Green Synthesized Silver Nanoparticles: A Potential New Insecticide for Mosquito Control

Abstract

Mosquitoes are blood-feeding insects and serve as the most important vectors for spreading human diseases such as malaria, yellow fever, dengue fever, and filariasis. The continued use of synthetic insecticides has resulted in resistance in mosquitoes. Synthetic insecticides are toxic and affect the environment by contaminating soil, water, and air, and then natural products may be an alternative to synthetic insecticides because they are effective, biodegradable, eco-friendly, and safe to environment. Botanical origin may serve as suitable alternative biocontrol techniques in the future. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, this study was undertaken to assess the larvicidal activity of the synthesized silver nanoparticles (Ag NPs) and aqueous leaf extracts from the medicinal plant Feronia elephantum, Heliotropium indicum and Sida acuta against the medically important mosquito vectors, Anopheles subpictus, Aedes albopictus and Culex tritaeniorhynchus (Diptera: Culicidae). Synthesized Ag NPs were characterized by UV-vis spectroscopy, fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) with EDX, transmission electron microscopy (TEM) and XRD analysis. Range of concentrations of synthesized Ag NPs (8–60 μg/mL) and aqueous leaf extract (30–300 μg/mL) were tested against the larvae of A. subpictus, A. albopictus and C. tritaeniorhynchus. Among the Ag NPs tested, the Ag NPs of F. elephantum were highly effective against third instar larvae of A. subpictus, A. albopictus and C. tritaeniorhynchus with LC50 and LC90 values were 20.01, 21.59, 24.04 μg/mL and 34.76, 37.06, 40.86 μg/mL, respectively. The control showed nil mortality in the concurrent assay. x2 values were significant at p ≤ 0.05 level. From the three plant aqueous leaf extract and Ag NPs tested against late third instar A. subpictus, A. albopictus and C. tritaeniorhynchus, the highest larvicidal activity was observed in F. elephantum, moderate larvicidal activity was observed in H. Indicum and lowest larvicidal activity was observed in S. acuta. Results obtained from this study biosynthesized silver nanoparticles as novel biolarvicidal agent and can be used along with traditional insecticides as approach of Integrated Pest Management (IPM). This is the first report on the mosquito larvicidal activity of the plant aqueous extract and synthesized silver nanoparticles.