Download Main pests of oak forests in South East Europe

MAIN PESTS OF OAK FORESTS IN SOUTH EAST EUROPE
Oaks are trees or shrubs in the genus Quercus (Latin "oak tree"), which includes approximately 600 extant species native to the Northern Hemisphere. Both deciduous and evergreen species are found
extending from cool temperate to tropical latitudes. Quercus petraea, the sessile oak, native to most of Europe, into Anatolia and Iran, is a large deciduous tree up to 20–40 m tall. The leaves are 7–14
cm long and 4–8 cm broad, evenly lobed with five to six lobes on each side, and a 1 cm long petiole. The flowers are catkins, produced in the spring. The fruit is an acorn 2–3 cm long and 1–2 cm
broad, which matures in approximately six months (http://en.wikipedia.org/wiki/Quercus_ petraea) . The health status of individual oak trees is characterized mainly based on defoliation, i.e. the relative
foliage loss of a tree crown compared to that of a fully-leafed, healthy reference tree growing in the same stand and site conditions. Tree crown defoliation is a non-specific damage symptom, normally
connected with various harmful factors, each of which may act separately or together. To determine the effects of single factors on the amount of damage and their importance is usually very difficult. It
is usually impossible to separate the influence of climate change from other harmful factors (insects, pathogens, air pollution) affecting the health status in forest ecosystems.
No defoliation - 0
Figure 1. Natural range (http://www.euforgen.org) of sessile oak
(Quercus petraea) and morphology of its leaves (A), acorns (B) and
buds (http://commons.wikimedia.org/).
A
B
C C
B
1
Moderate defoliation - 2
Main foliage-feeding caterpillars. Caterpillars are the larval stage of moths or butterflies. Many
species feed on leaves of oak trees. Some caterpillars consume entire leaves (Figure 4.A),
others skeletonize them, while some others roll the leaves to form shelters (Figure 4.B). Severe
defoliation can lead to attack by secondary pests and pathogens (e.g. bark and longhorned
beetles, pathogenic fungi).
A
D
D
B
2
2
1
Severe defoliation - 3
Figure 2. Oak defoliation is defined as leaf loss in the assessable crown as compared to a reference tree. Defoliation is
assessed in 5 classes: 0 (0 – 10 % defoliation); 1 ( 11 – 25 % defoliation); 2 (26 – 59 % defoliation); 3 (60 – 99 % defoliation);
4 (100 % defoliation), (Photos: P. Fabianek).
Main pests on acorns and seedlings. Larvae of various insect species can develop in oak
acorns (e.g. acorn weevil, Figure 3.A,B, acorn tortrix, Figure 3,C) and destroy the entire acorn
production. Powdery mildew causes severe injury, altering the appearance of the leaves. It
infects younger leaves and soft shoots, especially the second growth of leaves in summer. Its
severity varies according to the weather conditions in a particular year; optimal conditions for
mildew development are wet summers with high humidity (Figure 3.D).
A
Slight defoliation - 1
5
C
C
66
5
9
Figure 3. Major pests on acorns and seedlings. A: Acorn weevil - beetle (Curculio spp.); B:
Acorn weevil - larva, (Photos: Gy. Csóka); C: Cydia splendana larva, (Photo: Gy. Csóka); D:
Oak powdery mildew (Microsphaera alphitoides), (Photo: S. Mirtchev).
Figure 4. Major pests on oak leaves. A: Gypsy moth (Lymantria dispar), (Photos: F. Lakatos); B:
Green oak moth (Tortrix viridana), (Photos: P. Kapitola and Gy. Csóka); C: Goldafter (Euproctis
chrysorrhoea), (Photos: F. Lakatos and Gy. Csóka).
Oak decline and main pests on trunks: Oak decline is a complex problem caused by a combination of insects, pathogens and other agents (such as droughts) which act together to cause serious
stress to the trees. The first symptom observed on a declining tree is the deterioration of the foliage. Leaves may be smaller than normal, and are often pale green or yellowish. Several factors (e.g.
canker diseases, bark beetles, mistletoes and decay fungi are very important components in the decline process. Canker-causing fungi (Figure 5.A) commonly invade wounds in bark tissues. The
yellow mistletoe (Loranthus europaeus) is considered a hemiparasitic plant because it synthesizes its own chlorophyll but depends on the host (Figure 5.B) for its supply of water and minerals. A large
number of bark and wood inhabiting insects (e.g. bark beetles, Figure 5.C) attack oak trunks. The most damaging forest pathogens from the wood decay group (Figure 5.D,E) are root rot fungi (Figure
5.F), which attack and destroy the tree root system, resulting in growth loss and death of infected trees. Trees with root disease are also more susceptible to attack by pests, especially bark beetles.
A
B
C
C
D
D
EE
EE
F F1 F
F2
F
Figure 5. Major pests and damage on oak branches and trunks. A: Nectria canker (Nectria ditissima), (Photo: S. Mirtchev); B: Yellow mistletoe (Loranthus europaeus), (Photo: S. Mirtchev); C: Oak bark
beetle (Scolytus intricatus), (Photos: F. Lakatos – galleries and M. Jurc – beetle); D: Sulphur polypore (Laetiporus sulphureus), (Photo: C. Young); E: Oak mazegill (Daedalea quercina), (Photo: S.
Mirtchev); F: Honey fungus (Armillaria mellea), [Photos: J. Sevcik – fruit bodies (F1) and S. Mirchev – rhizomorphs (F2)].
For additional information visit
www.fao.org/forestry/pests/en/
This publication has been made possible by the generous support of the Ministry for Foreign Affairs of Finland
Disclaimer
The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether
or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO.
© FAO, 2014v
FAO encourages the use, reproduction and dissemination of material in this information product. Except where otherwise indicated, material may be copied, downloaded and printed for private study, research and teaching purposes, or for use in non-commercial products or services, provided that appropriate acknowledgement of FAO as the source and copyright holder is given and that FAO’s endorsement of users’ views, products or services is not implied
in any way.
All requests for translation and adaptation rights, and for resale and other commercial use rights should be made via www.fao.org/contact-us/licence-request or addressed to [email protected].
FAO information products are available on the FAO website (www.fao.org/publications) and can be purchased through [email protected]