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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #97875
Title: GEOGRAPHICAL DISTRIBUTION AND INCIDENCE OF ORCHARDGRASS CHOKE, CAUSED BY EPICHLOE TYPHINA, IN OREGON

Author
item Pfender, William
item Alderman, Stephen

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: A 1998 survey was conducted in the Willamette Valley of Oregon, the major U.S. production area for orchardgrass seed, to determine the extent and severity of orchardgrass choke disease. This disease is a severe constraint to orchardgrass seed production in other parts of the world, but was unknown in Oregon prior to 1997. Thirty-seven fields, representing 27 cultivars and the geographical extent of production in the Willamette Valley, were surveyed. Choke was found in 26 (70%) of the fields, and the amount of disease ranged from <0.05 to 28% tillers affected. In a survey of 16 fields located within 3.5 km of the 1997 discovery, choke was found in 14 fields, of which 3 had more than 20% disease. Increase in the amount of disease between 1997 and 1998 was as much as 3-fold. One year after its presence was confirmed in Oregon, choke disease of orchardgrass is well-established throughout the orchardgrass seed producing region at damaging levels and is apparently able to increase and spread under the prevailing climatic and cultural conditions.

Technical Abstract: A 1998 survey was conducted in the Willamette Valley of Oregon, the major U.S. production area for orchardgrass seed, to determine the extent and severity of orchardgrass choke disease in Dactylis glomerata. This disease was unknown in Oregon prior to 1997; it is a severe constraint to orchardgrass seed production in other parts of the world. In 37 randomly selected fields, representing 6% of the acreage and nearly the full geographical extent of orchardgrass produced for seed in Oregon, choke was found in 26 (70%) of the fields and in 5 of 6 counties. Where present, disease incidence ranged from <0.05% to 28% tillers affected. Five of the 37 fields had only trace levels of the disease, but four of the fields, representing 3 counties, had incidences >10%. A systematic survey of 16 fields within a 3.5-km radius of the 1997 discovery showed 14 affected fields, of which 3 had incidences >20%. Increase in disease incidence between 1997 and 1998 ranged from 2.2- to 2.3-fold in the three fields where disease increase was measured. One year after its presence was confirmed in Oregon, choke disease of orchardgrass is well-established throughout the orchardgrass seed producing region at damaging levels and is apparently able to increase and spread under the prevailing climatic and cultural conditions.