Integration of botanical and bacterial insecticide against Aedes aegypti and Anopheles stephensi

The present study evaluated the Orthosiphon thymiflorus leaf extract and the bacterial insecticide spinosad, testing the first to fourth instars larvae and pupae of two important vector mosquitoes, viz., Aedes aegypti, Anopheles stephensi. The fresh leaves of O. thymiflorus were washed thoroughly in tap water and shade-dried at room temperature (28 ± 2 °C) for 5 to 8 days. The air-dried materials were powdered separately using a commercial electrical blender. From the plants, 500 g powder was macerated with 1.5 L organic solvents of petroleum ether sequentially for a period of 72 h each and then filtered. The larval and pupal mortality was observed after 24 h of exposure; no mortality was observed in the control group. The first- to fourth-instar larvae and pupae of A. stephensi had values of LC(50) = 309.16, 337.58, 390.42, 429.68, and 513.34 ppm, and A. aegypti had values of LC(50) = 334.78, 366.45, 422.97, 467.94, and 54.02 ppm, respectively. Spinosad against the A. stephensi had values of LC(50) = 384.19, 433.39, 479.17, 519.79, and 572.63 ppm, and A. aegypti had values of LC(50) = 210.68, 241.20, 264.93, 283.27, and 305.85 ppm, respectively. Moreover, in combined treatment, the A. stephensi had values of LC(50) = 202.36, 224.76, 250.84, 288.05, and 324.05 ppm, and A. aegypti had values of LC(50) = 217.70, 246.04, 275.36, 315.29, and 353.80 ppm, respectively. Results showed that the leaf extract of O. thymiflorus and bacterial insecticide spinosad are promising as a good larvicidal and pupicidal against dengue vector, A. aegypti and malarial vector, A. stephensi. This is an ideal eco-friendly approach for the control of target species of vector control programs.