Eco-friendly pesticide based on peppermint oil nanoemulsion: preparation, physicochemical properties, and its aphicidal activity against cotton aphid

Using organic insecticides including plant oils, it is possible to design a new perspective for the control of insect pests. In this research, nanoemulsion formulations of Mentha piperita, wild-type essential oil (EO) were prepared utilizing high-energy ultrasonication process. Physicochemical properties of nanoemulsions were precisely studied by measurement various parameters including pH, viscosity, conductivity, and zeta potential. Experimental design by the aid of response surface methodology (RSM) was used to highlight the physicochemical roles of EO percentage (1% to 5% (v/v)) and surfactant concentration (3% to 15% (v/v)) for achieving minimum droplet diameter with high physical stability. The nanoemulsion formulations were then characterized using dynamic light scattering, transmission electron microscopy, and optical clarity. Afterward, an appropriate model between the variable factors (EO percentage and surfactant concentration) and the response (hydrodynamic particle size) was statistically developed. Under the optimum conditions, nanoemulsion with hydrodynamic particle size less than 10 nm with high physical stability is obtainable. Bioassay experiments were carried out to elucidate the effects of nanoemulsion on the cotton aphid. Synthesized nanoemulsion formulations showed relatively high contact toxicity (average value of LC₅₀ was about 3879.5 ± 16.2 μl a.i./L) against the pest. On the basis of the obtained results, prepared nanoemulsion using M. piperita is potentially applicable as organic insecticides against cotton aphid.