Koch, P.L., Kerns, J.P. 2012. Relative resistance of creeping bentgrass cultivars to Sclerotinia homoeocarpa and Typhula incarnata. Online. Applied Turfgrass Science doi: 10.1094/ATS-2012-1022-01-RS.
The primary diseases of creeping bentgrass and annual bluegrass in the Great Lakes region of the United States are dollar spot, Typhula blight, and Microdochium patch. Successful management of these diseases can require ten or more fungicide applications per year. This study was conducted to determine whether spring and fall fungicide applications have a cumulative impact on development of these primary turfgrass diseases relative to spring and fall applications alone. A significant impact may result in reduced disease severity and lower fungicide requirements. Combinations of fungicide applications made in early fall, late fall, early spring, and late spring were evaluated in 2009, 2010, and 2011 in Wisconsin for their ability to manage Microdochium patch, Typhula blight, and dollar spot throughout the year. In general, treatments containing two springtime fungicide applications provided the most significant reductions in dollar spot development into late July of both 2009 and 2010. Treatments containing only one springtime fungicide application also provided a significant reduction in dollar spot into July, while early fall applications provided a minor reduction. Late fall applications did not reduce dollar spot severity but were required for acceptable management of Typhula blight. Springtime fungicide applications delayed dollar spot onset until mid to late July, which could eliminate the need for one or possibly two fungicide applications without sacrificing turfgrass quality. Even this minor reduction in fungicide usage can result in significant financial and environmental benefits for the golf course manager.