ALBANY — Cucurbit downy mildew (CDM) was confirmed 6/28 in southern New Jersey (Salem County), southeastern Michigan (Monroe County) and north central Ohio (Wayne County) on cucumbers and on 6/27 in southern Ontario (Essex County) on cucumber and cantaloupe. CDM spores spread on air currents, so the storms forecast for much of the region through the July 1 weekend run the risk of bringing the pathogen to New York. In order for CDM to infect plants, leaves must be wet for several hours, so any cultural and irrigation practices to reduce leaf wetness should be used. Cucumbers are at the highest risk of infection at this time.
All cucurbit growers should carefully scout their crops, especially after the forecasted storms through the July 1 weekend, that can carry CDM spores, for CDM symptoms. More information on how to identify CDM symptoms can be found at Veg MD here. You can track the reports of CDM outbreaks at http://cdm.ipmpipe.org/. We recommend that conventional growers only apply protectant fungicides, such as those with active ingredients chlorothalonil and mancozeb, now. Organic growers can apply copper products, but run the risk of causing foliar burning on sensitive cucurbits, especially if applied during warm sunny weather.
We will continue to monitor the spread of CDM in the region and send another alert when it is confirmed in Eastern New York along with targeted fungicide recommendations as the risk of infection increases.
–CCE Eastern NY Commercial Horticulture Program
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