A pair of cucurbit diseases have been observed in South Carolina.
Downy mildew disease was discovered in a research plot at the Coastal Research and Education Center in South Carolina, according to the South Carolina Grower and Clemson Plant Pathologist Tony Keinath.
The disease was found on May 21, though the spores arrived approximately 10 days prior. It infected the popular picking cucumber ‘Gershwin,’ as it had 10 times as much disease as the other susceptible check cultivars.
All conventional and organic cucumbers in the lower half of South Carolina should be sprayed with a recommended fungicide. Applications should be repeated every week until one week before the final harvest.
The resistant cultivar DMR-NY-401 does not need to be sprayed under organic production and can be sprayed with only chlorothalonil or mancozeb in conventional production.
Another disease has been observed as well; this one in watermelon in the Central Savannah River Area. Gummy stem blight was found on five of 23 watermelon samples. The disease starts inside the canopy, and on a healthy crop, the first symptomatic leaves are often hidden by the healthy foliage above them. Proper scouting must be done on foot by walking diagonally across the field, Keinath wrote.
While the field had been sprayed with Miravis Prime, the presence of expanding lesions indicate that no fungicide works 100% and environmental conditions are favorable for the fungus development.
Growers should follow the 2025 Watermelon Fungicide Guide to stay on top of gummy stem blight and other diseases.