Distribution and Characteristics of the Eastern Filbert Blight Epidemic in Western Oregon. J. N. Pinkerton, USDA-ARS, Research Plant Pathologist, Horticultural Crops Research Laboratory, Corvallis, OR 97330. K. B. Johnson, K. M. Theiling, and J. A. Griesbach. Assistant Professor, Research Assistant, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; and Survey Plant Pathologist, Oregon Department of Agriculture, Salem 97301. Plant Dis. 76:1179-1182. Accepted for publication 25 July 1992. 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, 1992. DOI: 10.1094/PD-76-1179.

In October of 1986, eastern filbert blight (EFB), caused by Anisogramma anomala, was found in a hazelnut (Corylus avellana) orchard located in Oregon’s Willamette Valley. This was the first detection of EFB within Oregon’s principal hazelnut production area. Hazelnut plantings in nine Willamette Valley counties were surveyed in fall and winter during 1986–1990 to determine the prevalence and distribution of the disease. EFB was found at 326 of the 1,207 survey sites. Disease incidence and severity were greatest in the northeastern Willamette Valley. Currently, 30% of Oregon’s hazelnut plantings are affected or in proximity to diseased plantings. An apparent focus of disease was centered 25 km southeast of the location where EFB was first found in Washington State in 1970. Affected orchards were found up to 20 km south and 50 km west of the focus, but disease incidence and severity decreased with distance from the focal center. Patterns of disease distribution within orchards indicate that most local spread of disease occurs to the north and northeast, which is the direction of the prevailing winds that accompany spring rains. It is likely that these meteorologic conditions have slowed dispersal of rain-disseminated ascospores to orchards located south of the infected area.