Controlling Powdery Mildew on Zucchini and Cucumbers

Powdery mildew appears as white powdery spots on leaves, spread by wind and rain. It weakens plants and reduces yield. Effective treatments include lime sulfur (traditional fungicide) or copper-based fungicidal soap (e.g., Gardens Alive Soap Shield).

Application Tips

• Spray at first sign, covering both leaf surfaces.
• Repeat every 7-10 days.
• Apply in morning or evening, not in hot sun.
• Improve air circulation by spacing plants and pruning.

Prevention

Choose resistant varieties. Water at soil level, not overhead. Rotate crops yearly.

Resource

Ohio State fact sheet: ohioline.osu.edu/hyg-fact/3000/3047.html