Aggressiveness of Three Snow Mold Fungi on Creeping Bentgrass Cultivars under Controlled Environment Conditions

Abstract

Snow molds are the most important winter diseases of turfgrass in the United States and Canada. Eight isolates of three snow mold fungal species (three isolates of Typhula ishikariensis, three of T. incarnata, and two of Microdochium nivale) were collected from infected turfgrasses on golf courses. The isolates were evaluated for their relative aggressiveness on three cultivars (L-93, Penncross, and Providence) of creeping bentgrass (Agrostis palustris) under the same controlled conditions. Four plant ages (15, 19, 23 and 27 week-old plants from germination to inoculation) were evaluated for their susceptibility to the three pathogens and for the recovery of the plants. Regardless of age or cultivar of the host plant, M. nivale was found to be more aggressive and faster to infect and colonize than Typhula species. After three weeks recovery, M. nivale-inoculated plants showed higher disease severity than plants inoculated with the two Typhula species. Plants infected by Typhula species displayed no significant difference in disease severity. As creeping bentgrass plants get older, the severity of disease caused by three snow molds gradually decreases. This effect was observed in all cultivars tested, suggesting expression of age-related resistance as the bentgrass plants matured.