Integrating bioassays and transcriptomics to detect neonicotinoid resistance in Australian Bemisia tabaci MEAM1.

BACKGROUND: Bemisia tabaci MEAM1 is a highly invasive and polyphagous pest species of agricultural and horticultural crops worldwide. It has developed resistance to numerous insecticides, including neonicotinoids. Over-expression of the cytochrome P450 CYP6CM1 gene has been associated with neonicotinoid resistance. In this study, we used transcriptional analysis (RNAseq and RT-qPCR) to assess the expression of CYP6CM1 and bioassays to quantify levels of neonicotinoid resistance in the B. tabaci resistant GR15-1R strain and 10 field populations collected from Australian cotton in 2023. RESULTS: Foliar bioassays showed that the GR15-1R strain has partial cross-resistance to neonicotinoids with responses ranked as very high to imidacloprid, clothianidin and thiacloprid, high to thiamethoxam, moderate to acetamiprid, but susceptible to dinotefuran. The transcriptional analysis revealed constitutive over-expression of multiple cytochrome P450 genes, with CYP6CM1 being the most highly expressed. Bioassays of field populations and CYP6CM1 expression levels indicated moderate to high levels of resistance to clothianidin, while the response to imidacloprid was more variable, ranging from low to very high resistance; no resistance to dinotefuran or acetamiprid was observed. CONCLUSIONS: The over-expression of CYP6CM1 is associated with resistance to imidacloprid, clothianidin, thiacloprid and thiamethoxam. Combining molecular techniques with bioassays is useful for identifying biologically relevant levels of resistance. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.