Potential for Reduced Fungicide Applications to Control Dollar Spot Using Ultraviolet Light.

Previous research has shown that ultraviolet B (UVB) radiation may limit fungal growth and reduce disease severity caused by Sclerotinia homoeocarpa, the pathogen that is the causal agent of dollar spot disease in turfgrass.  Methods of altering the dose of UV radiation could provide a novel tool for golf course superintendents and sports field managers to manage diseases and reduce reliance on chemical applications.  The objective of this study was to determine if the duration of fungicide efficacy was reduced when UVB radiation was withheld from a turfgrass stand.  Treatments consisted of plots covered with a polystyrene sheet that allowed UVB radiation to pass through (UVB+) and plots with a polystyrene sheet and Mylar film that blocked most UVB radiation (UVB-).  A threshold of three infection centers was set for re-application. When a treatment reached the threshold in any plot, an application of iprodione was applied to all plots within that particular treatment.  The total number of fungicide applications and the average interval between fungicide applications were collected and analyzed.  At this time, both treatments reached the threshold at approximately the same time and have been sprayed once with iprodione.  Preliminary results suggest that little difference is observed in UV+ and UV- plots.  However, until the complete data set can be analyzed once this first season is complete, it is difficult to draw any firm conclusions regarding the impact of UV radiation on fungicide efficacy.