Laboratory Evaluation of Two Meliaceae Species as Larvicides Against Culex quinquefasciatus Say (Diptera: Culicidae)

Mosquitoes present a key threat to millions of people worldwide, since they are vectors for dangerous pathogens and parasites of diseases such as malaria, filariasis, yellow fever, dengue, chikungunya and Zika virus disease. Culex quinquefasciatus is the principal vector of bancroftian filariasis and also a potential vector of several arboviruses like West Nile virus (WNV) and Rift Valley fever virus. To prevent proliferation of mosquito-borne diseases and to improve quality of environment and public health, mosquito control is essential. Plants enriched with phytochemicals are reported to possess insecticidal properties particularly mosquitocidal. Therefore, in the present study, the larvicidal efficacy of crude petroleum ether, chloroform, ethyl acetate and methanol leaf extracts of Melia dubia and Swietenia mahagoni against Culex quinquefasciatus was studied at concentrations of 62.5, 125, 250, 500 and 1000 mg/L. Larval mortality was assessed 24, 48 and 72 hours after treatment. The results revealed that the petroleum ether leaf extract of Melia dubia and Swietenia mahagoni showed the highest larvicidal activity than the other extracts. One hundred per cent larval mortality was observed in petroleum ether extract of both plants at 500 mg/L after 48 hours. The LC₅₀ values of crude petroleum ether leaf extract was 380.11 and 80.31; 70.51 and 52.70 mg/L after 24 and 48 hours, respectively. Among the two plant species tested, Swietenia mahagoni was found to show higher activity as its LC₅₀ value was five times less than the LC₅₀ value of Melia dubia after 24 hours treatment. Further investigations are needed to elucidate this activity against a wide range of all stages of mosquito species and also the active ingredient(s) of the extract responsible for larvicidal activity should be identified

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