P-097 - Fungicide Efficacy and Timing for Management of Tar Spot in Corn in Indiana

Tar spot, caused by Phyllachora maydis, is a fungal disease that reduces corn grain yield and quality. Tar spot of corn was first reported in the U.S. in 2015 and has caused significant yield loss in Indiana. Data on optimal application timing of foliar fungicides has been is limited. From 2020 to 2022, corn trials were conducted to assess the effectiveness of different applications timings of the fungicides mefentrifluconazole + pyraclostrobin (M+P) and flutriafol + bixafen (F+B) on tar spot. The products were applied at first detection, V8, tassel/silk (VT/R1), or milk (R3) corn growth stages, with a second application three weeks later (3WAT). Disease severity was measured as the percentage of stromata on ear leaf of five plants in each plot. Tar spot was first detected in the trial in 2020 at VT, in 2021 at V6, and in 2022 at dent (R5). In 2020, both fungicides provided acceptable disease management when applied at first detection and VT/R1 growth stage, and a second application was not needed. In 2021, optimum timing for M+P was a V8 followed by (fb) 3WAT and for F+B at VT fb 3WAT. In 2022, tar spot severity was less than 2% and all applications of M+P reduced disease in all timings, although the application of fungicide was not necessary for yield protection. Fungicide treatments significantly improved canopy greenness in all years, and application M+P increased corn grain yield in 2021. This research provides valuable insights into the optimal timing of fungicides for managing tar spot in corn, contributing to enhancement of disease control strategies.