Effects of Mowing Frequency and Dew Removal On Fungicide Efficacy for Dollar Spot Control.

Dollar spot (Sclerotinia homoeocarpa F.T. Bennett) can be a severe and expensive disease problem on creeping bentgrass (Agrostis stolonifera L.) fairways in the northeastern United States. The objectives of this study were to evaluate the effects of mowing frequency and dew removal on fungicide efficacy for dollar spot control.  In 2009, a factorial experiment involving mowing frequency (2, 4, and 6 d wk^-1), dew removal on days turf was not mowed (dew removed or no dew removed), and fungicides (chlorothalonil, propiconazole, iprodione) was conducted on a ‘Penneagle’ creeping bentgrass fairway.  All mowing and dew removal treatments were performed between 0700 and 0800 daily. Dollar spot was assessed by counting infection centers in each plot. Dew-removal treatments (removal of dew on days turf was not mowed) provided up to 55% fewer dollar spot infection centers when compared to treatments in which dew was not removed.  The 6 d wk^-1 mowing treatment provided up to 44% fewer infection centers when compared with the 4 d wk^-1 treatment, and 57% compared to the 2 d wk^-1 mowing treatment. The dew removal treatment resulted in up to 72% fewer infection centers in iprodione plots compared to iprodione plots receiving mowing treatments only. Results of this experiment indicate that both increased mowing frequency and dew removal improves fungicide efficacy and reduction of dollar spot incidence.