Nano-encapsulated Litsea cubeba essential oil in chitosan nanoparticles induces toxicological and physiological disruption in Nilaparvata lugens

The brown planthopper (Nilaparvata lugens) is a destructive rice pest in Asia, causing significant yield losses through sap feeding and virus transmission. We developed an eco-friendly nano-encapsulation system using chitosan nanoparticles (CS NPs) loaded with Litsea cubeba essential oil (Lc EO), a potent botanical insecticide. GC–MS analysis identified citral (48.5%) as the dominant component of Lc EO. CS-Lc NPs (282 nm in diameter) were successfully synthesized via emulsion-ionic gelation, exhibiting enhanced thermal stability and sustained release. Bioassays showed significantly higher insecticidal activity in CS-Lc NPs with LC₅₀ values of 391.41 mg/L at 72 h and 229.14 mg/L at 120 h, compared to unloaded CS NPs (1034.54 mg/L at 72 h and 627.78 mg/L at 120 h). The nano-formulation caused severe damage to the midgut epithelium, as observed through histopathology, elevated salivary flange production, disrupting the activities of detoxification enzymes (POD, SOD, CAT, AChE, AKP, ACP). Molecular analysis confirmed the upregulation of key detoxification genes, with a significant increase in NlCYP6AY1v2 expression, highlighting the enhanced bioavailability and sustained insecticidal activity provided by nano-encapsulation. CS-Lc NPs enhanced both the stability and bioavailability of Lc EO, significantly improving its efficacy against BPH. This approach offers a promising alternative to reduce reliance on chemical pesticides in rice farming.