Insecticidal activity of Green Synthesized silver Nanoparticles using Coleus aromaticus and Wrightia tinctoria Leaf Extracts against Culex quinquefasciatus

Abstract

Background Mosquitoes transmit dreadful diseases, causing millions of deaths every year. The use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. The plant extracts seem to be a better alternative to control mosquitoes due to the presence of many bioactive compounds. In addition, the green synthesized silver nanoparticles have a vital application in biological research. The present study addresses the green synthesized silver nanoparticles (AgNPs) of Coleus aromatics and Wrightia tinctoria leaf extract and their larvicidal and pupicidal activity against Culex quinquefasciatus. Methods The synthesized AgNPs were characterized by UV-Vis spectrum, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy analysis (FTIR) and XRD measurements. The II, III, IV instar and pupa of C. quinquefasciatus were exposed to different concentration of silver nanoparticles (5 ppm to 50 ppm) for 24 hours. Results: LC50 values of II, III, IV instars and pupa of C. quinquefasciatus were 13.37 ppm and 16.26 ppm, 36.07 ppm and 41.47 pp. LC90 values are 35.47 ppm, 53.57 ppm and 67.60 ppm, 76.68 ppm against Coleus aromatics. Likewise, Wrightia tinctoria LC50 values were 14.56 ppm, 18.77 ppm, 42.76 ppm and 51.06 ppm and LC90 values were 46.03 ppm, 62.17 ppm, 79.89 ppm and 93.16 ppm. Conclusion: Biosynthesis of silver nanoparticles using leaf aqueous extract of Coleus aromaticus, Wrightia tinctoria provides a potential source for the larvicidal and pupicidal activity against Cx. quinquefasciatus. Between the two plants studied, the LC50 and LC90 values indicate that Coleus aromatics synthesized silver nanoparticles were more effective than Wrightia tinctoria.