Acute and sub-lethal toxicity of eight essential oils of commercial interest against the filariasis mosquito Culex quinquefasciatus and the housefly Musca domestica

The massive use of synthetic insecticides led to negative effects on the environment and human health. Therefore, researchers looked at natural products as effective alternatives to conventional pesticides. Here, commercially valuable essential oils (EOs) were selected from mint (Mentha x piperita, Mentha spicata), basil (Ocimum basilicum), helichrysum (Helicluysum italicum), yarrow (Achillea ligustica), geranium (Pelargonium odoratissimum), cinnamon (Cinnamomum verum) and ginger grass (Lippia alba). The chemical composition of these EOs assayed was analyzed by GC-MS. Then, we investigated their insecticidal potential in acute and sublethal toxicity assays against mosquito vectors of filariasis (Culex quinquefasciatus) and house flies (Musca domestica). Against C. quinquefasciatus 4th instar larvae, the most toxic EO was C. verum (LC50 = 40.7 mu L-I), followed by L. alba (LC50 = 59.6 mu l L-1), while against M. domestica adults, the most toxic EOs were C. verum and H. italicum (LD50 = 42 mu g adult(-1)). The exposure of mosquito larvae to a sub-lethal concentration (LC30 = 25 mg L-1) led to a reduction of adult emergence and fertility. Besides, adult flies that survived after exposure to a sub-lethal dose of C. verum EO (LD20 = 10 mu g adult(-1)) showed a marked decrease in male and female longevity, as well as to a reduction in fecundity, fertility, and natality. Overall, C. verum and H. italicum EOs showed a highly promising insecticidal potential on two key insect vectors and pests. The relatively low prices of the selected EOs, their availability on the market and the noteworthy global production of the bulky materials, make them as ideal candidate ingredients to be used in insecticidal formulations.