Identifying and Controlling Powdery Mildew on Squash and Cucumbers

What Is Powdery Mildew?

A common fungal disease, powdery mildew appears as white, powdery spots on leaves of cucumbers, squash, zucchini, and melons. Spores spread via wind and rain splash. While rarely fatal, heavy infections cause premature leaf drop and reduced yields.

Effective Treatments

• Lime sulfur — broad‑spectrum fungicide; apply at first sign.
• Copper‑based fungicides — e.g., Gardens Alive's Soap Shield (copper + soap).
• Fungicidal soaps — good for early, light infections.

Key: Spray immediately when you see the first white patches. Once the fungus covers large leaf areas, control becomes difficult.

Prevention Strategies

• Space plants for good air circulation.
• Water at soil level (drip irrigation), not overhead.
• Choose resistant varieties when available.
• Rotate crops — avoid planting cucurbits in the same spot year after year.
• Remove and destroy severely infected leaves.

Product Resource

Gardens Alive Soap Shield (copper fungicide)