Insecticide resistance in Myzus persicae collected from sweet pepper

Populations of the green peach aphid, Myzus persicae, rapidly develop resistance to insecticides applied in agriculture, necessitating regular resistance monitoring of pest populations. Previous research identified two dominant multilocus genotypes (MLGs) in conventional (using insecticides + biological control agents) Dutch sweet pepper greenhouses: MLG-A under pymetrozine application and MLG-R under flonicamid application. This suggests positive selection for the genotypes by the application of these insecticides. However, no resistance of M. persicae to these insecticides has been reported yet. To investigate whether the insecticides were selectively driving the emergence of these specific MLGs, we compared the sensitivity of MLG-A and MLG-R to pymetrozine and flonicamid to that of six other genotypes from the same crop system. Additionally, we screened the M. persicae populations from Dutch sweet pepper greenhouses for known mutations conferring resistance to carbamates, pyrethroids, neonicotinoids, and tetronic and tetramic acid derivatives. Our results show that both MLG-A and MLG-R are less sensitive to pymetrozine compared to the other genotypes investigated. Furthermore, full mortality for MLG-R, the genotype least sensitive to flonicamid, was not achieved at the recommended field dose for this insecticide. Resistance mutations for carbamates and pyrethroids were prevalent among the MLGs, including MLG-A and MLG-R, while mutation A2226V, which is linked to resistance to tetronic and tetramic acid derivatives, was absent. Notably, the neonicotinoid resistance mutation R81T was found only in MLG-R, making this the northernmost detection of R81T in M. persicae to date. This study shows that various resistance mechanisms can accumulate in a single aphid genotype and that insecticides likely play a role in selecting for the dominant genotypes of M. persicae in conventional greenhouses.