Savannah Valley District

Cotton Diseases & Fungicide Trial

Rogan Gibson, Dr. John Mueller, Joe Varn, & Charles Davis

During the 2023 growing season, three cotton fungicide trials throughout the Savannah Valley have been monitored weekly since early July 2023. One trial is at the Edisto Research and Education Center, while the other two are on-farm demonstrations in Allendale and Calhoun Counties. Two significant diseases observed during the growing season were target spot and areolate mildew. Farmers can lose up to 200-250 lbs. of lint if these two diseases’ defoliation is severe enough.

At the Allendale on-farm trial, Agents Rogan Gibson and Joe Varn identified target spot during the 4th week of bloom but found no areolate mildew throughout the season. At this location, a fungicide application was applied during the first week in August, using a generic azoxystrobin and Miravis Top while leaving a check plot unsprayed to compare the two products. Miravis Top was applied to 4 acres of the field at 13.8 oz/ac and azoxystrobin at 10 oz/ac on 30 acres. The carrier volume with both products was 5 gal/ac.

Early season target spot
Late season target spot. Center of spots disintegrated due to age.

While monitoring the separate treatments during the season, there was a noticeable difference in defoliation caused by the target spot. Also noted during the season was that the target spot moved through the plant’s canopy quicker in the 1-acre untreated check plot compared to the treated areas. The trial will be harvested during mid – to – late November and harvest data will be collected to be presented to farmers across the state.

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