Grape Downy and Powdery Mildew Control

Symptoms

Two key fungal diseases. Downy mildew shows yellow oily spots on the upper leaf with a white downy growth underneath in wet humid weather, and rotting of flowers and berries. Powdery mildew shows a white powdery coating on leaves, shoots and berries in dry warm conditions, causing berries to crack, scar and fail to develop.

Damage

Both mildews are among the most destructive grape diseases. Downy mildew can destroy leaves and whole bunches in a humid spell, while powdery mildew scars and cracks berries, ruining table and wine quality. Untreated outbreaks can cause very heavy yield and quality loss, especially around flowering and early berry growth.

Organic & cultural control

Train vines on the trellis with good canopy management and leaf thinning so air and light reach the bunches and the canopy dries fast. For powdery mildew, wettable sulphur sprayed every seven to fourteen days during vulnerable periods is a trusted control. Improve drainage to reduce humidity for downy mildew, and remove and destroy infected leaves and mummified berries.

Chemical control

For downy mildew, protectant fungicides such as copper or mancozeb and systemic ones like metalaxyl or dimethomorph are used before and during wet weather. For powdery mildew, sulphur plus triazoles such as hexaconazole or penconazole and other registered actives are rotated to prevent resistance. Always read and follow the label, observe the pre-harvest interval strictly on table grapes, and consult your KVK or agronomist.

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 a well drained airy site and a suitable training system, and manage the canopy by leaf and shoot thinning to lower humidity around bunches. Time pruning and irrigation to avoid leaf wetness during susceptible stages. Follow a planned spray schedule based on weather and crop stage, rotate fungicide groups, and keep the vineyard clean of infected debris.