representing the increasing percentage of plants with systemic symptoms. Thus, in Benin, systemic infection was most severe in the SS, followed by the SGS, the NGS and the FSM zone where in 60, 57, 30 and 25% of sites (percentage data not shown), respectively more than half of the plants were systemically infected, corresponding to incidence classes 4 and 5. Sites with a systemic infection incidence of 90–100% of plants (incidence class 5) were observed in each ecozone. Statistical analysis of the incidence—plants in symptom classes 2–5—of the disease by ecozones revealed significant differences (Table 1): disease incidence was lower in the FSM zone than in the SGS and the SS of Benin. Nevertheless, 36% of infected plants (classes 2–5) in the FSM zone showed dieback symptoms (class 5). In the NGS, CBB incidence was lower than in the SGS (P=0.087) and the SS (P=0.075). The incidence was 100% in large governmental cassava multiplication farms in North Benin.