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Efficacy of Chlorine for Decontaminating Water Infested with Resting Spores of Plasmodiophora brassicae. L. E. Datnoff, Former Graduate Student, Virginia Polytechnic Institute and State University, Blacksburg 24061. T. K. Kroll, and G. H. Lacy. Former Graduate Student, and Associate Professor, Virginia Polytechnic Institute and State University, Blacksburg 24061. Plant Dis. 71:734-736. Accepted for publication 2 April 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0734.

Irrigation water artificially infested with 1 106 resting spores of Plasmodiophora brassicae per milliliter was exposed to NaOCl concentrations of 0, 0.2, 2, 20, and 200 mg Cl/L. Resting spores also were exposed to the equivalent of 20 mg Cl/L for intervals of 0, 1, 5, 10, 30, 60, 180, 360, 720, and 1,440 min. Chlorine was effective in reducing the incidence of clubroot of cabbage at concentrations as low as 2 mg Cl/L when exposure time was at least 5 min. In field trials, clubroot incidence was reduced significantly by treatment of infested irrigation water with 200 mg Cl/L compared with the inoculated control; however, treatments with 200 mg Cl/L also significantly reduced plant height, fresh weight, and stand count. More information about chlorination and its influence on plant growth is required before chlorine can be used effectively to control P. brassicae in irrigation water.

Keyword(s): chemical control, irrigation water treatment.