Downy mildew

Downy mildew is a group of plant diseases caused by oomycetes, typically marked by yellowish leaf patches and downy growth on leaf undersides.

Oomycetes: Oomycetes are fungus-like stramenopile organisms that include many plant pathogens. These organisms, rather than true fungi, cause downy mildew.
Grape downy mildew: Grape downy mildew is a disease of grapevines caused by the oomycete Plasmopara viticola. It is a major crop-specific form of downy mildew with distinctive leaf and fruit symptoms.
Plant disease diagnosis: Plant disease diagnosis identifies the cause of abnormal symptoms in plants. Yellow leaf patches and underside growth must be distinguished from look-alike diseases.
Powdery mildew: Powdery mildew is a group of plant diseases caused by true fungi that form powdery surface growth. Its surface coating and fungal causes distinguish it from oomycete downy mildew.
Sporangium: A sporangium is a structure in which spores are formed or contained. Downy mildew oomycetes produce sporangia that help disperse infection.
Potato late blight: Potato late blight is a destructive disease caused by the oomycete Phytophthora infestans. It is another oomycete disease, but its name and characteristic symptoms differ from downy mildew.
Plant disease resistance: Plant disease resistance is a plant’s ability to limit infection or damage by a pathogen. Resistant cultivars can reduce the impact of downy mildew in crops.
Botrytis cinerea: Botrytis cinerea is a fungus that causes gray mold on many plants and stored produce. Gray mold can resemble downy mildew damage but is caused by a true fungus.
Zoospore: A zoospore is a motile, flagellated spore produced by certain algae and fungus-like organisms. Many downy mildew pathogens release swimming zoospores that reach susceptible plant tissue.
Cucurbit downy mildew: Cucurbit downy mildew is a disease of cucurbit crops caused by Pseudoperonospora cubensis. Its angular leaf lesions are a familiar crop-specific expression of downy mildew.

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