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
All contents copyright © 2016 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   /PMG/GARDEN/VEGES/DISEASES/ID/idcudownymildew.html revised: September 20, 2016. Contact webmaster.