5.1.) "To suppress residual oleoresin exudation in pine needles
by wounding for protection of neonate larvae" is known in the sawflies Neodiprion sertifer and
Diprion pini.
W. Thalenhorst (1953a) has observed that females of these species at oviposition cut trenches
on pine needles that sharply decreases oleoresin exudation and lay their eggs on the treated
needles in clusters. These species of the sawflies are among the most abundant defoliators of
Pinus sylvestris. Contrary, the sawfly Gilpinia frutetorum F. exerts only weak wounds to the
needles and lays eggs solitary. This species is known as a satellite of the above-mentioned
species, and it produces independent infestation spots very rarely.
The sawflies Neodiprion sertifer and Diprion pini have the well-expressed SS 5.1.1.3.1.(5.1.)
"To suppress oleoresin exudation in pine needles by wounding for protection of neonate larvae."
This expression is "High." In Gilpinia frutetorum, an expression of this SS is "Weak." As to
expression other SSes in above species, the data are too limited to evaluate it. Nevertheless, the
difference in the behavior traits of the females of the species allows explaining the difference in
their capacity to reach abundance.
An operation of SS 5.1.1.3.1.(5.2.) "To tolerate residual antibiosis in needles in initial larval
instars" is characteristic for the Siberian pine moth, 5.1.1.3.1.1. Dendrolimus sibiricus and the
European pine moth 5.1.1.3.1.2.Dendrolimus pini.
Dendrolimus sibiricus is a leader in the group 5.1.1.3.1. as to a capacity to produce widescale of outbreaks. This capacity is realized exclusively in the conditions of distinct continental
climate of Siberia. Here, summer is short, but usually hot and dry that suppresses Antibiosis.
Nevertheless, it is common an onset of weather situation favorable for partial restoring of
Antibiosis.
Larvae of Dendrolimus sibiricus are able to tolerate a partial restoration of Antibiosis at such
a weather situation that has been noted by V.O.Boldaruev (1969, p. 100), namely: "…in
reservations of the Siberian pine moth in larch and fir forests of the Krasnoyarsk Region, as well
as in reservations in Buryatia, in a cold rainy season, two-year term of the development prevails,
whereas in a worm season, especially, when August is worm, a participation of the one-year
development becomes higher. In a result, a flight of the moth takes place every year." Because in
cold rainy seasons, oleoresin exudation in evergreen coniferous trees becomes noticeable, but
young larvae survive, there are the grounds to suppose that expression of SS 5.1.1.3.1.(5.2.) "To
tolerate residual antibiosis in needles in initial larval instars" in the species is "High."
Further, the above data suggest that larvae of Dendrolimus sibiricus, unlike to Porthetria
dispar, are rather tolerant to weather stresses, although cold rainy seasons interrupt arising of
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outbreaks. Therefore, an expression of SS 5.1.1.(15.) "To tolerate weather stresses in the stages
from larvae to adults." 5.1.1.(15.1.) "Cool and rainy weather in the larval and adult" is "High."
In most part of Siberia, morning frost occurs over all the summer. Larvae of Porthetria
dispar do not tolerate it, whereas larvae of Dendrolimus sibiricus survive in spite onset of the
frost. This is an evidence of "High" expression of SS 5.1.1.(15.) "To tolerate weather stresses in
the stages from larvae to adults" 5.1.1.(15.3) "The late frost."
When conditions of the developments are worse, for example at a progress of an outbreak, or
in north areas of the range, the development increases to two or three years (Boldaruev, 1969,
p. 97). One may see in this trait an operation of SS 5.1.1.(16.) "To develop behavior traits to
overcome limitations of short season". Its expression is "High."
In Siberia, the season of larval development is short. The neonate larvae appear in the middle
of July, and in September they are forced to descent for hibernation. This species spend
hibernation in the larval stage. Depending on suitability of environmental conditions, the
hibernation takes place one, two or even three winters. Winter temperatures in Siberia are very
low. Nevertheless, the larvae tolerate them even after short period of feeding in young instars.
The larvae in older instars descent to hibernation lately in fall, when falling snow. Therefore, an
expression of SS 5.1.1.(15.) "To tolerate weather stresses in the stages from larvae to adults",
5.1.1.(15.4.) "Low temperatures at hibernation in the larval stage" is "High."
Contrary, the larvae die if forest litter, where they hibernate, becomes wet. Therefore, an
expression of SS 5.1.1.(15.) "To tolerate weather stresses in the stages from larvae to adults",
5.1.1.(15.2.) "High moisture of media at hibernation in the larval stage" is expressed "Weak."
Outbreaks of Dendrolimus sibiricus arise in a result of potent factors suppressing ESPPs.
They are drought in summer, ground forest fires, severe winters at weak snow cover. All they
stressors exert destructive effect on natural enemies, especially parasites. On the other hand, over
progress of outbreaks, when conditions for abundance of natural enemies become favorable, they
sharply decrease insect host density to very Low values. Therefore, expression of SS 5.1.1.(10.)
"To develop self-protection against natural enemies by behavior traits", 5.1.1.(10.2.)
"Invertebrate predators and parasites" is "Weak."
The advanced capacity to migrate in the adult stage suggests "High" expression of "SS
5.1.1.(13.) "To leave infestation spots as early as possible, when virulence of pathogens and
activity of other natural enemies begin to grow."
V.O. Boldaruev (1969, pp. 60-61) reported about capacity of Dendrolimus sibiricus to force
out other species of defoliators, which produce outbreaks after droughts and ground forest fires.
Hence, expression of SS 5.1.(17.) "To forestall competitors or evade from competition" in this
species should be evaluated as "High."
The range of Dendrolimus pini embraces most part of the range of the Pinus silvestris in
Eurasia. (Il’insky and Tropin, 1965, p. 232). But area of its outbreaks is much shorter. They are
known in separate pine ecosystems within the southern part of the Forest Deciduous biome, and
in all the Forest-Steppe biomes as well as Europe and the West Siberia (Ibid., pp. 232, 235).
Climate of most part of the Forest biome in Europe, which is more humid than that in Siberia,
precludes outbreaks of these species.
The outbreaks are common in an extreme southwest of the West Siberia, and they are rare to
the east. This fact suggests that frost-tolerance of larvae of Dendrolimus pini is less than that in
D. sibiricus.
Outbreaks of Dendrolimus pini are known in forest stands growing in xeric conditions with
scarce grass cover (Ibid., pp. 234-237). At hibernation, the larvae aggregate near by bases of
trees, and avoid retaining themselves in wet forest litter. They ascent in tree crowns very early in
spring, when snow around bases of trees begins to melt leaving the moist media as soon as
possible. High moisture of forest litter induces mass affection of hibernating larvae by diseases
(Ibid., p. 236). Nevertheless, this species is more tolerant to this stressor that Dendrolimus
sibiricus does.
Also, the larvae very susceptible to an onset of cool rains, when they die due to diseases
(Ibid., p. 236).
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Larvae of Dendrolimus pini suffer heavily due to parasitization and predation by ants,
although its larvae are well-protected against rodents that implies a "Weak" expression of SS
5.1.(10.) To develop self-protection against natural enemies by behavior traits, 5.1.(10.2.)
"Invertebrate predators and parasites." Nevertheless, the larvae are well-protected against
mammal predators –5.1.(10.3..), i.e. expression of this SS is “High.”
The young larvae feed by needles of current year nibbling them on edges. In older instars, the
larvae are able to feed by needles with high oleoresin exudation (V.I. Grimal’s’ky, pers. comm.).
This is an evidence of "Moderate" expression of SS 5.1.1.3.1.(5.2.) "To tolerate significant level
antibiosis in host-trees."
The trait to leave infestation spots at growth of density in Dendrolimus pini is developed
poorly, so that SS 5.1.(13.) "To leave infestation spots as early as possible, when virulence of
pathogens and activity of other natural enemies begins to grow" is "Weak." Probably, this trait is
a result of absence of evolutionary experience to reach High density. The outbreaks of
Dendrolimus pini, are relatively new phenomena. They are induced by destruction of forest
ecosystems by people.
Outbreaks of Dendrolimus sibiricus spread on vast areas of Siberian forests, but in Europe
they have been recorded only on a very small area in the eastern part of the Trans –Volga Basin.
This fact might be explained by high susceptibility of the larvae to moisture in the period of
hibernation that is characteristic for more humid climate of Europe. The area of its outbreaks is
limited by regions of distinctly continental climate in Siberia. This is a result of "Weak"
expression of SS 5.1.1.(15.) "To tolerate weather stresses in the stages from larvae to adults",
5.1.1.(15.2.) "High moisture of media at hibernation in the larval stage."
SP of Dendrolimus pini shows that it is a serious pest of the pine. Because its capacity to
tolerate high moisture of media of hibernation is better that that in Dendrolimus sibiricus, areas
of its abundance spreads of Europe, i.e. on regions with more humid climate than that in Siberia.
Abundance of Dendrolimus pini in Siberia is limited by less expression of SS 5.1.1.(15.4.) "To
tolerate low temperatures at hibernation in the larval stage."
Thus, both the above species have SS 5.1.1.3.1.(5.2.) "To tolerate significant level antibiosis
in host-trees" with an expression "Moderate", but other SS in their SP are different. This
determines the difference in areas where they are able to produce outbreaks.
As to the species 5.1.1.3.1.3. The pine beauty moth, Panolis flammea Schiff. and 5.1.1.3.1.4.
The pine looper, Bupalus piniarius L., there are the grounds to suppose that SS 5.1.1.3.1.(5.3.)
“To limit feeding by needles with insignificant antibiosis in all the larval instars” with expression
“High.” Other SSes, noted for species of the group 5.1.1.3.1., are presented with expression
“Moderate.” These levels of expression of SSes means that at significant decrease of host-tree
Antibiosis, these species are able to produce vast outbreaks.
Above data allow proposition an operation of following SSes in SP of diverse subgroups of
5.1.1.3.1. Openly feeding defoliators of evergreen coniferous tree species:
5.1.1.3.1.5. The sawflies Neodiprion sertifer and Diprion pini
5.1.1.3.1.(5.) To avoid self-protection of host-trees by feeding in early larval instars by
needles with absent or residual antibiosis, High.
5.1.1.3.1.(5.1.) "To suppress oleoresin exudation in pine needles by wounding for protection
of neonate larvae, High.
The sawfly Gilpinia frutetorum
5.1.1.3.1.(5.) To avoid self-protection of host-trees by feeding in early larval instars by
needles with absent or residual antibiosis, Moderate.
5.1.1.3.1.(5.1.)"To suppress oleoresin exudation in pine needles by wounding for protection
of neonate larvae, Weak
The Siberian pine moth, Dendrolimus sibiricus
5.1.1.3.1.(5.) To avoid self-protection of host-trees by feeding in early larval instars by
needles with absent or residual antibiosis, High
5.1.1.3.1.(5.2.) To tolerate residual antibiosis in needles in initial larval instars, High.
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5.1.1.(15.) To tolerate weather stresses in the stages from larvae to adults, 5.1.1(15.4.) Low
temperatures at hibernation in the larval stage, High.
5.1.1.(15.) To tolerate weather stresses in the stages from larvae to adults, 5.1.1.(15.1.) Cool
and rainy weather in the larval and adult stages, Moderate.
5.1.1.(15.) To tolerate weather stresses in the stages from larvae to adults, 5.1.1.(15.2.) High
moisture of media at hibernation in the larval stage, Weak.
5.1.1.(15.) To tolerate weather stresses in the stages from larvae to adults, 5.1.1.(15.3) The
late frost, High.
5.1.1.(13.) To leave infestation spots as early as possible, when virulence of pathogens and
activity of other natural enemies begins to grow, High.
5.1.1.(10.) To develop self-protection against natural enemies by behavior traits, 5.1.1.(10.2.)
Invertebrate predators and parasites, Weak.
5.1.1.(16.)To develop behavior traits to overcome limitations of short season, High.
5.1.(17.) To forestall competitors or evade from competition, High.
5.1.1.3.1.2.The European pine moth, Dendrolimus pini
5.1.1.3.1.(5.) To avoid self-protection of host-trees by feeding in early larval instars by
needles with absent or residual antibiosis, High.
5.1.1.3.1.(5.2.) To tolerate residual antibiosis in needles in initial larval instars, High.
5.1.(10.) To develop self-protection against natural enemies by behavior traits, 5.1.(10.2.)
Invertebrate predators and parasites, Weak; 5.1.1.(10.3) Mammal predators, High.
.5.1.1.(15.) To tolerate weather stresses in the stages from larvae to adults, 5.1.1.(15.4.) Low
temperatures at hibernation in the larval stage, Moderate.
5.1.1.(15.) To tolerate weather stresses in the stages from larvae to adults, 5.1.1.(15.1.) Cool
and rainy weather in the larval and adult, Weak.
5.1.1.(15.) To tolerate weather stresses in the stages from larvae to adults, 5.1.1.(15.2.) High
moisture of media at hibernation in the larval stage, Moderate.
5.1.(13.) To leave infestation spots as early as possible, when virulence of pathogens and
activity of other natural enemies begin to grow, Weak.
5.1.(17.) To forestall competitors or evade from competition, Moderate.
5.1.1.3.1.3. The pine beauty moth, Panolis flammea
5.1.1.3.1.(5.3.) To limit feeding by needles with insignificant antibiosis in all the larval
instars, High.
5.1.1.3.1.4. The pine looper, Bupalus piniarius
5.1.1.3.1.(5.3.) To limit feeding by needles with insignificant antibiosis in all the larval
instars, High.
The formulae of SSe of some species of the group 5.1.1.3.1. Openly-feeding defoliators of
evergreen coniferous tree species are as follows:
SP (5.1.1.3.1.5. Neodiprion sertifer and Diprion pini)= 5.1.1.3.1.(5.)- High; 5.1.1.3.1.5.(5.1.) –
High.
SP(Gilpinia frutetorum)== 5.1.1.3.1.(5.)- Moderate; 5.1.1.3.1.5.(5.1.) – Weak.
SP(5.1.1.3.1.1.,Dendrolimus sibiricus)= 5.1.1.3.1.(5.) -High; 5.1.1.3.1.(5.2.) –High; 5.1.1.(10.2.)
– Weak; 5.1.1.(13.) – High; 5.1.1(15.4.) – High; 5.1.1.(15.1.) – Moderate; 5.1.1.(15.2.) – Weak;
5.1.1.(15.3) – High; 5.1.1.(16.)– High; 5.1.(17.) – High.
SP(5.1.1.3.1.2.,Dendrolimus pini) =5.1.1.3.1.(5.) –High; 5.1.1.3.1.(5.2.) – High; 5.1.(10.2.) Weak; 5.1.1.(10.3.) – High; . 5.1.(13.) – Weak; 5.1.1.(15.4.) – Moderate; 5.1.1.(15.1.) – Weak;
5.1.1.(15.2.) – Moderate; 5.1.1.(15.4.) – Moderate; 5.1.(17.) – Moderate.
SP (5.1.1.3.1.3. Panolis flammea)= 5.1.1.3.1.(5.) –High; 5.1.1.3.1. (5.3.) – High.
SP (5.1.1.3.1.4. Bupalus piniarius)= 5.1.1.3.1.(5.) –High; 5.1.1.3.1. (5.3.) –High.
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5.1.1.3.2. Bud-mining and web-making defoliators of coniferous species
The spruce budworm, Choristoneura fumiferana Clem. produces vast outbreaks in North
America in fir-spruce forests that implies a very advanced SP of this species. In this context, it is
advisable to put the question: why do relative tortricid species in Eurasia on relative species of
host-trees are much less active?
In fact, the budworm, Zeiraphera (Semasia) rufimitrana H.-S. is a closest species to
Ch. fumiferana as to life history, and it has the Holoarctic range. Nevertheless, the outbreaks of
the former species actually have not been recorded. The review reported about a "significant
damage of the spruce in the Kiev Region" (V.P. Pospelov, 1908, cited in E.N. Pavlovsky and
A.A. Stakelberg, p. 99). Other reviews cite the same reports. In the Kiev Region, the spruce is an
exotic species. It grows on minute areas in parks and plantations.
A. I. Il’ínsky and I.V. Tropin (1965, p. 341-349) providing the data about outbreaks of
numerous pest species over the area of USSR, only in passing mentioned about the group
5.1.1.3.2. As to the European fir budworm, Choristoneura murinana Hb., it was reported that
"outbreaks were not recorded" (Ibid., p. 341).
On western slopes of the Sikhote-Alin Mountain Ridge (the Russian Far East) in 1965-1968,
it took place an outbreak of Choristoneura murinana in fir forests on the area of more three
million hectares (Dlussky et al., 1971). Other reports about outbreaks of the species in USSR are
unknown.
Outbreaks of Epiblema (Epinotia) tedella Cl. took place in Central Europe. They arose in
weakened fir forests - in old (70 - 100 years) overthinned stands growing on slopes exposed to
intensive sunshine, as well as in monocultures established on the place of cutover oak and beech
forests, i.e. outside of ecological optimum for the fir (Schimitschek, 1963). The scale of these
outbreaks is much less than the affection of North American fir-spruce forests by Choristoneura
fumiferana.
To explain the above differences, let’s turn to S.A. Graham, (1939, pp. 169-170): "The life
history of the spruce budworm exhibits a number of interesting features. The eggs are deposited
during late summer…The young larvae that soon hatch from these eggs seek out, without
feeding, suitable places of concealment on the tree, spin a light covering of silk about
themselves, and go into hibernation….In the spring, about the time that the buds of the balsam fir
are expanding, the larvae emerge from hibernation and begin feeding upon the fresh foliage of
the host. As they work they web the needles together to form a crude shelter. The larvae develop
rapidly and, under favorable conditions, in the course of three weeks are full grown."
This passage shows that the species has very advanced traits. First of all, this is a presence of
the larvae at beginning of spring vegetation of the fir. This trait allows to the larvae to enter in
activity correctly at appearing of a vulnerable phase of host-trees.
Further, it is important that the eggs, larvae, and pupae spend all their development under
protection by covering. In a result, they are inaccessible for parasites if the density is not so
High, at which the larvae are forced to migrate in search for foodstuff.
It is notably that the larvae develop rapidly, in the course of three weeks, importantly, "under
favorable conditions." The favorable conditions consist in presence of appropriate foodstuff. The
best foodstuff is the staminate "flowers." They are free from antibiotic factors and rich by vitally
important for consumers substances, which are contained in pollen. The pollen is a surprisingly
potent resource of vitamins, minerals, amino acids, bioflavonoids, and fat acids. Flushing leaves
are also serviceable for feeding, whereas full-grown needles are inaccessible as a foodstuff. A
deficiency of the favorable foodstuff increases the term of larval development and exposes them
on matured needles with Antibiosis.
In most seasons, the favorable foodstuff is in deficiency. Therefore, the population stays on
Insignificant level. The conditions, when the foodstuff becomes abundant, are known well. They
are drought and old age of host-trees that promote "flowering" and retard maturation of needles.
High participation of the fir in composition of the dominants is important also. In such
conditions, the larvae are more successful in search for the favorable foodstuff.
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Obviously, expression of SS 5.1.1.3.2.1.(5.4.),”To provide synchronization of feeding of
neonate larvae with vulnerable stage of host-trees” in SP of Choristoneura fumiferana is “High.”
The short term of larval development suggests "High expression of SS 5.1.(11.) "To evade
from impact of pathogens by means of shortage of a life cycle."
The development of the larvae under covering promotes affection of them by pathogens at
wet weather. Therefore, at drought in the larval stage, the population occurs to be healthy. This is
one more cause of the outbreaks, which, however, was not noted in literature. Therefore, an
expression of SS 5.1.(10.):”To develop self-protection against natural enemies by behavior
traits”, is “High.”
The competitors of Choristoneura fumiferana are unknown. This suggests that the species
has unique traits, so that an expression of SS 5.1.(17.) "To forestall competitors or evade from
competition", is "High." Probably in its evolutionary history, Choristoneura fumiferana forced
out its competitors.
EEs of the group 5.1.1.3.2. suggest that entomophagous organisms have minor significance
in suppression of these species at least on not too High values of density. Therefore, expression
of SS 5.1.(10.) "To develop self-protection against natural enemies by behavior traits"
5.1.(10.1.) "Avian predators" and 5.1.(10.2.) "Invertebrate predators and parasites" in SP of Ch.
fumiferana is “High.”
In SP of Choristoneura fumiferana, it presents the following SSes:
5.1.1.3.2.1.(5.4.) To provide synchronization of feeding of neonate larvae with vulnerable
stage of host-trees, High.
5.1.(10.) To develop self-protection against natural enemies by behavior traits,
5.1.(10.1.) Avian predators, High,
5.1.(10.2.) Invertebrate predators and parasites, High.
5.1.(11.) To evade from impact of pathogens by means of shortage of a life cycle, High.
5.1.(15.) To tolerate weather stresses in the stages from larvae to adults.
5.1.(15.1.) Cool and rainy weather in the larval and adult stages, Moderate or Low.
Consider the traits of the species - relatives of Choristoneura fumiferana in Eurasia from the
view of ESPPs.
Yu.A. Kostyuk (1971, p. 293) reported about Zeiraphera rufimitrana H.S. that its larvae
hatch in spring and strive to penetrate into buds; since then, they feed by flushing needles. The
penetration into buds is accompanied by high mortality. The penetration is successful on
condition that of significant weakening of the host-trees. So that an expression of SS
5.1.1.3.2.1.(5.4.), "To provide synchronization of feeding of neonate larvae with vulnerable
stage of host-trees" is "Weak."
Other tortricid species of coniferous tree species belong to the special group. They are webmaking, but not bud-mining. Such species as Choristoneura murinana, Epinotia redella,
Epinotia nigricana H.- S., and Cymolomia hartigiana Rtzb. oviposite on needles in summer.
They mine needles and later produce a web cover.
The oviposition on needles in summer suggests that they use SS 5.1.1.3.1.(5.3.) “To limit
feeding by needles with insignificant antibiosis in all the larval instars " Because a capacity of
these species to produce outbreaks is limited, an expression "Moderate or Weak."
A number of species of defoliators of the fir in Siberia are more active. Dendrolimus sibiricus
prevails. The geometrid moth, Boarmia bistortata Goeze in 1928-1934 caused a decline of 500
thousand hectares of fir stands in the southern part of the Krasnoyarsk Region and the Tuva
Republic (Il’insky and Tropin, 1965, p. 267). The tent caterpillar moth, Selenephera
(Cosmotriche) lunigera Esp. formed in 1960-ies infestation spots in diverse Regions of Siberia
on the area 200 thousand hectares (Kobzar, 1971). The fir stands affected by the defoliators are
colonized by diverse stem borers, particularly the longhorned beetle, Monochamus urussovi
Fisch., and undergo a decline (Rodd, 1930).
It might be in their SP, it presents SS 5.1.1.3.1.(5.2.) “To tolerate residual antibiosis in
needles even in young larval instars.”
Also, they might surpass the tortricid species as competitors. This implies "High" expression
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of SS 5.1.(17.) "To forestall competitors or evade from competition." in above species.
In Europe, the spruce undergoes complete defoliation surprisingly rare comparing with that
in North America. As explanation of this inequality might be proposed the idea that in Europe
there are potent competitors of defoliators – numerous species of stem borers, especially Ips
typorgaphus. They kill weakened trees giving no chance for defoliators to reach High density.
SP (Choristoneura fumiferana) = 5.1.1.3.2.1.(5.4.) – High; 5.1.(10.1.) – High; 5.1.(10.2.) –
High; 5.1.(11) - High; 5.1.(15.1.) – Moderate or Low.
SP (Zeiraphera rufimitrana)= 5.1.1.3.2.1.(5.4.) – Weak; no data as to other SSes.
Management implications as to the groups 5.1.1.3.1. and 5.1.1.3.2.are as follows:
i) Reforestation should be conducted with measures, which ensure maintenance of proper
physiological state of dominants. It includes:
In the conditions of the shallow effective depth of the soil, before the planting or sowing, it is
need to increase the depth with usage of special mechanisms, which drill the soil breaking hard
layers that interrupt penetration of tree roots in the deep soil area. This measure also normalizes
the moisture regime in the soil.
Loosely spacing of trees of coniferous species with the aim to provide them by a volume the
soil sufficient for normal vital activity of trees. This measure is of crucial importance in the
conditions of the dry sandy soils. The worse a habitat as to the poor and dry soil or low effective
depth of the soil, the more tree spacing should be practiced.
Enrichment of species composition in establishing ecosystems by admixture of nitrogenfixing plants. Assortment of these plants depends on soil and climatic conditions. For pine
plantations on the dry and poor soils, it might be recommended the black locust, Robinia
pseudoacacia L. On more rich soils, it is relevant to use the Siberian locust, Caragana
arborescens Lam. or the river locust, Amorpha fruticosa. As a good admixture in spruce and fir
forests, it serves diverse species of the alder Alnus spp. (for review see T.A. Rabotnov, 1983,
pp. 29-31). Thus, Alnus crispa and A. glutinosa carry into the soil up to 225 kg. of nitrogen per
hectare per year. The alders provide coniferous species not only by nitrogen, but also other
nutrients, because the presence of their fell leaves stimulates mineralization of the inert needle
fall. The alders can be used in the wide range of environmental conditions. In Alaska, Alnus
crispa is a pioneer tree species occupying areas after a retreat of ice fields. Thereupon, it is
displaced by Picea sitchensis. Therefore, the elder is not endangered for the spruce as a
competitor. The grey alder, Alnus incana (L.) Moench. is able to grow up to the north border of
forest (Sochava, 1956a, p. 161). In diverse countries, it is used as an admixture to coniferous
trees nine species of the alders (Tarrant and Trappe, 1971, cited in T.A.Rabotnov, 1983, p. 31).
