Answer: The white talcumlike powder is a sure sign of powdery mildew disease. Powdery mildew causes leaf yellowing and eventual dieback on melons and other cucurbits. If leaf injury is severe, it can cause the melons to ripen prematurely and lose flavor. Powdery mildew fungi spread quickest when the humidity is high and temperatures are between 50oF and 90oF. To discourage the disease, plant on sites with good air drainage, give the plants plenty of space, water during the morning only, allow the soil to dryout between waterings and choose resistant melon varieties such as Ambrosia, Classic and Saticoy. For heavy infestations of powdery mildew, sulfur or copper sprays can be applied weekly, starting in July in your area.
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