Vegetables and Herbs

Cucurbit Downy Mildew

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Disease Spotlight 

Cucurbit Downy Mildew (CDM) is a devastating disease of cucumbers, pumpkins, squash, watermelon, cantaloupe. The disease is caused by Pseudoperonospora cubensis, a water mold that favors cool nighttime temperatures (55 to 75 degrees F) along with prolonged periods of high humidity.

Symptoms: Yellow spots are first observed on the upper surface of leaves. As the disease progresses, the spots turn brown. The underside of the spots contains gray spores, which give the spots a downy appearance.

Management: The spores are spread in the air currents and can move large distances in a short period of time. For this reason, early detection and accurate diagnosis are critical to prevent widespread outbreaks of the disease. Although disease management relies heavily on the use of preventative fungicides, disease-resistant or -tolerant varieties of cucumbers, squash and cantaloupes are available. There are no resistant watermelon varieties. Avoid overhead irrigation and select growing sites with full sun exposure. The following resources provide detailed information of managing CDM: LSU AgCenter Louisiana Plant Disease Management Guide and National Sustainable Agriculture Information Service (organic strategies).


 IPM Resources for Vegetables and Herbs


Plant Pathology Disease Identification and Management Series 

8/25/2014 11:42:50 PM
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