BERMUDAGRASS RESISTANCE TO SPRING DEAD SPOT CAUSED BY OPHIOSPHAERELLA-HERPOTRICHA

Field and greenhouse studies were conducted to evaluate the resistance of seed- and vegetatively propagated bermudagrass entries (Cynodon sp p.) to spring dead spot caused by Ophiosphaerella herpotricha. In Kans as greenhouse studies, O. herpotricha caused root discoloration and ro ot weight reductions in all entries tested. However, in Kansas field p lots, root weight reductions were not different among entries and were not correlated with disease severity ratings. In an inoculated field study in Oklahoma, diseased areas ranged from 47 cm(2) for the entry J ackpot to 262 cm(2) for Poco Verde in 1995, and from 121 to 1,810 cm(2 ) for the entries Guymon and Common in 1996. African bermudagrass (Cyn odon transvaalensis) exhibited the greatest number of live shoots per diseased area in both years, due in part to its greater shoot density, but also indicating greater potential to recover from the disease. Af rican bermudagrass, Guymon, Sundevil, Midlawn, Midfield, Ft. Reno, Mir age, and several experimental seed-propagated entries were most resist ant to spring dead spot, having the lowest diseased area and greatest number of live shoots within diseased areas. In Oklahoma, severity of spring dead spot among bermudagrass entries was correlated with feeeze injury that occurred during the first winter after planting.