Essential Oils from Cameroonian Aromatic Plants as Effective Insecticides against Mosquitoes, Houseflies, and Moths

Recently, spices have attracted the attention of scientists and agrochemical companies for their potential as insecticidal and acaricidal agents, and even as repellents to replace synthetic compounds that are labeled with detrimental impacts on environment and human and animal health. In this framework, the aim of this study was to evaluate the insecticidal potential of the essential oils (EOs) obtained from three Cameroonian aromatic plants, namely <i>Monodora myristica</i> (Gaertn.) Dunal, <i>Xylopia aethiopica</i> (Dunal) A. Rich., and <i>Aframomum citratum</i> (J. Pereira) K. Schum. They were produced by hydrodistillation, with yields of 3.84, 4.89, and 0.85%, respectively. The chemical composition was evaluated by GC-MS analysis. The EOs and their major constituents (i.e., geraniol, sabinene, α-pinene, <i>p</i>-cymene, α-phellandrene, and β-pinene) were tested against the polyphagous moth pest, i.e., <i>Spodoptera littoralis</i> (Boisd.), the common housefly, <i>Musca domestica</i> L., and the filariasis and arbovirus mosquito vector, <i>Culex quinquefasciatus</i> Say. Our results showed that <i>M. myristica</i> and <i>X. aethiopica</i> EOs were the most effective against <i>M. domestica</i> adults, being effective on both males (22.1 µg adult⁻¹) and females (LD₅₀: 29.1 µg adult⁻¹). The <i>M. myristica</i> EO and geraniol showed the highest toxicity on <i>S. littoralis,</i> with LD₅₀₍₉₀₎ values of 29.3 (123.5) and 25.3 (83.2) µg larva⁻¹, respectively. Last, the EOs from <i>M. myristica</i> and <i>X. aethiopica</i>, as well as the major constituents <i>p</i>-cymene and α-phellandrene, were the most toxic against <i>C. quinquefasciatus</i> larvae. The selected EOs may potentially lead to the production of cheap and effective botanical insecticides for African smallholders, although the development of effective formulations, a safety evaluation, and an in-depth study of their efficacy on different insect species are needed.