sweet orange essential oil nanoformulation aPPlied as cold aerosol against TRIBOLIUM CONFUSUM and CRYPTOLESTES FERRUGINEUS

Common control strategies to manage stored product pests are mainly based on the use of synthetic insecticides for direct applications and as fumigants. The use of chemical pesticides in food industry is strictly regulated, limiting the range of available products. However, the rising demand of consumers for pesticide-free food and the increasing resistance of pests to traditional insecticides, dictate the need to evaluate alternative control methods and to develop new eco-compatible insecticides. For this purpose, many sustainable techniques have been tested for the control of stored product pests. Plant essential oils (EOs) have been extensively studied due to their acknowledged antimicrobial, insecticidal, antioxidant and antifungal activity, and Citrus essential oils can represent a valid alternative to synthetic insecticides. An oil in water nano-emulsion of Sweet Orange EO has been formulated with the aim to maximize its efficacy as insecticide against two stored product pests. The developed insecticide, applied as cold aerosol, was 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 average size of the developed formulation belonged to the nanometer scale (average size 230.3 nm), with low polydispersity index (Pdi 0.274). The stability over time of the tested formulation was confirmed by the relatively high zeta potential value obtained (ζ= 26.93). The efficacy of the tested formulation showed a dose-dependent response and the cumulated mortality of the exposed insects increased until 24h of exposure. Tribolium confusum proved less susceptible to the tested formulation (LC50=86.30 ppm; LC99 631.14 ppm) than C ferrugineus (LC50=36.79 ppm; LD99=209.7 ppm). The results obtained in these trials, together with the large availability at reasonable costs of Sweet orange EO, are promising for the potential development of new tools to control stored product pests.