The feeding behaviour and life history changes in imidacloprid‐resistant Aphis gossypii Glover (Homoptera: Aphididae)

BACKGROUND: Imidacloprid (IMI) is a major neonicotinoid insecticide used to control Aphis gossypii Glover. However, resistance to IMI developed rapidly in A. gossypii. The feeding behavior and life history changes associated with IMI resistance were studied in A. gossypii. RESULTS: The resistant population with a point mutation (R81T) in the nAChR beta1 subunit showed an IMI resistance ratio of 58.12. This IMI-resistant A. gossypii became more active in finding an appropriate position for feeding. They made more intercellular apoplastic stylet pathway events (C) than the susceptible population. Moreover, the probing and feeding behavior of two aphid populations were dramatically altered by IMI. The phloem ingestion (E2) duration was significantly longer for IMI-resistant aphids on IMI-treated plants (WDI: 208.70 +/- 17.38 min) than on control plants (WDI: 133.80 +/- 16.37 min). However, IMI statistically reduced the ability of susceptible aphids to find and feed from the phloem. The number and duration of phloem-related activities were sharply decreased for the susceptible aphids treated with IMI. In addition, the resistant population showed an increased relative fitness of 1.36. The fecundity of IMI-resistant adults was dramatically higher than that of the susceptible population. This difference also led to an increase in the net reproductive rate (R0 ) for the IMI-resistant A. gossypii. CONCLUSIONS: Imidacloprid provoked phloem-feeding more rapidly and effectively in IMI-resistant A. gossypii, but significantly suppressed the feeding of susceptible A. gossypii. Therefore, the resistance to IMI can result in stimulated feeding and fecundity and subsequent population outbreaks, which make the control of IMI-resistant A. gossypii more challenging. (c) 2019 Society of Chemical Industry.