USE OF ELISA AND ISOLATION FOR DETERMINING THE DISTRIBUTION OF RHIZOCTONIA-SOLANI AND OTHER RHIZOCTONIA SPP IN ASYMPTOMATIC CREEPING BENTGRASS

A commercial Rhizoctonia-specific ELISA was compared with isolation on antibiotic-amended water agar for the detection of Rhizoctonia solani and other Rhizoctonia spp. in asymptomatic creeping bentgrass near active brown patch disease centres. A greater number of positive samples were indicated by ELISA than by isolation in tests of foliage and root tissues. Over 75% agreement was found between ELISA and isolation with foliage, but the presence of Rhizoctonia spp. in root tissues could not be confirmed by isolation from any of the ELISA-positive samples. There was poor agreement between the two methods in assays of organic matter from thatch. Greater numbers of thatch samples were positive for Rhizoctonia spp. by isolation than by ELISA. Pathogenic R. solani was found by both methods in asymptomatic foliage as far as 30 cm from the margins of brown patch disease areas. There was a more restricted distribution of the fungus in the thatch. Detection of the fungus in root tissues from asymptomatic areas by ELISA could not be confirmed by isolation.