Preparation and characterizations of essential oil and monoterpene nanoemulsions and acaricidal activity against two-spotted spider mite (Tetranychus urticae Koch)

Abstract

ABSTRACTThe present study aims at preparing nanoemulsions of two types of plant essential oils (EOs) (Callistemon viminalis and Origanum vulgare) and two monoterpenes (R-limonene and pulegone) as acaricidal agents against two-spotted spider mite, Tetranychus urticae Koch. The oil-in-water nanoemulsions (10% active ingredient) were spontaneously formed by adding dropwise an EO or monoterpene into an aqueous solution containing 20% of a surfactant (Tween 80) with continuous stirring followed by a high-energy (ultrasonication) emulsification process for 15 min. The characterizations of nanoemulsions including viscosity, pH, thermodynamic stability, droplet size, and polydispersity index (PDI) were investigated in detail. All nanoemulsions were prepared with droplet size in the range of 7.07–10.18 nm and a PDI of 0.249–0.620. Nanoemulsions exhibited high acaricidal activity against T. urticae mites with a 100% reduction at 5000 mg/L after 2–3 days of application on bean plants (Phaseolus vulgaris L.) under greenhouse conditions. No symptoms of phytotoxicity were observed in treated plants during the experiments (21 days). The stability of prepared nanoemulsions, high acaricidal activity, and the absence of organic toxic solvents make the formulations suitable as acaricidal products. The results suggest that appropriate nanoemulsions containing EOs and/or monoterpenes can be developed to control T. urticae on plants.