Deciding whether to apply a fungicide on cotton fields to control foliar diseases is a tough choice. Research shows that fungicides will control such diseases as wet weather blight, cotton leafspots and others, and field trials show a slight yield advantage.
“It’s frustrating,” says Bob Kemerait, University of Georgia Extension specialist. “We know we can control the diseases, but does it make a difference?”
Kemerait discussed cotton diseases and fungicide options during the cotton consultant’s conference at the Beltwide Cotton Conferences last month in New Orleans.
He said fungicides like Quadris or Headline show some yield advantage when applied to control foliar diseases. “But the increase is not statistically significant. Farmers get about 100 pounds per acre advantage. We don’t yet know the potential for fungicide application. What can we afford to apply even if we know we can absolutely control the diseases? We’re trying to come up with better answers. Currently, we’re not recommending fungicide applications.”
He said a 100-pound per acre yield increase, however, could convince farmers to apply fungicides, especially with the recent outbreak of leafspot diseases across the Southeast.
Kemerait said seed treatment for seedling diseases is another matter and farmers typically use at least the base treatment that comes on the seed. That may not be enough for some situations, however. And seed treatments may not provide the residual control farmers can expect from in-furrow fungicide applications.
“Seed treatments have become popular,” he said. “It’s convenient. In-furrow applications have declined.”
Rhizoctonia is the No. 1 cotton seedling disease across the Cotton Belt, Kemerait said. The base seed treatment may not be enough to control the disease. “In hot zones the base treatment is not as effective as the newer seed treatments.”
He said in a worst case scenario, fungicide efficiency may decline. “The choice of product may make a difference and with the extra treatment farmers can expect a better stand and better yield. If growers are going into poor planting conditions and using a lower seeding rate they may need additional protection. ”
He said in-furrow treatments may do as well as or better than seed treatments, “but growers are moving away from those applications.”
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