Analysis - view details of type of pest/disease/disorder
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Powdery mildew | deutsch

Symptoms    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.
Impact    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
Control    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).
Hosts   Maple; All tree species; Apple; Beech; European mountain ash; Oak; Ash; Elder; Rose; Horse chestnut;
Affected plant parts    Leaf; Shoot/Twig/Branch;


Powdery mildew: fruiting bodies in various stages of development
Leaf of Fraxinus with Phyllactinia fraxini
Phyllactinia fraxini: fruiting bodies
Leaf of Aesculus hippocastanum with the American Horse chestnut powdery mildew Erysiphe flexuosa (recently spreading over Europe)
Fruiting bodies of Erysiphe flexuosa with characteristic appendices


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