The Viruses and Virus Diseases of Cassava in Africa

This review summarises the available information on the viruses and virus diseases of cassava in Africa. It then considers the distribution, prevalence and epidemiology of the two most important of these diseases: African cassava mosaic, which occurs in all the main cassava-growing areas, and cassava brown streak, which seems to be restricted to parts of eastern and southern Africa. The epidemiology of African cassava mosaic has been studied in few of the very diverse agro-ecological zones in which the disease occurs and there is even less information on brown streak. These are serious constraints in attempts to develop effective control measures. Information is also lacking on possible interactions between the two diseases and on their effects on the response of cassava to bacterial blight and other disease and also to arthropod pests, nematodes and weeds. This emphasizes the scope for a multi-disciplinary holistic ecological approach in any further studies aimed at developing fully integrated control measures to combat the whole range of cassava pests, diseases and weeds