P-292 - Influence of cultivar selection and fungicide applications on foliar diseases and yield on Alabama cotton

Areolate mildew (AM; Ramularia spp.) and Target spot (TS; Corynespora cassiicola) are both yield-limiting diseases of cotton (Gossypium spp.), which caused 32,145 and 14,374 bales, respectively, in yield losses across the cotton belt in 2023. AM and TS are managed by fungicide applications and planting tolerant cultivars, but data is limited. Cultivar performance and fungicide efficacy can also vary from year to year and location due to changes in disease pressure and weather. Thus, the goal of this study was to assess the impact of cultivar selection under the influence of fungicide inputs on AM and TS severity and yield across the state of Alabama. From 2021-2024, a factorial set of treatments were arranged as a split plot design with nine cultivars as the main plot and  fungicides (treated vs. nontreated) as the sub-plots in central and south Alabama. DP1646 and DP2127 were the most susceptible to both diseases whereas PHY480 and PHY580 were susceptible to AM and TS, respectively. In contrast, PHY332, PHY400, and DP2020 were the most tolerant to AM and TS; however, ST5091 was also tolerant to AM whereas DP1840 and DP2012 were tolerant to TS. Fungicides only significantly reduced disease severity on susceptible cultivars when compared to nontreated controls. However, highly susceptible cultivars such as DP1646 and DP2127 still had significantly higher yields when compared to other more tolerant cultivars at several locations. This study indicates that tolerant cultivars can be used to provide AM and TS control and reduce economic inputs due to fungicide applications.