Striga species are noxious weeds that are widespread constraints to the production of staple cereal crops in semi-arid areas, principally attacking finger millet, maize, sorghum, and upland rice. They have been estimated to infest some 40 percent of the cereal producing areas of sub-Saharan Africa. Work by the DFID Crop Protection Programme (CPP) project R6654 showed how sorghum, the preferred staple, has been replaced by pearl millet, which is not attacked by Striga in parts of Missungwi district in Mwanza Region. In the Kyela district of Mbeya Region, cassava has increased in importance as a less profitable break crop, where once farmers had a rice monoculture, due to declining soil fertility and a build-up of Striga.