Nonstable Parathion and Endosulfan Resistance in Green Peach Aphids (Homoptera: Aphididae)

Parathion and endosulfan insecticide resistant colonies of green peach aphids, Myzus persicae (Sulzer), collected from various potato fields in Wisconsin, reverted to susceptible conditions after being maintained in greenhouse insecticide-free enviroments. The amounts of time which field-collected aphids remained as insecticide-resistant colonies varied from as few as 10 to as many as 27 generations after their collection from the fuield. Stability of resistance varied in splinter colonies which were derived from aphid colonies in different phases of transition from resistant to susceptible conditions. Reversions to parathion susceptibility were paralleled by near-simultaneous reversions to endosulfan susceptibility. Once begun, the reversion process proceeded rapidly and was completed within approximately four generations.