BIOLOGY AND CONTROL OF RHIZOCTONIA-SOLANI ON RAPESEED - A REVIEW

Rhizoctonia solani AG2-1 is the principal pathogen causing damping-off and seedling and mature plant root rot (brown girdling root rot) in o ilseed rape and canola (Brassica napus and B. rapa) in western Canada and the United States; AG4 isolates mainly attack adult plants and cau se basal stem rot. Seedling infection by AG2-1 is favoured by cool wea ther at the time of planting, whereas warm weather late in the growing season is more conducive for infection of mature plants by AG4 isolat es. Survey data show that disease development is favoured by high soil moisture, low levels of nitrogen, phosphorus and potassium and high l evels of copper in fine-textured soils. Moderate resistance in condime nt mustard (Sinapis alba) and some other species appears to be genetic ally controlled and should be utilised in breeding programmes. Carboxi n and iprodione in mixtures with insecticide gamma-HCH are recommended in Canada as seed treatments to control damping-off and seedling root rot, but do not control brown girdling root rot.