Nanopesticidal effects of Pongamia pinnata leaf extract coated zinc oxide nanoparticle against the Pulse beetle, Callosobruchus maculatus

Abstract

Callosobruchus sp. is the major cause of damage to stored pulses. Recent advances in nanotechnology have provided us a promising tool for the management of insect pest of essential commodities. In the present study, we report the green synthesis and biological evaluation of Pongamia pinnata leaf extract coated zinc oxide nanoparticles (Pp-ZnO NPs) on the pulse beetle, C. maculatus. The green synthesized Pp-ZnO NPs were bio-physically characterized by UV–vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Selective area electron diffraction (SAED), Energy dispersive X-ray (EDX) analysis and zeta potential. The bio-physical characterization revealed that the Pp-ZnO NPs has a hexagonal wurtzite structures with a mean particle size of 21.3 nm. In addition, zeta potential measurement demonstrated that the Pp-ZnO NPs are negatively charged (−12.45 mV) and are moderately stable. The pesticidal effect of Pp-ZnO NPs was tested against the pulse beetle, C. maculatus. Pp-ZnO NPs reduced the fecundity (eggs laid) and hatchability of C. maculatus in a dose-dependent manner. A significant delay in the larval, pupal and total development period of C. maculatus was observed after treatment with Pp-ZnO NPs at 25 μg mL−1. Furthermore, Pp-ZnO NPs are more effective in the control of C. maculatus and caused 100% mortality at 25 μg mL−1. The LC50 value was estimated to be 10.85 μg mL−1. In addition, treatment with Pp-ZnO NPs decreased the mid-gut α-amylase, cysteine protease, α-glucosidase, β-glucosidase, glutathione S-transferase (GST) and lipase activity in C. maculatus. This study concludes that Pp-ZnO NPs are effective against C. maculatus and could be used as an alternative pest control agent in the management of stored grain insect pests in the future.