Tactics for Managing Pesticide Resistance in Arthropods: Theory and Practice

The evolution of resistance to insecticides and acaricides by arthropod pests can be viewed and studied from two contrasting perspectives. At a fun­ damental level, resistance provides an almost ideal model of adaptation to withstand severe environmental stress. Work on the genetic (127, 128), biochemical (30, 82), and more recently, the molecular basis of resistance mechanisms (32) has cast light on the nature of this adaptation in several insect species, leading in some cases to diagnostic assays for specific genes or gene products (3, 22, 45). Similarly, population geneticists have exploited opportunities to analyze the selection of resistance in laboratory and field experiments (94, 95), and to predict, using theoretical models, how fast resistance genes are likely to evolve under different pesticide exposure re­ gimes ( l lS, 120). Unlike most evolutionary phenomena, however, resistance is also of great practical and economic significance. Not only have resistant species increased greatly in number (56), but the severity and extent of some resistance prob­ lems has increased alarmingly. For example, in some populations of the diamondback moth, Plutella xylostella (6), and Colorado potato beetle, Lepti­ notarsa decemlineata (50), resistance to virtually all available insecticides has