Cytochrome P450 Monooxygenase-Mediated Resistance to Insecticides

Insecticide resistance is one of the major obstacles to the control of agriculturally important arthropod pests. Resistance results in increased application frequencies, increased dosages, decreased yields, environmental damage, and outbreaks of human and animal diseases when vectors cannot be controlled. The World Health Organization has called insecticide resistance "the biggest single obstacle in the struggle against vector-borne disease" and one recent estimate suggested that the cost of resistance may be 81, 400,000,000 annually in the United States. 2 For these reasons, it is essential to understand the mechanisms by which insects become resistant so that we are able to intelligently design strategies to delay the onset of this potentially devastating problem. 3 Resistance can occur by different mechanisms, and one of the most important is increased detoxication mediated by the cytochrome P450 monooxygenases. 4 5) This resistance mechanism is very important because it can confer high levels of resistance, 67) effects many classes of insecticides and may also confer cross-resistance to unrelated compounds due to the breadth of substrates the monooxygenases can metabolize. 8 Furthermore, monooxygenase-mediated detoxication has been found as a mechanism of resistance in a large number of important pests. 9 P450-mediated resistance could occur as a change in the amount of a