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Influence of Soil Temperature, Water, and Texture on Thielaviopsis basicola and Black Root Rot of Cotton. C. S. Rothrock, Department of Plant Pathology, University of Arkansas, Fayetteville 72701; Phytopathology 82:1202-1206. Accepted for publication 26 June 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-1202.

The influence of soil temperature, water, and texture on natural populations of Thielaviopsis basicola was examined. The decrease in population of T. basicola in soil averaged 2% per week over all treatments, a rate of reduction much lower than in soil artificially infested with chlamydospores produced in vitro. Survival was significantly lower at soil temperatures of 24 or 28 C than at 16 C. The presence of cotton plants substantially increased soil populations of T. basicola. Increases in soil populations of the pathogen were correlated with disease incidence, disease severity, and the number of infection sites. Disease incidence was lower at 28 C or at a matric potential of 30 J/kg than at the other temperatures or matric potentials examined. Disease severity was lower at 28 C than at 24 or 20 C. Soil texture did not influence T. basicola populations or black root rot.

Additional keywords: Chalara elegans, water potential.