Application of Propiconazole in Management of Stem Rust in Perennial Ryegrass Grown for Seed. RONALD E. WELTY, Agricultural Research Service, U.S. Department of Agriculture, National Forage Seed Production Research Center, 3450 S.W. Campus Way, Oregon State University, Corvallis 97331-7201. MARK D. AZEVEDO, Agricultural Research Service, U.S. Department of Agriculture, National Forage Seed Production Research Center, 3450 S.W. Campus Way, Oregon State University, Corvallis 97331-7201. Plant Dis. 78:236-240. Accepted for publication 24 November 1993. 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, 1994. DOI: 10.1094/PD-78-0236.

Stem rust caused by Puccinia graminis subsp, graminicola was controlled by propiconazole in perennial ryegrass (Lolium perenne) grown for seed. Between 1986 and 1992, the fungicide was applied up to six times per year to plants in different stages of growth. A two-application treatment (126 a.i./ha) was effective for increasing seed yield and controlling stem rust, with the first application when spikes began to emerge from the boot and the second when spikes were fully emerged. Stem rust was first observed as early as 29 April and as late as 16 July. Seed yields were smaller when stem rust epidemics began in early spring. A threefold to 10-fold increase in seed yield was observed among cultivars treated with propiconazole compared with nontreated controls. Regardless of treatment, cultivars Birdie II and Linn produced greater seed yields than Palmer, Delray, Yorktown II, and Ovation. Significant differences occurred in thousand seed weight and biomass dry weight (seeds and straw) between fungicide treatments and among cultivars.