Resistance to carbamate, organophosphate and pyrethroid insecticides in the potato aphid (Macrosiphum euphorbiae).
A large number of Macrosiphum euphorbiae clones, initiated from field samples collected on potatoes in the UK since 1998, have produced cross-reactions in an immunoassay previously developed to assess levels of E4/FE4 carboxylesterase resistance in peach-potato aphids (Myzus persicae). Mean immunoassay values of each Macrosiphum euphorbiae clone fell within the S-R2 range used to categorize individual M. persicae (representing susceptible to highly resistant forms). These values were associated with resistance of the M. euphorbiae clones to pirimicarb and λ-cyhalothrin measured in laboratory leaf-dip bioassays. This suggests that this species has developed a metabolic resistance mechanism based on over-production of an esterase analogous to that in Myzus persicae. Furthermore, levels of esterase resistance appeared to be sufficient to confer selective advantages in the field as a substantial majority of the aphid samples taken from crops recently treated with insecticides contained high esterase forms compared with samples that had not received treatment. Biochemical studies indicated that resistance to dimethoate is primarily conferred by a mechanism based on AChE insensitivity (MACE).