Downy Mildew of Cucurbits Control

Symptoms

Pale yellow angular spots bounded by the veins appear on the upper surface of leaves. On the lower surface beneath these spots a purplish grey downy fungal growth appears in humid weather, especially in early morning. The spots turn brown, leaves dry and curl, and severe infection defoliates the vine from the older leaves upward.

Damage

Downy mildew is a fast spreading destructive disease of cucumber, gourds and melons in humid and rainy conditions. It can defoliate a vine within days, cutting off photosynthesis so fruits remain small, poorly coloured and few. Losses of 30 to 60 percent or more occur in susceptible crops when weather stays cool, cloudy and wet.

Organic & cultural control

Grow resistant or tolerant varieties and use wider spacing with proper trellising to improve air movement and reduce leaf wetness. Avoid evening irrigation and overhead watering. Remove and destroy infected lower leaves early. Spray a copper based or other approved organic fungicide preventively in humid weather, and keep the field weed free.

Chemical control

Begin protective sprays with a contact fungicide such as mancozeb when weather turns favourable, and for active spread use a recommended systemic or combination fungicide containing actives like metalaxyl plus mancozeb or cymoxanil plus mancozeb as advised. Rotate fungicide groups to avoid resistance. Use only labelled products at the correct dose, follow the pre-harvest interval and consult your KVK or agronomist before spraying.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

Choose resistant varieties and a planting time that avoids long cool wet spells. Train vines on a trellis or stakes, keep wide spacing, ensure good drainage and avoid overhead and evening irrigation. Scout regularly for early angular spots and remove infected leaves, and start preventive sprays before the disease takes hold.