Evidence for a possible fitness trade-off between insecticide resistance and the low temperature movement that is essential for survival of UK populations of Myzus persicae (Hemiptera: Aphididae)

Apterous aphids need to move from ageing to younger leaves in order to survive UK winters. This behaviour was studied at low temperatures in field and laboratory trials using Myzus persicae (Sulzer) clones representing all five recognized categories of esterase-based insecticide resistance found in UK populations. Both studies showed that the tendency of aphids to move from deteriorating leaves was inversely related to their insecticide resistance level. This maladaptive behaviour associated with greater insecticide resistance could lead to increased risks of aphids becoming separated from plants after leaf fall, and subsequent death from starvation when adverse cold and wet conditions prevent return. Revertant clones, that had spontaneously lost extreme resistance to insecticides by ceasing to express their amplified esterase genes, tended to show similar behaviour to aphids that had retained their high resistance phenotypes. This implies that rates of movement were not related directly to esterase production.