The Q&A Archives: Squash leaves turn yellow and die

Question: This year my winter squash grew fine until two weeks after they formed runners, when the leaves turned light yellow, got brown around the edges and died. What's wrong? Joe Deneault East Falmouth, MA

Answer: It's probably downy mildew, says Alden Miller, vegetable specialist at the University of Massachusetts Eastern Massachusetts Cooperative Extension Center in Waltham. We usually see this disease in the fall with the onset of cool nights in the 60s and heavy dew. Since you live close to the ocean, however, the cool breezes and high humidity could cause the symptoms to appear earlier. Telltale signs of the disease are yellow blotches on the leaf tops and a white, fuzzy mass on the undersides of leaves. If severe, downy mildew can kill the plant. To control the disease, explains Miller, plant squash in the sunniest area of your garden and provide extra room between plants for good air circulation. Several weeds, especially wild cucumber, also host the disease, so keep the garden weed free. If the infestation is sever, you can spray weekly with a fungicide such as copper or chlorothalonil.

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