Optimizing liquid‐applied iron sulfate rate and application interval for dollar spot suppression on golf course fairways

Abstract Iron sulfate applications reduce dollar spot severity on golf course turfgrass, but further optimizing the use of iron sulfate may increase efficacy and encourage more widespread adoption by golf course superintendents. Three iron sulfate rates (9, 18, 36 kg ha −1 ), two application intervals (7 and 14 days), three water volumes (306, 612, and 1223 L ha −1 ), and combinations with fertilizer and fungicide products were evaluated at field locations in Madison, WI, Bloomington, MN, and Blacksburg, VA, in 2018 and 2019. Iron sulfate rate decreased dollar spot at all locations in a dose‐dependent manner, and 7‐day applications were more efficacious than 14‐day applications. Water volume had no impact on disease severity at any location and combining iron sulfate with fertilizer had minimal impact as well. These results demonstrate improved iron sulfate strategies for dollar spot management and can be implemented by golf course superintendents in areas where fungicide resistance and fungicide regulations limit the use of traditional fungicides.