Efficacy of Citrus sinensis Peel Essential Oil and its Copper Nanoparticle-Based Formulation as Eco-Friendly Larvicides and Adulticides for Anopheles gambiae Management

Introduction: The increasing resistance of Anopheles gambiae to synthetic insecticides necessitates the development of eco-friendly and sustainable alternatives for malaria vector control. This study evaluated the larvicidal and adulticidal efficacy of Citrus sinensis peel essential oil and its copper nanoparticle-based formulation counterpart Methodology: This study employed a laboratory-based completely randomized experimental design. Essential oil was extracted via hydrodistillation and subsequently formulated into a copper nanoparticle (CuNP)-based nano-formulation for enhanced bioactivity. Larvicidal bioassays were conducted at concentrations of 5-25 mg/L based on preliminary range-finding assays, using three replicates per treatment (20 larvae per replicate), while adulticidal activity was assessed using WHO cone bioassay at 100-500 µL/mL (crude oil) and 400-1200 µL/mL (CuNP-based nano-formulation), each performed in four replicates per concentration. Results: Both the crude essential oil and its CuNP-based nano-formulation exhibited concentration- and time-dependent larvicidal and adulticidal activity against A. gambiae. The nano-formulation demonstrated higher efficacy, achieving a maximum larval mortality of 93.33% compared to 85.00% for the crude oil at 25 mg/L after 24 hours. Probit analysis revealed lower LC₅₀ values for the nano-formulation (9.54 mg/L) than the crude oil (15.93 mg/L), indicating greater potency. In adulticidal assays, the nano-formulation produced rapid knockdown and achieved 100% mortality within 1 hour across all tested concentrations, whereas the crude oil showed delayed toxicity. Conclusion: The nano-formulated essential oil demonstrated enhanced efficacy, faster action, and improved dose-response characteristics. These findings highlight the potential of C. sinensis peel-derived nano-insecticides as sustainable alternatives for malaria vector management under laboratory conditions.