Rhizoctonia Disease

a disease occurring primarily on the roots and the basal portion of the stem in many plants. The disease is caused by soil fungi of the genus Rhizoctonia of the class Basidiomycetes. Manifestations include the appearance of lead-gray spots with very small black sclerotia on the affected part of the stem and root. The mycelium of the causative agents not only is preserved but develops saprophytically in the soil. Most harmful are rhizoctonia disease of potato, sugarbeet, carrot, cotton, cucurbits, and crucifers. Control measures include crop rotation, liming of acid soils, application of organic fertilizers, good presowing treatment of the soil, use of high-quality seeds, and disinfection of hotbed soil with fungicides.