Mohammad_2026_Sci.Rep__

Neonicotinoids such as imidacloprid and thiamethoxam remain widely used for managing the whitefly, Bemisia tabaci, yet intensive applications have selected for resistance in many production systems. Here, we quantified stage-resolved susceptibility to imidacloprid and thiamethoxam across eggs, second-instar nymphs, and adults in five field populations of B. tabaci molecularly confirmed as MEAM1 by COI sequencing and phylogenetic analysis. The study further examined whether population-level resistance patterns were associated with detoxification enzyme activity measured in adults. Standardized leaf-dip bioassays on colonies reared on eggplant under controlled conditions were analyzed by probit methods to estimate LC(50) values and resistance ratios (RRs) relative to a field-derived reference population (Marand). Across life stages, among-population differences were consistent, with Jiroft showing the highest LC(50) and RR values. In adults, imidacloprid resistance in Jiroft approached ~ 60-fold, whereas thiamethoxam resistance reached ~ 24-fold. Second-instar nymphs showed lower RRs than adults but still exhibited meaningful resistance (imidacloprid RR = 15-fold in Jiroft), and eggs also displayed elevated tolerance relative to the reference population. In adult biochemical assays, resistant populations showed increased cytochrome P450 monooxygenase and glutathione S-transferase activities and/or elevated carboxylesterase activity, consistent with a metabolic component to resistance. These results delineate a life-stage-resolved resistance profile within a single MEAM1 lineage and under the present assay framework, second-instar nymphs appeared to be the most operationally responsive stage for potential intervention, but are no longer fully susceptible in highly selected populations, underscoring the value of stage-explicit monitoring in intensive vegetable systems.