| Summary: | The silverleaf whitefly, <i>Bemisia tabaci</i> (Gennadius, Hemiptera: Aleyrodidae), is a major threat to field and horticultural crops worldwide. Persistent use of insecticides for the management of this pest is a lingering problem. In the present study, the status of sensitivity of <i>B. tabaci</i> to two neonicotinoids, imidacloprid and thiamethoxam, was evaluated. The expression pattern of two cytochrome P450 (<i>cyp</i>) genes and changes in the relative amount of symbionts in insecticide-treated <i>B. tabaci</i> were also assessed. Quantitative PCR (qPCR) studies indicate that the <i>CYP6CM1</i> and <i>CYP6CX1</i> genes were always expressed higher in imidacloprid-treated whitefly, suggesting a correlation between gene expression and the insect’s ability to detoxify toxic compounds such as insecticides. In addition, the thiamethoxam-treated population harbored higher <i>Portiera</i> and lower <i>Rickettsia</i> titers, whereas the imidacloprid-treated population harbored more <i>Rickettsia</i> at different time intervals. Interestingly, we also examined that an increase in exposure to both the insecticides resulted in a reduction in the mutualistic partners from their insect host. These differential responses of endosymbionts to insecticide exposure imply the complex interactions among the symbionts inside the host insect. The results also provide a deeper understanding of the molecular mechanism of resistance development that might be useful for formulating effective management strategies to control <i>B. tabaci</i> by manipulating symbionts and detoxifying genes.
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