Pest identification
and confirmation—Downy mildew
Downy mildew gets its name from the downy masses of spores it produces on 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. The white sporulation of powdery mildew covers much of both the lower
and upper sides of the leaf. Downy mildews are favored by cool, moist conditions while powdery mildew
are favored by warm, dry conditions. Downy mildew spores are produced on branched stalks that look like
little trees, whereas powdery mildew spores occur in chains on a single stalk. Areas affected with powdery
mildew enlarge in a circular pattern, spreading a white, dusty growth over the whole leaf; there is no
clear veinal delineation as there is in downy mildew infections.
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Spores
of downy mildew
Spores
of powdery mildew
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