Factors Affecting Fungicide Performance when Targeting Dollar Spot Disease in Creeping Bentgrass

Abstract

Creeping bentgrass (Agrostis stolonifera) is commonly grown on golf course fairways and dollar spot (Sclerotinia homoeocarpa) is perhaps the most chronically severe disease of bentgrass. Field studies were conducted to: a) determine the influence of simulated rainfall and two mowing timings (AM and PM) on the performance of four fungicides, and b) to assess the effects of two fungicide spray volumes (468 and 935 L water ha-1) and application timings (AM and PM) on dollar spot control in creeping bentgrass. Fungicide effectiveness generally was reduced by simulated rain imposed about 30 minutes after application. Boscalid and chlorothalonil were most and least rain-safe; respectively, and propiconazole and iprodione were intermediate in rain-safeness. Fungicide performance was improved by mowing in the AM prior to fungicide application. A tank-mix of chlorothalonil + propiconazole was unaffected by spray volume or application timing, but the performance of chlorothalonil and propiconazole applied separately was inconclusive.