Powdery Mildew on Watermelon Found in South Carolina

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Dr. Anthony Keinath, Vegetable Pathologist at Clemson University Coastal Research & Education Center, has informed us that powdery mildew was found this week on seedless watermelon at the Coastal Research and Education Center in Charleston, SC. Symptoms of yellow and brown spots looked similar to those in Fig. 1. White mildew growth and short chains of clear powdery mildew spores were visible on the leaf underside.


Fig. 1: watermelon infected with powdery mildew. Leaves presented yellow and brown spots. White mildew growth and short chains of clear powdery mildew spores were visible on the leaf underside (Photo credit: Dr. Anthony Keinath, Clemson University Coastal Research & Education Center).

Because powdery mildew can reduce yields of watermelon, and it is still early in the growing season with plenty of time for powdery mildew to develop until harvest, Dr. Keinath recommends that all watermelon growers in South Carolina should apply a fungicide with specific activity against powdery mildew. Recent fungicide trials in South Carolina indicate that fungicides such as Luna Experience, Quintec, or Torino have good efficacy in controlling powdery mildew in watermelon. North Carolina growers should scout for this disease and apply an effective fungicide, especially if infected plants are detected.

If you think you have plants infected please contact your local Extension Agent and send photos and/or physical samples to the Plant Disease and Insect Clinic for confirmation.

See this fact sheet for general information about powdery mildew in cucurbits and effective fungicides according to North Carolina fungicide trials.

See the NCSU Vegetable Pathology Lab website for the latest fungicide trial results.

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