Mite and Insect Pests of Cassava

Abstract

Cassava (Manihot esculenta), a major energy source for 300--500 million people, is grown throughout the tropical regions of the world. It is cultivated mainly in developing countries on small farms with little technology. As a result, it has received limited attention from scientists and technologists. The Food and Agricul­ ture Organization estimates for 1977 indicate an annual global production of 105 million tons on II million hectares (ha), of which at least 55 million are consumed by humans. Although cassava is now cultivated in some 90 countries, 80% of the world's production comes from only 10; the six leading producers are Brazil (31 %), Indonesia, Zaire, Nigeria, Thailand, and India (83). In many parts of the world, especially West Africa, cassava appears to be the most economical, lowest risk subsistance crop for the small farmer. The increasing world popUlation and the limited availability of energy has prompted a recent surge of interest in cassava-not only for traditional uses as a human food and for specialized starches including tapioca, but also for animal feedstuffs and industrial uses (55). There is an excellent potential for increasing both yield and area under cultivation. Two international centers for tropical agriculture, one in Colombia (Centro Internacional de Agricultura Tropical [CIAT]) and an­ other in Nigeria (International Institute of Tropical Agriculture), carry out exten­ sive research on cassava in addition to other tropical crops (83). Emphasis is placed on developing high-yielding germplasm for low-input conditions. Present world cassava yields under small-farm conditions average only 5-15 tonslha. Experimen­ tal yields of 55 tons in Colombia (23) and 70 tonslha elsewhere (82) have been obtained. Commercial yields with low input in Colombia have exceeded 40 tonslha. These figures indicate that undoubtedly there are several factors limiting production under farm conditions, one of which is pests. It frequently has been reported that cassava is generally free of arthropod pests; however, present research at CIAT and other centers reveals that mite and insect damage does limit cassava production, e.g. the recent introduction into Africa and