Alnus incana and A. crispa appear in spruce ecosystems before the climax stage (Ibid., p. 214).
In such mixed coniferous-alder forests, outbreaks of the budworms do not arise in spite of old
age of them. The participation of the alder in a species composition of a stand promotes to early
flushing of coniferous trees. This would lead to early maturation of needles, i.e. to an increase of
resistance of them to the budworms. Because a damage by Choristoneura fumuferana is a
problem also in young plantations (Miller, 1977), the usage of the alders as an admixture of
coniferous species is prospective.
In pure overstocked plantations of coniferous tree species, physiological state of the trees
might be improved by means of thinning and application of mineral fertilizers.
ii) Promote to activity of natural enemies by:
Protection of forest ants and transferring of anthills into the ecosystems with deficiency of
these predators.
Sowing or planting of plants with abundant blossoming.
Application of insecticides is necessary for survivorship of affected stands if a forecast shows
that pest density threatens to exceed threshold of damage. It gives a possibility to stop losses of
needles on the level tolerable for affected trees. In the conditions of drought, not too much losses
of needles might be of benefit for vitality of trees due to a decrease of transpiration, so that an
application of insecticides stops defoliation on the level, which maintain physiological state of
affected trees. Also, bringing of insect bodies into the soil acts in this direction. Mortality of
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affected trees becomes partia, rather than complete one, and an ecosystem survives.
5.1.1. Defoliators
5.1.1.1. Defoliators of deciduous tree species
Defoliators of deciduous trees are presented by a number of guilds including the species well
studied in diverse environmental conditions. They offer abundant material, which open wide
prospects for comparison of taxa from the view of SP. These guilds are the following: earlyspring, spring-summer, summer-fall, and fall-spring ones.
5.1.1.1.2. Bud-mining and web-making defoliators of deciduous tree species (the earlyspring guild)
5.1.1.1.2.1.The green oak moth, Tortrix viridana L.
5.1.1.1.2.2.The winter moth, Operophthera brumata L.
Tortrix viridana is known as the most abundant defoliator of the English oak in East Europe.
O.V. Dunaev (2001, pp. 53-54) offered the data for density the early-spring guild on
twelve sampling plots distributed in diverse places in the Kharkiv Region (Ukraine) for twentysix years from 1970 to 1996. Tortrix viridana was present every year over this study. In
fifteen years of them, it was a dominant species. A.I. Vorontsov (1967, pp. 245-247) in the
textbook on forest entomology began description of defoliators of deciduous tree species with
Tortrix viridana that reflected his view as to its abundance.
Larvae of the Tortrix viridana hatch in spring in the period of bud-bursting in the oak.
Depending on weather situation, they hatch from the end of April to the second part of May. The
newly hatched larvae move to the buds. In so doing, they go short pass, because the females lay
their eggs on twigs close to oak buds. Then, a larva attempts to penetrate into a bud, and it
succeeds if in that time a bud stays in the stage of "a green cone." In a bud, a larva feeds and
finds shelter against natural enemies during the first and the second instars. At the beginning of
the third instar, a larva is able to make shelter for itself by spinning a web. In so doing, a larva
curls leaves and entwines them with its web. The larval stage continues in average 20-25 days.
This is short term comparing with that in Porthetria dispar. The larvae pupate under a web
cover. The pupal stage continues no more than two weeks. The moths are well protected from
avian predators by green color. The eggs are laid singly or by little clusters (two-three eggs) and
are covered by shields. They are scattered on twigs of host-trees. A form and color of the shields
so perfectly simulate structures of a surface of the twigs that it is difficult to find them at
counting of moth’s density. Tortrix viridana stays in the egg stage up to ten months – from the
first 10-day period of June to the end of April.
What kinds of advantages take place in the above-mentioned traits? They are numerous. In
fact, nearly ten months per year, Tortrix viridana stays in the state of perfect protection against
all the natural enemies. The larvae hatch in the period, when all the parasites are inactive being
in sites of hibernation, and the newly-borne larvae have a good chance to find protection against
them in the buds.
Beginning with the third instar, the larvae, and than the pupae are protected against parasites
by a web cover. This cover ensures a significant protection even against avian predators. In fact,
G.E. Korol’kova (1957) reported that birds encounter difficulties, when drew out larvae and
pupae of Tortrix viridana from curled with a web foliage. A success of the predation was
determined by the individual faculty, rather than by species traits. Only a less part of birds within
a species is able to do it.
F.N. Semevsky and S.M. Semenov (1978) reported about predation of pupae of this species
by the starlings. However, their effect on the population was insignificant, because a correlation
between percentage of predation and density of this population in next year was absent.
Green butterflies of the species are little visible for birds on a background of foliage.
There are direct data on the weak effects of birds on Tortrix viridana (Inozemtsev, 1978,
p. 223). Birds consumed the same number of larvae, pupae and adults of the moth in the forest
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plot, where measures to attract birds were conducted, and in the check plot. Other natural
enemies also exerted weak effect: parasites 15% (in both plots), ants -5.4-3.8%, and diseases –
10%.
Obviously, in Tortrix viridana, expression of SS 5.1.(10.) "To develop self-protection against
natural enemies by behavior traits", 5.1.(10.1.)"Avian predators" is "High."
The eggs are laid close to host-tree buds. When they are closed, the neonate larvae are able
to migrate on neighbor trees. Therefore, in stands with mixed phenological forms of the oak the
larvae have a good chance to find the buds in the proper stage.
Expression of SS 5.1.1.1.(9.) "To develop the traits directed on affection of host-plants in
vulnerable stages of their life cycle" is "High." Nevertheless, in the ecosystems with participation
of the only phenological form of the oak, CESPPs 2.1.2.1.1. "Superevasion from herbivores"
ensures such protection of the dominants that Tortrix viridana, which presents in Low or
Intermediate densities nearly annually, but does not exceeds threshold of damage of dominants.
E.N. Ierusalimov (2002) paid attention on the fact that species of the early-spring guild
consume the insignificant part of host-tree resources allocated by the trees for producing of
foliage. The maximum of their feeding in average takes place 19 May. This is a very early term
comparing with Porthetria dispar (8 June) and the notodontid moth, Notodonta (Peridea) anceps
Goeze (27 June). The latter species consumes nearly all the resource.
Because the effect of Tortrix viridana on vitality of host-trees is insignificant, they tolerate
even High density of this species without any changes in character of ecosystems, rather that the
High density in undisturbed by humans forests is hardly repeats in next season.
This is evidence of the usage of SS 5.1.1.1.(6.) ”To exert the least negative impact on vitality
of host-plants by means of reduction of development.” Its expression is obviously "High."
What kinds of CESPPs limit duration of Tortrix viridana outbreaks? They are of the category
2.1.2.1.1. "Superevasion from herbivores, 2.1.2.1.1.4. Starvation (exposition to 2.1.1.2.1.1.1.)",
when larval hatching occurs in the period of closed buds of host-trees. When the hatching occurs
after the stage "a green cone" has gone, the larvae are unable to make a web cover and suffer due
to parasites. It this case, it operates CESPPs 2.1.2.1.1."Superevasion from herbivores,
2.1.2.1.1.2. Exposition to 2.2.1."
Because weather situation in seasons varies, the coincidence of most part of Tortrix viridana
population and bud-bursting in host-trees is rather exclusion than a rule. Therefore, High density
of the Tortrix viridana takes place in the minor part of seasons. Contrary to defoliators of other
guilds, Tortrix viridana and its satellites are able to reach High density in the ecosystems with a
richest fauna of entomophagous organisms. These ecosystems stay on the level of ESPPs 3.1.
"Proper control" for the rest of guilds of defoliators. Nevertheless, on the level 3.1."Proper
control", the High density is of short duration. Due to weather changes, it occurs rarely more
than one season.
The quite another situation takes place in the ecosystems disturbed by human interference.
Here, it is common outbreaks of Tortrix viridana, which continue up to eight years (Il’insky and
Tropin, 1965, p. 302). Features of the ecosystems, where such outbreaks are recorded, allow to
suppose that CESPPs 2.1.2.1.1."Superevasion from herbivores" is too weak to suppress most part
of Tortrix viridana larvae. They reach High density over a number years in succession, and the
outbreaks are stopped by activity of CESPPs of the Intrinsic class - 2.5. "Effects of crowding."
Hence, such ecosystems stay on the level of ESPPs 3.3. "Late control."
Contrary to Porthetria dispar, it was not recorded an affection of a Tortrix viridana
population at a decline of its outbreaks with acute form of infection and parasitization that
suggests a lack of operation of CESPPs 2.5.3. "Increase activity of pathogens and parasites in the
specific conditions of high herbivore density", 2.5.3.1.4. "Mass mortality due to affection by
acute form of infection and parasitization." This is a sign of a well protection of Tortrix viridana
against vectors of infection, and weak activity of parasites in poor ecosystems. The outbreaks
decline under the effect of 2.5.3.1.5. "Spontaneous or winter mortality of embryos."
Due to a weak negative impact of Tortrix viridana and its satellites on vitality of host-trees,
they are able to tolerate their feeding even on the level ESPPs 3.3."Late control", when
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physiological state of dominants is decreased. Here, long-lasting outbreaks of these species
induce only a little increase of the annual stem fall (Vorontsov et al., 1967). Heavy damage over
four years by Tortrix viridana does not increase stem fall, whereas the damage by the fall-spring
guild, in particular the golden-tale moth, Nygmia phaeorrhoea L., causes significant host-tree
mortality in a result three years defoliation (Vorontsov and Mozolevskaya, 1968). However, this
comparison is not quite correct, because the former conclusion concerns better conditions of oak
growth (the Moscow Region) than the latter (the southeast part of the Forest-Steppe biome).
Above discourse shows, why Tortrix viridana is the most abundant defoliator in oak
ecosystems in East Europe.
The winter moth, Operophthera brumata dominated in the early-spring guild four years of
twenty-six ones occupying the third place after Tortrix viridana and Archips crataegana (Dunav,
2001, pp. 53-54). This fact suggests that SP of the former species is less perfect than that of the
two latter. Compare traits of Operophthera brumata with those in Tortrix viridana.
In Operophthera brumata, larval hatching takes place in the same time as in Tortrix viridana.
It might be that the coincidence of the hatching and bud-bursting on host-trees is more successful
than that in Tortrix viridana. There exists the view that the uncommon trait of Operophthera
brumata - wingless females serves just for the better coincidence with bud-bursting on a given
tree. Duration of the larval stage in the both species is equally short, and the effect of their
feeding on host-tree vitality is insignificant.
Nevertheless, there exists a difference in self-protection of the larvae against parasites.
Larvae of Operophthera brumata stay under web shelter only over daylight hours, while at night
they feed openly. This trait contributes activity of the parasite, Cyzenis albicans Fall. (Varley,
1970, p. 61). As to Tortrix viridana, the parasites with such a trait have a little importance, if
any, because larvae of this species make a nest by means of covering of foliage with web at once
they leave buds in the third instar, and they stay in the nests up to pupation.
For pupation, larvae of Operophthera brumata need to leave their shelter and move to forest
litter, where this species spends 5-6 months in the pupal stage. The larvae over their way and the
pupae in forest litter are exposed to much more danger on the part of natural enemies comparing
with that in Tortrix viridana, which spends both the larval and pupal stages in a shelter.
This suggestion proposed apriory might be proved to rather extent factually by a success of
introduction into Canada of the pupal parasite Cratichneumon culex Muell. and the larval
parasite Cyzenis albicans. The pupal parasite has two generations per year, and it is considered
as the most important suppressive factor at low population density of Operophthera brumata
(Varley et al., 1975).
In this context, it is notable that Operophthera brumata often dominates in flood plane oak
forests, and in such conditions outbreaks with dominance of this species are lasting (see for
example R.A. Zubov, 1968; A.T. Naumenko, 1973). The German village Kleine Kirche is
known by often outbreaks of Operophthera brumata in a near by oak forest. This forest is
situated in a flood plain (M.D. Lomakin, pers. comm.).
The effect of flooding might be explained by possible mortality of the second generation of
the parasite due to flooding as well as destruction of predators. Among them, it is known the
staphilinid beetle, Philonthus decorus (Varley, 1970). Further, a descent of the larvae into forest
litter implies the significant role in their mortality forest ants and mammal predators. Expression
of SS 5.1.(10.) "To develop self-protection against natural enemies by behavior traits" 5.1.(10.1.)
"Avian predators", 5.1.(10.2.) "Invertebrate predators and parasites", 5.1.(10.3.) "Mammal
predators" on the last larval instar and pupal stage should be evaluated as "Moderate."
Despite moths of Operophthera brumata fly in the period of year, when most of species of
insectivorous birds have left the range of this species, their mortality due to predation of nonmigrating species is rather high. Here is the report by G.E. Korol’kova (1957) about the number
of Operophthera brumata moths found out in a stomach of a bird in the second part of October:
Sitta europea L. – 80, Dryobates leucotes Bechst. – 100, D. medius L. – 1150.
Because the egg stage in Operophthera brumata takes place in the period, when natural
enemies of the eggs are inactive, they are laid on host-tree twigs without any masking.
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To sum up, the composition of SP in Operophthera brumata is the same as in Tortrix
viridana; an expression of –5.1.1.1.(6.) and 5.1.1.1.(9.) is close in the species, but expression of
5.1.(10.1.), 5.1.(10.2.), and 5.1.(10.3.) in O. brumata is less.
The moth Aclerus crataegana dominates in the guild more often than Operophthera brumata
does. A.I. Vorontsov (1967, pp. 248-249) gave description of this species immediately after that
of Tortrix viridana that implied the second place of Aclerus crataegana as to frequency of the
dominance.
Available data for Aclerus crataegana are limited, though the valuable information has been
given by A.A. Inozemtsev (1978, p. 223). In this study, it was compared mortality this species
and Tortrix viridana due to natural enemies in two forest plots – one with measures to attract
insectivorous birds, and a check plot. The data are presented in the Table 34.
Table 34. Mortality of Tortrix viridana and Aclerus crataegana in larval, pupal and adult stages
in oak stands due to natural enemies (Inozemtsev, 1978, p. 223).
Plots
Species under
Mortality due to natural enemies, percents
study
Ants
Parasites
Birds
Pathogens
With attraction Tortrix viridana
3.8
15.0
2.0
About 10
of birds
Aclerus crataegana
4.8
25.4
1.9
About 10
Tortrix viridana
5.4
15.0
2.0
About 10
Check
Aclerus crataegana
5.0
25.4
1.9
About 10
The Table 34 shows that the species are close in their capacity to counteract natural enemies,
although Aclerus crataegana is less protected against parasites. Notably, that attraction of birds
in a forest plot does not increase mortality of both species due these predators.
Consider the question: why does affection by the acute form of infection is not characteristic
for the early-spring guild of defoliators in spite of their larval development takes place in web
cover? As it has been shown above, this trait is useful for protection from parasites and
predators, but promotes affection of pathogens, because increases moisture of media. To answer,
it should paid attention on particularly early beginning of feeding and a very short duration of the
larval stage in this guild. The larvae have a good chance to finish their development during warm
and dry weather, which is common in East Europe at the end of April and most part of May.
Since then, it occurs an onset of rainy and cool weather, having the common name "bird cherry
cools" coinciding with flowering of the bird cherry. Such weather endangers the larvae by
promotion of pathogen’s activity.
Contrary, if the insects have time to pupate before an onset of such a weather situation, the
humid media does not lead to affection with pathogens. The short duration of the larval stage
allows the population to evade from these stressors. That is why, density of the early-spring guild
much often is higher on the early flushing form of the oak than that on the late flushing form.
Further, outbreaks of the guild spread on over the range of the oak in East Europe – much farther
to the north than those of other guilds, for example Porthetria dispar. In particular, outbreaks of
the early-spring guild are common in the Moscow Region, where outbreaks of Porthetria dispar
arise very rarely.
In this context, it should cite R.I. Zlotin et al. (1984, p. 70, Fig. 1, Graph IV). They found out
that maximal biomass of the early-spring guild in the pupal stage depended on the value of
precipitation in May-June. If the value of precipitation was less 100 mm, the pupal weight was
approximately 120 gr., whereas at the value was more 100 mm, the weight was 70 gr. They
noted high susceptibility of late-instar larvae of the guild to humidity and low air temperatures
(Ibid., p. 69). On the late-flushing form of the oak, the probability of the coincidence of the
larval stage with the "bird cherry colds" is greater. This idea explains the less affection of the late
flushing form of the oak.
The different expression of the traits 5.1.(11.) "To avoid impact of pathogens by means of
shortage of life cycle" and 5.1.(17.) "To forestall competitors or evade from competition" allows
explanation a difference in abundance of species within a guild.
In this concern, consider the report of N.A. Kharchenko and V.V. Tsaralunga (1985). They
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compared Tortrix viridana and Archips rosana L., which develop jountly, but continualy density
of the former was greater than that of the latter.
These scholars suppose that the cause of the difference consists in very short development of
Tortrix viridana. Its larvae begin to pupate May 15, when larvae of Achrips rosana stay only in
the third instar. In a result, "Tortrix viridana finishes the active part of its life cycle in the
optimal weather conditions for the central part of the Forest-Steppe in the shortest period
comparing with other defoliators, whereas Archips rosana suffers due to worse weather and
intensive competition for foodstuff" (Ibid., p. 112).
In some seasons, rainy and cool weather occurs over all the May that would suppress density
of the guild. Therefore, as the cause of wide fluctuations of the density in space and time, it
might serve not only a level of the coincidence of larval hatching and bud-bursting, but also the
above mentioned weather fluctuations. The cases of such an affection were recorded by
V.S. Znamensky (1968, p. 111), namely: "The most important among the diseases were
mycoses, especially in the years with cold and wet spring." On the other hand, in the guild
"…caterpillars and pupae seldom died from polyhedroses, protozoonoses and bacteriouses"
(Ibid., p. 111). Although, protective traits against pathogens in the guild are rather effective,
expression of SS 5.1.(10.) "To develop self-protection against natural enemies by behavior traits,
5.1.(10.4) Pathogens" is “High” or ”Moderate" in all the guild.
The capacity of females of Operophthera brumata to oviposit on the same tree year after year
implies that the role of CESPPs 2.1.1.4.1. "Evasion from herbivores" is less in suppression of
this species than that in Tortrix viridana. Therefore, in Operophthera brumata, expression of SS
5.1.1.1.(9.) ”To develop the traits directed on affection of host-plants in vulnerable stages of
their life cycle” is Very High., and SS 5.1.1.1.(6.) “To exert the least negative impact on vitality
of host-plants by means of reduction of development” is High.
The retention of High density of Operophthera brumata in North America until parasites of
this species were introduced from Europe is an evidence that suppression by parasites is more
efficient than that due to a lack of the coincidence of larval hatching and bud-bursting.
Expression of SS 5.1.(11.) "To avoid impact of pathogens by means of shortage of a life
cycle" is close to that in Tortrix viridana, i.e. "High or Moderate."
In conclusion, the two species of the early-spring guild defoliators possess the following
categories of SSes (Tortrix viridana “i”, Operophthera brumata – “ii”):
5.1.1.1.(6.) To exert the least negative impact on vitality of host-plants by means of reduction
of development,
i)
High
ii)
High.
5.1.1.1.(9.) To develop the traits directed on affection of host-plants in vulnerable stages of
their life cycle,
i)
High
ii)
Very High.
5.1.(10.) To develop self-protection against natural enemies by behavior traits,
5.1.(10.1.) Avian predators,
i)
High
ii)
Moderate (adults),
5.1.(10.2.) Invertebrate predators and parasites,
i)
High (eggs)
ii) High (eggs)
i)
High (larvae and pupae)
ii)
Moderate (larvae and pupae)
5.1.(10.3.) Mammal predators,
i)
High
ii) Moderate (pupae)
5.1.(10.4) Pathogens
i) Moderate
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ii) Moderate.
5.1.(11.) To avoid impact of pathogens by means of shortage of life cycle,
i)
High or Moderate,
ii) High or Moderate depending on phenological form of the oak.
5.1.(17.) To forestall competitors or evade from competition,
i)
High
ii)
High.
Because expression of these SSes is not equal in both species, it takes place the different
frequency of their dominance in the early-spring guild over years.
The available data suggest for SPs of two species of the early-spring guild of oak defoliators
the following rows:
SP(5.1.1.1.2.1.Tortrix viridana)= 5.1.1.1.(6.) - High; 5.1.1.1.(9.) - High; 5.1.(10.1.) and
5.1.(10.2.) – Eggs - High, all larval instars – High, Pupae - High, Adults – High; 5.1.(10.4.) –
Moderate 5.1.(11.) – High on the early-flushing form of the oak and Moderate on the late
flushing form; 5.1.(17.) – High.
SP(5.1.1.1.2.2.Operophthera brumata)= 5.1.1.1.(6.) - High; 5.1.1.1.(9.) – Very High; 5.1.(10.1.),
Eggs, larvae and pupae – High, Adults –Moderate; 5.1.(10.2.), Eggs –High, all larval instars –
Moderate, Pupae - Moderate; 5.1.(10.3.) – the last larval instar and the pupae – Moderate;
5.1.(10.4.) – Moderate; 5.1.(11.) – High on the early flushing form of the oak and Moderate on
the late flushing form; 5.1.(17.) – High.
Management implications:
i) To limit control of the early-spring guild with the usage of insecticides.
ii) Promote to natural enemies by:
Limitation of grazing,
Protection of forest ants and transferring of them into ecosystems with deficiency of
these predators.
iii) At reforestation, it needs to establish forest stands with acorns of a single phenological
form of the oak.
Defoliators
5.1.1.1. Defoliators of deciduous tree species
5.1.1.1.1. Openly-feeding defoliators of tree species (the spring-summer guild)
5.1.1.1.1.1. The gypsy moth, Porthetria dispar L.
The spring-summer guild of oak defoliators includes the gypsy moth, Porthetria dispar L.,
the lackey moth, Malacosoma neustria L., the pale tussock moth, Dasychira pudibunda L., bufftip moth, Phalera bucephala L., the notodontid moth, Notodonta trepida Goeze=[(Peridea)
anceps Goeze] and others.
Porthetria dispar is a species very convenient for understanding of the nature of SP. This
species has properties, which impart it to be hazardous for vegetation on the very wide range of
environmental conditions. It has the vast number of host-plants (several hundreds of plant
species), huge fecundity (in some situations more 1000 eggs), and high ecobiotic adaptability,
which allows it to inhabit a territory from the Tropics (the southern China) to the regions, where
winter temperatures drop up to 50º C below zero.
The spectacular example of progress in realization of SP of Porthetria dispar in a recently
infested area - the outbreak in New England States after 1880 – was provided by E.H. Forbush
and Ch.H. Fernald (1896).
Nevertheless, within its natural range, there are separate ecosystems or vast areas with divers
ecosystems, where outbreaks of Porthetria dispar are rare or never occur in spite of the
dominants are plant species favorite for resident ecotypes of this species.
Further, in most part of East Europe, Porthetria dispar is not a leader as a mass defoliator
neither in oak forests, nor in apple-tree orchards. On the oak, it comes down Tortrix viridana and
some other species of the early-spring guild. On the apple-tree, this species is less abundant than
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Hyponomeuta mallinelus and the complex of leaf-rollers.
EEs of Porthetria dispar on the levels ESPPs 3.1. "Proper control" and 3.2. "Lag control"
show that its SP interacts with such CESPPs: 2.1.1.3.1.2. "Tolerance to herbivores, Repair or
compensation of losses of host-plant tissues", 2.2.1. "Natural enemies of invertebrate
herbivores", in cooperation with diverse subcategories of CESPPs 2.3. "Routine weather
suppression."
The differences among diverse populations of Porthetria dispar as to ability to counteract EE
of ESPPs are significant and they have a hereditary character. Therefore, a number of taxa
should be stated within this species.
Consider the traits of the species responding on above challenges of the environment.
The traits, which concern 5.1.1.1 (6.) To exert the least negative impact on vitality of
host-plants by means of reduction of development
Comparing with the early-spring guild, Porthetria dispar larvae feed by foliage during longer
time, that implies the greater negative effect on vitality of their host-trees. Nevertheless, this
damage is negligible if ESPPs stays on the levels 3.1.”Proper control” and 3.2. “Lag control.”
This damage is tolerable for dominants on the level ESPPs 3.3. “Late control”, if their
physiological state is good, and frequency of heavy defoliation is not too big.
There are no data about the traits directed on shortening of duration of the feeding in some
populations of this species that would reduce damage of the feeding. Therefore, expression of SS
5.1.1.1 (6.)”To exert the least negative impact on vitality of host-plants by means of reduction of
development” should be evaluated as “Moderate” in all the taxa of Porthetria dispar.
The traits, which concern SS 5.1.1.1.(7.) To minimize negative impact on host-plants by
leaving of infestation spots as early as possible, when density reaches the high level
In the environmental conditions, where heavy and repeated defoliation is possible and it
endangers dominants by the destructive effect on their vitality, it appears well expressed SS
5.1.1.1.(7), which is directed on decrease of this effect.
As to operation of CESPPs 2.1.1.3.1.2. "Tolerance to herbivores, Repair or compensation of
losses on host-plant tissues", it is important that damage exerted by this species to host-trees
depends on circumstances. Outbreaks of Porthetria dispar in oak stands are often accompanied
by decline of the trees. Some scholars accuse Porthetria dispar as being a direct cause of the
decline. This view is doubtful one. The matters of fact, outbreaks of Porthetria dispar in Eurasia
arise in stands disturbed by human activity, and in addition stressed by weather situation. Both
stresses not only suppress natural enemies, but also worsen physiological state of host-trees of
Porthetria dispar that can be the main cause of the decline of these trees. Therefore, the role of
the outbreak in the decline merits a discussion.
