Abstract: Turf dollar spot, caused by Clarireedia spp., is one of the most destructive fungal diseases on turf. 6-Pentyl-2H-pyran-2-one (6PP) is a critical antifungal secondary metabolite produced by Trichoderma spp. In order to explore the antifungal activity of 6PP against Clarireedia spp. and its control efficacy to Turf dollar spot, the inhibition activity of 6PP on Clarireedia spp. was measured by mycelial growth rate method, and the protective and curative activities of 6PP against the disease was measured on detached leaves and potted plants. The changes in mycelial structure and activities of stress resistance related enzyme of the pathogens under 6PP treatment were analyzed. The results showed that 6PP had efficient inhibition activity on C. jacksonii and C. monteithiana. The average effective inhibitory medium concentration (EC₅₀) of 6PP to C. monteithiana was 0.37 μg/mL, and the average EC₅₀ value to C. jacksonii was 0.04 μg/mL. After being treated with 6PP, mycelial of both C. jacksonii and C. monteithiana grew abnormally, cell membrane permeability and relative conductivity as well as peroxidated cell membrane increased. The peroxidase (POD) activity of C. jacksonii increased significantly although its pH remained unchanged, while the superoxide dismutase (SOD) activity, pH and exopolysaccharides (EPS) of C. monteithiana increased significantly. The preventive effects of 1 μg/mL 6PP on dollar spot were 91.14% in vitro and 72.21% in pots. 6PP has a significant inhibitory effect on Turf dollar spot and has a good control efficacy on the disease in vitro and in pots. The study revealed the potential of 6PP to be an eco-friendly fungicide preventing Turf dollar spot.