Baseline susceptibility and biochemical mechanism of resistance to flupyradifurone in Bemisia tabaci

Bemisia tabaci (Gennadius) is one of the world's most devastating crop pests, and many populations show high resistance to various insecticides. To determine B. tabaci susceptibility to flupyradifurone and understand mechanisms of resistance, we conducted field monitoring and cross-resistance, synergism, and metabolic enzyme activity assays with two resistant strains: Wuhan (WH) and Xiangyang (XY). Results showed that most field populations were highly susceptible to flupyradifurone. However, WH and XY populations, with resistance ratios of 21.95- and 29.03-fold, respectively, showed a low level of flupyradifumne resistance but no cross-resistance to imidacloprid or cyantraniliprole. Synergism tests demonstrated that piperonyl butoxide (PBO) and triphenyl phosphate (TPP) significantly inhibited flupyradifurone resistance in the XY strain, while PBO significantly inhibited resistance in the WH strain. Increased cytochmme P450 monooxygenase and esterase activity correlated with flupyradifurone resistance in the two resistant strains, indicating putative involvement of these enzymes in detoxification. By rotating flupyradifurone with other chemical agents that lack cross-resistance, development of resistance could be delayed, making flupyradifurone an effective agent for whitefly management in China.