Geographic Distribution, Cultivar Susceptibility, and Field Observations on Bentgrass Dead Spot.

Bentgrass dead spot (BDS) is a disease of creeping bentgrass incited by Ophiosphaerella agrostis. This project was designed to determine the susceptibility of field-grown bentgrass cultivars to BDS and to gather information regarding the geographic distribution and field conditions favoring the disease. In a field cultivar evaluation trial, all major Agrostis spp. used on golf courses, including colonial, creeping, and velvet bentgrasses, were shown to be susceptible to an isolate of O. agrostis. Velvet bentgrass cvs. SR7200 and Bavaria were among the most and least susceptible cultivars, respectively. Among creeping bentgrass cultivars, L-93 generally was the most susceptible and Pennlinks, Penncross, and Crenshaw were among the least susceptible. Although recovery of BDS patches in the autumn was slow, Bardot colonial bentgrass and Crenshaw, Imperial, L-93, and Penn G-6 creeping bentgrasses showed the most rapid recovery prior to winter. Variation in the virulence of isolates and the potential for races of the pathogen, however, may affect cultivar susceptibility. The disease was most commonly found on 1- to 4-year-old golf greens and disease severity declined 1 to 3 years after it first appeared. BDS only was found on sand-based greens, collars, and tees and has not been observed in bentgrass grown on native soil. Between 1998 and 2001, O. agrostis was isolated from diseased leaves, roots, crowns, and stolons of creeping bentgrass and hybrid bermudagrass turf samples received from 13 states. The disease was most severe in sunny and exposed locations, especially on ridges, mounds, and slopes. In the mid-Atlantic region, BDS appeared as early as May and remained active as late as December. The disease was most active in July and August, and usually became inactive with the advent of frost in October.