How to Manage Pests

Pests in Gardens and Landscapes

Seasonal development and life cycle—Powdery mildew

All powdery mildew fungi require living plant tissue to grow. Most powdery mildew fungi grow as thin layers of mycelium on the surface of the affected plant part. Spores, which are the primary means of dispersal, make up the bulk of the powdery growth and are produced in chains that can be seen with a hand lens. Spores are carried by the wind to new hosts. Spores are killed and germination is inhibited by free moisture. Moderate temperatures and shady conditions are generally the most favorable for development. Spores are sensitive to extreme heat and direct sunlight.

Spores of powdery mildew
Spores of powdery mildew


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