VIEW ARTICLE

Ecology and Epidemiology

Characteristics and Distribution of Propagules of Verticillium dahliae in Ohio Potato Field Soils and Assessment of Two Assay Methods. V. L. Smith, Former graduate student, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691, Present address of senior author: Department of Plant Pathology, North Carolina State University, Raleigh 27650; R. C. Rowe, associate professor, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 74:553-556. Accepted for publication 20 January 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-553.

Soils from 82 Ohio potato fields were assayed for numbers of viable propagules of Verticillium dahliae by using a wet-sieving technique. About 75% of the samples had less than or equal to ?25 propagules per 10 g of air-dried soil, although as many as 172 per 10 g were found. Propagule size distribution was similar among 24 fields assayed in a second study, with the majority of propagules 38- 75 μm in diameter. The distribution of propagules in one naturally infested field was found to be nonrandom. Numbers of viable propagules in air-dried field soil declined with increasing time of storage at room temperature. The wet-sieving technique and the Anderson Air Sampler were compared for effectiveness of propagule recovery from soils containing low numbers of propagules. There were no significant differences in propagule recovery between the two techniques, but results with wet-sieving were less variable.