Impact of Punica granatum-based green larvicide on the predation rate of Polypedates cruciger for the control of mosquito vectors, Anopheles stephensi and Culex quinquefasciatus (Diptera: Culicidae)

Abstract

Mosquitoes can transmit the causal agent of various human diseases, resulting in millions of deaths every year. In the present study, four simple and inexpensive leaf extracts of Punica granatum, prepared with methanol solvents of increasing polarity, against various developmental stages of the malarial vector, Anopheles stephensi and filarial vector, Culex quinquefasciatus were assessed. The compound composition in each methanol extract was first identified using a gas chromatograph–mass spectrophotometer analysis and the main component was phenol, 2-methyl-5-(1-methylethyl); then it was analyzed by nuclear magnetic resonance (NMR) spectral analysis of 1H NMR. The LC50 and LC90 values of the methanol-derived extract against mosquito larvae were 125.78 and 225.98; 115.28 and 209.50 ppm, against both vectros. Under laboratory conditions, the predation rate of the Polypedates cruciger against An. stephensi and Cx. quinquefasciatus larvae was assessed. The mean number of mosquito prey per larval instars (I to IV) consumed daily by the tadpoles was 22.16 (I), 20.78 (II), 18.96 (III), 15.17 (IV) and 21.30 (I), 19.72 (II), 18.04 (III), 13.78 (IV) for An. stephensi and Cx. quinquefasciatus. Post-exposure to the methanol-derived leaf extract of P. granatum, the mean number of mosquito larvae prey consumed per tadpole per day increased which indicates that this natural mosquito larvicide on non-target tadpoles is compatible and can be used as part of a biological control program against these mosquitoes. This study suggests that the effective plant crude methanol-derived extracts has potential as an alternative eco-friendly approach for vector control of these mosquito larval pests.