A Probable Virus Disease of Sweet Potato

Abstract

In March, 1944, what is suspected to be a virus disease of sweet potato was discovered at Kwanda by Mr. J. D. Jameson, amongst a collection of native varieties kept here for reference. A detailed survey of the distribution of the disease in Uganda has not yet been possible, but records have been obtained from widely separated areas and there is thus reason to suspect its general distribution. Recently reports have been received of its occurrence in Ruanda-Urundi and in the adjoining parts of Tanganyika. 1 am informed by the authorities of the Congo Beige that they suspect its occurrence in serious amounts in the area west of Lake Albert, where the crop has suffered severely and has virtually been abandoned as a food supply to the Kilo Mines. In view of these records the disease is thus potentially of serious importance in those parts of East Africa where the sweet potato is a major source of food supply. Hitherto investigations have been limited to field observations and detailed experimental research is only being commenced, so that no information is yet available on the possible origin of the disease, on its method of transmission from plant to plant, or on its relation to virus diseases of other crop plants in East Africa. Both in the Congo Beige and at Kawanda large numbers of white flies (Aleyrodidae) have been noticed in affected plots, and we suspect these as possible vectors of the disease. They have not yet been identified but appear to be close allies of the species of Bemisia known to be the vector of the mosaic