How to Manage Pests

Pests in Gardens and Landscapes

Pest identification and confirmation—Powdery mildew

Powdery mildew is often confused with downy mildew. Both downy mildew and powdery mildew produce whitish collections of spores on the leaf surface, but similarities end there. In powdery mildew the white sporulation covers much of both the lower and upper sides of the leaf; downy mildew spores appear mostly on the undersides of leaves. 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 in downy mildew infections. Powdery mildew thrives in warm weather; downy mildew is a cool-weather disease.

Spores of powdery mildew
Spores of powdery mildew

Spores of downy mildewSpores of downy mildew

Statewide IPM Program, Agriculture and Natural Resources, University of California
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