Insecticidal activity of essential oils extracted from the leaves of three Lippia sp. against Callosobruchus maculatus (Fabricius, 1775)

Abstract Callosobruchus maculatus (Fabricius, 1775) is considered the main pest that damages stored Vigna unguiculata (L.) Walp grains. Control of this insect is usually achieved through the use of synthetic insecticides, whose residual effects pose risks to human health and the environment. Given the important economic losses caused by the infestations of this pest and the need to develop less harmful control methods, this study aimed to evaluate the insecticidal potential of essential oils (EOs) from Lippia thymoides Martius & Schauer, Lippia lasiocalycina Schauer, and Lippia insignis Moldenke against C. maculatus . The chemical constituents of the EOs were analyzed, and an in vitro bioassay was conducted using a concentration of 10 µL mL − 1 . Distilled water and a 1% Tween ® 20 solution were used as negative controls, and Lambda-cyhalothrin was used as a positive control. Insect mortality was recorded at 24 and 48 h after treatment. The results showed that among the tested species, L. insignis was the most effective, causing 100% mortality after 48 h. Subsequently, the EO of L. insignis was tested at five different concentrations (0.625, 1.25, 2.5, 5 and 10 µL/mL) to determine the median lethal concentration (LC₅₀), which was found to be 3.11 µL/mL. Based on this result, a concentration of 5 µL/mL was selected to assess the efficacy of two application methods: topical contact and exposure to contaminated surfaces. Both methods proved to be effective in controlling C. maculatus.