Cassava (manioc) plants are under observation at the International Institute for Tropical Agriculture at Ibadan, protected from mealy bugs and green spider mites by ventilated bags, as part of a biological pest-controlled project. The tuberous roots of this major staple food are a rich source of nutritious starch usually processed into flour and tapioca. - - Biological Pest Control. The UN Food and Agriculture Organization (FAO) is one of several agencies helping the International Institute of Tropical Agriculture (IITA) to eradicate the cassava mealy bug and green spider mite, which are jeopardizing the diet of about 200 million people living in Africa's cassava growing belt, who rely on cassava for about 50% of their calories. The pests, accidentally brought from South America around 1971, spread rapidly since they have no natural enemies in Africa. The IITA has conducted successful studies on biologically safe ways to combat the pests with exotic natural enemies that do not upset the ecological balance of other insects and crops. The introduction of these beneficial insect and mite enemies has been welcomed because cassava is a low-income crop grown by poor subsistence farmers who cannot afford the pesticides, which have had only minimal success in controlling the pests. Cassava losses have ranged up to 80% of the total root yield in 30 African countries, with an estimated produce loss valued at USD 2 billion a year.