Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 15, 1995
Publication Date: N/A
Interpretive Summary: Stem rust is a serious disease in the Willamette Valley of Oregon where tall fescue is grown for seed. The farm value was estimated to be $28 million in 1994. Fungicides are commonly used by grass seed producers to control stem rust and repeated applications are needed to control this disease. Data are lacking from field studies to estimate seed yield losses in tall fescue due to stem rust. Furthermore, nothing is known about year-to-year variation in stem rust occurrence in fields and what effect this has on seed yield. Between 1991 and 1994, a fungicide (propiconazole) was applied to stem rust susceptible or stem rust resistant plants to compare seed yield and disease response. When stem rust was first observed in June, fungicide treatments of susceptible plants provided no increase in seed yield. Seed yield among stem rust resistant plants were similar regardless of fungicide treatment or time of occurrence of the disease. The study documents seed yield losses in tall fescue due to stem rust and emphasizes the need for developing stem rust resistant cultivars and weather-related models to predict stem rust occurrence and development to reduce dependency on fungicides for disease control.
Technical Abstract: Stem rust caused by Puccinia graminis subsp. graminicola is a serious disea tall fescue (Festuca arundinacea) grown for seed in the Willamette Valley o Oregon. Between 1991 and 1994, propiconazole was applied to five stem rust susceptible or five stem rust resistant genotypes to compare seed yield and disease response. When stem rust was observed in mid-May, as in 1992 and 1 1seed yield and 1000 seed weights among stem rust susceptible genotypes wer significantly larger (P>/-0.05) than nontreated controls in three of five propiconazole treated genotypes. When stem rust was not observed until mid as i 1991 and 1993, seed yield and 1000 seed weights among susceptible geno treated with propiconazole were not significantly larger (P<0.05) than nont controls. Seed yield and 1000 seed weights among stem rust resistant genot treated with propiconazole were not significantly different (P=<0.05) from nontreated controls. Dates when stem rust was first observed in stem rust susceptible genotypes and the rate of stem rust development were different year.