An Investigation into the Biological Activities of Four Lamiaceae Essential Oils Against Thrips flavus, Crops, and Weeds

In recent years, with the increasing awareness of environmental protection and food safety, essential oils (EOs) have gained significant attention as safer and more environmentally friendly alternatives. This study investigated the insecticidal activity of four Lamiaceae EOs (patchouli oil, catnip oil, lavender oil, and mint oil) against <i>Thrips flavus</i> and their effects on crops and weeds. The results show that patchouli oil, catnip oil, and lavender oil exhibited better insecticidal activity, with patchouli oil having the strongest toxicity, with an LC₅₀ value of 0.31 mg/mL. Additionally, catnip oil and lavender oil had significant attractive effects on <i>T. flavus</i>, where lavender oil only had a significant attractive effect on male <i>T. flavus</i>, with an attraction rate of 71.88% (<i>p</i> = 0.03), suggesting that it could be a potential alternative to insect lures. In pot experiments, these EOs demonstrated sustained insecticidal effects and varied impacts on crops. Lavender oil only significantly affected the shoot length of soybeans (<i>Glycine max</i>), while mint oil did not significantly affect the growth of <i>G. max</i>. Finally, we preliminarily analyzed the chemical composition of the EOs to provide insights into their active components. These findings indicate that EOs have potential applications as natural agrochemicals, but further research on their mechanisms and application conditions is required.