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Cassava varieties resistant to the cassava green mite, Mononychellus tanajoa (Bondar) ( Acari:Tetranychidae) have been reported in many parts of Africa where the pest has been introduced. However, the resistance mechanisms have not been identified. Laboratory studies on biology and feeding behaviour of cassava green mite were carried out at the International Institute of Tropical Agriculture (IITA), in order to determine whether this resistance is mainly due to pubescence.Cassava pubescence was found to have no antibiotic effect; both pubescent and non-pubescent varieties were preferred by the mite for oviposition, food and shelter. In addition, pubescence does not afford a mechanical barrier to cassava against green mite infestation.

The influence of larval host age on the levels of mortality and parasitization of the vegetable leafminer, Liriomyza sativae Blanchard, by Chrysonotomyia formosa (Westwood) and Opius dimidiatus (Ashmead) was determined by exposing separately host larvae of 3 ages (24, 72, and 120 h) in bean plant ( Phaseolus sp.) foliage to C. formosa and O. dimidiatus females for 24 h in the greenhouse. Host mortality and parasitization by C. formosa were significantly greater in 120-h-old larvae than in 24, and 72-h-old hosts. Host age and mortality were linearly correlated. Host age did not significantly affect parasitization by O. dimidiatus although higher levels were recorded for the 72-h-old host larvae.