Mutations in the voltage-gated sodium channel gene associated with deltamethrin resistance in commercially sourced Phytoseiulus persimilis

The implementation of Integrated Pest Management (IPM) in current agricultural practice is a convenient and very effective strategy to maintain pest populations under control. The use of Biological Control Agents, like Phytoseiulus persimilis, is key for the success of such approach. This predatory mite is widely used since it is very effective for controlling the two spotted spider mite (Tetranychus urticae), one of the most devastating pests worldwide. Here we show the identification of mutations located in the Voltage Gated Sodium Channel (VGSC) of P. persimilis, that correlate with the reduced susceptibility to deltamethrin observed in commercially sourced colonies of this predatory mite. We have found that the mites from each source have intrinsic genotypic differences that correlate with their phenotype when tested with different concentrations of deltamethrin. Thus, the mites from Syngenta carrying the mutations M918L and A1536T were able to survive up to 10 ppm, while the mites form Koppert with the combination M918L, L925V and S1539T survived the treatment with 40 ppm. These mutations are located in a particular region of the channel, previously proposed as the binding site for this family of pesticides and a hot spot for resistance mutations. The potential implications for optimised integration of P. persimilis within an IPM strategy are discussed.