Abundance of Bacteria, Fungi, and Sclerotinia homoeocarpa in the Thatch and Soil of Golf Courses

Thatch management in turfgrass has been recommended as part of integrated pest management; however, there is limited understanding of the microbial community in thatch. Previous studies on the turfgrass phytobiome mostly focused on the soil; however, culture-based studies have suggested that the thatch layer of golf courses contains higher bacterial and fungal abundances than the soil. In our study, quantitative PCR was used to investigate total abundance of bacteria, fungi, and the turfgrass pathogen, Sclerotinia homoeocarpa (causal agent of dollar spot) in the thatch and soil of three golf courses on two sampling dates. Additionally, we compared the abundance of these organisms among roughs, fairways, and putting greens, which are under different management intensities. Our results demonstrate bacterial abundance was higher in May than in September, but not consistently higher in the thatch or soil among the three golf courses or management areas. Fungi, and specifically S. homoeocarpa, are more abundant in the thatch than in the soil. These results show the necessity for future turfgrass phytobiome studies to analyze both thatch and soil to obtain a complete picture of bacterial and fungal microbial community structure and dynamics on golf courses. Despite the differences in fungicide usage and management inputs, there were no differences in S. homoeocarpa abundance among the three management areas in the soil. S. homoeocarpa abundance was higher in the thatch on the conventional golf course fairway in September. These results may have important practical implications for development of integrated disease management strategies and for understanding the epidemiology of S. homoeocarpa on golf courses.