Efficacy and Yield Protection from Developmental Fungicides Compared for the Control of Target Spot in Cotton.

Studies were conducted in 2019 to determine the yield protection and efficacy of developmental fungicides for the control of target spot on Stoneville 6182 GLT and Deltapine 1646 B2XF cotton at the Brewton Agricultural Research Unit (BARU). The experimental design for both studies was a randomized complete block with four (4) replications. The study utilizing Stoneville 6182 GLT but not Deltapine 1646 B2XF was irrigated and both were managed to maximize yield. With the exception of the Priaxor + Bravo WeatherStik umbrella program, the remaining fungicide treatments were applied at the third and fifth week of bloom. Target spot intensity was assessed on a 1 to 10 intensity scale at 7 to 14 day intervals. On Stoneville 6182 GLT, target spot symptoms, first noted on 28 July, intensified into mid-September. Significant differences in defoliation were noted among fungicide programs with the non-fungicide control having the greatest leaf loss. When compared with the non-fungicide control, defoliation levels were lower for the all rates of BAS 75302F (Provysol™) along with Priaxor, Miravis Top alone or tank mixed with Quadris and the Priaxor + Bravo positive control. In contrast, Propulse, Provost Silver, along with both Aproach programs failed to reduce defoliation when compared with the non-fungicide control. On the rainfed Deltapine 1646 B2XF, fungicide applications were initiated after target spot onset. When compared with the non-fungicide control, significant reductions in premature defoliation were obtained with all fungicides except for the Aproach programs and Provost Silver. The low level of defoliation recorded for BAS 75302F was equaled by the Priaxor + Bravo WeatherStik positive control and Priaxor standard. Superior disease control was provided by the two higher compared with lowest rate of BAS 75302F.  Despite significant differences in disease-incited defoliation, similar seed cotton yields were recorded for all fungicide programs.