Concluding Remarks

Research on the topic of insecticide resistance has provided invaluable insights into the origin and nature of adaptations, and these are proving to have broad significance for understanding genetic responses to change in the environment. In many respects the continuing battle against resistance is as good an example of coevolution as any and is a clear illustration of how such processes generate biological diversity. In this instance, however, the diversity being created is undesirable from a human standpoint and, because of the threat posed to susceptible genotypes, probably temporary.

It is important to note that the pest management problems posed by the evolution of resistance are not unique to control strategies that use conventional insecticides. The utilization of host plant resistance is a case in point. Resistance to insects in crop plants is selected by screening for genes that provide resistance in the laboratory or in field plots, then crossing those genes into crop strains with other desirable characteristics. At least six major genes for resistance to the Hessian fly (Mayetiola destructor) have been successively bred into wheat over the past two decades. In each instance, the introductions of new resistant mutations in the plant were rendered useless by the evolution of corresponding protective adaptations in the fly. Another example of such coevolution comes from the use of semiochemical tools for pest control. In many parts of Asia, a synthetic pheromone is used to disrupt mating in the tea tortrix moth (Adoxophyes honmai), the larvae of which can cause severe damage in tea plantations. Researchers in Japan have recently reported the evolution of a new biotype of this species that exhibits reduced sensitivity to the pheromone. Such events make it clear that regardless of whether the major strategies for pest management continue to use conventional chemicals, the "arms race" between insect evolution and human ingenuity will continue to present major challenges.

See Also the Following Articles

Agricultural Entomology • Biotechnology and Insects • Genetically Modified Plants • Genetic Variation

Further Reading

Denholm, I., and Rowland, M. W. (1992). Tactics for managing pesticide resistance in arthropods—Theory and practice. Annu. Rev. Entomol. 37, 91-112.

Devonshire, A. L., Field, L. M., Foster, S. P., Moores, G. D., Williamson, M. S., and Blackman, R. L. (1998). The evolution of insecticide resistance in the peach-potato aphid, Myzus persicae. Philos. Trans. R. Soc. Lond. Ser. B, Biol. Sci. 353, 1677-1684. ffrench-Constant, R. H., Pittendrigh, B., Vaughan, A., and Anthony, N. (1998). Why are there so few resistance-associated mutations in insecticide target genes? Philos. Trans. R. Soc. Lond. Ser. B, Biol. Sci. 353, 1685-1693.

Forrester, N. W., Cahill, M., Bird, L. J., and Layland, J. K. (1993). Management of pyrethroid and endosulfan resistance in Helicoverpa armigera (Lepidoptera, Noctuidae) in Australia. Bull. Entomol. Res. suppl. 1.

Horowitz, A. R., Forer, G., and Ishaaya, I. (1994). Managing resistance in Bemisia tabaci in Israel with emphasis on cotton. Pestic. Sci. 42, 113-122.

Martinez Torres, D., Devonshire, A. L., and Williamson, M. S. (1997). Molecular studies of knockdown resistance to pyrethroids: Cloning of domain II sodium channel gene sequences from insects. Pestic. Sci. 51, 265-270.

McKenzie, J. A. (1996). "Ecological and Evolutionary Aspects of Insecticide

Resistance." R. G. Landes, Austin, TX. Pimental, D., Acquay, H., Biltonen, M., Rice, P., Silva, M., Nelson, J., Lipner, V., Giordano, S,. Horowitz, A., and Damore, M. (1992) Environmental and economic costs of pesticide use. Bioscience 42, 750-760.

Raymond, M., Chevillon, C., Guillemaud, T., Lenormand, T., and Pasteur, N. (1998). An overview of the evolution of overproduced esterases in the mosquito Culex pipiens. Philos. Trans. R. Soc. Lond. Ser. B, Biol. Sci. 353, 1707-1711.

Roush, R. T. (1989). Designing resistance management programs—how can you choose? Pestic. Sci. 26, 423-441. Roush, R. T. (1997). Bt-transgenic crops: Just another pretty insecticide or a chance for a new start in resistance management? Pestic. Sci. 51, 328-334.

Soderlund, D. M., and Bloomquist, J. R. (1990). Molecular mechanisms of insecticide resistance. In "Pesticide Resistance in Arthropods" (R. T. Roush and B. E. Tabashnik, eds.), pp. 58-96. Chapman & Hall, London.

Tabashnik, B. E., Liu, Y. B., Malvar, T., Heckel, D. G., Masson, L., and Ferre, J. (1998). Insect resistance to Bacillus thuringiensis: Uniform or diverse? Philos. Trans. R. Soc. Lond. Ser. B, Biol. Sci. 353, 1751-1756.

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