Dollar spot on bentgrass influenced by displacement of leaf surface moisture, nitrogen, and clipping removal

Dollar spot (Sclerotinia homoeocarpa F.T. Bennett) is a common fungal disease of creeping bentgrass (Agrostis palustris Hudson). Field experiments were conducted to quantify the effects of leaf surface moisture displacement, N fertilization, and collecting or leaving clippings on severity of dollar spot. Tests were conducted on A. palustris cv. Penncross maintained at 0.6 cm (putting green height) and on turf containing A. palustris cv. Penncross and annual bluegrass (Poa annua L.) maintained at 1.1 cm (fairway height). Six mowing treatments, four of which displaced morning leaf surface moisture and three of which collected clippings, were imposed on turf fertilized with 0, 36.6, and 73.2 kg N ha^-1 in 1992 and 1993. Significant reductions of dollar spot after morning mowing or paling treatments, or both, were recorded on turf at both heights of cut and in both years. Maximum reductions of disease due to mowing treatments across all N levels were 81% on fairway turf in 1992 and 53% on putting green turf in 1992. Collecting or leaving clippings did not consistently affect the severity of dollar spot. The effects of N fertilization were significant at various levels in both tests and in both years. Maximum disease reductions comparing 0 and 73.2 kg N ha^-1 were 57% on putting green turf in 1992 and 44% on fairway turf in 1993. There were no consistent interactions in the severity of dollar spot among mowing treatments and N levels.