Mowing Strategies and Dew Removal to Minimize Dollar Spot on Creeping Bentgrass

Abstract

Dollar spot (DS) disease (caused by Sclerotinia homoeocarpa F.T. Bennett) on bentgrass (Agrostis spp.) can be greatly reduced by implementing mowing and other cultural practices that reduce leaf wetness duration (LWD). Field studies were conducted in 2004 and 2005 to discern the effects of dew removal time (mowing at 0400, 1000, or 2200 h), method of dew removal (mowing with sharp or dull mower or squeegee), and frequency of dew removal (daily or alternate days) on the incidence of DS on fairway height (16 mm) creeping bentgrass (Agrostis stolonifera L.). The severity of DS was studied in laboratory experiments with 6, 12, and 18 h LWD. Dollar spot incidence on field test plots was lowest when mowing treatments were conducted at 0400 h. In addition plots mowed at 2200 h had significantly lower DS incidence than plots mowed at 1000 h. Mowing with either a sharp or dull reel mower proved more effective in reducing DS than alternating mowing with a squeegee for dew removal. Dull mower blades were as effective as sharp mower blades in reducing DS in our field studies. Dollar spot incidence was also lower when dew was removed daily than when dew was removed on alternate days. Mowing at 0400 h daily was the most effective treatment for reducing DS on creeping bentgrass plots in both 2004 and 2005. In laboratory experiments, DS lesion size increased as LWD increased. Specifically, disruption of leaf moisture after 6 h of uninterrupted LWD appeared to be most effective in reducing DS lesion diameter.