Rhizoctonia Crown Rot of Canola in Indiana. D. M. Huber, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. E. P. Christmas, L. J. Herr, T. S. McCay-Buis, and R. Baird. Agronomy Department, Purdue University, West Lafayette, IN 47907; Plant Pathology Department, Ohio State University, Wooster 44691; and Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Plant Dis. 76:1251-1253. Accepted for publication 3 August 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-1251.

Dead and declining canola (winter rape) plants during the winter of 1990 had a severe crown (basal stem) rot with varying degrees of cortical necrosis caused by Rhizoctonia solani (cardinal temperatures of 4, 16–24, and 30 C). The fungus was compatible with Rhizoctonia anastomosis group 2 type 1. Aminopeptidase profiles were characteristic of R. solani but distinct from those of several other Rhizoctonia anastomosis groups profiled. Crown tissues were infected by early winter, but root tissues below the crown generally were not infected until midwinter and spring. The base of leaves frequently had a dark brown to black necrotic lesion that was associated with leaf death. Early-seeded plants, which grew extensively in the fall, were more severely infected than late-seeded plants, which were smaller; however, very small plants appeared to be the most susceptible and seldom survived through the winter. Infection of crown tissues appeared to be by direct penetration near the soil surface as well as through leaf scars. A late winter (January) and early spring (March) survey of canola fields in Indiana during 1990, 1991, and 1992 showed a plant kill of 0–100%, depending on the cultivar and seeding date. The winters and early springs of 1990, 1991, and 1992 were cool with abundant moisture. Crown rot was generally more prevalent in wet and poorly drained areas of fields but also was severe on early-seeded canola on sandy soils. This disease will be a limiting factor for production of canola in Indiana and adjacent states. Seeding date, nitrogen use, and cultivar selection may be important considerations in reducing severity of this disease.