Downy Mildew in Grapes: Early Detection and Control

Downy mildew is one of the most destructive diseases in grape farming. It can destroy an entire vineyard in just a few days if not caught early. The good news is that with regular monitoring and the right treatment, it is completely manageable. Here is what you need to know.

How to Identify Downy Mildew

The first sign of downy mildew is oily yellow spots on the top surface of leaves. Turn the leaf over and you will see white fluffy growth on the underside. This is the fungus producing spores. As the disease progresses the spots turn brown and the leaves dry up and fall. Affected berries turn brown, shrivel, and fall off.

When Does it Spread?

Downy mildew spreads fastest during warm and wet weather. The spores need water on the leaf surface to germinate. That is why the disease is most severe during and just after the monsoon season. Early morning dew can also trigger spread even without rain. Check your vines carefully every day during wet weather.

Treatment and Control

At the first sign of infection, spray Metalaxyl plus Mancozeb at the recommended dose. This combination treats existing infection and protects healthy leaves. Repeat every 7 to 10 days during wet weather. Bordeaux mixture is a traditional and effective preventive spray that many farmers use at the start of the monsoon before disease appears.

Prevention is Better than Cure

Good canopy management is the best prevention. Prune your vines so sunlight and air can reach all parts of the plant. Wet leaves dry faster in good airflow and this reduces disease. Remove and destroy any infected leaves or berries immediately. Never leave infected material on the ground as the spores survive and reinfect the next season.