using improved genotypes ( Nweke, 1994). Due to the expansion of cassava production into more marginal areas and the exploitation of soils, production constraints are increasing, and among them pests and diseases contribute considerably to low yields. Major diseases in Africa are cassava mosaic virus disease (CMD), cassava bacterial blight (CBB) caused by Xanthomonas campestris (Pammel Dowson) pv. manihotis (Arthaud-Berthet) Starr. ( Bondar, 1912) (synonym Xanthomonas axonopodis pv. manihotis Vauterin et al., 1995), anthracnose (CAD) caused by Colletotrichum gloeosporioides f. sp. manihotis Henn. (Penz.) Sacc. (Glomerella manihotis Chev.), blight leaf spot (BlLS) caused by Cercospora (Mycosphaerella) vicosae Muler and Chupp, brown leaf spot (BLS) caused by C. (Mycosphaerella) henningsii Allesch and white leaf spot (WLS) caused by C. caribaea Cif. (Phaeoramularia manihotis), as well as root rots.