Cotton Variety and Fungicide Evaluation in Tattnall County, Georgia

The use of fungicides on cotton is becoming an increasing trend in Georgia, especially with the prevalence of target spot of cotton, caused by the pathogen Corynespora cassiicola.  Target leaf spot can cause premature defoliation of cotton and drastically reduce yields, depending upon severity.  In 2012, Tattnall County Extension Agents conducted a cotton variety trial evaluating the use of Twinline fungicide.  The trial consisted of 4 cotton varieties, PHY 499, ST 4145, ST 5445, and FM 1944.  Each variety was replicated 6 times in the trial.  With 6 replications of each variety in the trial, 3 replications of each variety were treated with Twinline fungicide at a rate of 8.5 ounces per acre, leaving 3 of the varietal replications untreated.  In this trial, the fungicide applications were applied at late bloom.  Yield and fiber data was taken at harvest to compare the differences between the varieties as well as the treated and untreated plots.  In this trial, the presence of target spot was very low, however, there were some numerical differences among varieties between those that were treated and untreated.  More research needs to be done to evaluate varietal resistance to target spot as well as varietal response to fungicides.