Combinations of plant essential oils and their major compositions inducing mortality and morphological abnormality of Aedes aegypti and Aedes albopictus

Abstract

Extensive uses of synthetic insecticides to control mosquito's populations have induced the insects to develop resistance against them, rendering them ineffective today. Moreover, they cause serious impacts on human health and the ecosystem. Therefore, safe and effective natural alternatives are needed. This study evaluated the larvicidal and pupicidal activities of essential oils (EOs) from Illicium verum and Zanthoxylum limonella and the major constituents against Aedes aegypti and Aedes albopictus mosquitoes as well as recorded their morphological aberrations at death. The GC-MS analysis showed that trans-anethole was the major constituent of I. verum EO, and limonene was the major constituent of Z. limonella EO. Both were more effective against the larvae and pupae of Ae. aegypti than those of Ae. albopictus. A 2.5% I. verum EO + 2.5% trans-anethole combination showed the highest larvicidal and pupicidal effects against Ae. aegypti and Ae. albopictus with an LT50 ranging from 0.2-6.9 h. Between the two tested constituents, trans-anethole exhibited stronger larvicidal and pupicidal activities (LC50 ranging 2.4–3.4%) against the two tested mosquito species than d-limonene (LC50 ranging 2.5–3.7%). Most importantly, 5% trans-anethole, 5% d-limonene, and 2.5% I. verum EO + 2.5% trans-anethole were more effective (LT50 ranging 0.1–0.3 h) than 1% (w/w) temephos (LT50 ranging 2.9–3.1 h). Morphological aberrations at death observed were such as color pigment and thorax shape abnormalities. To conclude, trans-anethole, d-limonene, and a combination of I. verum EO + trans-anethole, are natural compounds that not only are as effective as temephos at the time of this study, but should be also be much safer to human health.