Mentha spp. essential oils: Toxicity to Alphitobius diaperinus, activity against poultry pathogenic bacteria, and Beauveria bassiana compatibility

Abstract

The botanical insecticides market is growing because of limitations placed on the use of certain synthetic chemical insecticides. Consequently, this study explored the following hypotheses: i) essential oils (EOs) derived from Mentha spp. are toxic to Alphitobius diaperius (Coleoptera: Tenebrionidae), a common poultry pest; ii) these EOs are compatible with Beauveria bassiana, the natural enemy of the poultry pest, that parasite A. diaperinus; iii) these EOs also exhibit activity against bacteria that are pathogenic to poultry. In topical applications and ingestion tests, EOs from Mentha arvensis, Mentha spicata, and Mentha piperita were toxic to A. diaperinus. Chromatographic analyses revealed that menthol is the predominant compound in M. arvensis and M. piperita, whereas carvone is the major compound in M. spicata. Both (-)- and (+)-menthol, along with (-)- and (+)-carvone, underwent testing with A. diaperinus. Nevertheless, their activity was not as potent as that of the EOs, suggesting a possible synergistic and/or additive effect. The EOs did not have any adverse effects on the conidial germination, vegetative growth, or conidia production per colony of the entomopathogenic fungus B. bassiana. Consequently, these EOs are compatible with this natural enemy. The EO extracted from M. spicata exhibited significant toxicity against Staphylococcus aureus (ATCC 25923), whereas the remaining EOs displayed moderate toxicity against this bacterium. The EOs derived from Mentha spp., as assessed in this study, hold promise for the development of botanical insecticides tailored for the control of A. diaperinus. These insecticides are selective in favor of the natural enemy B. bassiana, and can also serve as effective sanitizers, thanks to their antibacterial properties.