Rapid expansion of insecticide resistance in Acyrthosiphon kondoi and opportunities to improve chemical and biological control

Abstract The bluegreen aphid ( Acyrthosiphon kondoi ) is a global pest of pasture and legume crops, damaging plants through feeding and the transmission of plant viruses. Since 2018, Australian growers have reported insecticide control failures involving A. kondoi , with subsequent bioassays confirming the first cases of insecticide resistance in this species worldwide. To better inform management strategies, we conducted a surveillance programme of 36 field populations across southern Australia, testing for resistance to organophosphates, carbamates, and synthetic pyrethroids. Resistance was detected in 19 populations, most commonly within alfalfa ( Medicago sativa ) seed production regions. We then generated baseline sensitivity data for two insecticides, sulfoxaflor and flonicamid, recently introduced for A. kondoi control in Australia , and found that both provide promising new options for resistance management. In parallel, we assessed biological control potential by surveying parasitoid wasps attacking A. kondoi . Aphidius ervi was the only species detected parasitising A. kondoi across southern Australia. Follow-up laboratory assays demonstrated high parasitism and successful emergence of A. ervi from A. kondoi and more variable performance across co-occurring aphid pests, highlighting its broader biocontrol potential in pasture and legume systems. Together, these findings demonstrate the rapidly expanding distribution of insecticide resistance in A. kondoi , confirm the value of newly available insecticides, and identify a key parasitoid for integration into management strategies. These findings provide a foundation for integrated management approaches to slow resistance evolution in A. kondoi in Australia and elsewhere.