Effects of crop residues in soil on phymatotrichum root rot of cotton

The effects of cropping pea or barley and the decomposition of their residues on Phymatotrichum root rot of cotton were studied for five years. Little or no changes occurred in pH, content of carbon or moisture in the soil, but there were significant increases in populations of competitive microflora. Best control was obtained in infested soil which was cropped to either pea or barley in winter or in soil which received the higher tonnage of Papago pea plants. Reduction in incidence of root rot may be attributed to premature germination of overwintering propagules making hyphae vulnerable to the chemicals of decomposition and to competition of microflora in the soil.Former Graduate Assistant in Research, Associate Professor, Professor, and Former Professor of Plant Pathology