How to Manage Pests

Pests in Gardens and Landscapes

Pest identification and confirmation—Downy mildew

Downy mildew growth may initially be confused with 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. Generally, there is more mycelium found on plants infected with powdery mildew than on plants infected with downy mildew. Characteristic of downy mildew are the angular spots found on the leaves.

Downy mildew on cantaloupe leaf
Downy mildew on cantaloupe leaf

Powdery mildew on cucurbit leaves
Powdery mildew on cucurbit leaf

 


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