Farmers' perceptions and knowledge of cassava pests and diseases and their approach to germplasm selection for resistance in Ghana

Cassava farmers in 10 villages in Ghana had specific names for large or colony-forming pests but Bemisia tabaci, the relatively inconspicuous whitefly vector of cassava mosaic disease (CMD), was not mentioned and farmers used descriptors borrowed from other circumstances to identify cassava diseases, different farmers sometimes describing the same symptoms using different terms. Disease susceptibility was rarely a main reason for abandoning a landrace and few farmers were aware of the disease resistance of modern varieties although they were aware that their spreading habit enabled them to shade out weeds. While weeds were generally well controlled, CMD was common and appeared to be the main biotic constraint to cassava yields. Cassava anthracnose disease and brown leaf spot, although present, were generally not severe. In on-farm collaborative breeding trials, high yield - an indirect measure of pest and disease resistance - was the farmers' main selection criterion; those directly involving pest, disease or weed resistance were less commonly mentioned. Despite this, farmers selected for accessions with no or only mild CMD, perhaps through the effect CMD had on yield. These insights about farmers' perceptions of cassava pests and diseases provide a basis for further collaborative germplasm development in Africa.