Clemson, South Carolina, USA
February 16, 2016
South Carolina watermelon producers now have information they need to make their 2016 crops more profitable with the release of the updated Watermelon Spray Guide for 2016.
Released by the Clemson University Cooperative Extension Service, the guide provides growers with a look at some major diseases of watermelon leaves in the southeastern United States as well as a step-by-step guide to spraying. Information found in the guide comes from a study by Anthony “Tony” Keinath, a Clemson professor of agricultural and environmental sciences, and Gabriel Rennberger, a graduate research assistant. Data was gathered from 21 fields in Bamberg, Barnwell, Beaufort, Clarendon, Colleton and Hampton counties.
Downy mildew begins as dark, irregular spots that spread quickly on watermelon plants’ leaves. Image Credit: Tony Keinath
Two of the major diseases addressed are downy mildew and powdery mildew.
“We found downy mildew in half of the fields surveyed and we found powdery mildew in three-quarters of the fields,” Keinath said. “Both diseases were more widespread than I thought they would be.”
Downy mildew begins as dark, irregular spots that spread quickly on watermelon plants’ leaves. Once infected with downy mildew, diseased leaves immediately curl.
Powdery mildew produces yellow spots on the tops of the leaves of watermelon plants and white powdery mildew on the undersides. Image Credit: Tony Keinath
Powdery mildew produces yellow spots on the tops of leaves and white powdery mildew on the undersides. Both diseases can be detrimental to watermelon crops, Keinath said. Powdery mildew can lead to 43 percent fewer melons, while crops infected with downy mildew produce fruit with less sugar, as well as the possibility of producing fewer melons. Both downy and powdery mildew can lead to sun burning and sun scalding of fruit not shaded by leaves.
Another major disease highlighted in the guide is gummy stem blight. This disease produces large, round, target-shaped spots on the edges of leaves and cankers on the stem.
Spraying fungicides can help lessen the damage of these diseases on watermelon crops.
Gummy stem blight produces large, round, target-shaped spots on the edges of leaves and cankers on the stems of watermelon plants. Image Credit: Tony Keinath
“Some growers think only about the cost of the fungicides and don’t realize the benefits of spraying,” Keinath said. “Also, some growers may think they can’t spray their crops once harvest starts because of fungicide residues. However, as long as growers follow the instructions on fungicide labels, including how much to spray and how many days to wait between spraying and harvesting, there will be no to minimal residues by the time consumers purchase the melons.”
Growers also need to know it is now important to spray their crops during dry as well as wet seasons.
“Some growers may have tried to cut back on spraying during dry periods,” Keinath said. “This may have worked 25 years ago when the main disease was gummy stem blight, but it does not apply today as downy mildew and powdery mildew have become problems on watermelons.”
The Watermelon Spray Guide for 2016 also addresses anthracnose, bacterial fruit blotch, bacterial leaf spots and Cercospora leaf spot. The guide features a step-by-step spraying guide, as well as fungicide programs for spring crops and fall crops. It can be found by going to this link http://bit.ly/1TdcDn6.
The watermelon planting season in South Carolina is from early March to the end of April for the main spring crop. A few plants may be planted in late July for a fall crop. The South Carolina watermelon harvest season is mid-June until Labor Day for the spring crop. The harvest season for the fall crop can go into October.
Species
