Potential of Bursera graveolens essential oil for controlling bean weevil infestations: Toxicity, repellence, and action targets

Abstract

Plant essential oils are promising tools for the management of insect infestations in stored beans. However, how these biorational products exert their insecticidal actions remains unknow. Here, we evaluated the insecticidal and repellent potential of Bursera graveolens essential oil against the bean weevil species Acanthoscelides obtectus and Zabrotes subfasciatus. By using chemical and in silico analyses, we evaluated the molecular interactions of the essential oil constituents with two potential physiological targets in stored beans: acetylcholinesterase (AChE) enzymes and transient receptor potential (TRP) channels. Our results revealed limonene (44%), phellandrene (24%), cymene (13%), and menthofuran (11%) as the major constituents of the essential oil. Both bean weevil species were similarly killed by the fumigant essential oil. However, while Z. subfasciatus individuals were repelled only at high essential oil concentrations (LC95 = 156 μL/L), the essential oil LC15 (44 μL/L) was enough to repel A. obtectus individuals. Our computational predictions revealed that all essential oil constituents formed stable molecular interactions (binding affinity < −5.5 kcal/mol) with the binding sites of acetylcholinesterase and TRP channels, suggesting the involvement of these targets in the essential oil actions. Altogether, our findings show that B. graveolens essential oil may exert its insecticidal actions by disrupting the functions of AChE and TRP channels and that it may be used as an alternative tool for the control of bean weevils