Puccinia graminis Development in North America During 1986. A. P. Roelfs, Research Plant Pathologist, Cereal Rust Laboratory, ARS, USDA, University of Minnesota, St. Paul, 55108. D. L. Long. Plant Pathologist, Cereal Rust Laboratory, ARS, USDA, University of Minnesota, St. Paul, 55108. Plant Dis. 71:1089-1093. Accepted for publication 17 July 1987. 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, 1987. DOI: 10.1094/PD-71-1089.

Wheat stem rust was unusually severe in 1986, more so than in any of the last 20 yr. The frequency of virulence/avirulence phenotypes identified in 1986 was similar to other recent years. In contrast, oat stem rust (a similar disease) was less severe than normal, indicating that the favorability of the environment for stem rust development was near normal for both diseases. The more severe wheat stem rust development in the southern Great Plains was due to a severe epidemic in a small area along the Texas Gulf Coast during the winter that generated inoculum that was transported northward. An additional area of overwintering stem rust occurred on susceptible winter wheat cultivars in western North Dakota that resulted in abnormally severe disease in that area.