ABSTRACT
There is a large gap between potential yields and actual yields harvested by farmers. Average yields for most crops, particularly in the developing countries, are only one-third or less of the potential yield, and insect pests are one of the major constraints in crop production. Insect pests have high reproductive rates, a fast generation turnover, wide genetic diversity, and an ability to withstand, metabolize, and avoid toxic chemicals. As a result, it is diffi cult to control several insect species through currently available insecticides. To harvest the potential yields of high-yielding cultivars, the farmers resort to heavy use of insecticides. However, even if 90% of the insects are killed as a result of insecticide application, the remaining population multiplies at a much faster rate in the absence of natural enemies (which are killed by the insecticides) (Knipling, 1979), and the farmers have to apply insecticides more frequently and at higher doses, which fi nally results in failure of control operations and environmental pollution. Failure to control insects has forced farmers to give up cultivation of some crops in different countries. Indiscriminate use of insecticides has resulted in adverse effects on nontarget organisms, insecticide residues in food and food products, pest resurgence, development of resistance, and environmental pollution. The current sensitivities about environmental pollution, human health hazards, and pest resurgence as a consequence of improper use of synthetic insecticides has led to greater emphasis on alternative methods of insect control.
