Comparative survival of insecticide-susceptible and resistant peach-potato aphids, Myzus persicae (Sulzer) (Hemiptera: Aphididae), in low temperature field trials

The survival of Myzus persicae (Sulzer) clones, representing the full range of the recognized levels of insecticide resistance, was measured after 3-4 week exposure to the winter climate in the field. Ten separate trials were carried out using known numbers of first/second instar nymphs on unsprayed oilseed rape and groundsel. These predominantly showed a negative association between resistance level and the proportion of aphids recovered alive after exposure. The strength of the relationship correlated closely with three meteorological variables: the length of time that aphids spent below 2 degrees C, mean rainfall and mean windspeed. We conclude that selection for resistance to insecticides is subject to counteracting selection by cold, wet and windy conditions in the UK winter. Revertant clones, that had spontaneously lost extreme resistance to insecticides despite retaining resistance genes, survived no better than aphids that had kept their high resistance, indicating that overproduction of esterase was not the reason for poor survival.