Temporary Depression of Rhizoctonia solani Field Populations by Soil Amendment with Laetisaria arvalis. H. J. Larsen, Research Associate, Department of Plant Pathology, University of Nebraska, Lincoln 68583. M. G. Boosalis and E. D. Kerr, Professors, Department of Plant Pathology, University of Nebraska, Lincoln 68583. Plant Dis. 69:347-350. Accepted for publication 31 October 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-347.

Fall application of Laetisaria arvalis sclerotia to sugar beet field plots naturally infested with Rhizoctonia solani increased L. arvalis and reduced R. solani populations during winter and early spring. Spring application of L. arvalis increased L. arvalis populations throughout the summer and depressed R. solani populations in midsummer although the declines were not statistically significant. In both instances, L. arvalis populations peaked 3 mo after soil treatment and R. solani populations reached a minimum of 40–45% of control plot levels at that time or 1 mo later. Spring application of L. arvalis increased sugar beet survival in August, but neither fall nor spring application reduced sugar beet losses caused by R. solani at harvest.