Larvae of Porthetria dispar reaches maximal value of leaf consumption in average at 8 June,
i.e. they exert the greater negative impact on host-trees than larvae of the early-spring guild, in
particular Tortrix viridana does. The average date of maximal feeding activity of the former is
June 8, whereas that in the latter is May 19 (Ierusalimov, 2002).
Nevertheless, in East Europe, even at the level of ESPPs 3.3. "Late control", complete
defoliation by Porthetria dispar over two-three seasons does not destroy ecosystems. In a result
of such defoliation, a percentage of tree mortality increases, but it spreads on trees of the least
classes of vigor (Il’insky, 1959, pp. 34-35).
Mortality of the most part of dominants occurs, when the outbreaks take place simultaneously
with potent stressors of different character. For example, heavy drought results in a long-lasting
lowering of level of the water table. Roots of trees, in particular, the oak, which in these
conditions inhabit the upper soil layer, dry out, and the trees die. The same events take place in
oak stand growing in the soils of the podzol type with a hardpan, so that their roots are limited by
upper soil layer –often only two feet depth. Nevertheless, a decline or dieback of oak in the
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conditions of the shallow effective depth of the soil are common at the absence of Porthetria
dispar outbreaks, so that the latter should not be considered as bearing of secondary contribution
to decline of host-trees.
In the extreme southeast of East Europe (Bashkiria – an area on the border with Asia) and
over Asia, Porthetria dispar has obviously more expressed SS 5.1.1.1.(7.) than that in the rest of
East Europe. In Bashkiria, when the eruptive phase of an outbreak coincides with a drought, this
phase increases on several years, and all the duration of an outbreak increases up to 10 years,
whereas its common duration is six years (Khanislamov et al. (1958, pp. 41-42). Nevertheless,
these scholars, who offered a great many information about population dynamics of Porthetria
dispar on this area for the period of 100 years, nowhere reported about a decline of oak stands in
this area.
Further, in the area bordering with Bashkiria – the Chelyabinsk Region, (Western Siberia),
outbreaks of Porthetria dispar arise often (nearly every decade) and are long lasting ones. In
addition, these forest plots are usually affected by the summer-fall guild of defoliators. However,
noticeable mortality of host-trees – the birch has not been recorded (P.M. Rafes, pers. comm.;
Sokolov, 1988).
What kinds of factors allow host-trees to tolerate defoliation by Porthetria dispar?
The answer on this question one may find in the report of M.G. Khanislamov et al. (1958). It
occurred to be, long lasting outbreaks take place in an area-wide scale, whereas in a given forest
plot, High density continues in the initial stage of outbreak only a season. The infestation spots
have a nomad character. In fact, " Often even narrow forest clearings and roads serve as a border
between two little infestation spots, one of which is defoliated completely, whereas the second –
weakly. Next year, a distribution of the larvae, as a rule, becomes opposite: the larvae are scarce
of on the side defoliated heavily in the preceding year, and the abundant larvae are on the side,
which has been affected weakly" (Ibid., p. 12). It might be, the behavior trait providing the
mobility of infestation spots allows the insect to minimize negative effect of the feeding on a
vitality of host-trees, so that feeding resource of the species is not exhausted.
What kinds of the traits allow Porthetria dispar to co-exist with its host-trees in the
ecological optimum of the species, where its SP is realized in the most degree? This is a capacity
of the females to fly on large distance. This fact was observed again by M.G. Khanislamov et al.,
(1958, p. 13), namely: "In Bashkiria, the females often were trapped in open steppe in 8-12 km
from forest plots. In fall of 1952, the egg-masses were found out in the southeastern part of the
Trans-Ural Region on telegraph piles situated nearly 15 km apart of nearest forests." Long
distant flight in Bashkirian populations of Porthetria dispar was also noted by
Yu.N. Baranchikov and B.A. Kravtsov (1981).
In the rest of Europe, females of Porthetria dispar are able to fly on the distance no more
several hundreds of meters. Because of the Bashkirian population differs on the hereditary level
from the rest European populations, the former is a separate ecotype. Let it be, the Bashkirian
ecotype, whereas the rest populations belong to the Main European ecotypes.
The capacity of the females to fly gives a possibility to the species not only minimize damage
for host-trees, but also to reach High density every year. In fact, in Bashkiria "Here and there, the
gypsy moth presents at high or intermediate density actually every season" (Khanislamov et al.,
1965, p. 117). The infestation spots do not move by chance. They appear in the stands with
characteristics of the lowest level of stability to Porthetria dispar. Usually, they are southeastern
and eastern edges of forest groves. In an innocuous phase of population dynamics of Porthetria
dispar, an overall area of such nomad infestation spots is not too large – "less than 1% of the
area of the host-trees" (Yafaeva, 1963, pp. 8-9).
Above discourse suggests that the Bashkirian ecotype of Porthetria dispar exerts less
negative effect on its host-trees than do the Main European ecotypes. In other words, the former
is more developed as to expression of SS 5.1.1.1.(7.) "To minimize negative impact on hostplants by leaving of infestation spots as early as possible, when density reaches high level", and
the difference might be explained by unequal behavior traits of the ecotypes.
In this context, consider the traits in the Main European ecotypes concerned this SS. At Low
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and Intermediate densities, the females demonstrate the least mobility. Usually they stay in sites
of eclosion waiting the males. After fecundation, they move in a lower part of stem of their hosttrees and lay egg-masses. The neonate larvae turn up in crowns of the same trees.
The behavior of the females and neonate larvae changes, when a population reaches High
density. The first sign of the change is an increase of height of a stem’s part, where the eggmasses are laid. V.M. Kondorsky (pers. comm.) observed in Moldova (the Former Soviet Union)
the direct dependence of an extent of the region on a stem with egg-masses on their density in a
forest plot. This change might be explained as an attempt to make better chances for the larvae at
competition for foodstuff. In fact, the greater height of laying of egg-masses on a stem, the
earlier they begin to develop in spring due to better heating by sunrays, the earlier neonate larvae
reach foodstuff, because the way to it becomes less. These egg-masses, which are laid on stems
above a snow cover, suffer due to increased bird predation. Although, the advantage to forestall
competitors prevails over greater mortality due to predation.
The second sign of a population response to increased density is activity of the females to
make ready their brood for emigration from an infestation spot. The females reveal a capacity to
fly on the distance up to hundreds of meters, and lay egg-masses on objects, which stand out
against a background of a plot. In mixed oak stands, the favored places for the laying are stems
of the birch. The author observed in the Kyiv Region (Ukraine) that in an infestation spot of
Porthetria dispar, in the eruptive phase, the number of the egg-masses per stem of the oak
equaled from several pieces to several dozens, whereas on scattered birches, the number of the
egg-masses reached thousands. Nearly a whole lower part of a birch stem with rough bark was
covered with the egg-masses.
The choice of the birch might be explained easily. Its white stems attract the females. Also,
being a pronounced light-requiring species, the birch rises its crown above a canopy of the oak,
and birch branches are flexible swinging widely by the wind. This property of the birch allows
the larvae to fly over a canopy of the oak.
Any tall objects can be chosen by the females as a starting point for emigration of neonate
larvae. For example, in an infestation spot of Porthetria dispar, there were no more several eggmasses per stem of hundreds of oak trees, whose height did not exceed 10 meters. On the other
hand, on large oak trees with height nearly 30 meters (the number of such trees was only three)
egg-masses covered all the surface of their stems and limbs, so that the trees acquired uncommon
orange color. The number of egg-masses on each of the trees reached many thousands. This case
was observed by M.V. Torchik (pers. comm.) in the southern Belarus (the Former Soviet Union).
It has been suggested that the proportion of the neonate larvae, leaving an infestation spot,
depends directly on their population density (Semevsky, 1971a; Kokhmanyuk, 1975). They are
able to be transferred by the wind on large distance – 40 -150 km according to reports of diverse
scholars (for review see V.I. Benkevich, 1984).
There are no data about the differences in duration of the larval stage in the Main European
and Bashkirian ecotypes.
The above discourse gives the ground to suppose that an expression of SS SS 5.1.1.1.(7.) "To
minimize negative impact on host-plants by leaving of infestation spots as early as possible,
when reach the high level" is "Moderate" in the Main European ecotypes and "High" in the
Bashkirian ecotype.
The traits, which concern SS 5.1.(10.) To develop self-protection against natural
enemies by behavior traits 5.1.(10.1.) Avian predators, 5.1.(10.2.), Invertebrate predators
and parasites, 5.1.(10.3.) Mammal predators, and 5.1.(10.4.) Pathogens
Unlike to the early-spring guild, on the levels of Low and Intermediate densities, the neonate
larvae of Porthetria dispar do not take any steps for self-protection against natural enemies. F.S.
Kokhmanyuk (1975) studied behavior of the larvae and concluded that in the first instar they
tend to keep themselves of host-trees.
If the density exceeds a foodstuff resource on a given tree, the young larvae are able to
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regulate their density leaving the crowns. In so doing, they demonstrate a rather complicated
behavior responding on density of web threads laid by individuals, which have climbed to a
crown before them. It seems, the neonate larvae are able to forecast availability of foodstuff that
will be at completion of their larval development.
The neonate larvae have no noticeable attractiveness for natural enemies. However, yet in the
second instar they are exposed to attacks on the part of parasites. In the author’s studies, the
second instar larvae were collected after exposition of the egg-masses in nature and placed into
sleeve cages with oak twigs. Since the third instar, cocoons of the parasites, Apanteles spp. might
be seen on the rearing larvae. Even in a not so rich ecosystem (an abandoned fruit orchard), the
number of affected by parasites in the second instar larvae reached one third of the reared group.
The young larvae are attacked also avian predators, namely: "Several species of birds prey on
young caterpillars. Both nuthatchers and downy woodpeckers pick up insects on the tree bole,
while scarlet tanagers tend to pick from the leaves and twigs in the tree crown" (Campbell, 1974,
p. 8).
The impact on the part natural enemies becomes more and more great as the insects progress
in the development. In the author’s studies, at exposition of the egg-masses on the base of shade
trees in Kyiv, where birds (the sparrows and the titmice) were actually the only natural enemies,
a sharp decrease of the exposed larvae began in the second instar. The last of observed on trees
larvae were in the fourth instar. Because the number of exposed eggs was evaluated five
thousand per tree, and mortality in the first instar is little of probable, the rate of predation was in
average approximately ten-fold per instar.
Further, late-instar (fourth-sixth) caterpillars and pupae of Porthetria dispar were transferred
from an infestation spot in an oak forest ecosystem of the level ESPPs 3.1. "Proper control." At
exposition of the groups with hundreds of such insects, it occurred to be that all of them
disappeared on the next day being consumed by birds.
Therefore, survivorship of Porthetria dispar in the ecosystems with significant activity of
natural enemies is possible on condition that a presence of advanced traits of self-protection
against the enemies. Such traits, indeed, exist, and they are diverse depending on the
environmental conditions. It should consider behavior traits of the larvae and explain the traits
from the view of their protective role taking into account the environmental conditions.
The diurnal migrations of Porthetria dispar larvae in North America are studied well. Here,
in the mesophytic habitats, at common weather situation, the larvae beginning with the middle
instars (in the fourth and some larvae in the third instar) in early day hours stop feeding and
move in shelters. In so doing, these larvae descent in forest litter or hide in any nooks above the
soil surface. In these sites, they spend day-hours. At onset of darkness, the larvae return in tree
crowns for feeding. The pupation takes place also in shelters. "Dry weather may produce
conditions on mesophytic sites that will cause an otherwise sparse larval population to stay in the
trees and this in turn may trigger an outbreak" (Campbell, 1961, cited in R.W. Campbell et al.,
1978, p. 21). Thus, the shift in the behavior is considered as a turning point in population
dynamics of Porthetria dispar. In the xerophytic habitats, at any weather situation, the larvae do
not leave crowns of host-trees and pupate here (Bess, 1961).
The report by H.R. Smith and R.A. Lautenschlager (1981) shows that a daytime resting in
forest litter is not too dangerous for Porthetria dispar larvae. Indeed, "In a sparse gypsy moth
population…larvae apparently favored these mammal tunnels as a resting locations (Paszek
1977)" (Ibid., p. 97). Moreover, "An…field crew collected approximately 8,000 female, sixthinstar larvae, prepupae, and pupae within a 52-ha area almost exclusively from small mammal
tunnels located at the base of oak trees. Few pupae were found anywhere else. Small mammal
predation was evident in these tunnels by the large number of pupal fragments found" (Ibid.,
p. 97). Further, "…Campbell and Sloan (1976, 1977a)…estimated that vertebrate killed
70 percent of the pupae in a series of sparse stable populations…’’(Paszek, p. 97).
The larvae are able to protect themselves against the predators. The pupae are protected
worse, although they stay under cover of larval skins with thorns.
Why does "…100 years has not been sufficient time for this behavior of migrating to a
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resting location to change…?" (Ibid., p. 97). Because this trait is considered by some scholars as
harmful for survivorship of the American population, it should consider the trait in detail.
The retention of this behavior trait in mesophytic forests might be explained only by the idea that
at absence of the drought, mortality of the pupae spending daytime tree crowns is more than that
in forest litter, i.e. more than 70%.
At onset of the drought, which suppresses parasites and avian predators, the migration to a
resting location ceases. In xerophytic forests, it is not need to migrate to resting locations at any
weather situation, because in the xerophytic habitats activity of parasites and avian predators is
continually low.
To evaluate the protective role of the diurnal migrations, it is advisable to consider behavior
of Porthetria dispar larvae in Europe. R.W. Campbell and R.J. Sloan (1976) gave a list of
European entomologists, who were asked by them about diurnal migrations of Porthetria dispar
larvae in Europe. All they answered that such migrations were unknown for them.
However, the migrations take place in Europe, although in the specific habitats. The report
about them already had been published. This was done by V.A. Kolybin and L.M. Zelinskaya
(1975, pp. 77), who observed that older larvae spent daylight hours in diverse shelters – under
loose bark, in stem holes, in bird’s nests, and in forest litter. A.G.Kotenko (1977) confirmed this
report.
It should pay attention to features of the ecosystems, where these observations were done.
They are ecosystems of two categories in south areas of Ukraine.
The first ones are presented by stands in flood plains, where flooding in spring suppresses
ground predators of the larvae and pupae.
The second ones are island forest stands growing in depressed terrain in the Steppe biome,
where the soil during the long period in spring and early summer stays wet due to an
accumulation of snow in winter and in an inflow of water at spring rains. The soil soaked with
water is unfavorable for the ground predators. Therefore, in such conditions, forest litter near by
bases of tree stems growing on hillocks is a safe place for the larvae.
In mid-summer, when Porthetria dispar pupates, a surface of the soil here becomes fairy dry.
Then, the predators are able to penetrate into these habitats from outer territory, and to kill the
pupae. That is why, in flood planes, larvae of Porthetria dispar pupate within trees - on stems at
Low density, and in tree crowns at High density searching shelters in them (Mamontova et al.,
1983, p. 115). Any shelter is used for the pupation. For example, V.S. Karasiov (1969, p. 14)
observed the pupation in web nests of the willow ermine moth, Hyponomeuta rorella Hb.
A.G. Kotenko (1977) has supposed that diurnal migrations into forest litter are aimed first of
all on self-protection against overheating in the conditions of hot climate in south of Ukraine,
and in the second this is a protection against predation and parasitization.
There are the grounds to suppose, however, that this trait is a means of protection against
natural enemies, rather than against sunrays. In fact, the sheltering in forest litter during daylight
hours takes place in an area of rather fresh climate – in the northern part of Ukraine – in the Kyiv
Region. In the author’s studies, egg-masses of Porthetria dispar were collected in a flood plain
area of the Dnieper River. A point of the collecting was on the bank of the river in ten miles
southeast from Chernobyl.
The egg-masses collected in this area were exposed in a shelterbelt on secadol. At further
observations, it was found out that the fourth-to-sixth instar larvae spent daytime hours in forest
litter within a radius up to two feet around the trees, where they fed during night. They pupated
also here.
This was the single case, when a part of the released larvae of the gypsy moth survived to the
pupal stage that might be explained by very unfavorable conditions for their natural enemies in
the plot – two rows of young oak trees without of undergrowth...
These insects kept the behavior trait characteristic for the native ecosystem. In this
ecosystem, trees up to 15 feet in height grew one by one on sparse hillocks among boggy terrain.
The latter was saturated with water over a season. In spring, a base of the trees (birches, aspens,
oaks) underwent flooding. Since in such conditions, ground predators had no admit to the areas
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close to a base of the trees. The older larvae were able to spend here daytime hours in safety.
Obviously, such a trait was induced by the habitat conditions rather than by climate.
A probable benefit of the diurnal migrations is searching for shelter from parasites and birds.
In fact, "The most forest insect parasites are active only during daylight hours" (Weseloh, 1976,
p. 66). The same is true for the avian predators.
The diurnal migrations are known in the forest ecosystems, which are favorable for
abundance of the avian predators. Indeed, "…high activity of birds is characteristic especially to
island forest plots in the Forest-Steppe biome and to small old steppe plantations, where the
density of birds reaches 30-40 pairs per hectare. On the other hand, in mixed coniferousdeciduous forests in the middle part of East Europe, density of birds reaches only 5 pairs per
hectare" (Doppelmeir et al., 1966, p. 337).
Thus, European data as to the diurnal migrations suggest that they take place in the
conditions, where activity of the bird predators and parasites is high, whereas that of the ground
predators is low.
V.A. Lozinsky (1957, p. 38) traced the behavior of Porthetria dispar also in south of
Ukraine, but in other conditions - on the secadol in plantations of steppe afforestation. He
recorded diurnal migrations of older larvae, which found shelter in bark crevices, and in forked
branches, rather than in a forest litter.
The author exposed near by Kyiv in a forest stand egg-masses of two Porthetria dispar
populations, sampled on secadol in south of Ukraine. Their behavior occurred to be unequal.
Older larvae of the population from a forest plot planted in steppe tended to spend daylight hours
in shelters on host-tree crowns – forked branches, plates of sleeve cages, which were used for
rearing of Porthetria dispar larvae, etc. This population is adapted to the same conditions as that
studied by V.A. Lozinsky.
Unlike, older larvae of another population sampled also in steppe, but in an ecosystem of a
specific character (a road-side row of young trees) did not show any temptation to search for
shelter. They spent daylight hours on leaves or twigs of host-trees. Then, at Low and
Intermediate densities, they did not feed, but stayed motionless clasping to leaves, leaf stalks or
twigs.
The behavior traits in the above cases might be explained high activity of ground predators
(the rodents) on areas, where soil treatment was not used. Here, activity of parasites is low.
Protection against avian predators consists in either sheltering within host-trees or the motionless
state (on young trees, where any shelters are in deficiency). The latter trait allows the larvae to
evade from bird attention.
At High density, the larvae fed during day-hours. It seemed, at foodstuff deficiency, they are
forced to neglect the danger on the part of their enemies, rather that, at High density of
Porthetria dispar, birds leave the infestation spots.
The larvae from the populations, which inhabit forests in the Kyiv Region on secadol,
behaved spending daylight hours in motionless state at Low and Intermediate densities. It is
observed at diverse levels of ESPPs – 3.1., 3.2., and 3.3. An explanation of the behavior is the
following. In this area, density of Porthetria dispar is mainly Insignificant or Low either in time
or place even in the ecosystems disturbed by people. Here, activity of natural enemies is greater
than that in the southern areas. The scattered larvae in rather large crowns of their host-trees are
little of taken notice by natural enemies. This trait is optimal for survivorship in the given
conditions. At High density, the larvae are forced to hurry in feeding even in the hours, when
natural enemies (parasites) are active. Avian predators leave infestation spots, when density of
Porthetria dispar becomes High.
It was recorded behavior traits of the larvae, which might be suggested as a self-protection
against pathogens. They are the following.
In the Russian Far East, it is known the migrations of the older larvae in daylight hours
(Turova, 1986). The movement of them started at 7 a.m. and continued mainly until 10-11 a.m.
Although, some larvae descended up to 4 p.m. At the same hour, the reverse movement began
that continued up to 10 p.m. The migrations took place at sunny and cloudy weather. At the
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latter, however, the number of migrating larvae decreased by 5-10 times. It was not reported
about aggregation of the larvae in forest litter. They stayed of a surface of host-tree stems. At
burlap banding, the larvae aggregated in these burlaps. The proportion of migrating larvae was
only 20%. The rest of them stayed in crowns continually.
In this report, it was mentioned that the same behavior of the larvae was recorded in the point
situated far from this territory – in the European part of the country near by the Volga River.
Because high temperatures suppress polyhedral viruses, it might be that the larvae expose
themselves on sunlight for treatment of the infection.
In the Transcarpathians Region (Ukraine), the older larvae began to descent into forest litter
only in afternoon (Baganich, 1988). This scholar explains the trait as a means of self-protection
against tachinid parasites, which are particularly active in early evening. Nevertheless, it should
explain, why the larvae do not descent before a daybreak, when avian predators are inactive. It
seems the larvae need to wait until a surface of the soil will dry. These observations were done in
poorly drained habitats. Here, humidity of the soil surface decreases significantly only in
afternoon due to heating by sunrays. A wet media is ruinous for the larvae inducing affection
them with pathogens. Thus, the above cases demonstrate SS 5.1.(10.) "To develop selfprotection against natural enemies by behavior traits, 5.1.(10.4.) "Pathogens."
The above discourse gives a possibility to draw some conclusions, namely:
i).
There exists a diversity of behavior traits of Porthetria dispar larvae, every of which is
characteristic for definite environmental conditions.
ii) Every of the traits is a result of natural selection under pressure on the part natural enemies,
operating in ecosystems of a certain type.
iii) A destination of the traits consists in minimizing mortality of a population due to natural
enemies.
iv) A population of Porthetria dispar keeps the behavior traits at transferring of it into an
ecosystem with different environmental conditions. Therefore, the traits have a hereditary
character, and populations of Porthetria dispar with the different traits should be considered as
different ecotypes of the species.
v) Spending daytime hours in forest litter by older-instar larvae and pupae takes place in the
habitats, where activity of ground mammal predators by exceeding moisture due to spring
flooding or accumulation of snow. These traits decrease of mortality in the instars and the pupal
stage due to avian predators and many species of parasites. Therefore, in above habitats, density
of Porthetria dispar tends to be greater than otherwise.
vi) The diversity of behavior traits of protective destination allows to state within the Main
European ecotypes the secadol ecotype and the flood plane ecotype.
vii) On south of the border of Europe and Asia, it inhabits the Bashkirian ecotype of Porthetria
dispar.
viii) The traits of above ecotypes determine diverse ability to withstand of their natural enemies,
and, therefore, differences in their abundance in place and time.
ix) The traits of the American population of Porthetria dispar suggests that it is an offspring of
the Main European flood plane ecotype.
Thus, these behavior traits concern SS 5.1.(10.) "To develop self-protection against natural
enemies by behavior traits."
Consider an operation of the subcategories of 5.1.(10.) on diverse stages or instars and their
expression.
In the first instar, when affection by natural enemies is unknown, expression of 5.1.(10.) is –
"High" as to all the subcategories of SS 5.1.(10.). In the second-sixth instars, the larvae have the
traits, which give them a possibility to inhabit ecosystems with wide diversity of ecological
conditions reaching in many of them High density. In some conditions (in reservations), the
density stays continually on the Intermediate level. The conditions of flood planes and island
forests in the Steppe, where prolonged moistening of the soil suppresses ground mammal
predators, density of Porthetria dispar tends to be often close to Intermediate. Probably, this is
due to behavior trait of spending older-instar larvae and pupae in forest litter. This trait provides
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superlative protection against all the natural enemies during the older instars and pupae stage.
Therefore, an expression of SS 5.1.(10.) in the Main European flood plane ecotype for these
instars and pupae is “High.” As to the rest instars and pupae in other ecotypes, an expression of
SS 5.1.(10.) is “Moderate.”
The data on mortality due to natural enemies in the egg stage are innumerous. B.V. Ryvkin
(1957) reported such values of parasitization by Anastatus disparis (Rusch.): in 74 sites on
diverse areas of USSR in 1951 – 1.9%; in 17 areas in 1953 – 1.3%. Only in few areas, the
parasitization reached 10-25%.
The titmouse sometimes feeds by the eggs, but there are no reports about a significant
decrease of the egg-masses due to predation. The character of oviposition provides adequate
protection against parasites and predators. It seems, an expression of SS 5.1.(10.1.) in egg stage
of Porthetria dispar is "Moderate."
Mortality of Porthetria dispar butterflies was "exceedingly low" (Bess, 1961, p. 25). On
the other hand, H.R. Smith and R.A. Lautenschlager (1981, p. 101) reported that "Shortly after
sunrise, blue jays (fig. 4-23) would begin to search systematically lower branches and tree trunks
for adult male gypsy moths. Captured moths were swallowed whole. By midmorning, the jays
changed their searching patterns: They searched the shrubs for adult moths on the underside of
the foliage."
Also N.A. Men’shikov (pers. comm.) observed actually complete consumption by the
sparrow a great many immigrated females of Porthetria dispar, which aggregated on walls of a
building for oviposition in the Perm Region (Russia). Again, I.F. Zayanchkovsky (1983, p. 127)
reported that in 1957 in Moscow appeared masses of butterflies of this species migrated from
southeastern areas. Nevertheless, they did not lay eggs, because were killed by the sparrow.
These reports concern the conditions of settlements, where a population of avian predators is
abundant. As to forest ecosystems, where Porthetria dispar has been developed as a species, its
mortality in the adult stage is much less.
