Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu and Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
Downy mildew was confirmed on seeded cucumbers in Cumberland County, NJ near the city of Vineland. There were no reported downy mildew infections on any transplanted cucurbits in this area. This is the first report of downy mildew on cucurbits in the Mid-Atlantic region this year. Downy mildew has also been increasing in North Carolina the last several weeks. This is a very long leap from NC to NJ if this infection was from air transported spores. Traditionally we can expect downy mildew to arrive here sometime around the 4th of July. DE and MD have sentinel plots for monitoring downy mildew on cucurbits and have been negative for downy so far. These are scouted regularly in addition to reports and samples that we receive from the field. Hopefully we can provide an early warning when it appears here so that timely fungicide applications with downy mildew specific fungicides can be made.
What growers should do:
● Now that downy mildew has been detected in the region growers should be scouting on a daily basis.
● In areas where rainfall has occurred, growers may want to apply targeted fungicides to cucumbers. Tank- mix Presidio, Ranman, or Previcur Flex with a protectant fungicide and alternate sprays with a material with a different mode of action. Because downy mildew has only been found in adjacent states on cucumber, targeted sprays on other cucurbits crops (pumpkin, squash, watermelon, etc.) are not necessary, at this time. Instead scout aggressively and continue a broad-spectrum spray program.
● All abandoned cucumber and summer squash fields should be sprayed with gramoxone or disced under immediately after last harvest to kill the foliage! Abandoned fields left unattended after use will only serve as a source of inoculum for other fields once downy mildew makes its way into our area.
● Please see the 2011 Commercial Vegetable Recommendations Guide for specific fungicide recommendations
● To track the progress of cucurbit downy mildew in the eastern US and to keep up with reports of Downy mildew from other states please visit North Carolina State University’s Cucurbit Downy Mildew Forecasting Center at http://cdm.ipmpipe.org/