How to Manage Pests

Pests in Gardens and Landscapes

Seasonal development and life cycle—Downy mildew

Peronospora parasitica requires cool, moist weather for infection and disease development to take place. The pathogen survives between crops on weed hosts or as resilient oospores in crop residue. Spores are airborne. This disease is most serious on young seedlings; if cotyledons and the first true leaves are severely infected, the young plant may die.

Spores of downy mildew
Spores of downy mildew


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