An Evaluation of Host Adaptation and Detection Methods for Sclerotinia homoeocarpa, the pathogen causing Dollar Spot of Turfgrass.

Dollar spot of turfgrass, caused by Sclerotinia homoeocarpa F.T. Bennett, is one of the most common and most costly diseases of high input turfgrasses, particularly on golf courses. There has been some research addressing the geographic dispersal and genetic diversity of the pathogen. However, it is unknown whether the same populations of S. homoeocarpa infect both cool and warm season turfgrasses. This is particularly important since the use warm-season turfgrass species, such as bermudagrass, are becoming widespread; and there is the possibility of both types of grasses occurring in the same location within the transition zone of the United States. Therefore, one aspect of this study was to determine the extent at which S. homoeocarpa isolates able to infect and cause disease on cool and warm-season grasses co-inhabit specific locations, the extent to which warm-season isolates have moved north, and the ability of these isolates to infect and/or cause disease on other host types under specific environmental conditions. Furthermore, as molecular detection techniques are increasingly used in various agricultural commodities, the need to apply these techniques to turfgrass diseases would be beneficial to determine inoculum thresholds at which disease occurs, especially to reduce unnecessary fungicide applications. As a result, detection methods based on both conventional and quantitative PCR using the ribosomal internal transcribed spacer (ITS) region have been developed for S. homoeocarpa. The results of these studies pertaining to the incidence of cool and warm-season S. homoeocarpa isolates occurring in the same location in the transition zone of the United States, the phylogentic analysis of these isolates, the ability of such isolates to cross-infect host types, and the results of molecular detection methods to determine the amount of fungal biomass necessary to incite disease are outlined in this presentation.