Nano-chitosan as a bio-enhancer for improving insecticide formulations: A study on indoxacarb and methomyl against cotton leafworm

Abstract

This study was designed to improve the effectiveness and safety of two commercial insecticides, Camvaal EC 15 % (indoxacarb) and Nudrin SP 90 % (methomyl), against Spodoptera littoralis (Boisd.) through nanotechnology. Insecticide nanoemulsions were enhanced using nano-chitosan as a natural biopolymer. Nanoformulations of Camvaal and Nudrin were synthesized and characterized by Transmission Electron Microscopy (TEM) and Zetasizer Nano instruments. The insecticidal efficacy against the 4th instar of S. littoralis larvae revealed that the nano-formulations were more effective than the commercial formulations. LC50 values decreased from 0.049 to 0.009 mg/L for Camvaal and from 20.82 to 4.97 mg/L for Nudrin, indicating 81.63 and 76.09 % increased efficiency, respectively. Semi-field persistence studies established higher residual activity of the nano-formulations with LT50 values extending from 16.75 days (commercial) to 40.66 days (nano-formulation with chitosan). Cytotoxicity tests on human skin cells showed that nano-chitosan effectively lowered the toxicity of the insecticides with mortality percentages of 10 % for Camvaal and 12.30 % for Nudrin nano-formulations at 1000 μg/mL, compared to 100 and 73.20 % for the commercial products, respectively. These results reveal that nano-chitosan can be used as a bio-enhancer for the formulation of safer and more effective insecticides for sustainable pest control in agriculture.