Insecticidal activity of essential oil from orange peels (Citrus sinensis) against Tribolium confusum, Callosobruchus maculatus and Sitophilus oryzae and its inhibitory effects on acetylcholinesterase and Na+/K+-ATPase activities

This study elucidates the fumigant toxicity and insecticidal mechanism of essential oil from orange peels against T. confusum, C. maculatus and S. oryzae. Essential oil from orange peels was obtained by hydrodistillation. The chemical constituents of the essential oil were identified by gas chromatograph/mass spectrometry (GC-MS). Fumigant toxicity of the essential oil was evaluated against the adults of T. confusum, C. maculatus and S. oryzae. The effect of the essential oil on acetylcholinesterase (AChE) and Na/K-ATPase activities in T. confusum, C. maculatus and S. oryzae homogenates were also determined. The major compounds that were identified in the essential oil include limonene (92.14%), beta-myrcene (2.7%), 1,8-cineole (0.33%), alpha-pinene (0.7%) and gamma-Terpinene (0.23%). In the fumigation assay, the essential oil displayed toxic effects against T. confusum, C. maculatus and S. oryzae. Percentage mortality of the insects increased with increase in concentration of the essential oil and exposure time while LC50 reduced with increase in period of exposure. Biochemical studies showed that the essential oil exhibited inhibitory effects on acetylcholinesterase (AChE) and Na+/K+-ATPase activities. This study indicates that essential oil from orange peels could be effective in the biocontrol of T. confusum, C. maculatus and S. oryzae and this may be associated to its inhibitory effects on acetylcholinesterase and Na+/K+-ATPase activity.