Inducing Soil Suppression to Cylindrocladium Black Rot of Peanut Through Crop Rotations with Soybean. Jill R. Sidebottom, Former Research Assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Marvin K. Beute, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Plant Dis. 73:679-685. Accepted for publication 17 February 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0679.

Crop rotations involving corn, soybean, and peanut were established in microplots and field plots to determine their effect on Cylindrocladium black rot (CBR) development in peanut. Corn is a nonhost to the pathogen Cylindrocladium crotalariae. Soybean is a host, but may reduce inoculum efficiency of microsclerotia. In the field, cultivar Ransom soybean or Pioneer corn hybrid 3389 planted in alternate years reduced the rate of CBR increase in a partially resistant peanut cultivar, NC 8C. The fastest rate of disease increase was observed in rotations where either corn or soybean was grown 2 yr before and peanut was grown the year immediately before the peanut crop. However, continuous monoculture of peanut resulted in a moderate rate of increase and low CBR incidence after 3 yr. Preplant microsclerotia densities each year in field plots were affected by overwintering conditions and were similar among rotations. In a microplot experiment with similar rotations, CBR severity was not reduced in peanut directly following soybean. The microsclerotia densities were higher following peanut and soybean than following corn and were higher in microplots than in field plots. In other microplot experiments involving peanut genotypes Florigiant and NC 18416, CBR severity was reduced following soybean regardless of inoculum density. Five soybean cultivars, in addition to Ransom, reduced CBR severity in NC 8C peanut, but the effects varied with year. Rotations with soybean also increased populations of Meloidogyne spp., the root-knot nematode, and Sclerotium rolfsii, the causal agent of southern stem rot of peanut. The increases in other pests may reduce the potential gain in yield from soybean and peanut rotations.

Keyword(s): Arachis hypogaea, cropping systems.