Role of Behavior in the Evolution of Insect Adaptation to Insecticides and Resistant Host Plants

A two-locus genetic model was developed for examining factors influencing adaptation by pests to compounds or plants that have both insecticidal and repellent properties. The model allows genetic variation in the pest population for physiological adaptation and behavioral avoidance. The biological assumptions of the model are appropriate for mobile pests such as Heliothis spp. The results of the model suggest that: (1) in many situations, physiological adaptation will evolve more slowly when insecticide formulations with high repellency are used instead of nonrepellent formulations; (2) Crop cultivars with both “antibiotic” and “nonpreference” types of resistance should often be less prone to counter-adaptation by oligophagous and polyphagous pests than cultivars exhibiting only antibiotic resistance; (3) It is reasonable to expect some insect populations to evolve behavioral avoidance of antibiotic crop cultivars and insecticides which were originally not repellent to them; (4) Pest mobility and the spatial patterns of insecticide/repellent use can influence the direction and rate of evolutionary change in the pest. Development of insecticide formulations containing noninsecticidal compounds with repellent properties could lower the rate of pest physiological adaptation to an insecticide. Use of such formulations may, in some cases, induce higher pest damage to untreated crops thus raising problems for producers and regulatory agencies. In special cases, it may be possible to influence the development of resistance by pest or natural enemy species by mass release of strains with appropriate behavioral and physiological characteristics.