Comparative efficacy of solid nano-dispersions and conventional formulations of some insecticides against Spodoptera littoralis, (Boisd.) under laboratory and field conditions

Abstract

Owing to the large quantity of pesticides utilized conventional pesticide formulations can have numerous negative environmental impacts such as side effects on human health and pest resistance development. Using nano-pesticide formulations can minimize the quantity of pesticides used, thereby lowering pest control costs, and environmental contamination. This work used self-emulsifying and solidification technology to convert chlorpyrifos, emamectin benzoate, and beta-cyfluthrin to solid nano-dispersions, all of which were examined for their properties and efficacy against the Egyptian cotton leafworm, Spodoptera littoralis (Boisd.). During the preparation of the formulation mixture, solid nano-dispersion particles with sizes ranging from 7 to 400 nm were developed. With the design of the nano-formulation, there were variations in the active ingredient, carrier, surfactant, and pesticide concentration types. The type of active ingredient, carrier, surfactant, and pesticide con­centration varied with the nano-formulation design. The nano-formulation with 1 to 5% pesticides, 8% a combination of Nonyl phenol ethoxylated surfactant (Unitop 100) mixed with Geronol surfactant (FF4), and sucrose as a carrier indicated the best polydispersity index, Z-average, and biological activity. Moreover, the surfactant and solvent content in the solid nano-dispersion formulation was lower than in conventional pesticide formulations. Based on the LC50 values, chlorpyrifos, emamectin benzoate, and beta-cyfluthrin solid nano-dispersions were more toxic (LC50 values were 0.17 and 0.07 for emamectin benzoate, 4.61 and 3.61 for beta-cyfluthrin, and 10.06 and 6.74 mg ∙ l–1 for chlorpyrifos after 24 and 48 h of treatment, respectively) than their conventional formulations (LC50 values were 0.85 and 0.36 for emamectin benzoate nano-dispersion, 19.19 and 15.30 for beta-cyfluthrin nano-dispersion, and 27.01 and 26.17 mg l–1 for chlorpyrifos-nano-dispersion after 24 and 48 h of treatment, respectively) against S. littorralis under labora­tory conditions. Under field conditions, chlorpyrifos, emamectin benzoate, and beta-cyfluthrin in nano-dispersion formulations were more effective against cotton leaf worms than the same insecticides in commercial formulation. Thus, nano-formulations could be recommended in pest control where they avoid organic solvents and reduce surfactants, control costs, and environmental pollution.