Occurrence and Populations of Plasmodiophora brassicae in Sediments of Irrigation Water Sources. L. E. Datnoff, Graduate Student, Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061. G. H. Lacy, Associate Professor, Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061, and J. A. Fox, Extension Plant Pathologist, Mississippi State University, P.O. Box 157, Decatur 39327. Plant Dis. 68:200-203. Accepted for publication 29 August 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-200.

Cabbage plants with clubroot were found in seedbeds with no history of cabbage production in the southwestern Virginia counties of Carroll and Patrick. These beds had been irrigated from farm ponds receiving run-off water from Plasmodiophora brassicae-infested fields. Clubbed roots developed on cabbage seedlings planted in farm pond sediments, indicating that P. brassicae was present in the irrigation source sediments. When comparing standard curves of resting spore populations with symptom incidence, estimated sediment populations ranged from none detected to as many as 2 × 10⁷ resting spores per gram of soil.

Keyword(s): Brassica oleracea var. capitata, crucifers.