Evaluate Fungicide Efficacy to Control Dollar Spot When Applied with Various Adjuvants on a Creeping Bentgrass Golf Tee, 2023

Dollar spot, caused by Clarireedia jacksonii, is a chronic fungal disease of creeping bentgrass in cool, humid environments in the United States. In closely mown golf playing surfaces, symptoms include small, circular, sunken spots of blighted turf that eventually coalesce if left untreated. This report evaluates the efficacy of fungicides applied with or without adjuvants to control dollar spot. A study was conducted on a mature creeping bentgrass, Agrostis stolonifera, driving range tee at North Shore Country Club in Glenview, IL. Area under the disease progress curve (AUDPC) analysis of 14 rating dates found two 28-day applications of the acropetal penetrant fungicide Chipco GT was not influenced by the addition of adjuvants. In contrast, the contact fungicide Daconil Action with the addition of adjuvants saw a trend of less dollar spot. Overall, adjuvants did not improve dollar spot control versus Daconil Action alone, but their addition did increase the likelihood that dollar spot severity would not exceed the study's acceptable threshold of 10%. Certain adjuvants can help golf course superintendents extend spray intervals of contact site-of-action fungicides while maintaining acceptable dollar spot thresholds in areas such as golf tees.