Rhizoctonia blight of millet is caused by the fungus Rhizoctonia solani and R. zeae. The disease cycle begins when wind-blown soil or splashing water deposits dormant resting structures of the fungus (sclerotia) onto leaves. The sclerotia germinate and penetrate the plant directly during wet or humid weather. These pathogens are widely distributed in most soils in the High Plains, and persist as dormant resting structures (sclerotia), saprophytically on decaying organic matter, and pathogenically on many other plants.
Rhizoctonia blight symptoms initially appear as irregular, water-soaked blotches on leaf sheaths and the bases of leaf blades. Lesions become light tan and develop into elongated blotches (2 to 3 inches in length), with brown borders that diffuse into healthy tissue. Diffuse white to tan mycelia grow over lesions and adjacent healthy tissue, and older lesions may be covered with tiny, red to brown to black sclerotia.
Yield loss estimates are not available for the High Plains, but the disease causes little if any damage to millet in the southeastern U.S.
No biological control strategies have been developed for Rhizoctonia blight.
Cultural controls probably are not necessary for Rhizoctonia blight, but a three-year or longer crop rotation, incorporation of infested crop debris, plowing before planting, and avoidance of overhead irrigation probably reduce the disease.
Chemical controls are not available or necessary.
Categories: Millet, Disease, Rhizoctonia Blight
Date: 03/22/2005