PATHOGENICITY OF RHIZOCTONIA-SOLANI AG-2-2 AND OPHIOSPHAERELLA-HERPOTRICHA ON ZOYSIAGRASS

Rhizoctonia solani AG-2-2 was consistently associated with a large pat ch disease of zoysiagrass in Kansas, Missouri, and Tennessee. In field inoculation tests, patch symptoms developed during both spring and fa ll as the turfgrass was entering or breaking winter dormancy. The fung us infected and colonized leaf sheaths, but not stolons or roots, at 1 0-30 C, with optimal infection at 20-25 C. Rhizoctonia large patch dev elopment was suppressed in summer by thatch temperatures exceeding 30 C. Ophiosphaerella herpotricha was isolated infrequently from diseased zoysiagrass but did cause extensive root discoloration and weight los s in the greenhouse and circular dead patches 1 yr after field inocula tions.