Cucurbit downy mildew action alert!

Posted: August 19, 2011

Outbreaks on cucumber, cantaloupe, pumpkin are being reported daily in the states surrounding PA.
Symptoms of downy mildew on the upper and lower leaf of pumpkin. Photo: Beth K. Gugino

Symptoms of downy mildew on the upper and lower leaf of pumpkin. Photo: Beth K. Gugino

The unsettled weather pattern has produced an elevated risk for downy mildew spread and development across PA. Additionally outbreaks have been reported on butternut squash, pumpkin and mixed gourds in northern New Jersey and on cantaloupe in Maryland, Ohio and unofficially in PA. At this time it is highly recommended that downy mildew specific fungicides be incorporated into fungicide programs for all cucurbit crops. See the 2011 Pennsylvania Commercial Vegetable Production Recommendations for a list of recommended fungicides or the 2011 FRAC Guidelindes for cucurbit downy and powdery mildew (

Please visit the Cucurbit Downy Mildew Forecasting website ( for the latest list of disease outbreak locations and forecasts. This information is updated by the end of the day on Monday, Wednesday and Fridays.

Confirmed reports from sentinel plots, commercial fields and home gardens are used to develop the forecasts and assign risk levels that are used to define the potential for disease development. You can help as well by reporting any suspected cases of cucurbit downy mildew to your local Penn State Cooperative Extension office and sending or bringing a sample (overnight delivery) for confirmation to Beth Gugino, Department of Plant Pathology, 219 Buckhout Lab, University Park, PA 16802. We will examine the sample under a microscope and look for the characteristic downy mildew spores.