It should note that extensive and undisturbed forest ecosystems characteristic for Europe
before radical changes caused by human activity in the last millennia stayed on the highest level
of ESPPs - 3.1. "Proper control." In that time, Porthetria dispar was usually suppressed to
Insignificant density. At such a density, it occurred to be nearly unnoticeable for its parasites and
predators, but increase in the density was early suppressed by the enemies.
In such conditions, vulnerable for avian predators females had no need to fly on large
distance to emigrate from infestation spots. In the case of increased density, the females can find
quickly white stems of the birch or any tall trees to lay on them their egg-masses. This aim might
be achieved during a night of their eclosion, when insectivorous birds are inactive. This trait
provides rather safe dispersion on large distance, because the neonate larvae are out of attention
of parasites and predators. Mortality of the males obviously greater, but this is not significant for
species density, because a male is able to fecundate many females.
Therefore, it would be realistic to evaluate expression of SS 5.1.(10.1.) and other
subcategories of 5.1.(10.) in adults of the Main European ecotypes of Porthetria dispar as
"High."
In the conditions of distinctly continental climate in Asia, the traits of the taxa have been
developed in island forest ecosystems, which occupy a minor part of the area. Because these
forests have grown long since on the border with the Steppe biome, the level of their ESPPs was
decreased. That was the levels of ESPPs 3.2."Lag control" or 3.3. "Late control." Because the
outbreaks were common, and a directional flight of the females at once the density reached the
value High was advantageous at searching for untouched forest islands. In such conditions,
expression of SS 5.1.(10.1.) and other subcategories of 5.1.(10.) in adults of the Asian taxon of
Porthetria dispar as "Moderate."
The destination of behavior traits consists in protection against all the natural enemies, and
the diversity of them is determined by specificity of environmental conditions, where an ecotype
has been formed evolutionary.
Nevertheless, this capacity is not absolute. All the ecosystems, where the density reaches the
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High or Intermediate levels, are characterized by suppression of activity of natural enemies.
Unlike to the early-spring guild, there exist ecosystems, where density of Porthetria dispar is
continually Low or Negligible. In some conditions (in reservations), the density stays continually
on the Intermediate level.
Thus, protective efficacy of SS 5.1.(10.) in Porthetria dispar is less than that in the earlyspring guild.
Comparing expression of all the subcategories of SS 5.(10.) in the early-spring guild with
that in Porthetria dispar shows obvious prevalence of the former. Because in the former,
expression of SS 5.(10.) is “High”, in the latter, it prevails "Moderate."
In the Main European flood plane ecotype, expression of SS 5.1.(10.) as to older-instar larvae
and pupae is “High.” In other ecotypes, as to the eggs, the larvae for the second - the sixth larval
instars, the pupae, and the adult expression of SS 5.1.(10.) – 5.1.(10.1), 5.1.(10.2.), 5.1.(10.3.),
and 5.(10.4.) is "Moderate."
The traits, which concern SS 5.1.(13.) To leave infestation spots as early as possible,
when virulence of pathogens and activity of other natural enemies begin to grow, and
The role of emigration of Porthetria dispar larvae from infestation spots, as an evasion from
parasites was understood long ago. G.K. Pyatnistky (1935, cited in S.P. Ivanov et al., 1938,
p. 75) found out in the Crimea Peninsula (Ukraine) in infestation spots operating three years, 9095% of the larvae were parasitized, whereas in infestation spots appearing in a current year due
to immigration of the neonate larvae, the number of parasitization was only 0.5-1.0%. This is an
example of operation of SS 5.1. (13.) “To leave infestation spots as early as possible, when
virulence of pathogens and activity on other natural enemies begin to grow.” Although the given
case demonstrates “Weak” expression of this SS, because the emigration took place lately.
This means of emigration by chance from infestation spots seems to be less advanced than
the directed flight of females in the Bashkirian ecotype. In Europe, the duration of the eruptive
phase in a given infestation spot is more prolonged, than that particularly in Bashkiria, according
M.G. Khanislamov et al. (1958).
Although in the European ecotypes the neonate larvae demonstrate a capacity to migrate,
their infestation spots occupy the same ecosystems over a number of years. In them, the common
duration of the outbreak phase in a separate ecosystem is three years. This term is large one
comparing with that in other regions. Hence, a population is unable to migrate as soon as its
density has reached the value High. Thus, the Main European ecotypes do not have advanced
traits to counteract CESPPs 2.5.2. "Attraction of predators and parasites, increase of their
searching activity" and 2.5.3. "Increase activity of pathogens and parasites in the specific
conditions of high herbivore density."
Here is a case demonstrating the limited possibilities of Porthetria dispar in Europe to avoid
High density by early emigration provided by I. Zhikharev (1928, p. 299). In 1895, at a sublime
outbreak of Porthetria dispar in Russia, its larvae and larvae of the lackey moth, Malacosoma
neustria L. defoliated completely 200 ha of beautiful oak forests in the Fastiv forestry unit near
by Kyiv. Then, the larvae moved from the defoliated part of the unit to intact one. In so doing,
they covered a railroad on the distance of 1 km. In a result, trains had to stop.
A stopping of trains due to covering of a railroad by moving Porthetria dispar larvae was
noted by F. Keppen (1883, p. 62).
Therefore, in some European ecotypes, expression of SS 5.1.(13.) "To leave infestation spots
as early as possible, when virulence of pathogens and activity of other natural enemies begins to
grow" should be evaluated as "Moderate", and other as "Weak."
The above-cited report by M.G. Khanislamov et al. (1965) shows that this trait is well
developed in Bashkiria. "Here and there, the gypsy moth presents at high or moderate density
actually every season" (Ibid., p. 117). In the publication by M.G. Khanislamov et al. (1958,
p. 12), it was also paid attention on a nomad pattern of the infestation spots between the mass
outbreaks. Then, High density spreads on vast areas. The dispersion of the Bashkirian ecotype is
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proceeded both by flight of the females and transferring of the neonate larvae. In fact, after a
strong wind of the southern direction May 19, 1952, in vast forest stands free from Porthetria
dispar, it was observed the numerous young larvae that caused 50-fold increase of infestation
spot areas (Ibid., p. 13).
The mass outbreaks begun usually in the southeastern part of the Bashkiria, and during
several years spread to northwest direction. Thus, the eruptive phase in the southern Bashkiria
was recorded in 1952, while in the north part of this area – in 1956.
The advanced mobility of the Bashkirian ecotype results in the spread of the infestation spots
up to the Moscow Region, and nine females even up to Finland (Vorontsov, 1977). A.I. Il’insky
(1959, p. 10) observed the sudden appearance of myriad of Porthetria dispar females in Moscow
after strong wind of the southeastern direction. Further G.N. Gornostaev (1962) in the same
season trapped with usage of a mercurial lamp the numerous females. Although in the resident
population, the females are unknown to be able to fly.
The vast outbreak of Porthetria dispar in East Europe started in 1951 in the southeast part of
this area, and in 1957-1958 it spread far to the northwest up to the Moscow and Kalinin (now
Tver) Regions (Vorontsov, 1978, p.127). This scholar has supposed that such a direction of the
spread is characteristic for diverse species of oak defoliators.
It is logical to see in the mobility a means of evasion from natural enemies, whose activity
grows continually as the density progresses.
Thus, the Bashkirian ecotype demonstrates the well-developed trait of the category SS
5.1.(13.) "To leave infestation spots as early as possible, when virulence of pathogens and
activity of other natural enemies begins to grow. " Its expression is "High." This capacity allows
the ecotype to stay at High density continually on this area, although occupying a minor part of
the area. In the same time, its negative effect on host-trees is a little one, so that 5.1.1.1.(7.) "To
minimize negative impact on host-plants by leaving of infestation spots as early as possible,
when density reach the high level" should be considered as of "High" expression.
There exist the taxa of Porthetria dispar, in which migration traits are much more developed
than those in the European and Bashkirian ecotypes, and they have features, which are unknown
in these ecotypes. The traits were described at studies in the Asian part of Russia.
The long-distant migrations of Porthetria dispar moths were observed in the East Siberia
(Pleshanov and Rozhkov, 1971). Large masses of the moths flew in 1955 and 1963 in the north
direction over the Khaber-Daban Mountain Ridge situated to the south of the Baikal Lake. The
same flight took place over the East Sayan Mountain Ridge situated to the west of the Baikal
Lake. Supposedly, they moths flew from the south of the Transbaikal territory and Mongolia.
The distance of the flight was evaluated as reaching 200 km.
V.I. Epova and A.S. Pleshanov (1988) explained these migrations as "an evasion from
regulatory mortality factors." They noted that in the East Siberia the role of parasites in
infestation spots of Porthetria dispar is negligible. Therefore, the eruptive phase continues very
long – up to six years.
These facts are in a concordance with the view that in the conditions of severe continental
climate, parasites of Porthetria dispar are suppressed, and a deficiency of the parasites as well as
dry climate preclude the explosion of the acute form of infections. Only the slow form of
infections operates in such conditions. Further, an inapparent action of this form creates an
illusion that Porthetria dispar is suppressed by mainly “modifying”, i.e. density-independent,
mortality factors, in particular unhatching of the larvae under impact of winter frost.
The unhatching was observed in both old infestation spots, which had been left by a part of
Porthetria dispar population, and in new infestation spots, which had been established by the
immigrated insects. As to the new infestation spots, this suggestion is based on the report by
A.S. Pleshanov and V.I. Epova (1971). They stated that in vicinity of Irkutsk, the eggs laid by
the females, which had flew from the Transbaikal territory and Mongolia in 1955 and 1963,
occurred to be in most part died. One may conclude that the population that already had lost its
health made such migrations.
Yu.P. Kondakov (1963) observed normal hibernation of Porthetria dispar in the Krasnoyarsk
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Region of egg-masses situated above snow cover in spite of winter temperatures reached 40ºC
below zero. He also recorded mass mortality of the embryos in 1954-1955, and explained this
case by effect of polyhedrosis, whereas a healthy population of Porthetria dispar was not
affected by any winter temperatures.
Recently, the issue of migrations of Porthetria dispar in Siberia was studied by A.V.Il’inykh
(2002), who drew the same conclusions as did the above-cited scholars. He supposed that
appearance of Porthetria dispar in 1991 in the Novosibirsk Region (Russia) was a result of
emigration from Kazakhstan and the Omsk Region (Russia). In the Novosibirsk Region,
outbreaks of Porthetria dispar were not observed for all the fifty-two years of operation of the
local Plant Protection Station.
Mortality of embryos in the migrated population grew over 3-4 years. On the periphery of the
infestation, the increase of mortality was recorded mainly over 1-2 years spasmodically. In the
central part of the infestation, mortality increased over the longer period. In the same time, it
decreased fertility of females. In 1995, the fertility decreased sharply, so that in spring larval
hatching was only 22%. The rate of the mortality was the same, when egg-masses stayed in
outdoor and in the laboratory. Egg parasites were absent. Vitality of the embryos dropped after
finishing of diapause. In January, hatching was rather high, whereas in February and March the
embryos were died. Mortality due to entomophagous organisms reached 40-60%. They were the
families Tachinidae, Sarcophagidae, and Dermestidae.
The borders of the infestation established by the migrated population moved annually on
50-70 km in a side of dominant winds until it declined. The aim of the migration of this
population consisted in evading from virus infection.
Forest area occupied only 3.7-6% of total territory of the studies. That is why migrations in
the adult stage rather than in the stage of neonate larvae are vitally important for finding such
scattered host-trees.
The important role of SS 5.1.(13.) "To leave infestation spots as early as possible, when
virulence of pathogens and activity of other natural enemies begin to grow" as a factor of
abundance of a herbivore species is illustrated by the study of A.V. Il’inykh et al. (2002), who
compared two species in this respect. This well-developed trait in Porthetria dispar allows it to
move its infestation spots on 70 km annually. In a result, its population nearly is not affected by
the acute form of polyhedrosis, and the outbreaks are durable. On the other hand, the mobility of
its close relative species – Porthetria monacha is low. The acute form of infection affects
immobile infestation spots of the latter species at the beginning of the eruptive phase. That is
why in the south of Siberia, Porthetria dispar is a serious pest, whereas Porthetria monacha is
nearly unknown in this status.
Thus, comparing with Porthetria monacha, the Bashkirian and Siberian taxa of Porthetria
dispar demonstrates presence in the latter species well-developed trait of the category SS
5.1.(13.) "To leave infestation spots as early as possible, when virulence of pathogens and
activity of other natural enemies begin to grow" with expression "High." The same is true for SS
5.1.1.1.(7.) "To minimize negative impact on host-plants by leaving of infestation spots as early
as possible, when density reaches high level."
The traits, which concern SS 5.1.1. (16.) To develop behavior traits to overcome
limitations of short season, and SS 5.1.1.(14.) To tolerate low temperatures at hibernation
The literature reports show high demand of Porthetria dispar to warm in the larval, pupal,
and adult stages, as well as in the egg stage before beginning of diapause. In fact, V.D.
Kozhanchikov (1950, p. 89) reported that for the completion of the larval stage the insects
needed to gain the sum of temperatures above the threshold of development equaled 615.4°C
(males) and 781.7°C (females), while the pupae needed in the sum of 159°C (males) and the sum
of 148°C (females).
These values are higher comparing with ones in two other species of the Orgyidae family
considered in the cited book. Further, for the completion of the larval stage, Porthetria dispar
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needed 38 days at ambient temperature 30°C, and 121 days at the temperature 18°C (Schedl,
1936, p. 59). At the impact on the pupae of temperatures 6°C-8°C during 24 hours, the sterility
of both sexes was observed (Emeljanov, 1924, cited in V.D. Kozhanchikov, 1950, p. 92).
V.D. Kozhanchikov (1950, p. 372) stated that to overwinter successfully, the embryos need
to stay in the state of diapause during 20-25 days. The presence in this period of ambient
temperatures above the threshold of development for the species (8°C) is vitally important for its
successful overwintering. In the areas, where cold weather is common yet in August, this factor
lays insuperable obstacle for inhabiting of Porthetria dispar.
In the conditions of distinctly continental climate of Asia with short season, it has evolved
specific traits to counteract limitations of the short season that resulted in appearing of definite
taxa of Porthetria dispar.
The destructive effect of deficiency of warm at season on Porthetria dispar was recorded
many times. P.M. Raspopov (1974, p. 237) has described these observations as follows: "In
forests of the Chelyabinsk, Sverdlovsk, and Kurgan Regions, it has been noted mass mortality of
overwintering eggs of the gypsy moth (Ocneria dispar L.), which is caused by deficiency of
warm in summer and fall periods (1947, 1950, 1956, 1960, 1968 and 1969)… At the warm
deficiency, the embryos inside an egg cover are not successful in development up to the stage
necessary for entering into diapause. They die independently on severity of winter. The highest
mortality caused by the warm deficiency has been observed in the Forest biome and in northwest
part of Forest-Steppe biome, on slopes of north exposition, on north sides of tree stems, as well
as in stands with a closed canopy. In the same years, egg mortality due to the warm deficiency
has took place in the nun moth (Ocneria monacha L.), although at a lesser extent."
The Siberian taxa of Porthetria dispar have acquired the traits, which are necessary for
survivorship in the conditions of distinct continental climate with short period of air temperatures
above threshold of species’ demands, rather that this species is extremely vulnerable to low
temperatures in the pupal stage and first 20 days after oviposition until the embryos enter into
diapause.
These traits are the following: a capacity of the females to long-distant flight, choice for
oviposition of treeless hilltops, where the larvae hatch as early as possible, and tolerance of the
embryos to the hardest in an area winter frost although the eggs have no snow cover.
On the vast territory of the Forest-Steppe biome in Asia – from north Kazakhstan to the
Transbaikal Area, females of Porthetria dispar annually leave the stands, where they have
completed their development, and fly to stony treeless tops of hills. Here, they lay their eggmasses sheltering them in crevices of rocks. The distance of such flights reaches dozens of miles.
In spring, the neonate larvae are lifted by air-streams that arise on stony tops of the hills under
effect of sunrays. Then, large masses of the young larvae ("web carpers") are lifted on the height
up to several hundreds of meters and carried by the wind on the distance of many miles. Masses
of the larvae suddenly appear in stands on the distance over 20 miles to a nearest stony hill.
Often Porthetria dispar returns into the stands with High density of this species in preceding
season, so that such migrations do not obligatory shift Porthetria dispar density in a given stand.
G.I. Sokolov (pers. comm.), who has observed such migrations in North Kazakhstan,
explains them as a means to intensify the Porthetria dispar development that is necessary for its
survivorship at short season in the areas with distinctly continental climate. The case is that
hibernation in butt portions of stems as that in the Europe would be disastrous for Porthetria
dispar in Siberia. Here, under a forest canopy, ambient temperatures of the threshold of
development in spring set in too lately to finish life cycle before an onset on early frost.
Also, Yu.N. Baranchikov (1987, pp. 109-110) paid attention on the fact that hilltops and
other well-exposed objects provide egg-masses with better heating in late summer, so that the
embryos have success to ripe in time, i.e. before onset of frost.
The reports as to similar migrations are numerous. Yu.T. Kondakov (1963, pp. 44-45)
observed them in Khakasia (the Krasnoyarsk Region), where egg-masses covered in several
layers thousands stones on a hilltop. In the Western Sayan Mountains, he observed the eggmasses mainly on rocks of abrupt riverbanks. Here, the areas covered by several layers of the
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eggs reached ten square meters. In this paper, there is a list of reports on the migrations in divers
regions in south of Siberia.
E.E. Alekseeva (1969) observed such cases in Buryatia (the Transbaikal Area). I.A. Kostin
(1968) in the north Kazakhstan noted the abundant egg-masses on any tall object – buildings,
technical constructions, etc.
Thus, the migration for oviposition in the conditions of best insolation in early and late
periods of season (habitats and objects) is a trait, which allows Porthetria dispar to evade
shortcomings of climate. This behavior should be considered as concerned SS 5.1.1.(16.) "To
develop behavior traits to overcome limitations of short season." Its expression in the Siberian
taxa of Porthetria dispar is "High."
The long-distant migrations of the females and oviposition on a tall object were recorded in
east areas of East Europe -far north from the south of Siberia – the Perm Region (Russia). Here,
Porthetria dispar is usually unnoticeable. Nevertheless, in 1911 and 1979, its outbreaks were
recorded in the southern part of the Region, where it fed on the lime, Tilia cordata. In 1979, in
the town Osa, the females aggregated en masse on walls of a local townshall and began to lay
their eggs. These moths attracted sparrows, which consumed nearly all of them. In 1980 and
succeeding years, Porthetria dispar became unnoticeable again. These details were told to the
author by local entomologist N.A. Men’shikov.
The High density in 1979 arose probably due to migration the females from south-wart areas,
in particular from the Republic Tataria (the region in the lower part of the River Kama Basin),
where climate was quite favorable for Porthetria dispar, and where it fed by the lime
(B.M. Kondorsky, pers. comm.). The large areas are covered by the lime in Bashkiria. This is
another source of the migration.
Why did the females lay their eggs on walls of the house? In the Tataria, at High density, the
females are able to fly on a large distance, when searching for oviposition stems of the birch
(B.M.Kondorsky, pers. comm.). In the considering case, the females probably were attracted by
white walls of the highest house in the town confusing it with a birch stem.
Overwintering on hilltops, i.e. without snow cover at severe Siberian frost, needs in extreme
tolerance to this stress. Indeed, the Siberian taxa are champions in evolving of this trait.
In fact, Yu.P. Kondakov (1963, p. 40) reported that in the southern part of the Kranoyarsk
Region (in the Minusinsk pine forest belt), Porthetria dispar overwintered successfully in cracks
of pine bark mainly above snow cover in spite of ambient temperature 40°C below zero was
recorded here over many days. Furthermore, winter mortality of the eggs was negligible in the
north part of the Porthetria dispar range in this Region, where air temperature dropped up to
57°C below zero (Kondakov, 1963, p. 41).
In this area, the egg-masses were laid among stones on treeless hilltops and on rocks of
abrupt riverbanks (Kondakov, 1963, p. 53). In all the places, the egg-masses overwintered
successfully being without a snow cover. In Bashkiria, it was recorded winter air temperature
50°C below zero, but negative effect of it on survivorship of Porthetria dispar was not known.
In south of the Russian Far East (Amur River Basin), it was noted the traits of Porthetria
dispar, which suggested inhabiting here a special ecotype of the species. The scholars
(Lyubarsky and Nakonechny, 1970, p. 222) have reported the following: "The local form of the
gypsy moth has a very interesting ecological feature. Here, the females lay their egg-masses, as a
rule, on leaves of the Mongolian oak, which at an onset of fall cold become dry and mostly stay
on the trees up to spring. Rarely, egg-masses can be found out in crowns of other tree species
and on limbs."
These egg-masses are very tolerant to winter frost, which reaches 40-50°C below zero. The
scholars give such an explanation of advantage of the trait (Ibid., p. 223): "…forests of the Amur
Region, particularly oak stands with low stocking density, are endangered by often ground forest
fires. Oviposition on leaves and limbs, rather than on low parts of stems, promotes to better
survivorship of the population. In addition, this trait provides the population by the best
possibilities for dispersion in the stage of neonate larvae."
It should stress that the lack of negative effect of winter temperatures takes place on
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condition that a Porthetria dispar population is healthy. If it has been affected by the slow form
of infection, the effect of severe frost becomes devastative.
In Europe, the facts of oviposition along stems of the distance many meters from the ground
show that the Main European ecotypes also are frost-resistant at hibernation. Thus, in the
European taxa of Porthetria dispar, expression of SS 5.1.1.(14.) "To tolerate low temperatures at
hibernation" is "High." In the Siberian taxa, expression of 5.1.1.(14.) is “Very High.”
The limitations for vital activity of Porthetria dispar connected with short season bound the
W.C. Cook’s zones of normal (a) and occasional abundance (b) in Asia by the areas, where the
above traits allow it to finish development before onset of the unfavorable temperatures. These
zones spread from south and southeast foothills of the Urals Mountains through North
Kazakhstan to foothills of the Altay Mountains (the West Siberia). This is the Forest-Steppe
biome with island forest plots within vast grassland ecosystems. From the Altay to the east, i.e.
in the Central and the East Siberia, the zones are limited by a belt of roughly one hundred miles
wide along the southern border of Russia (Epova and Pleshanov, 1988).
In the Russian Far East, the outbreaks are common in flood plains of the Amur River and its
tributaries. In valleys of the latter, the outbreaks are common no far than fifty miles to the north
from the Amur (Turova, 1988). In the point of the city Khabarovsk, the region of frequent
outbreaks turns sharply to the south, and spreads on west foothills of the Sikhote-Alin Mountain
Ridge (on the border with the Steppe biome) up to the Pacific Ocean.
In regions to the north and east from these areas, in the biome of Mixed ConiferousDeciduous forests, infestation spots of Porthetria dispar have secondary (migratory) character
(G.I. Yurchenko, pers. comm.). They are short in duration, and defoliation in them does not
exceed 30% of foliage. This is the W.C. Cook’s zone of possible abundance (с).
Further to the north, in the biome of Coniferous forests of the taiga subtype, infestation spots
of Porthetria dispar have not been recorded. This is the W.C. Cook’s zone of possible
occurrence (d).
The above review gives a possibility to draw the following conclusion. In the conditions of
distinctly continental climate with short period of temperature regime admissible for completion
of development from larval hatching to entering of embryos in diapause, Porthetria dispar has
been evolved a complex of traits, which allow it to complete the development in time. They
concern SS 5.1.1.(16.). "To overcome limitations of the short season." Expression of this SS is
"High.”
The traits, which concern SS 5.1.1.(15.) To tolerate weather stresses in the stages from
the larvae to adult, 5.1.1.(15.3.) Late frost
5.1.(11.) To avoid impact of pathogens by means of shortage of a life cycle
Turning to the above report as to the lack of Porthetria dispar in the Perm Region that is
characteristic for the most years, it might be explained by inadequate climate of the territory. In
fact, "In the Perm Province, early morning frost occurs every month; in some seasons, even in
July, hoar-frost appears in low terrain, while in August, hoar-frost occurs often" (Vargin, 1913,
p. 9).
The supposition as to migration is agreeable with the fact of an onset heavy droughts in 1972
and 1975 and severe winter of 1971-1972. The effect of these weather situations spreads on vast
areas of East Europe and it was an obvious releaser of the Porthetria dispar outbreaks. As to
1979, Porthetria dispar had a good chance for survivorship in the Perm Region, because the
summer of this season was very hot, and morning frosts were not recorded. The lack of
Porthetria dispar in 1980 and in succeeding years might be related not only with killing of the
females by sparrows, but also be a result of returning of the usual weather situation with
common morning frost in summer.
There are further examples of detrimental effect of morning frost in summer on Portheria
dispar. In the forest with Porthetria dispar host-trees (the birch) on the plateau Ufa in Bashkiria,
where the frost occurs every season, Porthetria dispar is unnoticeable, whereas around of this
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territory, in localities situated lower, outbreaks of this species are common (Khanislamov et al.,
1958, p. 17).
The similar case was observed by N.G. Kolomiets (pers. comm.) in southeast part of the
West Siberia in the Barabinsk Lowland (the Novosibirsk Region, Russia). In this lowland, there
is a gradient of diverse biomes from coniferous forests of the boreal type in the north to the
steppe (grassland) in the south. On the border of the coniferous forest and steppe belts, there are
birch-aspen stands of the island type, very similar to those growing in the western part of the
West Siberia (the Chelyabinsk Region), where Porthetria dispar exists in its ecological
optimum. In the Novosibirsk Region, however, Porthetria dispar has not been found out that
might be explained by colder climate with frequent onset of low temperatures over a season
characteristic for this area. It is of interest that defoliators of the summer-fall guild including
several dozens of species are equally abundant in both mentioned parts of the Western Siberia
(Kolomiets and Artamonov, 1985).
