Cucurbit Downy Mildew Update – July 17, 2009

From: Bob Mulrooney, Extension Plant Pathologist;

So far down mildew has been found in Sussex County in the sentinel plot at the REC only on cucumber. Other detections in the region include southern NJ, MD, and Eastern Shore VA. The forecast on Wednesday indicates that there is a moderate risk of transport from eastern NC into the region on Thursday, July 16. Be sure to include a downy mildew fungicide in your spray program. Check the website often for the latest forecast at

From: Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

● Downy mildew on cucumber has been confirmed in Wicomico, Dorchester, Caroline, and Talbot Counties, MD and in Delaware.

● Downy mildew on zucchini squash in Prince Georges County, MD was confirmed July 10.

● Downy mildew on cantaloupe (muskmelon) was confirmed in Wicomico County, MD on July 14.

At this time targeted spray schedules for downy mildew should be applied on cucumber and cantaloupe (see the article titled Cucurbit Downy Mildew Found on the Eastern Shore of Maryland in WCU 17:17). Squash and pumpkin plantings should be scouted rigorously and treated with a protectant spray schedule (such as weekly applications of chlorothalonil). Once downy mildew is observed on the shore, switch to a targeted spray program.

Watermelons also should be scouted frequently and treated with a protectant fungicide schedule. The last (and closest) report of downy mildew on watermelon was on June 22 in Sampson County, NC. Downy mildew has not been observed on watermelon north of that location. When downy mildew is detected on watermelon in the Mid-Atlantic, a targeted fungicide program that includes one of the following: Presidio, Previcur Flex, Tanos, Gavel, or Curzate is warranted for watermelons.

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