Insect control through biotechnology is an outstanding example of the use of gene technology to enhance the efficiency and sustainability of production of broadacre crops. It is not without its risks, such as the development of resistance by the target insects and potential nontarget impacts in the environment. There must be a concerted effort to develop new insect tolerance genes to ensure that the existing technologies are not lost by overuse in the short term. However, finding highly potent insecticidal genes that are as effective as the first generation of genes based on delta endotoxins from Bacillus thuringiensis is not a simple matter. The new class of vegetative insecticidal genes from Bacillus species holds the most promise for the control of difficult lepidopteran and coleopteran pests, but they have yet to be expressed effectively in transgenic plants. Inhibitors of digestion used against lepidopterans and/or sucking pests have received a great deal of publicity but are yet to prove themselves commercially and will be challenged by the great adaptability of insects and the problems of antinutritional activity against humans and animals if they are used in food or fodder crops. They are most likely to be at their best with highly specialized insects that are very host specific, such as some of the stored grain pests, and do not possess well-developed adaptive mechanisms to cope with a wide array of digestive inhibitors in their diets. The area of secondary metabolite manipulation in host plants also holds promise, but a fuller understanding of the biochemical pathways involved and the complex interrelationships between both secondary and primary metabolism in plants is essential. The next decade will be an exciting time for biotechnologists and entomologists as they explore the full-scale commercial production of transgenic insect-protected crops.
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