Gummy Stem Blight a Problem for North Florida Watermelon Crop

Clint ThompsonFlorida, Watermelon

By Clint Thompson

North Florida’s watermelon crop continues to be impacted by increased disease pressure, though gummy stem blight remains the most difficult to control.

Photo courtesy of Tucker Price/UGA Extension: Shows gummy stem blight in a watermelon plant.

Bob Hochmuth, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Regional Specialized Extension agent in Live Oak, Florida, reported in his weekly email that gummy stem blight is causing the greatest concern among the many watermelon diseases.

“Downy mildew and powdery mildew are relatively easy to find in some fields. But our spray programs seem to be working much better on downy mildew and powdery mildew,” Hochmuth wrote. “The bottom line is that gummy is appearing to be very difficult this year. This difficulty in ‘running out’ of options points back to the importance early in the season to stay with chlorothalonil (Bravo and others) and mancozeb (Manzate and others) as long as we can. Once we switch away from them too early, we set up the situation for certain groups of chemistries to be ‘used up’ with maximum amounts per season.”

Producers have reported using the maximum rates for both Inspire Super (Group 9 and 3) and Aprovia Top (Group 7 and 3). Since both materials have similar Group 3 chemistries, the only other option for a rotation after these two with at least some level of control of gummy stem blight is Switch.

Hochmuth said if growers intend to keep fields active for an additional two weeks, they should maintain a good fungicide program.