VIEW ARTICLE

Disease Control and Pest Management

Soil Solarization and Thermal Death: A Logarithmic Relationship Between Time and Temperature for Four Soilborne Plant Pathogens. G. S. Pullman, Postgraduate research plant pathologist, Department of Plant Pathology, University of California, Davis 95616; J. E. DeVay(2), and R. H. Garber(3). (2)Professor, Department of Plant Pathology, University of California, Davis 95616; (3)Research plant pathologist, USDA, SEA-AR, Cotton Research Station, Shafter, CA 93263. Phytopathology 71:959-964. Accepted for publication 17 January 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-959.

Temperatures of 37–50 C for different time periods were lethal to mycelia, spores, and resting structures of Verticillium dahliae, Pythium ultimum, and Thielaviopsis basicola on an agar medium. At 37 C, exposure times for an LD₉₀ were 28.8, 25.8, 17.9, and 33.5 days, respectively, for V. dahliae (strains T9 and SS4), P. ultimum, and T. basicola. At 50 C, LD₉₀ values were 23, 27, 33, and 68 min, respectively, for the same fungi. Field-produced propagules of V. dahliae in moist field soil also were killed when incubated at temperatures of 37–50 C for specific time periods. Temperatures of 39 and 50 C killed cultures of Rhizoctonia solani on agar medium in 14 days and 10 min, respectively. A linear relationship existed between logarithms of times required to kill 90% of the propagules when plotted against temperatures. This linear relationship was observed for populations of fungi in both agar and soil tests. These fungi were killed in field soils solarized for the necessary time periods. The exposure times and temperatures necessary to kill these fungi are useful for evaluating the progress of soil solarization under field conditions.