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Disease Detection and Losses

Effect of a Seedling Disease Caused by Rhizoctonia solani on Subsequent Growth and Yield of Cotton. E. A. Brown, Graduate Student, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602; S. M. McCarter, Associate Professor, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602. Phytopathology 66:111-115. Accepted for publication 7 August 1975. DOI: 10.1094/Phyto-66-111.

The effect of damage caused by Rhizoctonia solani during the seedling stage on subsequent growth and yield of cotton was determined in greenhouse-, growth chamber-, and field tests. Under greenhouse conditions, damage caused by Rhizoctonia lesions ranged from no significant growth retardation, to a marked reduction in shoot and root growth, and in boll production. Temperature appeared to be a significant factor in the degree of damage observed in greenhouse studies conducted over a 2-year period. In growth chamber experiments, plants damaged by R. solani produced significantly less shoot and root growth than check plants at 19 C, but not at 28 C. Generally, growth differences between infected and check plants were greater in natural field soil than in fumigated field soil. Soil assays of organisms in the natural soil, plus the increased growth and yield of cotton in soil treated with methyl bromide or pentachloronitrobenzene, suggest that soil-borne organisms (particularly R. solani) contributed to marked stunting of plants in natural soil. In the field, plants with Rhizoctonia lesions generally grew as well as check plants, but they produced significantly less seed cotton.