AbstractBackgroundHorizontal gene transfer (HGT), an understudied evolutionary phenomenon, influences host adaptation and reproduction in insects while providing novel targets for pest control. The whitefly Bemisia tabaci Mediterranean (MED) is a globally invasive pest known for its rapid reproduction and adaptability, which make it an ideal model for investigating HGT functions. In this study, we explored the role of the plant‐derived Bt11S (11S globulin seed storage protein) in B. tabaci MED reproduction and assessed its potential for biocontrol applications.ResultsOur results suggested that Bt11S was horizontally transferred from plants to whitefly, and the exact transfer location was determined on scaffold 1. Expression profiling analysis revealed significant Bt11S expression in B. tabaci adults, with widespread distribution across various organs. RNA interference (RNAi)‐mediated silencing of Bt11S led to a marked reduction in whitefly fecundity, accompanied by depletion of the 11S protein and amino acids, underscoring the essential role of this gene in nutrient allocation for reproduction. Long‐term suppression of the gene via virus‐induced gene silencing (VIGS) consistently impaired whitefly fecundity, demonstrating its potential for pest control.ConclusionOur findings establish Bt11S, a plant‐derived gene, as a multifunctional protein involved in B. tabaci reproductive fitness that is associated with amino acids and feeding. This discovery provides insight into eukaryotic HGT and positions Bt11S as a promising target for RNAi‐based pest control strategies. By selectively targeting pest‐specific HTGs, this approach provides an environmentally sustainable solution for managing B. tabaci infestations while minimizing impacts on nontarget organisms. © 2025 Society of Chemical Industry.