By Clint Thompson
A ‘significant increase’ in watermelon diseases is expected across the Suwanee Valley region of North Florida following rainfall last weekend.
Bob Hochmuth, University of Florida Institute of Food and Agricultural Sciences Regional Specialized Extension agent in Live Oak, Florida, reported in his weekly email that reports over gummy stem blight and downy mildew should spike after rainfall impacted much of the Southeast.
“I feel like the fungal organisms are there and they’ve just needed that moisture to get things started,” Hochmuth said. “We anticipate that there is going to be a significant increase, especially in gummy stem blight, and probably we also want to be on the lookout for downy mildew. Downy has been pretty heavy in the southern part of the state.”
Gummy Stem Blight
Hochmuth recommended that growers consider a fungicide application of Inspire Super (7-day preharvest interval) or Aprovia Top (0-day preharvest interval) for gummy stem blight. An additional application of Quintec, Rhyme or Procure is recommended for powdery mildew.
Gummy stem blight causes lesions on the leaves and stems and leads to defoliation. The disease favors warm, wet conditions which are expected this week in the North Florida region.
Downy Mildew
For downy mildew management, growers should be ready with Ranman or Orondis Ultra. As those spray materials are narrow in target, producers may want to wait for confirmation in the Suwanee Valley.
Downy mildew can degrade or destroy the plant’s foliage very rapidly. It thrives in a wet, humid environment, and the fungi need the water on plant tissue to germinate and infect the plant.
Under favorable conditions, severe foliar infection can occur and cause the leaves to curl and eventually die. If the leaves are damaged, they cannot protect and shade the fruit. As a result, the watermelons can develop blisters or sunscald.