With permanent crops, like grapes, growers know that they may struggle with the same diseases year after year, due to the pathogens that overwinter in the bark of the vine. It is not a matter of if disease is present in the vine, but if weather conditions will be favorable for rapid disease development.

Powdery mildew and Botrytis are two of the most commonly occurring diseases in grapes. When warm temperatures and rain coincide, the overwintering structure of the fungi that remains from the previous year will germinate and release spores resulting in infection of young plant tissue. These diseases can spread very rapidly throughout the canopy if not properly monitored and treated.

The first sign of powdery mildew will appear in early vegetative growth as chlorotic spots on the top of leaves. After the initial infection, the fungus will continuously produce masses of spores for the duration of the growing season. When environmental conditions are favorable, the spore cycle can be as short as 7-10 days. These spores cover the grape leaves and result in the powdery white, or dusty, appearance that gives the disease its name.

Growers and PCAs can keep early-season diseases under control with a well-planned approach to disease management. An application of Pristine^® fungicide at the beginning of the season gives grapes a head start on preventing powdery mildew. It offers excellent disease control with two active ingredients and two modes of action. Applying a fungicide preventatively can provide optimum results because once the damage is done, it’s not reversible. 

“Pristine fungicide deprives fungal cells of their energy source and eliminates the availability of chemical building blocks for synthesis of essential cellular components,” said Katherine Walker, Technical Service Representative, BASF. “It also interferes with cell respiration and the production of energy.”

Season-long control depends on managing the initial infection and protecting new growth. Growers should closely monitor and utilize the powdery mildew risk assessment index from the University of California Integrated Pest Management Program. When the index indicates a high risk of infection, a disease control program should be immediately implemented.

To avoid the potential economic downfall of disease, growers should work with a trusted PCA to put together a season-long plan that addresses the vineyard’s specific disease pressures. Start disease management early, and be flexible with disease management strategies.

Powdery mildew and Botrytis pressure is nothing new to grape growers. It is always good to get a refresher on effective ways to control these diseases, and learn about new tools available to reach maximum yield potential. To learn more, contact your local BASF representative and visit www.GrowSmartGrapes.com for more information on BASF solutions for grape growers.