The recent reports (Il’inykh, 2002; Il’inykh et al., 2002) show that infestation spots of the
migratory origin are possible in this area.
To the south from the border of the Novosibirsk Region on the foothills of the Altay
Mountains (the Kemerovo Region, Russia), birch stands appear again. Here, local climate is
favorable for Porthetria dispar (morning frosts during summer are absent), and its outbreaks
arise often.
Obviously, expression of these traits, which concern SS 5.1.1.(15.) "To tolerate weather
stresses in the stages from the larvae to adult", 5.1.1.(15.3.) "Late frost" is "Weak." This is clear
if to compare the W.C. Cook’s zones of normal (a) and occasional (b) abundance in Porthetria
dispar and Dendrolimus sibiricus. Outbreaks of the latter species are known much further to the
north than those in Porthetria dispar.
The above cases demonstrate the following effects of climate on population behavior of
Porthetria dispar:
i) In areas, where morning frost is common over summer, resident populations of Porthetria
dispar either absent or unable to reach noticeable density.
ii) Infestation spots of Porthetria dispar in such areas arise in a result of mass immigration of
the females from the territories, where climatic conditions are favorable for reaching of
High density.
iii) The infestation spots are possible in seasons with lack of morning frost.
iv) A return of typical weather situation (an onset of morning frosts over summer) results into
decline of the infestation spots.
An expression of SS 5.1.1.(15.3.) in Dendrolimus sibiricus as to morning frosts is "High."
However, it is "Weak" as to the stressor of wet media at hibernation, i.e. SS 5.1.1.(15.) "To
tolerate weather stresses in the stages from larvae to adults", 5.1.1.(15.2.) "High moisture in
media of hibernation."
The climatic conditions, which result in failure of operation of SSes 5.1.1.(15.1) “Cool and
rainy weather in the larval and adult stages” and 5.1.1.(16) “To develop behavior traits to
overcome limitations of short season.” are insurmountable to the gypsy moth. Depending on
intensity of these CESPPs 2.3. “Routine weather suppression”, it takes place the W.C. Cook’s
zones (c) or (d).
Prolonged cool rains lead to heavy mortality of the larvae in the stages older than neonate
one. It is characteristic for the W.C. Cook’s zone of possible abundance (с). In the Moscow
Region belonged to the zone, the increases of density of the resident population were recorded in
beginning of 1950-ies and in 1980-ies after uncommon drought in spring and early summer.
A.I. Vorontsov (1987) suggested that the outbreak of 1950-ies was in fact due to a
combination of mass immigration of the moths from remote southeast areas, and an increase of
density of the resident population, whereas the outbreak of 1980-ies was the first known one of
the resident population.
Nevertheless, in the Moscow Region, the resident population is present steady with very Low
density as it has been demonstrated by F.N. Semevsky (1973). Hence, the local climatic
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conditions do not prevent the persistence of the population, but preclude its outbreaks. The most
probable climatic factor within these conditions is high frequency of cool rains often long
duration in May-June. These cold snaps are called by common people as "bird cherry cools",
because they often coincide with flowering of the bird cherry. As it has been shown earlier, in
this report, cool rains favor heavy affection of Porthetria dispar populations with pathogens.
Why does contrary to Porthetria dispar, the early-spring guild of oak herbivores produce
outbreaks in these conditions? That is why the guild uses SS 5.1.(11.) "To evade from impact of
pathogens by means of shortage of a life cycle" with expression "High." In Porthetria dispar,
expression of this SS is "Zero." That is why the areas, where the cool and rainy weather situation
is common, concern the W.C. Cook’s zones (с). Here, as a rule High density of Porthetria dispar
is a result of immigration outside of the zone.
Why do the rains do not cause extinction of Porthetria dispar in the zone of possible
abundance? That is why that existing on very Low or Insignificant densities a herbivore
population becomes free from the inapparent form of infection. Such a population stays in the
state of absolute healthy, and possibilities for a spread of an infection in it are minimal.
Steady high air humidity also promotes activity of pathogens, and, therefore, suppresses
Porthetria dispar in the areas with such a climate nearly to complete extinction. This cause is
suggested for continual very Low density of Porthetria dispar on the British Isles by
E.H. Forbush and Ch.H. Fernald (1896, p. 273), namely: "It may be thought that the worm, damp
climate of England would favor fungoid plants which are destructive to insect life." In fact, it has
been known that "fungoid plants" favor a quick spread the acute form of polyhedral infection
among the larvae.
The same is an opinion of S.A. Graham (1939, p. 178): "Cool, moist conditions followed by
warm weather during early June are favourable to the development of wilt disease which is
important natural check of this moth."
In foothills of the Carpathians Mountains (the L’viv and Ivano-Frankivs’k Regions, Ukraine),
it grows extensive oak forests. Here, outbreaks of defoliators of the early-spring guild are
common, but Porthetria dispar is unnoticeable. This fact might be explained by abundant
precipitation in spring and summer that is intolerable for vitality of Porthetria dispar,
particularly in the larval stage.
V.A. Lozinsky (1957a) reported that in the period of hatching of the larvae, frost suddenly
became back, and air temperature fell to 3°C below zero. After that, cool rain continued during
several days. After seven days of freezing temperature and cool rain, when worm returned, the
young larvae rose into tree crowns and began to feed actively. Therefore, neither late frost, nor
cool rain were detrimental for the neonate larvae. These observations were done in the
W.C. Cook’s zone of occasional abundance (b).
The available the data for the European ecotypes of Porthetria dispar allow to characterize of
an expression of SS 5.1.1.(15.) "To tolerate weather stresses in the stages from larvae to adults"
as "High" only in the stage of neonate larvae.
The W.C. Cook’s zone of possible occurrence (d) is characterized by a lack of the resident
population. This is an area to the north from the southern part of the St.-Petersburg (Leningrad)
Region, Russia up to the north border of the range of the oak and the birch. Porthetria dispar
occurs here very rarely due to occasional immigration from the south.
The case of such immigration was recorded in 1959, nine females of Porthetria dispar were
found out in Finland (Vorontsov, 1977). The capacity of these females to fly shows that they
arrived from very distant areas – at least from Bashkiria.
Another example was provided by A. Pictet (1919, cited in K. Schedl, 1936, p. 37). In
Switzerland in Wallis on the area elevated nearly 4000 feet (1200 meters) above sea level in
1907, it was recorded an outbreak of Porthetria dispar. It was supposed that the larvae were
transferred there by the wind. The outbreak declined soon, because low temperatures impeded
the insect’s development to such an extent that the moths had no time to lay their eggs before
onset of frost.
The similar effect of climate conditions was observed in the author’s experiment. In so doing,
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the egg-masses were collected in the vicinity of Kyiv on the locality no more than 200 meters
above sea level and they were carried to the Carpathians Mountains on the locality elevated on
750-850 meters above sea level (the Ivano-Frankivs’k Region, Ukraine). This is a region of wet
and rather fresh climate favorable for growth of forest with prevalence of the spruce, the fir, and
the beech. Here, as an admixture, it grows the birch, the aspen, and the mountain ash. They are
favored host-trees of Porthetria dispar. However, according to observations by the author over
the period of 30 years, any signs of Porthetria dispar in this locality have not been recorded.
In this experiment, egg-masses collected of stems of the birch and aspen were exposed at a
base of birch trees, whereas of the neonate larvae were set into sleeve cages on branches of the
same trees. At the exposition, the larvae were traced on the trees up to beginning of the fourth
instar – only few insects from thousands of the exposed eggs. As to the caged insects, a part of
them survived to the adult stage. However, the moths hatched only in the last third of September,
i.e. two months later than they did in the locality, where the eggs had been collected. A vitality
of the moths was low, and they did not lay eggs. The usage of traps with disparlure did not show
any presence of Porthetria dispar moths as it was in other seasons.
The above data show that an expression of SS 5.1.1.(16.) “To develop behavior traits to
overcome limitations of short season” in the all the European ecotypes of Porthetria dispar is
“Weak.”
The need to migrate in the adult stage on long distances with big numbers of eggs requires
heavy mass of female bodis. This resuls in the prolonged term of the larval stage. In turn, this
increases the tirm of exposition of the larvae to cool rains that endangered affection by
pathogens. The larvae of Porthetria dispar have no any protection against this stressor.
Therefore, an expression of SS 5.1.(11.) “To avoid impact of pathogens by means of shortage of
a life cycle”, is evaluated as “Zero” in all the taxa of Porthetria dispar.
The probability of cool and prolonged rains is important factors, which causes the difference
in density of Porthetria dispar in time and place predetermining the W.C. Cook’s zones of this
species.
The traits, which concern SS 5.1.(17.) To forestall competitors or evade from
competition
In the conditions of a long season with rare morning frosts and cool prolonged rains, as it
takes place on vast areas in Europe and in the southwest part of West Siberia, does not have
serious competitors. Hence, expression of SS 5.1.(17.) "To forestall competitors or evade from
competition" in all the European ecotypes of Porthetria dispar is "High."
Contrary, on the rest areas in Siberia, Porthetria dispar concedes to Dendrolimus sibiricus,
which much more adapted to distinctly continental climate. In the Siberian ecotype of Porthetria
dispar, an expression of SS 5.1.(17.) is "Moderate."
The traits, which concern SS 5.1.1.1.(8.) To expand the range of host-plants, when
density reaches high level
When stock of foodstuff on host-trees is exhausted in the course of an outbreak, older
caterpillars of Porthetria dispar are able to consume plant species, which unknown as hostplants for a given population, when it does not reach the level of High density. Such cases were
observed many times. For example, after complete defoliation of deciduous trees, the larvae
stripped thirty old trees of the spruce, which grew adjacent of this plot (Zhikharev, 1928, p. 299).
The author observed at an outbreak of Porthetria dispar in the Crimea Peninsula heavy
defoliation by the larvae of oak trees and significant defoliation of numerous species of
coniferous species – Cedrus spp., Juniperus spp., and Cupressus sp.growing near by.
In Europe, where High density of Porthetria dispar is probably evolutionary new
phenomenon caused by human interference, feeding by evergreen coniferous species takes place
nearly exclusively, as a result of exhaust of favorite foodstuff – foliage of deciduous trees.
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Contrary, in Asia, this species reached High density long since. In addition, in the conditions of
island forests of Forest-Steppe biome in Asia, there exist difficulties to find deciduous trees at
migrations of the larvae or moths. Therefore, the Asian ecotypes developed the traits to use as
favorite host-trees the larch and even evergreen coniferous tree species.
An activity of Porthetria dispar as a pest of evergreen coniferous tree species in Siberia is
significant. In 1950-ies, the area of coniferous stands killed by Porthetria dispar in the
Krasnoyarsk Region reached several thousands hectares. They are indeed evergreen coniferous
stands, because the larch does not die even at complete defoliation two-three seasons in
succession (N.G. Kolomiets, pers. comm.).
O.E. Dmitrievskaya (1956) reported that in the Altay Mountains in 1954-1955, Porthetria
dispar fed equally well by the birch, the Scots pine, the Siberian stone pine, the fir, and the larch.
In 1955, birch and larch stands were defoliated on the level 70-80%, and fir stands, which had
been defoliated in the previous season, began to die. Hence, the defoliation of the fir was heavy.
Further, a participation of the fir in these stands reached 90% (Khaitovich, 1959). These facts
implied that the population of Porthetria dispar was adapted to feed by the fir even in the stage
of neonate larvae.
A polyphagy does not preclude developing of populations, which are specialized to prefer a
single host-tree species. Thus, V.M. Yanovsky (1980) supposed the presence in Mongolia of
several separate populations of Porthetria dispar, which defoliate such a species that dominate in
a given area – the birch, the Siberian larch or the Scots pine.
An adaptation to the Scots pine and the Siberian stone pine, as preferred host-plants is a
problem for Porthetria dispar, because pine needles, which have grown in a preceding season,
are unfit for feeding by the neonate larvae (Kondakov, 1963, p. 44). Young needles of a current
season are fit for the feeding (Litvinchuk, 1988). However, the needles appear significantly later
of the hatching. The larvae hatch in the period of bud-bursting of the birch and the larch
(Kondakov, 1963, p. 63). That is why primary infestation spots of Porthetria dispar in the
Krasnoyarsk Region arise only in birch-larch stands, whereas in pure pine stands, the spots
appear by means of immigration after the density becomes High in the primary infestation spots
(Ibid., 52). In mixed stands, the pines can be defoliated by migration of the older larvae from
near by trees of other species.
It is possible existence of the ecotypes of Porthetria dispar, which prefer evergreen
coniferous species for foodstuff of young larvae. In the sympatric species Dendrolimus sibiricus
such ecotypes have been suggested. V.O. Boldaruev (1969, pp. 23-25) reported about the four
races or subspecies having diverse foodstuff preferences and constitutional traits, namely:
Dendrolimus sibiricus cembrae Roshk. (on Pinus sibirica), D. sibiricus laricis Roshk. (on the
larch), D. sibiricus manshuricus Roshk. (in larch, larch-pine, fir and pine-fir stands), D. sibiricus
abietis Boldarujev, ssp. n. (on the fir).
In the Main European ecotypes of Porthetria dispar, it was recorded only few cases, which
might be considered as adaptations to prefer evergreen coniferous species for feeding. In 1984,
in Belarus (now the Former Soviet Union), an outbreak of Porthetria dispar was observed in a
pine plantation 12 years on the area 17 hectares (M.V. Torchik, pers. comm.). Here, in spring, it
was several egg-masses of Porthetria dispar per pine tree, and numberless egg-masses on
innumerous large oak trees growing near by. In a result, the larvae stripped these trees – both the
pine and the oak. Pine trees in the infestation spot were in bad physiological state, being planted
on an old-field area.
A surprising case was observed by O.A. Grikun (pers. comm.) in the Crimea Peninsula
(Ukraine). In 1979 in a little park situated in the Steppe biome with trees of various species (the
oak, the birch, the black locust, and the red cedar, Thuja occidentalis Endl., the larvae of
Porthetria dispar fed only by the latter species. Nearly a half of trees of the red cedar occurred to
be defoliated.
Thus, expression of SS 5.1.1.1.(8.) "To expand the range of host-plants, when density of
defoliators reaches the high level" is "High" in the Siberian taxa of Porthetria dispar, and
“Moderate” or “Weak” in the Main European ecotypes.
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Further traits of Porthetria dispar taxa concerning differences in their SPs
The distinct differences in the behavior traits among the considered above taxa (European,
Bashkirian, and Asian) are accompanied by traits of another character. Indeed, body’s traits of
the moths from divers localities of Eurasia were compared by V.V. Vnukovsky (1926), and this
scholar revealed that the samples from them had significant differences as to body weight, length
of wings, wing-span, colors of wings.
Comparing with West European samples, the females of the Siberian "race", in particular
from the West Sayan Mountains and the Altay Mountains, had "very large sizes, yellow-smoke
colors of wings, and strong reduction of dark painting" (Ibid., p. 81). The males from this area
also had clearer color of wings. This scholar used the collections and reports of A. Meingard
(1904,1908, 1913) and V.D. Kozhanchikov (1923) as well as own collections. He stressed that
the above traits are durable for a locality. This fact gave him a possibility to describe the Siberian
"race" as a new subspecies and propose the name for it: Lymantria dispar L. asiatica, subsp. n.
Further, A. Meingard (1913) supposed that the Siberian "race" is a transitive to the "race" f.
japonica Motsch.
Now, accordingly to Yu.P. Kondakov (1963, p. 45), this subspecies is known as Ocneria
dispar asiatica Wnuk. Later in this text, this name (Porthetria dispar asiatica) will be used
instead of "the Siberian taxa (taxon)."
V.V. Vnukovsky also cited L.K. Krulikovsky (1909), who showed that samples of Porthetria
dispar from the extreme east of East Europe (the Vyatka Province, now the Kirov Region in the
eastern part of the River Volga Basin) differed from the Main European ecotypes. Again, the
females were larger.
In addition, the samples from the Vyatka Province, as Porthetria dispar asiatica, differ from
the European ecotypes by reduction of dark coloring of wings. This population will be named the
Trans-Volga ecotype of Porthetria dispar. To southward of this area, it is the range of the
Bashkirian ecotype of Porthetria dispar. To westward of the ranges of above ecotypes, it
inhabits the Main European ecotypes of Porthetria dispar.
What kinds of relations exist among behavior and body traits in taxa of Porthetria dispar, on
the one hand, and characteristics of their ranges (climate and peculiarities of vegetation)?
Obviously, climate and character of ecosystems, which depends on climate and human activity,
determine the traits of the taxa.
Black color of moths in diverse species of defoliators is a sigh of increased resistance to
pathogens, in particular to polyhedrosis. In the Main European ecotypes, at entering of
Porthetria dispar populations in the outbreak phase always is accompanied by appearing of
moths with well-expressed black color.
In fact, in Low-Dnieper Area, at High density of the moth, the number of the caterpillars
with black color was only 0.4% - 1.0%, whereas in the innocuous phase and especially at
beginning of density growth, the number of black insects reached 15% (Mamontova et al. 1983,
p. 116).
Contrary, black color was not noted in Porthetria dispar asiatica. V.V. Vnukovsky (1926, p.
81) characterized traits of this taxa by the words "…strong reduction of dark painting." The
explanation of differences in the traits of the above-mentioned taxa consists in effect of different
climatic conditions. In the conditions of dry season at the distinctly continental Siberian climate,
developed resistance to these pathogens needs not. In the Bashkirian and Trans-Volga ecotypes,
such a trend is also observed, although it is less expressed. Also, the pathogens are suppressed by
insolation in island forest plots situated in xeric habitats, as it is characteristic for Siberia and
southeast of Europe.
On the other hand, in wet temperate climate westward from the above area in vast tracts of
mesic deciduous forests with closed canopy, it was vitally important for survivorship of
Porthetria dispar to have the trait, which considered now as SS 5.1.(12.) "To enhance resistance
to pathogens."
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The same takes place in wet climate of Japan. This suggestion is based on the Figure 1.
“Examples of size and color variation in gypsy moth males (a) and females (b) from Japan (top
row) and from the United States (bottom row)” (Montgomery and Wallner, 1988, p. 355). The
insects from Japan painted black much more comparing with those fromUSA.
An expression of this SS is “High” the Main European ecotypes, “Moderate” in the
Bashkirian and Trans-Volga ecotypes, and “Weak” in Porthetria dispar asiatica.
It is possible, some European ecotypes of Porthetria dispar have reached a prominent
progress in expression of SS 5.1.(12.) at selective pressure in definite environmental conditions.
Thus, W.F. Fiske (1913, cited in R.W. Campbell et al., 1978, p. 42) noted the following case:
"Two outbreak areas in Southern Italy, where there were varied and abundant parasites but no
sign of wilt disease, were observed. Parasites killed 90 percent but the invasion spread back and
forth over the area, defoliating a part each year so that trees were defoliated every 2 or 3 years
for more than a decade." This is a case, when expression of SS 5.(12.) "To enhance resistance to
pathogens" is "Very High.”
Surprisingly, in this case despite of abundance of pathogen’s vectors, the population was not
affected by diseases. It might be high content of tannins in foliage, which is characteristic for
southern oak species, provides the resident population of Porthetria dispar with advanced
resistance to pathogens. Positive effect of content of tannins in foodstuff of caterpillars on their
resistance to pathogens has been recorded in literature.
Behavior and body’s traits of the taxa also might be explained if to take into account the
environmental conditions in evolutionary history of them.
In the conditions of extensive and undisturbed forest ecosystems with abundant natural
enemies characteristic for Europe before radical changes caused by human activity in the last
millennia, the life strategy of Porthetria dispar consisted in developing of the following traits:
i) Protection of the females from avian predators by means the short flight in night hours
soon after eclosion and fecundation.
ii) Protection of the all the stage against parasites and predators by means of dispersion of
neonate larvae on vast areas provided by oviposition on birch stems and any tall object.
iii) Developing of well-expressed protection of the larvae from pathogens, which active under
the closed canopy of rich deciduous forests.
Such traits result in existence of the population distributed evenly within forest tracts at the
level of density, where the insects are nearly unnoticeable for parasites and predators, where
there exist obstacles for arising of high-virulent strains of pathogens.
In the conditions of distinctly continental climate in Asia, where island forest ecosystems,
which occupied a minor part of the area, and ESPPs of them, stayed often on the level 3.3. “Late
control”, the life strategy of Porthetria dispar asiatica consisted in developing of the following
traits:
i) Exposition of egg-masses on well-insolated sites (hilltops and others) by means of
directional flight of the females on distance of miles that provides early hatching of the
larvae as well as adequate development of pupae and eggs resulting in completion of the
life cycle despite of short season.
ii) Capacity to fly on large distance in search for island forest plots free from High density of
this species; such plots are rare in the conditions of area-wide outbreaks.
iii) Weak expression of resistance to pathogens, the acute infection of which is suppressed by
the environmental conditions.
The need in flight on large distance results in "very large sizes” of the females, whereas low
activity of pathogens determines clear color of the moths (Vnukovsky, 1926, p. 81). Such traits
have led to very expressed nomad character of outbreaks of Porthetria dispar asiatica, which are
declined mainly under the ever-increasing effect of CESPPs 2.5.3.1.5. “Spontaneous or winter
mortality of embryos.” A self-protection against such a form of infection is probably beyond of
possibility of herbivores.
Often increases of density in the Bashkirian ecotype of Porthetria dispar and in Porthetria
dispar asiatica resulted in developing in them of well-expressed SS 5.1.(13.) "To leave
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infestation spots as early as possible, when virulence of pathogens and activity of other natural
enemies begin to grow."
In addition, due to such an emigration the negative effect on host-trees was minimized, so
that foodstuff resource occurred to be not exhausted. Therefore, it has been developed SS
5.1.1.1.(7.) "To minimize negative impact on host-plants by leaving of infestation spots as early
as possible, when density reach the high level."
The latter SS is very important for existence of the taxon, because in the Forest-Steppe biome
forest grows on the border its possibility. Heavy defoliation would result in extinction of this
forest.
Contrary, the Main European ecotypes have no evolutionary experience to reach often High
density. Therefore, in it an expression of SS 5.1.(13.) occurred to be “Weak.” Infestation spots of
this ecotype are retained on the same area over several years. Such situations have arisen in
recent centuries, so that andanced expression of SS 5.1.(13.) still has not been evolved.
The range of the Porthetria dispar population inhabiting island forest plots in the
Chelyabinsk Region is situated between the ranges of the Bashkirian ecotype and Porthetria
dispar asiatica. This fact gives the grounds to suggest a presence in the former of the traits close
to those in the latter. Nevertheless, neither P.M.Rafes, nor P.M.Raspopov and other scholars
dealing with the local population noted migrations in the adult stage, and peculiarities in the
body’s traits were not shown also. Further, the outbreak stage here is prolonged, and it is
accompanied by heavy defoliation up to several years in succession, although percentage of
tree’s mortality is low and concerns depressed trees. These traits are characteristic for the Main
European ecotypes of the species.
The long-distant migrations of a herbivore species are advisable, on condition that it is a
polyphagous organism. In a concordance with this supposition, Porthetria dispar asiatica, which
is particularly advanced the trait of migrations, has more expressed polyphagous properties than
the Main European ecotypes have. The advanced mobility of Porthetria dispar asiatica has
resulted in adaptation of some populations to feed by coniferous tree species, which prevail as
dominants in Siberian forests.
In short words, Porthetria dispar is a true gypsy, especially in Asia. It has specific life
strategy as to self-protection against natural enemies and shortcomings of climate. In this
context, it acquires a number of constitutional and behavior traits. They are the advancing
mobility directed on escape from the stressors by means of migrations on the wide range of
distance.
The life strategy of the early-spring guild is to escape from its natural enemies and weather
stresses in time occupying the same place. In the winter moth, Operophthera brumata L.,
micropopulations are adapted to inhabit separate trees providing the best coincidence of larval
hatching with terms of bud-bursting. The escape from pathogens is achieved by shortening of the
larval stage, which is especially vulnerable. The less duration of the vulnerable life stage, the less
probability of exposition to weather stresses inducing affection of the larvae by pathogens. The
weather stress is a wet and cool weather situation.
The larvae of Porthetria dispar developing during the prolonged time have no any protection
against this stressor. Therefore, an expression of SS 5.1.(11.) “To avoid impact of pathogens by
means of shortage of a life cycle”, is evaluated as “Zero” in all the taxa of Porthetria dispar.
The probability of prolonged and cool rains is important factors, which determine the
difference in density of Porthetria dispar in time and place within the W.C. Cook’s zones.
It is logical to put forward a question: why do the above taxa keep constancy of their ranges?
In fact, a crossing among them is not recorded although in a result of the migrations, insects of
all the ecotypes occur everywhere. The answer consists in a few suppositions. The Main
European ecotypes, when getting into Asia in the conditions of short season, are unable to finish
their development before onset of cold weather. In turn, Porthetria dispar asiatica in Europe
would be susceptible to polyhedrosis in climatic conditions, where onset of rainy weather at the
larval stage is common.
Consider prospects of management implications of the knowledge as to SP of Porthetria
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dispar. It seems this would be useful in the quarantine service. In fact, when penetration of
Porthetria dispar into an area situated outside of its range, it needs to evaluate possibilities of
naturalization of the invading insects. Taking into account climate of the endangered area,
knowledge of SSes of Porthetria dispar taxa, and study of invader’s traits allow solving this
problem.
In the areas, where morning frosts in the period of the larval (older than the first instar) and
pupal stages of Porthetria dispar are common, outbreaks of all the species’ taxa are impossible.
