Survival of Rhizoctonia solani AG-4 in Residual Peanut Shells in Soil. R. E. Baird, Department of Botany and Plant Pathology, Southwest Purdue Agricultural Program, Vincennes, IN 47591. D. K. Bell, D. R. Sumner, B. G. Mullinix, and A. K. Culbreath. Department of Plant Pathology, Statistical and Computer Services, and Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, GA 31793. Plant Dis. 77:973-975. Accepted for publication 31 May 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0973.

The survival of Rhizoctonia solani AG-4 in residual peanut (Arachis hypogaea) shells was studied for 2 yr. Surface sterilized mature peanut pods colonized by R. solani AG-4 and untreated pods were placed separately in fiberglass-mesh bags and buried at 0, 7.6, and 25.4 cm depths in Tifton loamy sand in field microplots. Shells of pods were sampled at 6-mo intervals and assayed on tannic acid-benomyl agar for the recovery of R. solani AG-4 and other soilborne fungi. Recovery of R. solani AG-4 after 6 mo was greater (P ≤ 0.05) from shells of treated pods placed on the soil surface than on those buried in the soil. Survival of R. solani AG-4 from shells at 12 mo was not different (P ≤ 0.05) from those at 6 mo. R. solani AG-4 was isolated from less than 1% of the total shells after 18 and 24 mo. The fungi most commonly associated with untreated shells were species of Fusarium, Gliocladium, Pythium, Trichoderma, and binucleate Rhizoctonia (CAG-3 and CAG-5). Fusarium spp. were recovered at a higher (P ? 0.05) level than other fungi during the last two sampling dates. Fusarium was the most abundant genus recovered at the conclusion of the study. Throughout the investigation, Trichoderma spp. were commonly isolated at a greater (P ≤ 0.05) frequency from treated than from untreated shells and at increased burial depth. The increase of these fungi after 12 mo indicated that the inoculum potential of R. solani AG-4 remaining in the shells was diminishing. Burial of peanut pods 20–25 cm deep with a moldboard plow could effectively reduce the inoculum from the root zone of the following crop.