Production and evaluation of mosquito repellent coil using orange (Citrus sinensis) peel extract

Mosquito-borne diseases remain a major public health concern, and continued reliance on synthetic mosquito coils raises issues of cost, insecticide resistance, and indoor air quality. This study produced and evaluated a plant-based mosquito repellent coil formulated from orange peel (Citrus sinensis) extract. Dried orange peels were extracted using ethanol and the extract was incorporated into a combustible base with starch solution as the binder. Gas Chromatography-Mass Spectrometry (GC-MS) analysis confirmed limonene (87.3%) as the major constituent, with linalool (2.1%), citral (1.8%), and α-pinene (1.2%) as minor components. Turmeric and camphor were included as botanical repellent enhancers, while activated charcoal was added to support steady combustion and improve smoke characteristics. Dose-response studies were conducted at 5%, 10%, 15%, and 20% extract concentrations, with 15% showing optimal repellency (91.2%) and burning characteristics. Performance was assessed using standardized WHO cone bioassay with Aedes aegypti, physical properties, burning time, mosquito repellency effectiveness, air quality emissions (PM2.5, CO, formaldehyde), stability over 3 months storage, and thermal degradation analysis. From 100 g of dried orange peel, 8.5 g of extract was obtained, giving a percentage yield of 8.5%. The formulated coils showed good structural integrity, produced moderate smoke, and had a characteristic, pleasant citrus odour. Statistical analysis (ANOVA) showed significant differences in repellency between concentrations (F = 24.36, p < 0.001), and t-test confirmed comparable burning time to commercial coils (t = 2.14, p = 0.067, 95% CI: -1.65 to 0.05). The average burning time of the 15% orange peel-based coil was 6.4 hours, compared with 7.0 hours for a commercial mosquito coil. Standardized bioassay revealed knockdown rates of 45% at 30 min and 78% at 60 min, with 82% mortality after 24h. Stability studies showed 94% essential oil retention after 3 months, and thermal analysis indicated 23% limonene degradation during combustion. Emission analysis demonstrated significantly lower PM2.5 (p < 0.01) compared to commercial coils. Overall, the orange peel-based coil demonstrated appreciable repellency, acceptable burning performance, improved safety profile, and satisfactory stability, suggesting potential for an affordable, eco-friendly household mosquito control product.