Contact Toxicity and Repellent Efficacy of Kaempferia rotunda L. to Three Stored Product Insects and Synergistic Interactions between Two Major Compounds Benzyl Benzoate and Bornyl Acetate

Abstract

This paper analyzed the chemical constituents of the essential oil (EO) of Kaempferia rotunda L. and the bioactivities of the predominant compounds. Results obtained from GC/MS analysis indicated 14 compounds, which accounted for 96.66% of the total extract. Among them, the most abundant compound was benzyl benzoate (81.13%), followed by bornyl acetate (4.51%). EO from the medicinal plant K. rotunda inhibited the potent toxicity of Lasioderma serricorne and Liposcelis bostrychophila (LD₅₀=17.1μg/adult and 18.6 μg/adult). K. rotunda oil also exerted strong repellency against three target insects at high concentrations. Based on the theory of the grey correlation analysis, EO from K. rotunda performed better than benzyl benzoate but worse than bornyl acetate on the repellency against Tribolium castaneum. Benzyl benzoate possessed excellent contact toxicity with three target insects. Meanwhile, the binary mixture of two main compounds (benzyl benzoate and bornyl acetate) was evaluated for contact toxicity with T.castaneum for the first time. The synergistic effect in natural ratios has been observed, suggesting that unique mechanisms of action should be responsible for EO toxicity. Plant-derived insecticides appear suitable for developing control means against stored product insects.

Keywords:

• Contact toxicity
• Repellent efficacy
• Stored product insects
• Synergistic interactions