SURVEY OF CASSAVA VIRUS DISEASES IN TANZANIA

A survey was carried out of African cassava mosaic geminivirus and cas sava brown streak virus diseases (ACMD and CBSD) in Tanzania. ACMD occ urred throughout the country at low to moderate incidences in the fift een different regions surveyed (1-64%). The incidence was generally hi gher along the coastal plain than in higher altitude areas in the inte rior. There was a significant correlation between numbers of adults of the whitefly vector, Bemisia tabaci, and incidence of recently infect ed plants (R = 0.77, p < 0.01), although most infection was attributab le to the use of infected cuttings. CBSD was more restricted in distri bution and, where present, incidence was low to moderate (1-36%). Cass ava plantings along the southern border with Mozambique link the highe st incidence area on the south-east coast near Mtwara, with the other important area of CBSD incidence along the shore of Lake Malawi. The e ffects of climatic parameters on ACMD and CBSD incidence are discussed . The survey data suggest that both diseases could be controlled in Ta nzania by the use of phytosanitation which involves the use of disease -free planting material and the removal (roguing) of diseased plants.