Farm Level Practices Relevant to Cassava Plant Protection

This paper is based on information collected during the Collaborative Study of Cassava in ten countries of Africa and considers the incidence of cassava mealybug (CMB) and green mite (CGM) pests and African cassava mosaic virus (ACMD) and bacterial blight (CBB) diseases of cassava in relation to farm practices. African cassava mosaic disease was the most widespread of the four problems assessed and was observed in almost all the representative villages in West Africa. Cassava mealybug was the least widespread, although the incidence was relatively high in Nigeria, Malawi and Tanzania. Cassava greenmite was most widespread in the countries of eastern and southern Africa, whereas CBB was widespread in Nigeria and Uganda. The problems of CGM, ACMD and CBB were not higher in any other climate zone, than in the humid climate zone, while those problems were not less severe in any other climate zone, than in the humid climate zone, while those problems were not less severe in any other climate zone than in the subhumid climate. While the incidences of the various pests and diseases varied between villages which used and others which did not use purchased inputs were used. In Nigeria where improved varieties were mostly used, the symptom severity scores of all four pest/disease problems were lower for the improved varieties that had been released in the 1970s than for the local land races. Similarly, based on information from the ten countries, the symptom severity scores of the four problems were lower among villages which had easy access to a market than in other villages. The symptom severity score of the four problem were lower when cassava was grown in rotation with other crops than in other situations. The problems were also lower under continous cultivation systems although the reason is not clear. There was a high rate of turnover in the land races grown and susceptibility to pests and diseases was on of the most frequently mentioned reasons for this.

Keywords
Africa, Cassava bacterial blight, fallow, green mite, marketing, mealybug, mosaic virus disease, pests, rotation