Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
Downy mildew on cucumber was confirmed in Dorchester County, MD on Wednesday. The cucumber crop should be protected with a fungicide that targets downy mildew. There are several fungicide options available: see http://extension.udel.edu/ag/vegetable-fruit-resources/commercial-vegetable-production-recommendations/. Orondis and Ranman have performed well on cucurbit downy mildew in Maryland and Delaware and across the southeast. Cantaloupes and other melons should be sprayed with a targeted downy mildew product, also. Watermelon, pumpkin, squash, and other cucurbits should receive a protectant fungicide, but do not need a downy mildew targeted fungicide at this time because we have not yet seen downy mildew on anything but cucumber. Scout your fields aggressively.
Water soaking caused by new infections on cucumber leaf (top) and sporulation (bottom) with downy mildew.