Cassava brown streak disease: a review of present knowledge and research needs

Cassava ( Manihot esculenta) is an important subsistence food crop in Africa where it is affected by two main virus diseases, cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). CMD occurs in all the cassava-growing countries on the continent and it has been much researched. CBSD occurs mainly on the East African coast, and although the disease was first reported in 1936, it has received much less attention than CMD. The aetiology and epidemiology of CBSD are still not fully elucidated, and no insect vector has been identified. There is renewed interest in CBSD owing to the discovery of its widespread occurrence in southern Tanzania and Mozambique, where the associated symptom of root necrosis is a major cause of economic loss in the cassava crop. In view of the present importance of the disease in eastern Africa, it is timely to produce a review of work carried out on the disease since it was first described.