The same is true for areas, where prolonged cool rains are common in the larval period (older
than the first instar). Depending of expression of these climatic factors, this area can the
W.C.Cook’s zones (c) оr (d) for all the taxa. In areas with distinctly continental climate, the taxa
having the traits of the Main European ecotypes have no chance to survive (W.C. Cook’s zone
(d), but those having traits of Porthetria dispar asiatica with high probalility will produce
outbreaks. Depending to expression of these climatic factors, this area, can be the W.C. Cook’s
zones (a) or (b). The latter subspecies in the rather wet European climate will be suffered due to
polyhedrosis, so that its survivorship unprobable (the W.C. Cook’s zone d).
Concluding remarks about SP of Porthetria dispar in Eurasia
The consideration of traits of Porthetria dispar on diverse stages of its life cycle with the
view of SP has given a possibility to reveal a number of categories of SSes pertinent to this
species. Studies in different parts of the Porthetria dispar range have shown that expression of
some categories is unequal. This fact allows the author to pay attention on existence of several
subspecies taxa (ecotypes, subspecies) within the species. The behavior differences among the
taxa are accompanied by body’s (constitutional) traits. It occurred to be possible to offered an
operation the following categories of SSes and expression of them:
5.1.1.1.(6.) To exert the least negative impact on vitality of host-plants by means of reduction
of development, “Moderate” in all the taxa. The expression of this SS in Porthetria dispar is
obviously less than that in the early-spring guild of defoliators.
5.1.1.1.(7.) To minimize negative impact on host-plants by leaving infestation spots as early
as possible, when density reaches high level, “High” in the Bashkirian ecotype and in Porthetria
dispar asiatica; “Moderate” in other taxa.
5.1.1.1.(8.) To expand the range of host-plants, when density reaches high level, “High” in
Porthetria dispar asiatica; “Moderate” or “Weak” in the Main European ecotypes.
5.1.(10.) To develop self-protection against natural enemies by behavior traits, eggs –
“Moderate” in all the taxa; the first instar larvae in all the taxa - “High”; in other instars and
stages - “Moderate” (with an exception is the Main European flood plane ecotype, where the
protection in older larval instars and pupae is “High”); adults – “High” in the Main European
ecotypes, and “Moderate” in other taxa, where adults fly on large distance.
5.1.(11.) To avoid impact of pathogens by means of shortage of a life cycle, “Zero” in all the
taxa.
5.1.(12.) To enhance resistance to pathogens, “Weak” in Porthetria dispar asiatica,
“Moderate” in other taxa; in some populations of the Main European ecotypes - ”High.”
5.1.(13.) To leave infestation spots as early as possible, when virulence of pathogens and
activity on other natural enemies begin to grow, “High” in Porthetria dispar asiatica and the
Bashkirian ecotype; “Moderate” in other taxa.
5.1.1.(14.) To tolerate low temperatures at hibernation in the egg stage,“Very High” in
Porthetria dispar asiatica, and “High” in other the taxa.
5.1.1.(15.) To tolerate weather stresses in the stages from larvae to adults,
5.1.1.(15.1.) Cool weather with prolonged rains in the larval and adult stages, “High” in the
first instar and “Weak” in others instars in all the taxa,
5.1.1.(15.3) The late frost, “High” in the first instar and “Zero” in others all the taxa,
5.1.1.(15.5.) Low temperatures at the pupal stage, “Zero” in all the taxa,
5.1.1.(16.) To develop behavior traits to overcome limitations of short season, “Weak” in the
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Main European ecotypes, “Moderate” in the Bashkirian and Trans-Volga ecotypes, and “High”
in Porthetria dispar asiatica.
5.1.(17.) To forestall competitors or evade from competition, “High” in the European,
Bashkirian and Trans-Volga ecotypes, “Moderate” in Porthetria dispar asiatica, because the
latter needs to compite with Dendrolimus sibiricus.
Over the taxa, an expression of above SSes is distributed as follows:
SP (Porthetria dispar, the Main European secadol ecotype) = 5.1.1.1.(6.) – Moderate;
5.1.1.1.(7.) – Moderate; 5.1.1.1.(8.) – Moderate or Weak; 5.1.(10.), in eggs – Moderate, in the
first larval instar – High, in other larval instars and pupae – Moderate, in adults – High; 5.1.(11.)
– Zero; 5.1.(12.) – Moderate, in some populations - High; 5.1.(13.) – Moderate; 5.1.1.(14.) –
High; 5.1.1.(15.1.) and 5.1.1.(15.3.) the first larval instar – High, in the rest instars - Zero;
5.1.1.(15.5) - Zero; 5.1.1.(16.) – Weak; 5.1.(17.) – High.
SP of the flood plane European ecotype differs from the above formula. The older-instar
larvae and pupae of this ecotype are protected better from avian predators and parasites by the
trait of diurnal migrations in forest litter. This trait concerns SS 5.1.(10.) "To develop selfprotection against natural enemies by behavior traits." An expression of this SS is "High."
Therefore, density of the insect in flood plane is usually greater than that on secadol.
The formula of SS is as follows:
SP (Porthetria dispar, the Main European flood plane ecotype) = 5.1.1.1.(6.) – Moderate;
5.1.1.1.(7.) – Moderate; 5.1.1.1.(8.) – Moderare or Weak; 5.1.(10.), in eggs – Moderate, in the
first larval instar – High, in the second and the third larval instars – Moderate, in older larval
instars and pupae – High, in adults – High; 5.1.(11.) – Zero; 5.1.(12.) – Moderate; 5.1.(13.) –
Moderate; 5.1.1.(14.) – High; 5.1.1.(15.1.) and 5.1.1.(15.3.) in the first larval instar – High, in the
rest instars - Zero; 5.1.1.(15.5) - Zero; 5.1.1.(16.) – Weak; 5.1.(17.) – High.
SP(Porthetria dispar, the Bashkirian and Trans-Volga ecotypes) =5.1.1.1.(6.) – Moderate;
5.1.1.1.(7.) – High; 5.1.1.1.(8.)- Moderate or Weak; 5.1.(10.), in eggs – Moderate, in the first
larval instar – High, in other larval instars and pupae – Moderate, in adults – Moderate; 5.1.(11.)
– Zero; 5.1.(12.) – Moderate; 5.1.(13.) – High; 5.1.1.(14.) – High; 5.1.1.(15.1) and 5.1.1.(15.3) in
the first larval instar – High, in the rest instars – Zero; 5.1.1.(15.5) – Zero; 5.1.1.(16.) –
Moderate; 5.1.(17.) – High.
There are too little of data to distinguish the Bashkirian and Trans-Volga ecotypes. They differ
from the Main European secadol ecotype by “High” expression of SSes 5.1.1.1.(7.) and 5.1.(13.).
SP(Porthetria dispar asiatica) = 5.1.1.1.(6.) – Moderate; 5.1.1.1.(7.) – High; 5.1.1.1.(8.) – High;
5.1.(10.), in eggs – Moderate, in the first larval instar – High, in other larval instars and pupae –
Moderate, in adults – Moderate; 5.1.(11.) –Zero; 5.1.(12.) – Weak; 5.1.(13.) – High; 5.1.1.(14.) –
Very High; 5.1.1.(15.1.) and 5.1.1.(15.3.) in the first larval instar – High, in the rest instars –
Zero; 5.1.1.(15.5.) – Zero; 5.1.1.(16.) – High; 5.1.(17.) – Moderate.
5.1.1.1.1.1 - 5.4.5. Porthetria dispar L. in North America
5.1.1.1.1.1. - 5.4.5.1. The generally infested area
5.1.1.1.1.1. - 5.4.5.2. The advancing front of the generally infested area and the island infestations
The population behavior of Porthetria dispar in America demonstrates a number of
surprising phenomena, which need in explanation. The usage of the concept of SP would bring
further contribution in understanding of this problem. These phenomena took place in the
following periods:
i) The period of waiting over approximately a dozen of years after the delivery of the
species, when it was unnoticeable (1868/1869- 1888),
ii) The period of euphoria, when the species behaved as a troublesome pest (1889- 1906),
iii) The period of very successful suppression of the pest by the parasite-pathogen complex in
a result of introducing of parasites beginning with 1905 (1907-1924),
iv) The period of bimodality, when until now the population has behaved differently in the
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two circumstances:
In the advancing front of the generally infested area and in the island infestations,
In the generally infested area.
In the period “i” (waiting), the population underwent emancipation from all the forms of
infection due to absence of vectors of infection. The emancipation proceeded under selective
pressure on the part of CESPPs 2.3. "Routine weather suppression", which eliminated
individuals with infection, i.e. those having decreased vitality. It survived healthy individuals.
Presence of Porthetria dispar was inconspicuous.
In 1889, when the period “i” had finished, and the period “ii”(euphoria) began, “The fronts of
the houses were black with caterpillars…” (Forbush and Fernald, 1896). Black color of
caterpillars (phaeism) was a true sign of emancipation of a population from all the form of
infection, i.e. great vitality of it. Other traits of this population - uncommonly large caterpillars
and huge fecundity reaching 1400 eggs – again pointed out to the vitality. Because the
population became healthy, it obtained developed tolerance to CESPPs 2.3. All the resident
natural enemies of Porthetria dispar occurred to be ineffective. In the conditions of a lack of
suppressive pressure on the part of pathogens and parasites, the population thrived, but
eventually it lost the traits of resistance to parasites and pathogens. This loss was a result of
absence of natural selection on the part of these natural enemies. Activity of Porthetria dispar
took features of natural hazard.
In the period “iii”, after introducing of parasites from Eurasia (efficacy of the introduced
parasite-pathogen complex began with 1907), the population of Porthetria dispar underwent a
decline due to affection by mainly pathogens, vectoring by the parasites. Success of the
introduction was based on weather situation favorable for activity of the parasites and probable
decrease of resistance of the Porthetria dispar population to introduced parasites and pathogens
evolved at the end of the period “ii.”
In the period “iv” (forming the bimodality of the population), after suppression of parasites
by the severe winters, it took place the great outbreaks. The decline of it under the effect of the
parasite-pathogen complex implies that interrelation between SP of the American population and
its EE has become close to that in the European population probably of the flood plane ecotype.
In the generally infested area, the population has had such a SP until now. Contrary, in the
advancing front of the generally infested area and in the island infestations, the population has
had the SP close to that in the period “ii” – euphoria.
A number of data concerned the above suggestions were considered in the part of this Section
at description of EE of Porthetria dispar of in America. Some additional facts demonstrating an
expression of SP are offered below.
It has been reported about the effect of defoliation on host-trees that "…where gypsy moth is
found the first time in New Jersey, mortality has increased from 6% in year 1 of defoliation to
69% in year 4…" (Leonard, 1974, p. 198, the data of J.D. Kegg, 1971). The prolonged
defoliation in the same plot shows that expression of SS 5.1.1.1.(7.) “To minimize negative
impact on host-plants by leaving infestation spots as early as possible, when density reaches high
level" is "Weak."
In the generally infested area, the negative effect of Porthetria dispar outbreaks is usually
less. An increase of tree mortality is known, but it is not obligatory a result of the defoliation. It
might be due to an intervention of other stressors – abiotic or biotic. Here is an example of such
a situation provided by G.R. Stephens (1976, p. 30) for the state Connecticut: "Severe outbreaks
of the gypsy moth occurred in 1957 and 1961-1964 but prior to the defoliation in the 1970’s tree
mortality was low, averaging 1 to 2% over a decade with not more than one defoliation and
increasing to 3 to 4% with two or three defoliations (Stephen 1971). Losses were slightly greater
on dry compared to moist sites and higher in oak than maples and birches. By 1972, however,
great oak mortality following defoliation was evident and ranged from about 20 to nearly 80%
over a 5-year period in selected areas (Dunbar and Stephens 1975). Attacks by the twolined
chestnut borer, Agrillus bilineatus Weber, was soon related to the observed mortality."
It might be, this high mortality was caused by increased virulence of the oak wilt fungus,
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Ceratocystis fagacearum Bretz. At arising of highly virulent strains of a phytopathogen, even
moderate weakening of trees due to defoliation can be sufficient to overcome host-plant
resistance to a pathogen. Just Agrillus bilineatus was reported to be a vector of the oak wilt
fungus (Dunbar and Stephen, 1976).
The book, from which above citations were taken, provided an example of high tolerance of
trees to defoliation that showed causes of the tolerance. G.H. Heichel and N.G. Turner (1976,
p. 38) reported that "Although 2 or 3 successive yrs of complete defoliation greatly diminished
tree vigour and total leaf area per tree (Fig.5), it failed to elicit death of any of the trees."
What is characteristic for this case? The growth conditions of the trees were quite comfort.
They were young of 9 to 11 years growing in a stand after thinning from 36 to 12 trees per plot.
In a result, their root systems had large volume of the soil for feeding, and attacks of Agrillus
bilineatus were unlikely to be on these young trees.
The problem of effects of defoliation by Porthetria dispar on forest stands in America has
been considered in detail in the Chapter 5 of the compendium by Ch.C. Doanes and M.L.
McManus (eds.), 1981. "The Gypsy Moth: Research Toward Integrated Pest Management." The
conclusion of its authors is identical to that cited above.
Considering the American population with the view of SS 5.1.(10.) "To develop selfprotection against natural enemies by behavior traits", there are no the grounds to suppose the
differences from the Main European ecotype, which inhabits flood plain ecosystems. In the
American population as that in the Main European flood plain ecotype, older-instar larvae have
the trait diurnal migration in forest litter, where they find shelter from parasites and avian
predators, whereas the ground predators are absent.
Importantly, this trait retains in North America more than hundred of years in diverse
ecosystems. The diversity of the European and Asian ecotypes as to the diurnal behavior of the
larvae and sites of the pupation suggests that these traits are undergo changing easily under
selective pressure operating in a given ecosystem. The retention this trait in America is an
evidence of its benefit in overall situations. Thus, expression of SP in the American population
of Porthetria dispar as to all the subcategories of SS 5.1.(10.) is as that in Main European flood
plain ecotype.
The traits of the American population concerned SS 5.1.(13.) “To leave infestation spots as
early as possible, when virulence of pathogens and activity on other natural enemies begin to
grow" it seems, are developed on the same level as that in Main European ecotypes, i.e.
"Moderate."
In particular, it was recorded a spread of neonate larvae on the distance up to 13.5 miles
(Collins, 1915, cited R.W. Campbell et al., 1978, p. 30). Nevertheless, in North America, a new
factor that related to this SS obtains significant importance. Here, (Telerico, 1981, p. 32) "Spread
of the gypsy moth occurs in two ways: By windblown dispersal of the newly hatched larvae, and
by inadvertent transport of the insect – primarily egg masses – attached to vehicles, building
material, and almost any other movable object. Wind dispersal results in local spread or
movement; movement on manmade objects causes long-distant movement."
The above report (Leonard, 1974, p.198) shows that possibilities of Porthetria dispar to
migrate at High density are limited. The defoliation on the same plot is occurred four years in
succession. Further, the cases of mortality of starving caterpillars in the advancing front of the
generally infested area imply the limited expression of this trait. Although, numberless moving
objects offer wide possibilities for migration of Porthetria dispar on an unlimited distance in the
phases of the population dynamics, when virulence of pathogens is low. This capacity increases
the danger of survivorship of the pest in hitherto uninfested areas. Therefore, expression of SS
5.4.5.(18.) “To spread on unlimited distance by means of usage of moving objects" is "High."
Now, the range of Porthetria dispar could be considered as the W.C. Cook’s zone (b).
The danger on the part of Porthetria dispar is most probable for regions with the distinctly
continental climate, which situated to the southwest of the contemporary range. The spread in
this direction is shown on the map in R.L. Telerico, 1981, p. 33). Low winter temperatures
hardly to exert a negative effect on winter survivorship of Porthetria dispar, but severe frost is
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able to suppress activity of its parasites and avian predators. This area would be the W.C. Cook’s
zone (a). Southern regions with dry and hot weather in late spring and summer (having the
climate of the Mediterranean type) also favorable for expansion of the High density, i.e. again
this would be the zone (a).
Contrary, to the north of the range in the biome of Coniferous-Deciduous forests, it might be
the W.C. Cook’s zone of possible abundance (с) with rare and short-lasting infestation spots
arisen due to emigration from the south. The coastal areas of maritime climate with abundant
rains and dew in summer also are little of fit for a raising of the High density.
The above discourse gives a possibility to propose such a composition for SP of the
American population of Porthetria dispar:
SP of the North American population of Porthetria dispar, is alike to that in the Main
European flood plane ecotype, and differs by presence of SS 5.4.5.(18.) “To spread on unlimited
distance by means of usage of moving objects" with expression “High” as follows:
SP(the North American population of Porthetria dispar) = 5.1.1.1.(6.) – Moderate;
5.1.1.1.(7.) – Moderate; 5.1.1.1.(8.) – Moderate; 5.1.(10.), in eggs – Moderate, in the first larval
instar – High, in the second and the third larval instars – Moderate, in older larval instars and
pupae – High, in adults – High; 5.1.(11.) – Zero; 5.1.(12.) – Moderate; 5.1.(13.) – Moderate;
5.1.1.(14.) – High; 5.1.1.(15.1.) and 5.1.1.(15.3.) in the first larval instar – High, in the rest
instars - Zero; 5.1.1.(15.5.) - Zero; 5.1.1.(16.) – Weak; 5.1.(17.) – High; 5.4.5.(18.) – High.
It needs to explain the difference in population behavior of Porthetria dispar between the
generally infested area (5.4.5.1.) and the advancing front of the generally infested area and the
island infestations (5.4.5.2.). In short words, the difference is the following: in 5.4.5.1., it
behaves as in Europe, in 5.4.5.2., it behaves as in North America during 1881-1907. There are no
the grounds to suppose that SP of the species differs depending on the areas, but EEs in them are
very different. On the level ESPPs 3.3. “Late control” characteristic for the area 5.4.5.2, they are
as follows:
5.4.5.1., 3.3., (b) LS(Porthetria dispar) = SP↔EE(2.1.1.3.1.2.+ 2.5.2.1.+ 2.5.1.5.1.+2.5.3.1.4.+
+2.3.3.1.+ 2.5.4.1.), Directly density-dependent, spasmodic, Temporal, Potent, Poor.
5.4.5.2., 3.3. (b), LS(Porthetria dispar)= SP↔EE (2.1.1.3.1.2.+ 2.5.1.5.1.+ 2.5.6.1.+ 2.5.2.1.),
Directly density-dependent, lately spasmodic, Temporal, Potent, Bad.
In 5.4.5.1., the composition of CESPPs is more rich, than that in 5.4.5.2., being a result of
absence of the developed parasite-pathogen complex in the area 5.4.5.2.
Although CESPPs 2.5.2.1. “Attraction of predators and parasites, increase of their searching
activity”, Mortality under effect of predators and parasites” operates, but indigenous parasites are
nearly unable to kill Porthetria dispar and to infest it by pathogens.
CESPPs 2.5.3.1.4.”Increase of activity of pathogens and parasites in the specific conditions
of high host density, Mortality due to affection by acute form of infection and parasitization”
does not operate.
CESPPs 2.5.4.1. “Fluctuations of herbivore host resistance to pathogens and parasites as well
as virulence of pathogens and aggressiveness of parasites, Suppression of herbivores over the
period, which provides a reprieve for restoring of vitality of dominants” does not operate too that
endangers heavy mortality of defoliated trees.
CESPPs 2.3.3.1. “Cool and prolonged rains in the larval stage of defoliators, Mortality of
larvae at inducing the acute form of infection” operates weakly, if any, because the population is
rather free of infection.
The above difference as to composition of EEs explains the bimodality of population
behavior of Porthetria dispar in North America.
The spread of the parasites vectoring pathogens on the population inhabiting the advancing
front of the generally infested area restores its LS to the level characteristic to the generally
infested area.
Management implications are as follows:
i) Let us begin with the recommendation, which should not be practiced, namely: the case is
provided by D.L.Leonard (1981, p. 28)"Altering the forest composition to reduce the
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percentage of oaks to about 15 to 25 percent of the dominant and codominant trees will
make the forest less susceptible to gypsy moth defoliation." Due to a decrease of
participation of the oak in ecosystems, such an advice would exert the worse damage for
forest than Porthetria dispar does.
ii) Although the composition of CESPPs, which counteract SP of Porthetria dispar is rather
wide, only parasites (CESPPs 2.2.1.1.) might be used in practice to suppress this pest.
There are two ways of usage of them – by introducing of the parasites at invading of the
insect in an area, where it does not inhabit earlier, and by promotion of activity of natural
enemies by means of cultural (silvicultural) practices, as follows:
a) In the island infestations, which appear in the areas of distinctly continental climate,
species of parasites, which are naturalized in the eastern part of the USA, hardly to be
effective for suppression of this species. Therefore, it would advisable to introduce the
species from Eurasian areas with similar climate.
b) In the advancing front of the generally infested area, it needs to introduce in the first place
stinging parasites – vectors of pathogens of Porthetria dispar.
c) It seems to be prospective to test an introducing of parasites in areas outside of the
advancing front, where, however, appearing of Porthetria dispar is very possible.
Because parasites of this species have the wide range of insect hosts (Zerova et al.,
1989), they have a chance to become naturalized before invasion Porthetria dispar. To
the point, Compsilura concinnata Mg. twenty - thirty years after its introduction was able
to affect 150 native lepidopterous and sawfly species of 23 families (Webber and
Schaffner, 1926; Schaffner and Griswold, 1934).
d) For promotion of natural enemies of Porthetria dispar, at reforestation in mesic habitats,
it should establish the stands with rich species composition and closed canopy.
e) In xeric habitats, where dominants are able to exist on condition that they are widely
spaced, favorable conditions for natural enemies are provided by means of establishing of
an undergrowth with diverse bushy species. On the rich (clay) soils, the undergrowth
should be dense for competing with grassy vegetation. On the poor (sandy) soils, the
undergrowth should be sparse.
f) It is prospective to establish of exploiting forest plantations with monocultural
composition of dominants having high stocking density. If the dominants are the species
favorable for feeding of Porthetria dispar, it is need to provide them with plots of land
sown by plants, which provide imaginal feeding for parasites. They are grassy species
with early and abundant blossoming. It seems to be prospective to treat the lawns with
microbiological preparations with the aim to bring in Porthetria dispar populations
pathogens. It is supposed that the parasites, which feed on the lawns in the imaginal
stage, would serve as vectors of pathogens.
iii) Physiological state of the monocultured plantations should be maintained by application
of fertilizers and irrigation.
Outbreaks with dominance of other species of the spring-summer guild of oak defoliators
[the lackey moth, Malacosoma neustria L., the pale tussock moth, Dasychira pudibunda L.,
buff-tip moth, Phalera bucephala L., the notodontid moth, Notodonta trepida Goeze=(Peridea)
anceps Goeze and others] arise more rarely than those of Porthetria dispar in time and space.
Often they are mentioned as satellites of Porthetria dispar in its outbreaks.
Defoliators
5.1.1.1. Defoliators of deciduous tree species
5.1.1.1.1. Openly-feeding defoliators of tree species.
5.1.1.1.1.2. The fall-spring guild
5.1.1.1.1.2.1. The little gypsy moth, Parocneria detrita Esp.
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Let us compare SP of Porthetria dispar with that of the little gypsy moth, Parocneria detrita
Esp. These species are close relatives and belong to close guilds. In particular, they can compete
for foodstuff in spring. Also they have similar EE on the level ESPPs 3.1. "Proper control."
Nevertheless, they are very different as to their capacity to reach High density in time and space.
This fact implies great differences in their SPs.
Due to the trait of feeding in older larval instars at the beginning of season, when concurring
species stay in initial larval instars, and, therefore, they are less voracious, Parocneria detrita is
an advanced competitor with defoliators of the spring-summer guild. Thus, expression of SS
5.1.(17.) "To forestall competitors or evade from competition" is "High."
However, this trait forces the species to overwinter on the stage of middle-instar larvae in
forest litter that endangers the larvae on the part of pathogens and ground predators. This trait
concerned to the subcategories of SS 5.1.(10.) "To develop self-protection against natural
enemies by behavior traits" - 5.1.(10.3.) "Mammal predators" and 5.1.(10.4.) "Pathogens" for
middle larval instars. The trait of overwintering in the larval state predetermines "Weak"
expression of SS 5.1.(10.4.) in wet conditions. Therefore, High density of this species is possible
in the conditions of xeric climate, where activity of pathogens is suppressed. In more wet
climate, an increase of the density is possible in xeric habitats at severe drought. The
overwintering are protected by dense hairy covering, so that expression of in them SS 5.1.(10.3.)
"Mammal predators" is "Moderate."
Young larvae are protected against parasites and predators by means of "jumping" from
leaves on the ground, where they are able to find shelter in forest litter. As to returning the larvae
on foliage of host-trees, there are no problems of the dwarfish trees, and is formidable on the tall
trees. Therefore, expression of SS 5.1.(10.1.) and 5.1.(10.2.) for initial larval instars is "High" on
the former, and "Weak" on the latter.
The older larvae, which reach the pupal stage during shorter time than those in other guilds,
have a moderate level of protection against natural enemies. The advantages of SS 5.1.(10.1.)
and 5.1.(10.2.) are realized in High density of the species in the xeric environmental conditions,
where activity of natural enemies, especially pathogens is suppressed, whereas host-trees have
the dwarfish habitus. In the mesic conditions, Parocneria detrita stays nearly continually on the
level of Insignificant density. Only in a result of heavy droughts, it is able to reach noticeable
density on dwarfish oak trees.
The low capacity of Parocneria detrita to reach High density outside of areas of arid climate
suggests that expression of SS 5.1.(12.) "To enhance resistance to pathogens" in this species is
"Weak."
