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A Vacuum Collection and Seed Separation Technique for Enumeration of Sclerotia of Claviceps purpurea in Perennial Ryegrass Fields. S. C. Alderman, Research Plant Pathologist, USDA-ARS National Forage Seed Production Research Center, Oregon State University, Corvallis 97331. D. B. Churchill, and D. M. Bilsland. Agricultural Engineer, USDA-ARS National Forage Seed Production Research Center; and Senior Faculty Research Assistant, Bioresouce Engineering Department, Oregon State University, Corvallis 97331. Plant Dis. 77:1020-1022. Accepted for publication 28 June 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, 1993. DOI: 10.1094/PD-77-1020.

A portable electric wet-dry shop vacuum run by a gas-powered generator was used to collect sclerotia of Claviceps purpurea from 1-m2 areas in a commercial field of perennial ryegrass. Sclerotia were separated from soil and straw residue using an air-screen (seed separation) machine, in which samples were partitioned based on particle width and thickness, and terminal velocity. The procedure also was used to determine the number of sclerotia in bales of annual ryegrass straw. Efficiency of recovery of sclerotia using the air-screen machine with known numbers of ergot was 98100%. Recovery by vacuum collection in the field of a known number of sclerotia distributed over surface residue and plant crowns was 83% 4% in areas without soil cracks, 73% 15% in areas with deep soil cracks, and 79% 13% in areas selected at random. In perennial ryegrass with 23% of heads infected (two sclerotia per infected head), 39 sclerotia per square meter of soil surface were recovered.