Pest identification
and confirmation—Downy mildew
Downy mildew gets its name from the downy masses of spores it produces on the undersides of affected
leaves. These downy growths initially may be confused with those of powdery mildew. However, the two diseases
differ in several important ways. Downy mildew produces spores mostly on the undersides of leaves and
only after rain or very heavy fog. Spores disappear soon after leaves dry out. Powdery mildew does not
require water on the leaf surface for spore formation, and the powdery growth appears on both sides of
leaves. Powdery mildew thrives in warm weather whereas downy mildew is a cool weather disease. Dry, desiccating
winds and clear, warm days inhibit growth and spread of downy mildew.
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Fuzzy
spores on underside of leaf
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