By Clint Thompson
Frost and wind damage have been common occurrences across North Florida watermelon fields early in the growing season. Producers may be inclined to protect their crop in the Suwanee Valley from disease buildup by making copper applications.
Bob Hochmuth, UF/IFAS Regional Specialized Extension agent in Live Oak, Florida, cautions growers against such a strategy this early in the season.
“Cucurbit crops in general, including watermelons, are sensitive to high rates of copper. The sensitivity is that it slows them down and stunts the new growth,” Hochmuth said. “I think because after the wind and the frost damage, we want these plants to grow out of that as fast as they can. I’m always worried that copper may make sense on one hand, but I’m always worried about slowing those plants down. Let them get going as quickly as possible, coming out of that damage.
“The reason I even mention copper, a lot of times in weather like we’ve had where you get damage, you can get some bacteria that will move in and that’s where copper would play a good role. The tradeoff on copper is always whether it’s going to help us on bacteria or slow the plants down.”
Hochmuth recommends a fungicide application, specifically chlorothalonil. He also does not recommend additions to the spray tanks of foliar fertilizers or other additives. Fertilizer salts will often lead to more burning than good.
A small fertigation application totaling 1 to 2 pounds per acre of nitrogen makes more sense.