Botanical insecticides, including essential oils (EOs), can be considered as appropriate alternatives to synthetic insecticides for controlling stored product pests. In this study, potential of nano-formulations of the Tasmanian blue gum (TBG) EO to control Callosobruchus maculatus Fabricius (Coleoptera, Bruchidae) were evaluated under laboratory condition. Two nano-emulsion formulations of the EO were provided using gum Arabic and Span 80 as surfactants. Contact as well as fumigant toxicities of the formulations to the beetle adults were compared with the bulk EO in 1, 2, and 3 d after treatment. Results showed that all formulations were toxic to the adults. After 1, 2, and 3 d of treatment, the estimated LC50 values in contact and fumigant applications varied from 1.37 to 8.53 ppm and 0.05 to 0.44 ppm for various formulations. Both nano-formulations cause significant stability enhancement of the EO. Moreover, the EO had significant repellent and ovicidal effects on the insect. The insecticidal effects of the EO in nano-formulations were significantly greater than in the bulk form. The EO constituted 22 compounds, from 5 classes. Eucalyptol (43.79%) is the main constituent of the TBG EO.
Keywords: stored product insects; botanical insecticide; essential oils; nano-formulation; toxicity.
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