Reaction of Cotton Cultivars and Breeding Lines to Target Spot in Alabama

Trials were conducted at the Brewton Agricultural Research Unit (BARU) and Prattville Agricultural Research Unit (PARU) to assess the reaction of cotton cultivars as influenced by an umbrella fungicide program to target spot. The experimental design was a factorial arranged in a split plot with the nine cotton cultivars as whole plots and a Priaxor+ Bravo Ultrex umbrella fungicide program as the split plot treatment. At BARU, final defoliation ratings differed by cultivar and fungicide program. Stoneville 6182 GLT suffered greater defoliation than all cultivars except PhytoGen 580 W3FE and Deltapine 1851 B3XF. In contrast, lowest defoliation noted for Deltapine 1646 B2XF was equaled by the remaining cultivars. Final target spot intensity was significantly lower for the fungicide than non-fungicide treated cotton. Open boll counts, which were greater also greater for Deltapine 1646 B2XF than all Stoneville but not the remaining Deltapine and PhytoGen cultivars, were similar for the fungicide and non-fungicide cotton. As indicated by a significant cultivar × fungicide program interaction, seed cotton yield differed by cultivar and fungicide program. For the fungicide-treated cotton, Deltapine 1840 B3XF outyielded all cultivars except Deltapine 1646 B2XF, Deltapine 1851 B3XF, and PhytoGen 350 W3FE. With the non-fungicide cotton, the former cultivar produced greater seed cotton yield than all cultivars except Deltapine 1646 B2XF and Stoneville 5818 GLT. Except for Stoneville 5600 GLT, seed yield for the fungicide and non-fungicide control were similar for all remaining cultivars. For the PARU location, defoliation differed by cotton cultivar. Stoneville 5471 GLT suffered less defoliation compared with all cultivars except for PhytoGen 440 WRF, PhytoGen 480 W3FE, Deltapine 1840 B3XF, and Deltapine 1851 B3XF. Differences in open, unopened, hardlocked, and rotted boll counts were noted between cultivars. Deltapine 1646 B2XF produced greater seed yields than all cultivars except Deltapine 1840 B3XF and Deltapine 1851 B3XF.