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