Seed Yield Responses of Five Selections of Tall FescueSusceptible or Resistant to Stem Rust with or without Propiconazole. Ronald E. Welty, Agricultural Research Service, U.S. Department of Agriculture, NationalForage Seed Production Research Center, Corvallis, OR 97331-7102. Mark D. Azevedo, Agricultural Research Service, U.S. Department of Agriculture, NationalForage Seed Production Research Center, Corvallis, OR 97331-7102. Plant Dis. 80:625. Accepted for publication 28 February 1996. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1996. DOI: 10.1094/PD-80-0625.

Stem rust caused by Puccinia graminis subsp, graminicola is a serious disease of tall fescue (Festuca arundinacea) grown for seed in the Willamette Valley of Oregon. Between 1991 and 1994. propiconazole was applied to five stem rust susceptible and five stem rust resistant selections to compare seed yield and disease response. When stem rust was observed in mid-May of 1992 and 1994, seed yield and 1,000-secd weights among stem rust susceptible selections were significantly larger (P < 0.05) than in nontreated controls in three of five propiconazole-treated selections. Stem rust was not observed until mid-June in 1991 and 1993, and seed yield and 1,000-sced weights among susceptible selections treated with propiconazole were not significantly larger (P < 0.05) than those of nontreated controls. Seed yield and 1,000-seed weights among stem rust resistant selections treated with propiconazole were not significantly different (P < 0.05) from those of nontreated controls. Dates when stem rust was first observed in stem rust susceptible selections and the rate of stem rust development were different each year. This study determined the influence of stem rust on seed yield in selections of tall fescue resistant and susceptible to stem rust and determined year-to-year variation in seasonal occurrence of stem rust and its influence on seed yield.