The Q&A Archives: Grape Vines With Strange Growths

Question: We have two grape vines growing on an arbor. They are gowing great and producing fine tasting fruit. The problem is we are see are strange bulbous growths on the vine and leaves. It seems to only be on new growth. We also saw this last year. We cut it off as soon as we see it and the plant seems to be fine. Is this some sort of bacteria or virus? And can we treat it? or do we just keep cutting off what we see?

Answer: It's difficult to diagnose from your description, but your grape vines may be showing damage from the feeding of of erineum mites, or may have symptoms of Downy Mildew. When mites feed on the undersides of leaves, the upper portion of the leaf can take on a blistered look. They don't generally affect the vines, though. Downy Mildew, a fungal disease, can affect both leaves and vines. The most prominent features of this disease are lesions on leaves and stems that look yellowish to reddish-brown, eventually turning to a felt or downy looking spot. You're wise in removing affected plant parts because you're stopping the spread of the problem. For an absolute diagnosis, take a sample of the problem to your local Cooperative Extension office. You'll find friendly, helpful folks at Cornell Cooperative Extension, 246 Griffing Ave., Riverhead 11901-3086. Phone (516) 727-7850.

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