Molecular screening and dose-response assays provide insights into pyrethroid resistance in four agriculturally important aphid species

Aphids are important pests that cause significant crop damage. In the UK, aphid species of particular concern in cereal systems include the grain aphid (Sitobion avenae), the bird cherry-oat aphid (Rhopalosiphum padi), and the rose-grain aphid (Metapolophium dirhodum); the peach-potato aphid (Myzus persicae) is a species of significant concern across several arable and horticultural cropping systems. Due to the impact aphids have on crop production, managing and controlling populations before they negatively impact yield is key. Pesticides are a central component in many management plans, however tightened regulations have left farmers mainly reliant on a single group of pesticides, the pyrethroids. This has led to an overreliance on pyrethroids, enabling resistance and tolerance to evolve in several species, including S. avenae and M. persicae. Frequent surveys of insect populations can monitor the prevalence of insecticide resistance and identify new species where reduced sensitivity (i.e., tolerance) is developing. These surveys inform farmers and ensure that control methods remain effective. Here, we survey multiple aphid populations for resistance or tolerance to pyrethroids. We use a combination of molecular approaches to identify known resistance mechanisms in S. avenae and M. persicae and dose-response assays to screen for reduced sensitivity in R. padi and M. dirhodum. We identify low prevalence of pyrethroid resistance in S. avenae and high levels of insecticide resistance in M. persicae, with 74 % of M. persicae populations harbouring at least one resistance mechanism. All M. dirhodum populations tested were highly sensitive to pyrethroids, although we identify reduced sensitivity in several R. padi populations, the first report of reduced sensitivity in this species in the UK.