Insect-resistant crops

It may come to mind that the introduction of crops that impact pesticide use will inevitably lead to shifts in pesticide residue patterns in foods derived from these crops. In insect-resistant crops, for example, reductions in insecticide sprays against the target insects can be anticipated and concomitant reductions in crop residues. For herbicide toler-... 

There are many other approaches of a long-term nature that have been explored (but too little) for a good many years. The development of insect-resistant crop varieties has sometimes been used when all other methods of control have failed. This is the case with the wheat stem sawfly. The development of sawfly-resistant wheat varieties permits the profitable growing of wheat on some 2,000,000 acres in Canada and on more than 600,000 acres in the North Central United States. Varieties of wheat bred for resistance to the Hessian fly are now grown on 4,500,000 acres in 26 states. 

Provides a coordinated crop protection industry response to the development of resistance in insect and mite pests. During the last decade, IRAC has formed several international working gi oups to provide practical solutions to mite and insect resistance problems within major crops and pesticide groups. 

Painter, R. H. Insect Resistance in Crops The University Press of Kansas Lawrence, KS, 1951. 

The levels of antifeedants can be raised safely only in plants such as forest trees or fiber crops, not in food plants for humans or livestock. Such problems have arisen inadvertently. For instance, a new insect-resistant potato cultivarhad to be withdrawn from the market because it contained high levels of the carcinogens solanine and chaconine (Renwick etal, 1984). In another example, an insect-resistant celery had 10 times the usual concentration of the carcinogen 8-methoxypsoralen (and related psoralens), which caused dermatitis in produce handlers (Seligman etal, 1987). 

Interactions Among Allelochemicals and Insect Resistance in Crop Plants... 

Such a strong impact on survivorship or fecundity, and on the fitness of individuals, means exerting strong natural selection on herbivorous insects. This should favor the rapid evolution of insect adaptations which overcome it. This is, of course, a common occurrence in the application of pesticides or the development of resistant crop plant cultivars (11). The supposition that plant defenses select for detoxication adaptations in insects is the foundation of the concept of coevolution (12). 

There are a number of possibilities for using plant secondary chemistry to control herbivory in crop plants. One possibility is to select for insect resistant lines and though it has been done in only a few cases, select for specific allomones. There are, however, some potential problems with this approach. There is a cost for the production of the secondary compounds which may be useful for defense ( ). Insect resistant soybean cultivars produce lower yields of seeds and accumulate nitrogen at a slower rate than insect susceptible varieties in the absence of herbivores 3 ). Conversely, varieties of crop plants selected for high yield are often more susceptible to insects, pathogens, and weeds (35). 

Several trophic levels must be considered. Breeding plants with greater allomone content in some cases causes specialist herbivores to accumulate higher levels of these compounds and discourages parasites that normally control herbivore levels (36). The presence of secondary compounds may also alter the usefulness of the crop plant to man or his domestic animals. Lines of cotton with high gossypol content have increased insect resistance with regard to a nunter of insects, but have reduced value as food materials for livestock. 

Price, P. W. "Insect Ecology", Wiley, New York, 1975. Dethier, V. G. XH "Chemical Ecology" (E. Sondheimer and J. B. Simeone, eds.) 83-102. Academic Press, New York, 1970. Painter, R. H. "Insect Resistance in Crop Plants",... 

The industry-led Insecticide Resistance Action committee (IRAC) records cases of insect resistance by crop and recommends strategies to reduce the impact and incidence of resistance. 

Devise a strategy to avoid or delay the onset of insect resistance using chemicals (both insect toxic and behaviour modifying), predators and parasites and transgenic crops ... 

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