Podosphaera clandestina

Kingdom: Fungi
Phylum: Ascomycota
Class: Leotiomycetes
Subclass: Leotiomycetidae
Order: Erysiphales
Family: Erysiphaceae
Genus: Podosphaera
Species: P. clandestina var.clandestina

 

Powdery mildew is a common disease of tart cherries (Prunus cerasus). It is caused by the ascomycete Podosphaera clandestina. This disease is characterized by a white mass of fungal growth on susceptible tissue. Much of this white mass consists of conidia, which are spread by wind to other new leaves and shoots, causing infection and consequently malformation of leaves, reduced vigor and reduced viability of buds. It also causes uneven ripening of fruits and makes mechanical harvest more difficult.

Podosphaera clandestina overwinters as cleistothecia on the orchard floor, on diseased, fallen leaves and on infected buds. When infected buds expand in the spring, they are overrun by the fungus, which attacks new tissues. Increase of disease depends on temperature and humidity. It is more common when temperatures are between 50 and 780F (10-260 C), and humidity is around 90%, but it can also occur when humidity is low.

Control of disease can be done with use of protectant fungicide on susceptible plants, use of biological fungicides like Serenade, which have a bacterium named Bacillus subtilis as the active ingredient, use of eradicant fungicide at first sign of infection (once disease is spread, control with fungicide becomes difficult), use of Sulfur, and use of cultural practices such as pruning.

Podosphaera clandestina spores

White masses of powdery mildew disease in sour cherry

http://extension.psu.edu/plants/gardening/fphg/stone/diseases/powdery-mildew

http://www.metos.at/tiki/tikiindex.php?page=Podosphaera+clandestina+(Powdery+Mildew)+risk&structure=Disease+models

http://eol.org/pages/6446276/details

https://en.wikipedia.org/wiki/Podosphaera_clandestina_var._clandestina

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