Chemical properties and efficacy of Sweet orange essential oil nanoemulsion applied as cold aerosol against two stored product beetles

Common control strategies to manage stored product pests are mainly based on the use of synthetic insecticides and fumigants. Consumer’s demand for pesticide-free food, and the increasing resistance of pests to traditional insecticides, dictate the need to evaluate alternative control methods. For this purpose, many sustainable techniques have been tested for the control of stored product pests. Among them, Citrus essential oils can represent a valid alternative to synthetic insecticides. The effects of Sweet Orange essential oil (EO) nanoemulsion applied as cold aerosol were evaluated against adults of Tribolium confusum du Val (Coleoptera: Tenebrionidae) and Cryptolestes ferrugineus Stephens (Coleoptera: Cucujidae). Both chemical and physical characterization of the EO-based formulation was carried out. The developed formulation had an average size belonging to the nanometer scale and a low polydispersity index. The relatively high zeta potential value confirms the stability over time of the developed formulation. The efficacy of the tested formulation showed a dose-dependent response and the cumulated mortality of the exposed insects increaseduntil 24h of exposure for C. ferrugineus and until 120h for T. confusum. The tested formulation was more effective against T. confusum adults (LD50= 86.30 ppm) than C. ferrugineus ones (LD50= 36.79 ppm). The results of this study coupled with the large availability at reasonable costs of Sweet orange EO, are promising for the potential development of new tools against stored product pests.