Effects of imidacloprid on feeding and osmoregulation in the aphid Myzus persicae

While primarily phloem-feeders, aphids occasionally feed on xylem to regulate water balance. Since the neonicotenoid insecticide imidacloprid moves through xylem when applied systemically, we hypothesized that it would more strongly affect aphids under high osmotic stress or late in their life cycle when they are less fecund. Alates of Myzus persicae (Sluz.) of differing ages were exposed to tobacco leaves systemically treated with Admire® Pro at one-half the recommended rate. After 24 hours nymph production and adult morbidity and mortality were scored. Imidacloprid and increased age both significantly raised adult morbidity/mortality. Nymph production decreased in response to increasing age and the presence of imidacloprid.

In a second experiment, alates and adult apterae of M. persicae were starved for 24 hours and similarly exposed to treated leaves. Imidacloprid caused significant morbidity/mortality among adult apterae and alates. Imidacloprid also reduced nymph production among both adult morphs. Starvation did not significantly affect survivorship in either morph, but starved alates and apterae produced more nymphs than unstarved controls. The increased nymph production in starved individuals may be due to a “bottleneck” of unborn nymphs during the starvation period or a response to the sudden influx of sucrose, which can be sequestered as offspring.