Download Microbial control of Potato Tuber Moth

Microbial control of Potato
Tuber Moth: an overview
Lerry Lacey
Insect Pathology
USDA-ARS
Wapato, WA
Adult
Life-cycle of PTM (right) and
the damage in potato tubers
(above).
Pupa
Damage in
leaves
Damage in
tubers
Larva
Eggs
PTM Natural Enemies
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Predators
– Invertebrate
– Vertebrate
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Parasitoids
– Egg parasites (Trichogrammatidae)
– Larval/pupal parasites (Eulophidae,
Encyrtidae, Braconidae, Ichneumonidae)
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Pathogens
Candidate Microbial
Control Agents
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Virus - PTM granulovirus
Bacteria – Bacillus thuringiensis (BT)
Fungi
– Biofumigant – Muscodor albus
– Typical fungal pathogen – Beauveria bassiana
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Insect Specific Nematodes (Steinernema &
Heterorhabditis species
Virtually Every Life Stage is Susceptible to
One or More Pathogens
Larvae and pupae in soil or tubers
Potential for virus, bacteria,
nematodes and fungus
Larvae in plants – leaf stems and mines
Potential for virus and bacteria
Pheromone
trap used for
survey of PTM
could enable
infection with
fungi or
dissemination
of virus
Bacillus thuringiensis
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Toxin based activity
Commercially produced
Good shelf life, applied with
conventional equipment
Used in field and storage
Specific for insects, safe for
humans and beneficial insects
UV sensitivity - requires repeated
application
Toxin genes have been
incorporated into potato
Potato Tuber
Moth Granulovirus
Healthy and infected
P. operculella
Occlusion bodies of P. operculella
GV 20,000 X .
Initial
granulovirus
development in
PTM larvae
Healthy fat body
Granulovirus-infected fat body
Insect-specific nematodes for control of PTM larvae
and pupae
Symbiotic bacteria in Steinernema carpocapsae
Steinernematid-killed
larva - left
(tan to ocher)
Heterorhabditid-killed
larva - right
(reddish)
Heterorhabditid-killed larvae;
luminescence in dark
Photorhabdus bacteria with
luminescence gene
S. carpocapsae
Nictating IJ
Ambush strategy
Soil surface
S. glaseri or Heterorhabditis sp.
Cruise strategy
Deeper soil profile
As PTM larvae mature
and move from the plant
into the soil to pupate
they will be in an ideal
position to be controlled
using insect-specific
nematodes. Similarly,
nematodes can enter
infested tubers in the
soil.
Effect of Steinernema feltiae on PTM larval mortality in soil
100
Mean % Mortality
80
60
40
20
0
Control
10,000
50,000
S. feltiae infective juveniles/m2
100,000
PTM larva – dissected to show infection with S. feltiae
Potato cull pile
Fungi
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Beauveria bassiana
Metarhizium
anisopliae
Muscodor albus
Biofumigation of PTM with
the Fungus Muscodor albus
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Effect of fungus
concentration
Effect of life stage
Effect of larval age
Muscodor albus formulated on
rye seeds
Effect of Biofumigation with the
Fungus Muscodor albus on Potato
Tuber Moth (15-30 g/ chamber)
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Adults
– 85-91% mortality
Neonate larvae
– 62-73% mortality
Effect of exposure time to Muscodor albus on PTM larval mortality in tubers at 25°C
24
% CO2
18
12
6
0
100
Control
Mean % Mortality
80
M. albus
60
40
20
0
3
7
Exposure time (days)
14
Effect of temperature on PTM larval mortality exposed to Muscodor albus for 7 days
12
% CO2
8
4
0
100
Control
Mean % Mortality
M. albus
80
60
40
20
0
10
15
o
Temperature ( C)
25
Benefits of Microbial
Pesticides
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Effective control
Safe to handle and apply
No pre-harvest interval
Resistance management
Resistance Management
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Tuber moth has rapidly developed resistance to a
wide variety of insecticides
Insect pathogens could provide a break from
continuous insecticide selective pressure due to
completely different modes of action
The various microbial agents each have very
different modes of action
Questions?