Oak powdery mildew
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Oak powdery mildew ( Erysiphe alphitoides ) |
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| Erysiphe alphitoides | ||||||||||||
| Griffon & Maubl. |
The oak powdery mildew ( Erysiphe alphitoides ) is a hose fungus of the order Erysiphales and belongs to the real powdery mildew fungi .
The fungus, presumably introduced from North America, first appeared in Europe in 1907.
The Oak mildew is considered forest pest and mainly affects English oak ( Quercus robur ) and sessile oak ( Quercus petraea ). It is also found on European beech ( Fagus sylvativa ) and sweet chestnut ( Castanea sativa ).
Young leaves are mainly attacked. The most significant damage therefore occurs in tree nurseries and on freshly planted young plants. On old plants, only the St. John's shoot and stick rashes are usually attacked.
Initially, cinnamon-colored spots form on the leaf, which quickly spread. The fungus forms a mycelium on the leaf of its host , from which it sends haustoria into the leaf cells. The white mycelium covers the entire leaf. In addition, conidia form on the mycelium , the appearance of which is reminiscent of white powder. Later the leaf curls up, turns brown and falls off prematurely.
In autumn, small fruiting bodies ( celistothecia ) with a diameter of 0.1 to 0.2 mm form - especially after hot summers.
The fungus usually overwinters as mycelium stored under buds.
Parasites
The powdery mildew parasite Ampelomyces quisqualis parasitizes as a hyperparasite on the oak powdery mildew, but can also live saprobiotically . But it can only be seen under the microscope.
literature
- Fritz Schwerdtfeger : The forest diseases . Paul Parey, Hamburg and Berlin 1981, ISBN 3-490-09116-7
- Hans Otto Schwantes: Biology of the mushrooms. Stuttgart 1996, ISBN 3-8252-1871-6
