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Effect of Soil Flooding and Paddy Rice Culture on the Survival of Verticillium dahliae and Incidence of Verticillium Wilt in Cotton. G. S. Pullman, Postgraduate research plant pathologist, Department of Plant Pathology, University of California, Davis 95616; J. E. DeVay, professor, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 71:1285-1289. Accepted for publication 26 March 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1285.

A single rotation with paddy rice controlled Verticillium wilt of cotton for 23 yr and increased lint yields by an average of 31% over 3 yr compared to areas in which cotton was grown continuously. Four years after treatment, soil population densities of Verticillium dahliae were still much lower than the initial populations. In field soil with V. dahliae, paddy rice culture compared to flooding alone reduced the time necessary to eradicate this fungus in both greenhouse and field experiments. Six weeks of soil flooding with or without rice was required before population densities began to decline. After 17 wk under paddy rice, V. dahliae was not detectable, while with flooding alone, 9% of the initial population was still present. Twelve weeks of flooding during the late fall and winter did not reduce soil population densities of V. dahliae or the incidence of Verticillium wilt in a subsequent cotton crop.

Additional keywords: Gossypium hirsutum, soilborne pathogens, biological control, soil anaerobiosis.