The above description might be formalized by the following categories of SSes:
SP(Parocneria detrita)= 5.1.(10.1.) and 5.1.(10.2.)- Eggs – Moderate, young larvae – High (on
dwarfish host-trees), and - Weak (on tall host-trees), 5.1.(10.3.) – middle-instar larvae –
Moderate; 5.1.(10.4.) -middle-instar larvae –Weak (in humid conditions), and - Moderate (in arid
conditions), 5.1.(10.1.) and 5.1.(10.2.) - older larvae – Moderate, pupae - Moderate; 5.1.(12.) Weak; 5.1.(17.) – High.
EE of Parocneria detrita on the level 3.1. "Proper control" was described above. In this EE,
the primary role is played by activity of pathogens during hibernation (CESPPs – 2.2.1.3.).
Further, it followed by activity of parasites (CESPPs 2.2.1.1.) and vertebrate predators (CESPPs
2.2.1.2.1.). Because natural enemies continually keep density of Parocneria detrita on the
Insignificant level, the role of Tolerance (CESPPs 2.1.1.3.1.2.) is the least. The effect of CESPPs
is Directly density-dependent, smooth, Persistent, Potent, and The best. Now, it will be shown
the full LS of the species including the composition of EE and SP as follows:
3.1., (b), LS(Parocneria detrita) = SP [5.1.(10.1.) and 5.1.(10.2.)- Eggs – Moderate, young
larvae – High (on dwarfish host-trees), and - Weak (on tall host-trees), 5.1.(10.3.) – middle-instar
larvae – Moderate; 5.1.(10.4.) -middle-instar larvae –Weak (in humid conditions), and Moderate (in arid conditions), 5.1.(10.1.) and 5.1.(10.2.) - older larvae – Moderate, pupae Moderate; 5.1.(12.) - Weak; 5.1.(17.) – High] ↔EE(2.2.1.3.+ 2.2.1.1.+ 2.2.1.2.1.+ 2.1.1.3.1.2.),
Directly density-dependent, smooth, Persistent, Potent, The best.
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The prerequisites of this EE are ecological conditions in ecosystems providing optimum for
all the natural enemies of Parocneria detrita that maintain high activity of them at any weather
situation. Such conditions are common in mesic habitats.
Above discourse suggests that High density of Parocneria detrita is possible in xeric
environmental conditions, where activity of parasites and pathogens is suppressed, on dwarfish
host-trees.
Defoliators
5.1.1.1. Defoliators of deciduous tree species
5.1.1.1.1. Openly-feeding defoliators of tree species in late summer and web-dwelling from
fall to beginning of summer in next season
5.1.1.1.1.2. The fall-spring guild
5.1.1.1.1.2.2. The browntail moth, Euproctis chrysorrhoea L.
The browntail moth, Euproctis chrysorrhoea L., belongs to the same guild as Parocneria
detrita. Unlike to the latter, outbreaks of the former are common, and sometimes spread on vast
areas. Numerous outbreaks of the species were recorded in XIX and XX centuries. The
advantage of this species consists in producing of a web net in the middle larval instars, and
possessing by poisonous bristles. Both these traits protect older larvae and pupae against
parasites and predators. This protection is far from to be absolutely. In fact, the oxeye, Parus
major L. in forest plantations of the Steppe biome in Ukraine over several months killed 36-74%
of the larvae extracting them from winter nests (Doppelmeir et al, 1966, p. 152.). In the Rostov
Region (Russia), affection of the larvae in the nest by the parasite Eupteromalus nidulans Forst.,
the family Pteromalidae reached 100% (Utchakina, 1968). The larvae were parasitized in fall
before making their web net.
Therefore, expression of SS 5.1.(10.) "To develop self-protection against natural enemies by
behavior traits" 5.1.(10.1.) "Avian predators" in Euproctis chrysorrhoea should be characterized
as "Moderate", whereas 5.1.(10.2.) "Invertebrate predators and parasites" in fall before nest
making is "Weak."
A serious limitation of SP of this species consists in the following: a web net protecting
against parasites and predators, provokes affection of the larvae by pathogens in the conditions
of humid weather situation. Often cases of mortality of Euproctis chysorrhoea due to affection
by the fungus Empusa aulicae at wet weather were noted, in particular, by V.P. Pospelov (1935).
Therefore, the W.C. Cook’s zone (a) and (b) of its range are situated in areas with climatic
conditions tending to aridization – the southeastern Europe. Expression of SS 5.1.1.1.(15.) "To
tolerate well weather stresses in the stages from the larvae to adult", 5.1.1.1.(15.1.) "Cool and
rainy weather in the larval stage", is "Weak."
An expression of SS 5.1.(12.) "To enhance resistance to pathogens" in this species is
"Moderate."
The knowledge of SP of Euproctis chrysorrhoea helps to explain events concerned to
performance of this species in North America. Here is the passage from the report by D.E.
Leonard (1981, p. 10): "Although the gypsy moth has emerged as the most successful colonizer,
the initial success and spread of the browntail moth were more spectacular. This insect defoliated
many of the same species of trees as the gypsy moth, spreading throughout New England and
into several of the Canadian Maritime Provinces in about 30 years… For reasons not completely
understood, the range of the browntale moth began to recede in the 1920’s. Today, the insect is a
maritime curiosity, with small colonies that persist on several islands in Casco Bay, of Portland,
Me., and on coastal sand dunes of Cape Cod, Mass."
Now, the "reasons not completely understood" are quite explicit ones. They are parasites of
the pest insect and vectoring by them pathogens. This parasite-pathogen complex established in
North America in 1920’s suppresses the moth everywhere, except the localities, where it cannot
operate effectively – in islands in a sea and in the coastal sand dunes.
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In spring, middle-instar larvae of Euproctis chrysorrhoea force out the larvae of the earlyspring guild (Zubov, 1968). Hence, expression of 5.1.(17.) "To forestall competitors or evade
from competition" is "High."
SP(Euproctis chrysorrhoea)=5.1.(10.1.) – Moderate; 5.1.(10.2.) in fall – Weak; 5.1.(10.2.) in
spring, summer –High; 5.1.1.1.(15.1.) – Weak; 5.1.(12.) – Moderate; 5.1.(17.) – High.
Thus, High density of the species is probable in the environmental conditions of suppressed
activity of parasites in fall, moderate activity of avian predators in winter and spring, and a lack
of cool and/or prolonged rains in spring and beginning of summer.
5.1.1. Defoliators
5.1.1.1. Defoliators of deciduous tree species
5.1.1.1.3. Web-worms of deciduous tree species
5.1.1.1.3.1. The apple ermine moth, Hyponomeuta malinellus Zell.
Consider peculiarities of SP of the apple ermine moth, Hyponomeuta malinellus Zell., an
effect of environmental conditions on its abundance, and compare it with those in Porthetria
dispar. As it was shown above at discourse of EE of Hyponomeuta malinellus, this species is
most abundant in the areas of moderate humidity – central and eastern parts of the Forest-Steppe
biome in Ukraine. To the south, west and north to these areas, the indices of abundance become
less, whereas abundance of Porthetria dispar increases in direction on south of this area.
Within its W.C. Cook’s zone (a), Hyponomeuta malinellus produces outbreaks in the
conditions, where density of Porthetria dispar is continually Insignificant – shade trees in
settlements, and abandoned fruit orchards.
In the areas with abundant summer rains (the biomes of Coniferous-Deciduous forests in
plain and mountain areas, the biome of Deciduous forest in western Regions of Ukraine close to
the Carpathians Mountains) both Hyponomeuta malinellus and Porthetria dispar are
unnoticeable.
The same is true for the relative species – Hyponomeuta padellus L., which prefers the plumtrees, apricot-trees, the thorn, Crataegus spp., and the black thorn, Prunus spinosa L.
In this context, it should consider the situation with abundance of the both species in the
mountain fruit-forest ecosystems in the West Tyan-Shan and Pamir-Alau Mountains in the
Central (Middle) Asia. In these unique natural ecosystems, it grows the apple-tree, pear-tree,
other Rosaceae species and the walnut-tree. They occupy the area nearly 170 thousand hectares.
In them, it is common High density of Hyponomeuta malinellus and H. padellus. According to
I.K. Makhnovsky (1963, p. 103), in most of seasons, a value of damage of the foliage was 7580%; in some seasons, the damage reached 100%.
Further, this scholar reported that for control of the moths, in 1959-1961, it was conducted
measures with the usage of solutions of DDT and in oil at treatments with aerozole generators
(mist), and BHC (fume) at the usage of smoke-boxes. The effectiveness of the treatments was
reported to be equal 91.3-95.2%. The treatments were conducted in May. They did not affect on
tachinid parasites that is significant for continued protection against the ermine moths, which are
controlled by tachinid parasites, when moths’ density reaches High values.
These protective measures have had long-distant consequences. The matter of facts, in the
publication by R.P. Karavayeva (1961), in pest insect fauna of these ecosystems, Porthetria
dispar even was not mentioned, although “In valley areas of Kirgizia, Ocneria dispar L. occurs
everywhere” (Prutensky, Karavayeva and Romanenko, 1954, p. 17). In 1980-ies, this species
was recorded as a serious pest of the orchard ecosystems (A.G. Kotenko, pers. comm.).
Further, it is interesting the report by A.A. Orozumbekov et al. (2002). It occurred to be in
these ecosystems, it takes place over last decades the "permanent outbreak" of Porthetria dispar.
These scholars explain the outbreak by "total treatments by insecticides" of the forest-orchard
ecosystems in 1970-1980-ies in May. Hence, in 1970-1980-ies, the treatments became even more
wide-scaled than those in 1959-1961. These treatments obviously were perilous for
hymenopterous parasites, and suppression of them is a logical explanation of the permanent
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outbreak of Porthetria dispar. Such an explanation of effect of the treatments seems to be more
substantiated than that given by A.A. Orozumbekov et al. (2002), namely: total treatments by
insecticides precluded the panmixia of Porthetria dispar micropopulations with diverse
physiological characteristics.
It is important the significant effect of climatic and weather factors on vitality of
Hyponomeuta malinellus.
The pupae are very sensitive to low air temperatures. A decrease of night air temperatures to
10°C-11°C over two-three 24-hour period led to mortality of the 87% pupae (Nekhay, 1983,
p. 45). This is an additional explanation, why the species is unnoticeable in mountains and
northern plain areas with common decreases of temperatures in summer. According to the
author’s observations, such a situation takes place in the Carpathians Mountains (on elevation
700 meters above see level and higher). The same is true for the biome of Coniferous-Deciduous
forest in the East Europe. The CESPPs operating in these climatic conditions suppress density of
both Hyponomeuta malinellus and Porthetria dispar to an Insignificant or may be Zero levels.
The areas with rainy May is little of favorable for grow the density, because the neonate
larvae are very sensitive to rainy cool weather in the period before penetrating under a leaf
epidermis (Nekhay, 1983).
The general decrease of Hyponomeuta malinellus density in the Steppe biome is determined
by the need in the imaginal feeding of the species. At deficiency of nectar, the fecundity is low
(Degtyaryov, 1966). In the steppe areas, a resource of nectar is limited, and it drops to a
negligible value at drought.
A capacity to compete with other defoliators in the ermine moths is well-developed, so that
expression of SS 5.1.(17.) "To forestall competitors or evade from competition" is "High."
Both Hyponomeuta malinellus and Porthetria dispar are unnoticeable in the conditions of
wet climate or undergo a sharp decrease of density at onset of wet weather situation anywhere.
Obviously, the cause of the suppression is affection of the populations with pathogens, which
become active in the wet media. Therefore, an expression of SS 5.1.1.(15.) "To tolerate well
weather stresses in the stages from the larvae to adult" 5.1.1.(15.1.) "Cool and rainy weather in
the larval stage" is "Weak." An expression of SS 5.1.(10.4.) "Pathogens" is "Weak."
Above data allow drawing the following conclusions:
iv) SPs of Hyponomeuta malinellus and Porthetria dispar differ significantly. The former
species is common at Intermediate or High densities in the ecosystems, where Porthetria
dispar is unnoticeable – the fruit-forest ecosystems, shade trees, abandoned fruit
orchards. This is an evidence of advanced SS of the category 5.1.(10.) "To develop selfprotection against natural enemies by behavior traits’’, 5.1.(10.1.) "Avian predators", and
5.1.(10.2.) "Invertebrate predators and parasites." Its expression is "High", whereas in
Porthetria dispar it is "Moderate." A web net provides reliable protection against these
entomophagous organisms in the conditions, where they very active.
v) The second feature is common in both species. This is a high sensitiveness to low air
temperatures in the pupal stage. This trait is a manifestation of the category SS 5.1.1.(15.)
"To tolerate well weather stresses from larval to adult stages", 5.1.1.(15.5.) "Low
temperatures in the pupal stage." Its expression is "Weak" as in Porthetria dispar. The
expression SS 5.1.1.(15.1.) "Cool and rainy weather in the larval stage" in H. malinellus
is "Weak" in all the larval stage.
vi) The effect of availability of nectar for imaginal feeding that is recorded in conditions of
dry climate might be considered as the usage also SS of the category 5.1.1.(15.6)
"Weather situation precluding imaginal feeding." Its expression is "Moderate."
SP(Hyponomeuta malinellus)=5.1.(10.1.) – High; 5.1.(10.2.) – High; 5.1.(10.4.) – Weak;
5.1.1.(15.1.), in all the larval stage – Weak; 5.1.1.(15.5.) – Weak; 5.1.1.(15.6.) – Moderate,
5.1.(17.)- High.
The group of web-worms embraces a great many species of the genera Hyponomeuta,
Nordmaniana, Ocnerostoma, Cedestis, Swammerdamia, Paraswammerdamia, and the fall
webworm, Hyphantria cunea Drury.
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Their SPs probably have a number the same SSes. Although, some of them do not need in
the imaginal feeding. Being independed from nectar, these species are abundant in areas of arid
climate. This is a W.C. Cook’s zone (a) for them.
In particular, this is characteristic for Hypenomeuta rorellus Hb., which is a pest in flood
plain willow ecosystems in the Low Dnieper Area (Ukraine), which is situated in the southern
part of the Steppe biome. To the north of this area, outbreaks of the species are unknown.
Being an invaded species, Hyphantria cunea becomes abundant in diverse tree plantings in
the south of Ukraine, in particular in the Crimea Peninsula (Ukraine). Within this area, its
W.C. Cook’s zone (a) embraces areas of arid climate characteristic for the region. Nevertheless,
in the Southern Beach of the Crimea, especially in Yalta, where rains in spring and beginning of
summer are common, this species has not accustomed.
This case might be considered as "Weak" expression of SS 5.1.1.(15.) "To tolerate well
weather stresses in the stages from the larvae to adult", 5.1.1.(15.1.) "Cool and rainy weather in
the larval stage" that induces heavy affection of a species with pathogens.
Management implications are as follows:
Taking into account the insignificant negative effect of the wet-making moths on vitality of
host-trees, application of insecticides should be very limited especially in shade and ornamental
trees, and reserves. In orchards, protection against the moths is advisable. Although, the special
measures usually need not, because these species are suppressed at control of the codling moth
and other carpophagous pest insects.
5.1.1.2. Defoliators of the larch
5.1.1.2.1. Bud-mining and web-making defoliators of the larch
5.1.1.2.1.1. The larch bud moth, Zeiraphera diniana Hb.
Within insect defoliators, Zeiraphera diniana has probably the most perfect SP, in which
majority of SSes demonstrate "High" expression. Taking into account the situation with this
species in the north Asia (Siberia, the Russian Far East, the north Mongolia), it is clear that
Zeiraphera diniata has adapted to feed by the most abundant genus of trees, Larix spp., which
occupy the greater part of forest area in Russia. Its outbreaks embrace actually all the range of
the host-trees, and do not exert significant damage of host-trees, although they are frequent.
Therefore, it is interesting to explain population behavior of this species in Asia and in Europe
comparing its SSes in above continents, as well as with those in other species of defoliators.
The studies of Russian scholars have not shown the significant role of CESPPs 2.1.1.4.1.
"Evasion from herbivores" everywhere excepts the plots with High density of the moth in a
preceding season. The Evasion at the density less than High one, is a rather rare event, and it
occurs after uncommonly severe winters, when the soil becomes frozen on a large depth
(Pleshanov, 1982, p. 143). Either pronounced continental climate, or some traits of Asian species
of the larch decrease the role of this CESPPs. Therefore, in Asia expression of SS 5.1.1.2. (9.)
"To develop the traits directed on affection of host-plants in vulnerable stages of their life cycle"
is "High or Moderate."
Eggs of this species are laid close to host-tree buds, and they are well masked. In fact, S.F.
Shabunevich and A.S. Pleshanov (1971, p. 129) have reported: “…egg-clusters of the pest are
common on twigs including most thin ones…the eggs are very small, and they are placed
stealthy under bark crevices, so that survey of them is extremely laborious and little correct.”
After the short way, the larvae occur to be well-protected from parasites feeding in the first
and the second instars within needle clusters, and in the fourth and the fifth instars, they live at
first in tube-like shelters and construct later an webbing along the branch axes (Baltensweiler,
1983, pp. 76-77). Thus, except of short term in the adult stage, the species spends its life cycle in
shelters.
These traits provide the egg, larval and pupal stages of the moth with advanced protection
against all the entomophagous organisns at least on the densities below High. The significant
affection by parasites and pathogens was recorded only at High density, especially in secondary
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infestation spots, i.e. in the advanced outbreaks, where the larvae are forced to leave shelters in
search for foodstuff (Pleshanov, 1982). Obviously, expression of the subcategories of SS
5.1.(10.) “To develop self-protection against natural enemies by behavior traits” is High.
Zeiraphera diniana has reached the same perfection of SS 5.1.(10.) as Tortrix viridana does.
Because in Siberia rains during the larval stage of the moth are rare events, affection of the
larvae by pathogens is less probable than that in the early-spring guild of oak defoliators.
Because this species is able to reach High density in the point of the world pole of frost in
Verkhovyansk (Yakutiya), it is obvious that expression of SS 5.1.1.(14.) "To tolerate well low
temperatures at hibernation" is "High."
The very short period of development, which allows to inhabit in Yakutia, implies of High
expression of SS 5.1.1.(16.) “To develop behavior trait to overcome limitation of short season.”
Expression of SS 5.1.1.2.(6.) "To exert the least negative impact on vitality of host-plants by
means of reduction of development" is also "High."
The trait to migrate as soon as the density has become High provides SSes 5.1.1.2.(7.) "To
minimize negative impact on host-plants by leaving of infestation spots as early as possible,
when density reach the high level", and 5.1.(13.) "To leave infestation spots as early as possible,
when virulence of pathogens and activity of parasites begin to grow" again with the quality
"High."
When foodstuff resource on the larch is exhausted, Zeiraphera diniana is able to feed by
evergreen coniferous species. Therefore, expression of SS 5.1.1.2 (8.) "To expand the range of
host-plants, when density of defoliators reaches the high level" is "High."
The subcategories of SS 5.1.(10.) "To develop self-protection against natural enemies by
behavior traits" are more expressed than those in Dendrolimus sibiricus. The significant
affection by parasites and pathogens was recorded only at High density, especially in secondary
infestation spots, i.e. in the advancing outbreaks, when the larvae are forced to leave shelters due
to foodstuff deficiency (Pleshanov, 1982). Expression of this SS is "High."
Only in one category of SS, Zeiraphera diniana in Asia demonstrates obviously decreased
expression. This is 5.1.(17.) "To forestall competitors or evade from competition." In this
respect, Dendrolimus sibiricus outdoes Zeiraphera diniana. In the last months of a season, larvae
of the former are able to feed by larch needles regrown after affection by Zeiraphera diniana,
and go ahead the former in the initial months of a season. Further, suppression of physiological
state of the larch in result of outbreaks of Dendrolimus sibiricus impedes development of
Zeiraphera diniana. Thus, expression of SS 5.1.(17.) in Zeiraphera diniana is "Moderate." As to
expression of SS 5.1.(12.) "To enhance resistance to pathogens" in the moth, there are no data for
Siberia.
Thus, SP of Zeiraphera diniana in Asia has the following composition:
SP(Zeiraphera diniana, in Asia)= 5.1.1.2.(6.) – High; 5.1.1.2.(7.) – High; 5.1.1.2.(8.) – High;
5.1.1.2.(9.) – High or Moderate; 5.1.(10.) – High; 5.1.(12.) - ?; 5.1.(13.) – High; 5.1.1.(14.) –
High; 5.1.1.(16.) – High; 5.1.(17.) – Moderate.
Compare the situations in Asia and in the optimal for Zeiraphera diniana belt zone in the
Engadin Valley on the elevation 1700 – 2000 meters above sea level. In the conditions of the
zone, SP of the species reaches maximal expression in all its SSes. Here, it is not known any
limitations for the coincidence of bud-bursting and larval hatching. Again, any competitors do
not prevent the species to reach High density. All the SSes have expression "High." That is why,
its outbreaks in the Engadin Valley are so frequent and regular. Only effects of CESPPs of the
Intrinsic class interrupt continuously of High density. In the progressive phase of their outbreaks,
the population of Zeiraphera diniana acquires qualities of the "the extreme strong type" of
individuals. They are highly resistant to pathogens (Clark et al., 1967, p. 134). This implies that
an expression of SS 5.1.(12.) "To enhance resistance to pathogens" in this species is "High."
Expression of SS 5.1.(17.) "To forestall competitors or evade from competition" in the Engadin
Valley is unknown because competitors are absent.
Thus:
SP(Zeiraphera diniana, in the Engadin Valley) = 5.1.1.2.(6.) – High; 5.1.1.2.(7.) – High; 5.1.1.2.
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(8.) – High; 5.1.1.2.(9.) – High; 5.1.(10.) – High; 5.1.(12.) – High; 5.1.(13.) – High; 5.1.1.(14.) –
High; 5.1.1.(16.) – High; 5.1.(17.) - ?
Outside of the belt zone, Zeiraphera diniana demostrates SP too weak to counteract of
CESPPs being unable to produce outbreaks. Its infestation spots appear due to immigration.
On the other hand, in Siberia, SP of the moth allows it to produce vast outbreaks actually
over all the range of the larch. Population behavior of Zeiraphera diniana in Siberia is less
regular than that in the Engadin Valley, but percentage of larch stands affected by the outbreaks
in the former is much more than that in Alps. This difference is an open problem.
Management implications are as follows:
It would be sound to use no suppressive measures against Zeiraphera diniana, when it affects
the common larch forests. The measures might be expedient in endangered larch seed plots, and
in forests of evergreen species.
Peculiarities of multispecies outbreaks of insect herbivores in the context of species
potential
The Russian literature abounds by reports about miltispecies outbreaks of defoliators.
Although the most part of publications deals with a single species of defoliators, one could sight
in some of them a presence of satellites, but most of scholars pay attention to a prevalent species.
In the Forest biome, in ecosystems with dominance of the oak, it is common a presence every
year numerous species of the early-spring guild. The Forest-Steppe and Steppe biomes situated
in the southeastern region of East Europe with rather arid climate are the areas of often outbreaks
of four guilds – early-spring, spring-summer, summer-fall, and fall-spring ones, which operate
sometimes in the same seasons.
In the Asian part of Russia, there is a belt of forest islands with dominance of the birch and
the aspen as an admixture, which spreads on several thousands of miles from the southern Urals
Mountains to the Altay Mountains.
P.M. Rafes (1974, p. 280) gave such a characteristic of species composition of defoliators in
this region: "…beginning with spring, foliage of the birch used to affect by many consumers of it
(the families Tortricidae, Chrisomelidae, Curculionidae, aphids, mites, and others)…These
consumers of the spring type do not reproduce en masse, and exert as a whole small damage to
foliage, which do not reach 30% of a leaf plate. This loss is compensated during the subsequent
growth of foliage. …Beginning with the middle of July, foliage of the birch is attacked by the socalled summer-fall group of the orders of Lepidoptera and saw-flies –Hymenoptera." In 1970
and 1971,"...the gypsy-moth and associated with it species were absent…"
G.I. Sokolov (1987) reported that outbreaks of the summer-fall guild took place in the
Chelyabinsk Region (Russia) in 1960-1965, 1968-1971, and 1975-1977, i.e. in the same years
with outbreaks of Porthetria dispar.
The spring-summer guilds is presented by the following species: “In infestation spots of the
gypsy moth, it is common Malacosoma neustria L., Ennomos autumnaria Wrnbg., Eriogaster
lanestris L., and Euproctis (Porthesia) similis Fssl.” (Gninenko, 1976, p. 5).
Among these satellites of the gypsy moth in this area, N.G. Kolomiets and S.D. Artamonov
(1985, p. 11) mentioned the birch moth, Endromis versicolora L., the pubescence moth,
Eriogaster lanestris L. and a number of unnamed species. High density of the guilds was noted
in the same season as that of the gypsy moth or in other seasons.
The summer-fall guild consists of “34 species of butterflies and sawflyes”(Ibid., p. 5).
According to Yu.I. Gninenko et al. (1971) for the western part of the belt, seven species are
prevalent (their overall participation reaches 56%), including Leucodonta bicolaria Den. et
Schiff., Biston betularius L., Lophopterix camelina, Cymatophora duplaris, Acronicta leporina,
Notodonta dromedarius L., Hylophila prasinana. Also, it has been mentioned Cidaria
hastata L., Drepana lacertinaria L., D. falcataria L., Eriogaster lanestris L., Stauropus fagi L.,
Mimas tilia L., Gonodontis bidendata Cl., Pheosia dictaecoides Esp., Ph. tremula Clerck.,
Phalera bucephala L., Acronicta psi L., Boarmia punctulata Schiff.
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All the above species have similar traits, namely: the main or the only host-tree is the birch,
hibernation in the pupal stage in the soil (in forest litter) or in old stumps and slash, the same
flight period and term of oviposition, larval hatching, duration of the larval and pupal stages.
