Characterization and Pathogenicity ofPythiumSpecies Isolated from Turfgrass with Symptoms of Root and Crown Rot in North Carolina

Thirty-three Pythium spp. were obtained from roots and crowns of bentgrass and other turfgrass species with symptoms of Pythium root and crown rot. The predominant species recovered were P. arrhenomanes, P. catenulatum, P. intermedium, P. oligandrum, P. periilum, P. torulosum, and P. vanterpoolii. Pythium complexes of two or more species from the same tissue sample were common. P. catenulatum and P. torulosum, which made up 58% of the total isolates, were the species most frequently found in combination with other species of Pythium. Pathogenicity of all Pythium species was analyzed in pre- and postemergence inoculation tests. Tests were conducted on seedlings of creeping bentgrass grown in tissue-culture well plates and incubated at 28 C and high relative humidity