Assessment of the Prevalence and Colonization Ability of Sclerotinia homoeocarpa on Commercial Creeping Bentgrass Seed

Sclerotinia homoeocarpa is the causal agent of dollar spot, a disease that causes sunken, straw-colored lesions on turfgrass swards. Management of dollar spot has become complicated due to the development of fungicide resistance, resulting in the need for novel approaches. The source of initial inoculum for this disease is unsure; however, recent research suggests that seed is a possible source of initial inoculum in creeping bentgrass, one of the most commonly used turfgrass species on golf courses. Creeping bentgrass cultivars have exhibited varying levels of susceptibility to S. homoeocarpa. This research aims to address the question of whether turfgrass seed serves as the source of initial inoculum for S. homoeocarpa. Six cultivars of creeping bentgrass, and two lots of each cultivar, were used in this research. To determine if the pathogen is naturally present on seed, seeds were plated on media semi-selective for S. homoeocarpa. Fungal colonies consistent with S. homoeocarpa morphology were subcultured to obtain a pure culture. Identity was confirmed through DNA sequencing and colony morphology. To determine if the fungus can colonize seed, seed aliquots were inoculated with S. homoeocarpa and the rate of infection was determined. Initial replications of these experiments show that S. homoeocarpa is present on seed and there may be a link between cultivar susceptibility and infection rate. If seed is determined to be the source of initial inoculum, research on seed treatments for S. homoeocarpa may reduce the need for repeated fungicide applications to manage dollar spot.