Shoring of the species within these forest plots is less stable than that in the early-spring guild
of forest defoliators. For example, occurrence of them in the diverse plots lies in such ranges:
Leucodonta bicolaria – 0 - 38%, Notodonta dromedarius 0 - 56%.
The areas embraced by infestation spots of this guild are vast. In particular, in 1970, the areas
equaled 174.2 thousand hectares of island forests in Chelyabinsk, Kurgan, and Sverdlovsk
Regions, Russia (Gninenko, 1976, p. 6).
N.G. Kolomiets and S.D. Artamonov (1985, pp. 18-20 and 118) gave for the eastern part of
this area (the Novosibirsk Region, Russia) more abundant list of species of the summer-fall
guild. The list includes forty-three names, including the families Noctuidae (11), Geometridae
(9), Tetheidae (4), Drepanidae (3), Lasiocampidae (2), Sphingidae (2), Saturnidae (1),
Endromididae (1), Lymantriidae (1). The main part (over 80%) of the insects is composed by
five species – Leucodonta bicolaria, Phalera bucephala L., Biston betularius, Eriogaster
lanestris, and Endromus versicolora L.
Outbreaks of the summer-fall guild arose as often as those of the spring-summer guild –
every 10 years (Ibid., pp. 9 and 10). Also, Yu.I. Gninenko (1976, p. 17) has reported: “Analysis
of literature and archives data allow to draw conclusions that the species of the summer-fall
group beginning with 1900 arise in Forest-Steppe and Steppe zones of the Trans-Ural, North
Kazakhstan, and West Siberia regularly with an interval approximately 10 years.”
Studies by R.A. Zubov (1968) showed that in the xeric oak stands of the Forest-Steppe
biome, outbreaks were formed by families Tortricidae, Pyralidae, Noctuidae, and Geometridae.
It was common High density of Tortrix viridana L., Archips crataegana Hb., and the genus
Acrobasis Z. (Pylalidae). These species compete with old-age larvae of Euproctis chrysorrhoea.
All they pretended on the same part of the crowns – an upper part.
The spring-summer guild was represented by Malacosoma neustia L., Apocheima hispidaria,
Phigalia pedalia F., the looper, Erranis marginaria Bkh., other loopers, and Noctuid moths of
the genus Monima.
In the southeastern part of Ukraine, in deciduous forest stands, M.M. Padiy (1993, p. 182)
recorded infestation spots of the guild of the geometrid moths having very similar life cycle,
including Phigalia pedaria F., Biston hispidaria Schiff., B. pomonaris Hb., B. stratarius Hun.,
and Lycia hirtaria Cl.
Similar species diversity takes place in outbreaks of needle-eating defoliators.
F. Keppen (1883, p. 62) reported that the moth Gnophria quadra L., which fed by the
lichens, as a rule accompanied the nun moth, Porthetria monacha. The scholar continued that in
coniferous forests, there were the following satellites of Porthetria monacha: the beauty moth,
Panolis flammea Schieff., the pine moth, Dendrolimus pini L., the pine looper, Bupalus
piniarius L., whereas in broad-leaved forests, the satellites were the gypsy moth, Porthetria
dispar L., the browntail moth, Euproctis chrysorrhoea L. (in oak stands), and the pale tussock
moth, Dasychira pudibunda L. (in beech stands).
Here is the report of O.V. Tarasova and V.G. Sukhovol’sky (1985, p. 110) for south areas of
the Krasnoyarsk Region: "The complex of needle-feeding insects embraces fifteen species of the
orders Lepidoprera and Hymenopreta, but only seven species occur constantly, namely:
Dendrolimus pini L., Bupalus piniarius L., Semiothisa liturata Cl., Hyloicus morio Rotsch. et
Jord., Gilpinia virens Kl., Microdiprion pallipes Fall., Panthea coenobita Esp. The surveys were
conducted in 1979-1984 in six localities of the Region." It is strange that the most important
species - Dendrolimus sibiricus Tschetv. is absent in this list.
In some conditions, however, there exist the opposite trend – every species forms own
infestation spot.
Here is the report by V.O. Boldaruev (1969, pp. 60-61): "In spring of 1961, in larch forests of
Buryatia, a short-running ground forest fires spread on huge areas…On all the area, where
the fire run, it took place a mass outbreak of needle-eating pest insects. Firstly, it appeared en
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masse the monocyclic species – Erranis jacobsoni Djak., Orgyia antiqua L., and Ocneria
dispar L., and after a year, in 1963 - the heterocyclic species Dendrolimus sibiricus Tschetv.
Outbreaks of the first and the second species occurred in the same stands, sometimes on the same
trees." Outbreaks of two rest species were recorded in separate stands.
"Simultaneously with outbreaks of the Siberian pine moth in pine forests of Buryatia, it was
noted outbreaks of the fir tussock moth (Dasychira abietis Schieff.), and the pine miner
(Ocnerostoma piniariellum Zell.)" (Ibid., p. 58). The outbreaks of the last two species were
situated in different locations and occupied different areas – 170 thousand and two thousand
hectares, respectively. They were caused by drought, rather than by ground forest fires.
This discourse shows the diversity of species’ behavior at High density. Some of them having
an advanced SPs at favorable conditions for growth of density tend to force out competitors from
infestation spots. Although this trend is not well expressed. Even such species as Porthetria
dispar often shores infestation spots with satellites. Other species with an advanced SPs (the
early-spring and summer-fall guilds) coexist with their competitors forming multispecies
infestation spots.
Yu.P. Kondakov (1964, p.152) noted some peculiarities of combined infestation spots
comparing with single species ones. In Khakasiya (south of Siberia), a combined infestation spot
of Dendrolimus sibiricus and Porthetria dispar in ecosystems with the larch as a dominant
declined simultaneously and earlier than ones of the first species in northern areas, where P.
dispar was unable to participate outbreaks with D. sibiricus due to activity of CESPPs 2.3.
“Routine weather suppression.” This scholar explains short duration of combined outbreaks of
above species by two-fold increased activity of the parasite Apanteles liparidis Bouche, which
needs in larvae of D. sibiricus for hibernation.
Another remarkable infestation spot in ecosystems with prevalence of the Scots pine was
produced by numerous species of defoliators – Bupalus piniarius L., Neodiprion sertifer Geoffr.,
Diprion pini L., Panolis flammea Schiff., Hypparchus papilionaria L., Aplecta prasina Schiff.,
Pheosia tremulae Cl., Eurois exusta Btl., Scoxogramma trifolii Rott., and Leucania conigera
Schiff. In this spot, it was developed a multispecies complex of mainly polyphagous
entomophagous organisms, which led to decline of the spot at not too high level of defoliation
(Ibid., pp. 153-154).
In fruit orchards, it is abundant the early-spring guild of defoliators.
K.A. Kudel (1960) found in orchards twelve species of the leaf-rollers. The participation of
the prevalent species – Tmetocera ocellana F. reached up to 95% of the insects. Pandemis
ribeana Hb., Cacoecia lecheana L., and Ancylis achatana F. occurred in significant densities,
whereas the rest eight species were recorded in the minute numbers.
When usage more advanced methods of studies, species composition in the same conditions
occurred to be much greater. Such studies were conducted by V.S. Shelestova (1995). Her
review of literature showed a presence in the orchards of the sixty species of the leaf-rollers. By
usage of fifty-seven preparations of synthetic pheromones, it was found out fifty-five species of
the leaf-rollers in orchards of diverse composition, and thirty-five species of the leaf-rollers in
apple-tree orchards. These species were recorded actually in the same years (1985-1991); nearly
all of them occupied the same ecological niche (leaves and fruits), and stayed mainly in
Intermediate density consuming from 34% to 51% of foliage and affecting 1% - 72% of fruits.
Protective measures in these orchards were not practiced. According to the order proposed by
V.S. Shelestova, the following eleven species were most abundant: Adoxophyes orana F.R.,
Archips podana Scop., Acleris variegana Den. u. Schiff., Spilonota ocellana F., Archips
rosana L., Pandemis ribeana Hb., Pandemis heparana Den. u. Schiff., Archips xylosteana L.,
Ptycholoma lecheana L., Laspeyresia pomonella L., and Hedya pruniana Hb.
The current knowledge on the defoliators producing the multispecies infestation spots is
insufficient to give detailed characteristics of their SPs. Nevertheless, it is probable that the
dominating within an outbreak species have SS of the category 5.1.(10.) "To develop selfprotection against natural enemies by behavior traits" with expression "High."
Ya.V. Chugunin (1951) noted peculiarities of multispecies outbreaks of defoliators, which
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were not traced in subsequent studies. This scholar studied development the Crimea Peninsula in
late 1940-ies the outbreak of numerous species, which arose in a result of a junction of separate
infestation spots of Porthetria dispar, Malacosoma neustria L., Euproctis chrysorrhoea L.,
Aporia crataegi L., Leucoma salicis L., Nymphalis polychlorus L., Acrobasis sp. , Lasiocampa
trifolii Schiff., Vanessa sp., Tortrix viridana, and others. This combined infestation spot declined
under effect of pathogens, mainly polyhedrosis. Notably, that the decline was accompanied by
disappearance of forest ants and carabid beetles. The scholar supposed that they died also under
effect of polyhedrosis. So that, outbreaks of defoliators lead to further disturbance of ecosystems.
Also, outbreaks of the defoliators return, when infection of polyhedrosis in ecosystems
disappears.
When studying of outbreaks of defoliators, scholars often direct their attention on most
serious pest species, while its satellites even are not mentioned. This is true for studies of
M.G. Khanislamov and co-workers in Bashkiria, who in a number of articles deal with a single
species – Porthetria dispar. Nevertheless, these outbreaks occurred to be multispecies ones. In
fact, when shaking off two oak-tree crowns, it was found out rich fauna of defoliators. The
numbers of fallen larvae were: on the first tree – Porthetria dispar - 43, the leaf-rollers (species
were not shown) – 56, the spanworms (species were not shown) – 38, on the second tree – 84;
208, and 62, respectively. This fact was reported by M.G. Khanislamov, L.N. Girfanova,
Z.Sh. Yafaeva, and R.K. Stepanova (1962, p. 53).
The next example of the same approach to studies is offered by A.S. Isaev et al. (1983).
When studying of decline of ecosystems of the fir defoliated by Dendrolimus sibiricus, these
scholars were limited by the only species of stem borers affecting this forest – the longhorned
beetle, Monochamus urussovi Fisch.. In reality, the defoliation results in colonization of the fir
by numerous species of stem borers. So, G.O. Krivolutskaya (1962) reported the following
number of species in this complex: the cerambycid (longhorned) beetles – fifteen, buprestid
beetles – two, bark beetles – five, horntale wasps – four, Lamiinae sp. – two, and Serropalpus
barbatus L. – one.
It is relevant to consider the cases of the multispecies outbreaks of defoliators in the context
of the competitive-exclusion principle - the rule or the law Gause (Gause, 1933,1934,1935;
Gause and Witt, 1935).. According to the principle, there exists the trend – every ecological
niche is occupies by one species of consumers. It is supposed that although a number of species
pretend on the same niche, the competition forces out all of them except one most adapted to
given conditions. In a result, "Two species cannot co-exist over an unlimitedly long time in the
same area, if they have identical ecological demands" (Mayr, 1970, Ch. 4).
Considering an ecological niche as first of all a foodstuff resource of a species, the reality
disproves validity of the Gause rule. Indeed, numerous species of defoliators compete with each
other in the conditions of High density, but their fauna does not become poor. In the East
Europe, where Intermediate and High densities of defoliators on Quercus robur take place often,
fauna of the defoliators includes 343 species (Dovnar-Zapol’sky, 1954).
The contradiction between the common presence of multispecies outbreaks of defoliators in
birch-aspen stands in Chelyabinsk Region (Russia) and the rule of Gause attracted attention of
P.M. Rafes and Yu.I. Gninenko (1973); P.M. Rafes (1974). In a result, it has drawn a conclusion
that "…competitive relations among populations of the consumers do not result in a forcing out
each other, but the relations establish interactions, which ensure coexistence of them" (Rafes,
1974, p. 283).
Again stem borers of coniferous tree species provide us by examples, which are disagree with
the rule of Gause. Any sample of bark from a bole of a pine or spruce tree colonized by stem
borers shows a presence up to a dozen species of stem borers - bark beetles, cerambycids,
buprestids, which intensively compete each other in the conditions of High density. Are their
ecological demands identical or not?
As to the producers, in every natural ecosystem, one can see numberless species of grass,
brush, and tree plants competing for limited soil resource.
The rule of Gause, which has been developed on observations of a few species of
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microorganisms in a laboratory at rearing in test-tubes (!), is in a surprising disparity with the
situation in Nature.
At last, it should paid attention on the fact that in the province of SP, the knowledge goes
only its initial steps. Here, the prospects for reflection are wide. This is true both for herbivores
and phytopathogens.
The list of SP for insect herbivores is given in the Table 35.
Table 35. A list of species potential in some taxa within groups of insect herbivores
Groups or guilds of
herbivores
1
Composition of taxa
within the guilds or groups
2
5.1.2.a.(I) Scolytus scolytus,
and S. multistriatus in the
5.1.2.a. Bark beetles species symbiosis with Cerastocystis
with increased
ulmi
aggressiveness
5.1.2.b. The groups of bark
beetle species with diverse
levels of usual
aggressiveness
5.1.2.a.(II) Dendroctonus
micans on Picea orientalis in
the Borzhomi Valley
5.1.2.b.(I) Primary
(Dendroctonus frontalis, D.
ponderosae, D. brevicomis,
Ips typographus,
Blastophagus piniperda)
5.1.2. b.(IIa) Secondary
(Dendroctonus rufipennis,
Scolytus ventralis, some Ips,
Blastophagus, and
Polygraphus species)
5.1.2. b.(IIb) Secondary
(Trypodendron spp.,
Xyleborus spp. Anisandrus
spp.)
5.1.2.b.(IIc) Secondary
(Scolytus ratzeburgi)
5.1.2..b.(III) Tertiary
(Scolytus kirshi, S. saitzevi ,
S. rugulosus , S. japonicus,
S. moravitzi)
5.1.1.3.1.5. Neodiprion
sertifer
Diprion pini
Gilpinia frutetorum
5.1.1.3.1. Openly-
Composition of species potential of the
taxa
3
5.1.2.a.(1.) – Weak (on Ulmus pumila),
Very High (on U. campestris), and
High (on the rest Ulmus species );
5.1.(10.1.) – Moderate or Low;
5.1.(10.2.) – High; 5.1.(10.3.) – High;
5.1.(10.4.) – High
5.1.2.(1.) – High; 5.1.(10.1.) – Moderate;
5.1.(10.2.) – High; 5.1.(10.3.) – High;
5.1.(10.4.) – High
5.1.2.b.(2.) – High; 5.1.(10.1.) – Moderate;
5.1.(10.2.) – High; 5.1.(10.3.) – High;
5.1.(10.3.) - High; 5.1.(17.) – High
5.1.2.(3.) – High; 5.(10.1.) - Moderate;
5.1.(10.2.) – High; 5.1.(10.3.) – High;
5.1.(10.4.) – High; 5.1.(17.) – Moderate
5.1.2.b.(3.) – High; 5.1.(10.1.) – High;
5.1.(10.2), - High; 5.1.(10.3.) - High;
5.1.(10.4.) – High; 5.1.(17.) – High
5.1.2.b.(3.) - High; 5.1.(10.1.)– Weak;
5.1.(10.2.) – High; 5.1.(10.3.) – High; 5.1.
(10.4.) – High; 5.1.(17.) – High
5.1.2.b.(4.) – High; 5.1.(10.1.) – Moderate;
5.1.(10.2.) – Moderate; 5.1.(17.) – High.
5.1.1.3.1.(5.)- High; 5.1.1.3.1.(5.1.) – High
5.1.1.3.1.(5.)- High; 5.1.1.3.1.(5.1.) – High
5.1.1.3.1.(5.)- Moderate; 5.1.1.3.1.(5.1.) –
Weak
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feeding defoliators of
evergreen coniferous
species
5.1.1.3.1.1. Dendrolimus
sibiricus
5.1.1.3.1.(5.) -High; 5.1.1.3.1.(5.2.) –High;
5.1.1.(10.2.) – Weak; 5.1.1.(13.) – High;
5.1.1.(15.4.) – High; 5.1.1.(15.1.) –
Moderate; 5.1.1.(15.2.) – Weak;
5.1.1.(15.3) – High; 5.1.1.(16.)– High;
5.1.(17.) – High
Table 35 (Continuation)
1
2
3
5.1.1.3.1.2. Dendrolimus pini 5.1.1.3.1.(5.) –High; 5.1.1.3.1.(5.2.) –
High; 5.1.(10.2.) - Weak; 5.1.1.(10.3.) –
High; . 5.1.(13.) – Weak; 5.1.1.(15.4.) –
5.1.1.3.1. Openly-feeding
Moderate; 5.1.1.(15.1.) – Weak;
defoliators of evergreen
5.1.1.(15.2.) – Moderate; 5.1.1.(15.4.) –
coniferous species
Moderate; 5.1.(17.) – Moderate
5.1.1.3.1.3. Panolis flammea 5.1.1.3.1.(5.) –High; 5.1.1.3.1. (5.3.) –
High
5.1.1.3.1.4. Bupalus
5.1.1.3.1.(5.) –High; 5.1.1.3.1. (5.3.) –
piniarius
High
5.1.1.3.2. Bud-mining and
5.1.1.3.2.1. Choristoneura
5.1.1.3.2.1.(5.4.) – High; 5.1.(10.1.) –
web-making defoliators of fumiferana in North America High; 5.1.(10.2.) – High; 5.1.(11.) - High;
evergreen coniferous tree
5.1.(15.1.) – Moderate or Low
species
Zeiraphera rufimitrana in
5.1.1.3.2.1.(5.4.) – Weak; there are no
Eurasia
data as to other SSes
5.1.1.1.(6.) - High; 5.1.1.1.(9.) - High;
5.1.(10.1.) and 5.1.(10.2.) – Eggs 5.1.1.1.2.1. Tortrix viridana
High, all larval instars – High, Pupae High, Adults – High; 5.1.(10.4.) –
Moderate 5.1.(11.) – High on the earlyflushing form of the oak and Moderate
on the late flushing form; 5.1.(17.) –
5.1.1.1.2. Early-spring guild
High
of oak defoliators
5.1.1.1.(6.) - High; 5.1.1.1.(9.) – Very
High; 5.1.(10.1.), Eggs, larvae and
5.1.1.1.2.2. Operophthera
pupae – High, Adults –Moderate;
brumata
5.1.(10.2.), Eggs –High, all larval
instars – Moderate, Pupae - Moderate;
5.1.(10.3.) – the last larval instar and
the pupae – Moderate; 5.1.(10.4.) –
Moderate; 5.1.(11.) – High on the early
flushing form of the oak and Moderate
on the late flushing form; 5.1.(17.) –
High
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5.1.1.2.(6.) – High; 5.1.1.2.(7.) – High;
5.1.1.2 (8.) – High; 5.1.1.2. (9.) –
High or Moderate; 5.1.(10.) – High;
5.1.(12.) - ?; 5.1.(13.) – High;
5.1.1.(14.) – High; 5. 1.1 (16.) – High;
5.1.(17.) – Moderate
5.1.1.2.1.1. Zeiraphera
5.1.1.2.(6.) – High; 5.1.1.2.(7.) – High;
diniana in the Engadin Valley 5.1.1.2.(8.) – High; 5.1.1.2. (9.) –
High; 5.1.(10.) – High; 5.1.(12.) –
High; 5.1.(13.) – High; 5.1.1.(14.) –
High; 5.1.1 (16.) – High, 5.(17.) - ?
5.1.1.2.1.1. Zeiraphera
diniana in Asia
5.1.1.2.1. Bud-mining and
web-making defoliators of
the larch
Table 354 (Continuation)
1
5.1.1.1.1.
2
3
5.1.1.1.(6.) – Moderate; 5.1.1.1.(7.) –
Moderate; 5.1.1.1.(8.) – Moderate or
Weak; 5.1.(10.), in eggs – Moderate, in the
5.1.1.1.1.1. Porthetria dispar, first larval instar – High, in other larval
The Main European secadol instars and pupae – Moderate, in adults –
ecotype
High; 5.1.(11.) – Zero; 5.1.(12.) –
Moderate, in some populations - High;
5.1.(13.) – Moderate; 5.1.1.(14.) – High;
5.1.1.(15.1.) and 5.1.1.(15.3.) the first larval
instar – High, in the rest instars - Zero;
5.1.1.(15.5.) - Zero; 5.1.1.(16.) – Weak;
5.1.(17.) – High
5.1.1.1.(6.) – Moderate; 5.1.1.1.(7.) –
Moderate; 5.1.1.1.(8.) – Moderare or
Weak; 5.1.(10.), in eggs – Moderate, in
the first larval instar – High, in the
5.1.1.1.1.1. Porthetria dispar, second and the third larval instars –
The Main European flood
Moderate, in older larval instars and
plane ecotype
pupae – High, in adults – High;
5.1.(11.) – Zero; 5.1.(12.) – Moderate;
5.1.(13.) – Moderate; 5.1.1.(14.) –
High; 5.1.1.(15.1.) and 5.1.1.(15.3.) in
the first larval instar – High, in the rest
instars - Zero; 5.1.1.(15.5) - Zero;
Openly-feeding
5.1.1.(16.) – Weak; 5.(17.) – High
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G.I. Vasechko STABILITY OF TERRESTRIAL ECOSYSTEMS TO PLANT PESTS: AN AXIOMATIC APPROACH.
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defoliators of tree species,
5.1.1.1.1.1. Spring-summer
guild of oak defoliators
5.1.1.1.1.1. Porthetria dispar,
the Bashkirian and TransVolga ecotypes
5.1.1.1.1.1. Porthetria dispar
asiatica
Table 35 (Continuation)
1
5.1.1.1.1. Openly-feeding
defoliators of tree species,
5.1.1.1.1.1. Spring-summer
guild of oak defoliators
5.1.1.1.1. Openly-feeding
defoliators of tree species,
5.1.1.1.1.2. Fall-spring
guild of oak defoliators
2
5.4.5.1. Porthetria dispar in
North America
5.1.1.1.1.2.2. Euproctis
chrysorrhoea
5.1.1.1.(6.) – Moderate; 5.1.1.1.(7.) –
High; 5.1.1.1.(8.)- Moderate or Weak;
5.1.(10.), in eggs – Moderate, in the
first larval instar – High, in other larval
instars and pupae – Moderate, in adults
– Moderate; 5.1.(11.) – Zero; 5.1.(12.)
– Moderate; 5.1.(13.) – High;
5.1.1.(14.) – High; 5.1.1.(15.1.) and
5.1.1.(15.3.) in the first larval instar –
High, in the rest instars – Zero;
5.1.1.(15.5.) – Zero; 5.1.1.(16.) –
Moderate; 5.1.(17.) – High
5.1.1.1.(6.) – Moderate; 5.1.1.1.(7.) – High;
5.1.1.1.(8.) – High; 5.1.(10.), in eggs –
Moderate, in the first larval instar – High,
in other larval instars and pupae –
Moderate, in adults – Moderate; 5.1.(11.) –
Zero; 5.1.(12.) – Weak; 5.1.(13.) – High;
5.1.1.(14.) – Very High; 5.1.1.(15.1.) and
5.1.1.(15.3.) in the first larval instar – High,
in the rest instars – Zero; 5.1.1.(15.5.) –
Zero; 5.1.1.(16.) – High; 5.1.(17.) –
Moderate
3
5.1.1.1.(6.) – Moderate; 5.1.1.1.(7.) –
Moderate; 5.1.1.1.(8.) – Moderate;
5.1.(10.), in eggs – Moderate, in the
first larval instar – High, in the second
and the third larval instars – Moderate,
in older larval instars and pupae –
Moderate, in adults – High; 5.1.(11.) –
Zero; 5.1.(12.) – Moderate; 5.1.(13.) –
Moderate; 5.1.1.(14.) – High;
5.1.1.(15.1.) and 5.1.1.(15.3.) in the
first larval instar – High, in the rest
instars - Zero; 5.1.1.(15.5.) - Zero;
5.1.1.(16.) – Weak; 5.(17.) – High;
5.4.5.(18.) – High
5.1.(10.1.) – Moderate; 5.1.(10.2) in fall
– Weak; 5.1.(10.2.) in spring, summer –
High; 5.1.1.1.(15.1.) – Weak; 5.1.(12) –
Moderate; 5.1.(17.) – High
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5.1.1.1.1. Openly-feeding
defoliators of tree species,
5.1.1.1.1.2.1. Fall-spring
guild of oak defoliators
5.1.1.1.3. Web-worms of
deciduous tree species
5.1.(10.1.) and 5.1.(10.2.)- Eggs –
Moderate, young larvae – High (on
dwarf host-trees), and - Weak (on tall
5.1.1.1.1.2.1. Parocneria host-trees), 5.1.(10.3.) – middle-instar
detrita
larvae – Moderate; 5.1.(10.4.) middle-instar larvae –Weak (in humid
conditions), and - Moderate (in arid
conditions), 5.1.(10.1.) and 5.1.(10.2.) older larvae – Moderate, pupae Moderate; 5.1.(12.) - Weak; 5.1.(17.) –
High
5.1.(10.1.) – High; 5.1.(10.2.) – High;
5.1.1.1.3.1. Hyponomeuta
5.1.(10.4.) – Weak; 5.1.1.(15.1.), in the
malinellus
all larval stage – Weak; 5.1.1.(15.5.) –
Weak; 5.1.1.(15.6.) – Moderate,
5.1.(17.)- High
166