RESISTANCE TO AVERMECTINS - EXTENT, MECHANISMS, AND MANAGEMENT IMPLICATIONS

The avermectins represent a group of natural compounds with potent pes ticidal activities. Because of their novel mode of action, they repres ent an important resource for pest control and resistance management. In the Colorado potato beetle, the house fly, and the two-spotted spid er mite, resistance to abamectin is usually autosomal recessive, and p olygenic. Although these aspects are beneficial in resistance manageme nt, the fact that resistance could be readily selected for suggests th at abamectin needs to be used in moderation. Furthermore, several majo r resistance mechanisms (e,g. excretion, oxidative metabolism, penetra tion) and minor factors (e.g. altered target site, conjugation, hydrol ysis/sequestration) have been implicated in abamectin resistance. Thus , the question is not whether resistance to abamectin will occur but i s simply when and how it will occur. To address this problem, we have gathered information on the genetics, biochemical mechanisms, effectiv eness of synergists, and cross-resistances to other insecticides from three abamectin-resistant insects. Judicious implementation of this in formation may prove useful in the resistance management of this natura l pesticide.