Return to Diseases

Powdery mildew (Podosphaera xanthii) affects all cucurbits. Symptoms appear first on leaves that are older or on shaded portions of the plant and appear as talc-like colonies on upper and lower leaf surfaces. As the disease progresses, the entire leaf surface will be colonized by the fungus, and symptoms can develop on stems and fruit. Severely infected leaves become yellow and then necrotic; these leaves die within a short period, which can result in large-scale defoliation. Powdery mildew is most severe after fruit-set and in densely planted fields.

Powdery mildew on upper pumpkin foliage.

(Photo: Kenny Seebold, University of Kentucky)

Powdery mildew on lower pumpkin foliage.

(Photo: Timothy Coolong, University of Kentucky)

Powdery mildew on cucurbit vine.

(Photo: Timothy Coolong, University of Kentucky)

Management:

• Resistant varieties (cucumber, muskmelon, and pumpkin)
• Fungicides

Return to Diseases