Distribution of sodium channel mutations associated with pyrethroid resistance in phytoseiid mite species in vineyards

For this study, first, the composition of phytoseiid mite species was examined at vineyards in Shimane Prefecture, western Japan, in 2023 and 2024 using quantitative sequencing (QS) and nucleotide sequencing. Amblyseius eharai and Amblyseius andersoni were the most dominant species. Then, the proportion of sodium channel mutations (M918L and L925V/M) involved in pyrethroid resistance was examined using another QS and nucleotide sequencing. Results revealed wide distributions of both mutations in A. eharai and the former mutation in A. andersoni. Results also revealed the presence of M918L in Neoseiulus barkeri and Neoseiulus californicus, but not in Euseius sojaensis. Genotyping for the other mutation sites using the collected phytoseiid mites revealed that all A. eharai and A. andersoni individuals had S1539T, as did some N. californicus individuals. These results suggest that phytoseiid mite species, with the exception of E. sojaensis, have reduced sensitivity to pyrethroids in vineyards in Shimane Prefecture.