Fomes fraxinophilus on Green Ash in North Dakota Windbreaks. James A. Walla, Instructor, Department of Plant Pathology, North Dakota State University, Fargo 58105. Jerry W. Riffle, Plant Pathologist, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Forestry Sciences Laboratory, University of Nebraska, Lincoln 68583. Plant Dis. 65:669-670. Accepted for publication 29 December 1980. 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, 1981. DOI: 10.1094/PD-65-669.

Incidence of Fomes fraxinophilus stem decay on green ash in North Dakota Prairie States Forestry Project windbreaks was determined using a 0.9% random sample of windbreaks. A total of 25,558 trees in 30 windbreaks in five counties was examined. Live green ash with sporocarps were found in four of five counties and in 47% of windbreaks examined. Mean incidence of 36- to 43-year-old trees with sporocarps was 0.29 ± 0.07% (0.95 confidence limit). A mean of 5.8 sporocarps per tree was present on 78 infected trees. Nearly all sporocarps were associated with branch stubs on the bole within 3.6 m of the ground. From this survey, we estimate that 8,700 trees, of an estimated population of 3 million living green ash trees in North Dakota, have sporocarps.