Duckweed (Lemna minor) biomass aqueous extract-mediated synthesis of silver nanoparticles as a novel formulation era for long-term efficacy against Tribolium castaneum and Sitophilus oryzae adults on wheat seeds

Abstract

AbstractPlant-based biological nanoparticles (NPs) synthesis is a new technique where biological molecules and their combinations in plant aqueous extract decrease metal salts, which have a dual role in the fabrication and stabilization of metallic NPs. Here, we used aqueous extract from the duckweed (Lemna minor) plant to biosynthesize silver NPs (AgNPs), which were verified by a shift in color from pale brown to dark brown. AgNPs were then further characterized.By High Performance Liquid Chromatography (HPLC) analysis, the most abundant compound in the aqueous extract were vanillic acid, benzoic acid, quercetin, resveratrol, ferulic acid, rutin, p-hydroxy benzoic acid, rosmarinic acid, ellagic acid, and o-coumaric acid. Scanning Electron Microscopy (SEM), micrograph revealed spherical-shaped synthesized AgNPs with an average size of 40.56 nm. Capping and stabilizing agents, present in the form of various biomolecules, were responsible for the prolonged stability of the produced AgNPs, as proven by FTIR analysis. The Zeta potential of the surface electric charges of AgNPs was determined to be − 27 mV. The UV–Vis spectrum indicates a broad surface plasmon resonance (SPR) absorption peak at 450 nm. The EDAX test confirmed the presence of silver in the suspension. Green-produced AgNPs had the highest insecticidal activity against Sitophilus oryzae, with LC50 values of 6.08 µg/mL compared to adults of Tribolium castaneum, which were 7.03 µg/mL. All the assays clearly showed that formulated AgNPs 1% DP showed that increasing exposure intervals and concentrations resulted in a gradual increase in the mortality of adult T. castaneum and S. oryzae exposed to treated wheat seeds. The effect of post-toxic levels of AgNPs on the progeny counts of adults of T. castaneum and S. oryzae showed that increasing exposure intervals and concentrations resulted in a gradual increase in the mortality of adult T. castaneum and S. oryzae exposed to treated wheat grains. The effect of post-toxic levels of AgNPs on the progeny counts of adults of T. castaneum and S. oryzae and resulted that concentration of 0.2 g/100 g seed being the most effective one, with higher reductions in F1-progenythan than other concentrations and malathion (1% DP) during storage for 1 year, as well as a significant positive effect on seed germination during storage. The present work suggests that eco-friendly biosynthesized and formulated AgNPs are promising green insecticides that can be used as an alternative method to control and protect seeds against adults of T. castaneum and S. oryzae to overcome the synthetic insecticide problems.