Abstract

Objective: To evaluate the mosquito larvicidal and pupicidal activity of the ethanolic extracts from Morinda citrifolia (M. citrifolia) plant and entomopathogenic fungi Metarhizium anisopliae (M. anisopliae) against malaria vector, Anopheles stephensi (An. stephensi). Methods: M. citrifolia leaves were collected in and around Alleppy districts, Kerala, India. M. citrifolia leaf was washed with tap water and shade dried at room temperature. An electrical blender powdered the dried plant leaves. A total of 500 g leaf powder was macerated with 1.5 L of ethanol sequentially for a period of 72 h and filtered. The crude plant extracts were evaporated to dryness in rotary vacuum evaporator. The larvicidal and pupicidal activity was assayed at various concentrations ranging from 100 to 500 mg/L under the laboratory conditions. The LC50 and LC90 values of the M. citrifolia leaf extract and M. anisopliae fungi were determined by Probit analysis. Results: The plant extract showed larvicidal and pupicidal effects after 24 and 48 h of exposure; all larval instars and pupae have considerably moderate mortality; however, the highest larval and pupal mortality appeared in combined treatment at 24 and 48 h. The LC50 and LC90 values of M. citrifolia and M. anisopliae and their combined treatment against the first to fourth instars larvae and pupae of the malaria vector were assessed. M. citrifolia had values of LC50=202.47, 95.75, 57.52, 18.30 and 97.78 mg/L; LC 90=384.37, 482.91, 631.22, 757.55 and 944.96 mg/L at 48 h. M. anisopliae had values of LC 50=1.40, 3.99, 5.56, 8.77 and 11.49%; LC90=13.84, 17.62, 22.20, 25.71 and 30.78% at 48 h; Combined treatment had values of LC50=3.71, 16.73, 29.71, 40.60 and 138.10 mg/L; LC90=122.29, 150.15, 156.90, 211.99 and 806.67 mg/L at 48 h, respectively. Conclusions: The plant and the fungi are promising larvicidal and pupicidal agents against malaria vector, An. stephensi. This is a new eco-friendly approach for the control of vector. Therefore, this study provides first report on the combined treatment of this plant extract and fungi from India.

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