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Relationships Between Inoculum Density of Rhizoctonia solani, Wirestem Incidence and Severity, and Growth of Cabbage. Anthony P. Keinath, Assistant professor, Department of Plant Pathology and Physiology, Clemson University, Coastal Research and Education Center, 2865 Savannah Highway, Charleston, SC 29414-5341; Phytopathology 85:1487-1492. Accepted for publication 12 September 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-1487.

Rhizoctonia solani AG-4 was grown on cornmeal sand and added to nonsterile sandy loam soil at rates of 0, 0.5, 1.0, and 2.0% vol/vol. Ten 2-week-old seedlings of cabbage cv. Gourmet were transplanted individually into infested soil in cells of plug trays. Incidence and severity of wirestem increased nonlinearly (monomolecular model) and fresh plant weight decreased nonlinearly (exponential decay model) as the inoculum density was increased. Experiments to simulate cabbage seedbed conditions were conducted in nonsterile soil in flats in the greenhouse and in fumigated soil in the field. Sclerotia produced on autoclaved green beans were added to soil at 0, 1.25, 12.5, 125, and 1,250 sclerotia/kg. In two greenhouse trials, emergence was reduced significantly at the highest inoculum density. Both incidence of wirestem and area under the disease progress curve increased linearly with the base-ten logarithm of the inoculum density. In field trials in the spring and fall, emergence and plant fresh weight decreased quadratically and incidence of wirestem increased linearly with the base-ten logarithm of the inoculum density.

Additional keywords: Brassica oleracea var. capitata, preemergence damping-off.