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Vector Relations

Insect Transmission of Sweet Potato Disease Agents in Nigeria. G. A. Schaefers, Visiting Entomologist, International Institute of Tropical Agriculture, PMB 5320, Ibadan, Nigeria, Present address: N. Y. State Agric, Exp. Station, Geneva, N. Y. 14456; E. R. Terry, Plant Pathologist, International Institute of Tropical Agriculture, PMB 5320, Ibadan, Nigeria. Phytopathology 66:642-645. Accepted for publication 17 October 1975. DOI: 10.1094/Phyto-66-642.

Two infective agents have been separated from a sweet potato disease complex in Nigeria. One is a nonpersistent virus [a filamentous rod (850 nm)] which is transmitted most efficiently by the aphids Myzus persicae and Aphis gossypii and less efficiently by A. citricola. It is latent in sweet potato, but produces marked veinclearing and leaf twisting in Ipomoea setosa. Following infection, symptoms disappear after about eight new leaves are produced. The disease is referred to as sweet potato veinclearing. The second agent is transmitted by the whitefly, Bemisia tabaci. It also is latent in the sweet potato cultivars tested. In I. setosa it produces mild chlorosis and severe stunting of the plant. The disease is referred to as sweet potato chlorotic stunt. In combination, the two disease agents produce severe symptoms in sweet potato. Depending on the cultivar, veinclearing, puckering, leaf strapping, chlorosis, and stunting may occur. Dual infection in I. setosa results in stunting, severe chlorosis followed by necrosis of older infected leaves, and a severe reduction in leaf lamina.