Preventing and Managing Powdery Mildew on Cucumbers

Second consecutive year: cucumbers start strong, then develop white powdery mildew, brown, and die. Owner seeks prevention and curative options.

Recognition and Timing

Powdery mildew appears as fuzzy white patches on leaf surfaces (usually upper). Causes premature browning and shriveling. In many regions, it arrives late—minimal impact. But early onset requires action.

Fungicide Program

• Start early: Apply at first leaf formation, continue per label.
• Effective products (chlorothalonil-based): Ortho Garden Disease Control, Garden Tech Daconil Concentrate, Hi-Yield Daconil Vegetable & Flower Fungicide.
• Thorough coverage: Spray entire plant, including leaf undersides.

Sanitation

Remove and destroy all crop debris at season end—fungus overwinters on dead tissue. Rotate cucurbits to new locations yearly.

Cultural Suppression

• Space plants for air circulation.
• Avoid overhead watering.
• Select resistant varieties (marked "PM resistant").

Early, consistent spraying plus cleanup breaks the disease cycle.