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Spatial Pattern of Claviceps purpurea and Gloeotinia temulenta in the Willamette Valley of Oregon. S. C. Alderman, USDA-ARS, Research Plant Pathologist, National Forage Seed Production Research Center, 3450 S. W. Campus Way, Corvallis, OR 97331-7102. Plant Dis. 75:1172-1175. Accepted for publication 20 May 1991. 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, 1991. DOI: 10.1094/PD-75-1172.

Incidence of blind seed, caused by Gloeotinia temulenta, among fields of perennial ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea) grown for seed was determined for three production areas within the Willamette Valley, Oregon, in 1988 and 1989. Incidence in the southern, central, and northern areas of the valley was 32, 21, and 0%, respectively, in 1988 and 15, 7, and 0%, respectively, in 1989. Spatial autocorrelation of blind seed incidence among tall fescue and perennial ryegrass fields in each of the three areas was not detected by means of a join-count technique. Spatial autocorrelation of ergot, caused by Claviceps purpurea, among bentgrass (Agrostis tenuis) and chewing festuca (F. rubra var. commutata) fields grown for seed in the east-central area of the Willamette Valley was not detected in 1988 or 1989. No spatial autocorrelation of ergot incidence was detected in 1988 or 1989 among grasses growing as weeds along roadways and field margins throughout the Willamette Valley. Results of this study suggest that assessment of blind seed could be based on random sampling of fields within each of the production areas and that assessment of ergot could be based on random sampling throughout the Willamette Valley.

Keyword(s): join-count analysis, spatial analysis.