Powdery Mildew of Cucurbits Control

Symptoms

White powdery patches appear first on the upper surface of older leaves and on stems, which spread to cover the whole leaf with a flour like coating. Affected leaves turn yellow, then brown, become brittle and dry up. Under heavy infection the vine is weakened, fruits are small, sunburnt and of poor quality.

Damage

Powdery mildew is one of the commonest diseases of cucurbits and peas, favoured by warm dry days with cool humid nights and unlike many diseases does not need leaf wetness. It reduces leaf area and vine vigour, leading to premature drying, smaller fruits and yield losses of 20 to 50 percent in severe cases.

Organic & cultural control

Grow resistant varieties where available and maintain wide spacing for good air flow. Spray wettable sulphur or a potassium bicarbonate solution at first sign, repeated as needed. Neem oil and diluted cow milk sprays also help check early infection. Remove and destroy heavily infected leaves and avoid excess nitrogen which produces soft susceptible growth.

Chemical control

Wettable sulphur is an effective and economical fungicide for powdery mildew but should be avoided during very hot weather and on sulphur sensitive crops. For heavier infection a recommended systemic fungicide such as a triazole like hexaconazole or a strobilurin may be advised, used in rotation to prevent 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 or tolerant varieties and avoid dense planting. Provide good sunlight and air movement, use balanced fertiliser and avoid excess nitrogen. Scout older leaves regularly for the first white patches and act early, since powdery mildew is much easier to control before it covers the canopy.