The Q&A Archives: White Powdery Substance on Grapes

Question: Our Reliance grapes have a white powder on them. Stems have noticeable brown marks, and some leaves are turning brown. Is this a disease and what can we do at this time?

Answer: It sounds like your grapes are suffering from either downy or powdery mildew. Unfortunately, most gardeners find it necessary to follow a carefully timed spray program (often beginning early in the season) in addition to following good cultural practices in order to produce a good crop of grapes. You might wish to contact your County Extension for both a positive identification of the problem and suggested controls, including the appropriate schedule and timing for sprays in your area. Their phone number in Cambria County is 472-7986.

In the meantime, be sure to remove and destroy any plant debris from the area during the growing season and in the fall, as well as after pruning. This will help to reduce sources of reinfection from year to year.

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