Formulation and physicochemical characterization of neem oil nanoemulsions for control of Sitophilus oryzae (L., 1763) (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae)

This report describes the development of environmentally-benign nanoemulsion formulations for control of adult Sitophilus oryzae(L., 1763) (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae). The formulations were emulsions of neem [Azadirachta indicaA. Juss (Sapindales: Meliaceae)] oil, nonionic surfactant (alkylpolyglucoside or polysorbate 80), and water using low-energy emulsification method. Four formulations were chosen and physicochemical characterization showed a particle size range of 208-507 nm in diameter. Bioassays were conducted using food and filter paper impregnation methods. The formulation comprised of polysorbate surfactant with 2.0 mL/kg azadirachtin caused a 100% mortality of S. oryzaeadults after only 24 h of exposure, with the food impregnation method. The toxicological studies carried out at Putra University of Malaysia toxicology laboratory between November 2014 and December 2015 indicated that S. oryzaeadults were more susceptible than T. castaneumadults to nanoemulsion formulations including 2.0 mL/kg azadirachtin according to median lethal times