Benzyl alcohol, benzyl benzoate and methyl benzoate as bio-insecticides against dried bean beetle Acanthoscelides obtectus (Coleoptera: Tenebrionidae)

Abstract

Acanthoscelides obtectus is most dangerous pest of preserved beans. The current study used benzyl alcohol (BA), benzyl benzoate (BB), and methyl benzoate (MB) to control A. obtectus. Contact and fumigant toxicity tests were performed to evaluate the efficacy of the used compounds. The contact toxicity assay revealed a significant mortality rate with LC50 reached at low concentrations of 0.57, 0.68, and 0.94 μL/g for BA, BB, and MB, respectively. BA possesses significant fumigant toxicity and outperforms MB and BB, with an LC50 achieved at concentration of 8.91 μL/L. In comparison to the control group, BA, BB, and MB have anti-feedant efficacy against A. obtectus. Furthermore, even at a low concentration of 0.5 μL/g, these compounds induced a significant suppression of A. obtectus F1 progeny production. The BA and BB activities persisted until day 5 after treatment while MB activity sustained for 3 days only. These compounds significantly inhibited acetylcholinesterase, decrease in the level of reduced glutathione (GSH), and elevated malondialdehyde (MDA). In conclusion, BA, BB, and MB are particularly promising choices for controlling the bean beetle A. obtectus because they are low in cost, of natural origin, and the European Food Safety Authority (EFSA) approved their use in animal feed.