First Report of Choke, Caused by Epichloe typhina, on Orchardgrass in Oregon

Abstract

During July 1997, Epichloe typhina (Pers.:Fr.) Tul. in Tul. & C. Tul., the cause of choke disease, was found in four fields of an unnamed, experimental cultivar of orchardgrass (Dactylis glomerata L.) grown for seed near Halsey, OR. Disease occurrence in each of three fields was estimated by counting choked tillers in about 50 quadrats, 1 × 0.3 m, taken at 30-m intervals along three or four diagonal transects. In two fields, the disease was present in most quadrats (3% tillers infected). In the third field, choke was clustered in two areas, each with 1 to 8% infected tillers. A collection of E. typhina was deposited at the Oregon State University Mycological Herbarium (accession number 56,395). The disease had not been previously observed in commercial cultivars grown for seed in Oregon, with the exception of an infected tiller collected from an orchard-grass seed field during 1996. This is the first report of choke in Oregon on orchardgrass. Choke is an important disease in France, where it reduces seed yields of orchardgrass. Ten Oregon cultivars of orchardgrass were evaluated under field conditions in France in 1993 and 1994 for susceptibility to E. typhina. All cultivars were found susceptible to the disease; incidence of infected tillers ranged from 4 to 11%, with a mean of 7% (G. Sicard and R. E. Welty, unpublished). During 1996, several fragments of stroma of E. typhina were found among seed from a seed lot submitted to the Oregon State University Seed Lab for purity testing. This indicates that stroma may occur as a contaminant with seed, although it is not known if E. typhina would survive with the seed. E. typhina has not been reported to be seed-borne in orchardgrass.