Yields and Response of Full Season Flex Cotton Varieties to Target Spot Reaction in Alabama

The reaction of cotton varieties to target spot was assessed at two irrigated Alabama sites.  In SW AL, cotton variety was the main plot and fungicide program, which consisted of four applications of Headline SC at 9 fl oz/A, was the split-plot treatment, while a randomized complete block design was used for the C AL cotton variety study.  A significant cotton variety × fungicide interaction were noted at the August 12, August 24, September 1, and September 15 but not July 21 and July 30 rating dates.  Characteristic target spot symptoms, which were first noted on the leaves of Phytogen 499 and Phytogen 487 on July 21, appeared on the remaining five varieties by July 30.  Noticeable defoliation, which was first observed on August 12, rapidly worsened on all varieties.  For the non-fungicide treated controls, equally high defoliation levels were noted for Phytogen 499, Phytogen 487, Stoneville 4946, and Fibermax 1944, while the low defoliation levels recorded for DPL 1538 were matched on Stoneville 6448, DPL 1252, DPL 1137, and Phytogen 575.  Significant reductions in defoliation were obtained with the protective fungicide program on all varieties except for DPL 1137, which had similar defoliation ratings for both the fungicide-treated and non-fungicide treated control.  The impact of the fungicide program on cotton yields will be discussed.  For the C AL study, significant differences in target spot incited-defoliation were noted among full-season flex cotton varieties.  Yields of all varieties will be presented.