Lecithin Exhibits Rapid Contact Toxicity Against Bemisia tabaci and Is Associated with Structural and Molecular Responses

Bemisia tabaci is a globally important crop pest and virus vector with widespread resistance to conventional insecticides. We evaluated the insecticidal activity of a soybean-derived lecithin preparation and associated physiological responses. Leaf-surface, dried-residue contact, artificial-diet, and egg bioassays were combined with RNA sequencing, untargeted metabolomics, RT-qPCR, histology, and transmission electron microscopy. Dried-residue exposure yielded a 4 h LC50 of 1.16 mg mL−1 (95% confidence interval, 0.948–1.403 mg mL−1), whereas 10 mg mL−1 lecithin caused 100% adult mortality within 4 h and reduced egg hatchability from 99.44% to 37.78%. No mortality was detected after adults were provided with a sucrose diet containing 10 mg mL−1 lecithin for 24 h. Exposure at the 4 h LC50 was associated with differential expression of 135 genes and changes in 599 metabolic features, including responses related to cuticle organization, lysosomal and autophagy pathways, and amino acid metabolism. Histology and transmission electron microscopy revealed altered abdominal tissue organization and cellular ultrastructure. These findings establish contact-associated and egg-stage activity of lecithin against B. tabaci under laboratory conditions and identify accompanying structural, transcriptional, and metabolic responses. The molecular events responsible for mortality and the contribution of ingestion-mediated exposure remain unresolved.