Symptoms
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Leaves, fruits or shoots with whitish, later darker, mealy large spots or coatings; in the spots yellow, orange and later black dots (fruiting bodies); often, but not always premature shedding of the leaves; maybe mistaken for dust layers.
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Impact
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Powdery mildews are true parasitic ascomycetes and mostly highly host specific. The spores infect young leaves entering them by germination tubes; subsequently they produce superficial mycelia, quickly developing spores in high numbers; other than leaf and needle attacking microfungi powdery mildews are favoured by long lasting warm and dry periods in spring and a wide amplitude of day and night temperatures. Further information (in German):Gehölzkrankheiten in Wort und Bild (TUM Weihenstephan): Acer; Corylus; Quercus; Ribes grossularia
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Control
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Adult trees commonly withstand mildew infestations quite well, young trees may need sometimes control of powdery mildews by fungicides (see official register of Plant Protection).
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Hosts |
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Maple;
All tree species;
Apple;
Beech;
European mountain ash;
Oak;
Ash;
Elder;
Rose;
Horse chestnut;
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Affected plant parts
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Leaf;
Shoot/Twig/Branch;
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