Characteristics and Distribution of Propagules ofVerticillium dahliaein Ohio Potato Field Soils and Assessment of Two Assay Methods

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Abstract
Soils from 82 Ohio potato fields were assayed for numbers of viable propagules of V. dahliae by using a wet-sieving technique. About 75% of the samples had .ltoreq. 25 propagules/10 g of air-dried soil, although as many as 172/10 g were found. Propagule size distribution was similar among 24 fields assayed in a 2nd study, with the majority of propagules 38-75 .mu.m in diameter. The distribution of propagules in one naturally infested field was 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 2 techniques, but results with wet-sieving were less variable.