Leptosphaerulina australis associated with intensively managed stands of Poa annua and Agrostis palustris

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Leptosphaerulina leaf blight has been sporadically documented affecting turfgrasses. Recently, a Leptosphaerulina species has been seen on diseased turfgrass samples from New England and New York State. In all cases where Leptosphaerulina has been observed in New England, it has been accompanied by a number of other turf pathogens on highly stressed hosts, so its pathogenic potential has been unclear. The purpose of this study was to identify isolates to species, determine their pathogenicity in the greenhouse, and characterize their fungicide sensitivity in vitro in the event that significant pathogenicity was demonstrated. Microscopic observation of spores and culture characteristics indicated that all examined isolates were Leptosphaerulina australis. The optimum temperature for growth was assessed and the relationship between temperature and sporulation was examined. After repeated experiments utilizing several grass species under a variety of environmental conditions, all four isolates examined were determined to be nonpathogenic. Isolates produced pseudothecia on senescent tissue but infection of live tissue was never observed. The fungicide sensitivity assay demonstrated significant variation among isolates. Based on the results of this study and other observational evidence, it is likely that this species is saprobic on senescent turfgrass leaves but not pathogenic. © 2004, Taylor & Francis Group, LLC.

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Canadian Journal of Plant Pathology