The extremely hot, dry weather in areas of New Jersey and the region has kept downy mildew in check the past few weeks. To date, cucurbit downy mildew (CDM) has only been detected on cucumber (Cucumis sativus) in the state. It has been found on cucumber and cantaloupe (Cucumis melo) in southeast PA, the eastern shore of Maryland, and in southern VA. Cucurbit downy mildew has also been reported on butternut squash (Cucurbita moschata) on the eastern shore of VA. Further south it has been reported on watermelon (Citrullus lanatus), cucumber, and cantaloupe  in North Carolina. In South Carolina, CDM has been reported on acorn and summer squash (Cucurbita pepo), cucumber, butternut squash, and giant pumpkin. All cucurbit growers are encouraged to scout on a daily basis. Maintenance applications for powdery mildew should already be initiated for all cucurbit crops. Downy mildew specific fungicides should already be incorporated into weekly maintenance applications for cucumber and cantaloupe. Growers of pumpkin, winter and summer squash, and watermelon should remain diligent and scout on a regular basis and begin to consider adding downy mildew specific fungicides into weekly maintenance programs as we head into the fall.

Cucurbit downy mildew was confirmed on cucumber in Caroline County, Maryland on the Eastern Shore on 6/27. This is the first report of cucurbit downy mildew in the mid-Atlantic region this growing season. All cucurbit growers should scout their fields on a regular basis and initiate a protectant fungicide program. Cucumber growers should include downy mildew-specific fungicide(s) in their weekly applications. For more control information on the control of cucurbit downy mildew please see the 2016 Mid-Atlantic Commercial Vegetable Production Recommendations Guide.

Cucurbit downy mildew was reported on watermelon in Dorchester County, Maryland and Sussex County, DE on 7/2.

This is the first report of cucurbit downy mildew in the region to date.  The most recent reports of cucurbit downy mildew on the east coast have been in cucumber and watermelon. There are at least 5 or 6 reported races of downy mildew on cucurbit in the US with each affecting a different set of cucurbit hosts. Unfortunately, very little is known about what races may be present in our region.

All cucurbit growers need to scout on a daily basis and consider adding a downy mildew specific fungicide to their regular maintenance programs. To track the progress of CDM in the US please visit http://cdm.ipmpipe.org/. For more information on the control of cucurbit downy mildew please see the 2015 Commercial Vegetable Production Guide.