Abstract
It is still an enigma to overcome mosquito outbreaks due to emergence of resistance against chemical insecticides. But, pesticides of botanical origin may demolish the resistance and become the suitable alternative in future. Larvicidal efficacy of Mentha piperita L. and Ocimum basilicum L. water and ethanolic leaves extracts was evaluated against 2nd, 3rd and 4th instar larvae of Culex quinquefasciatus (Diptera; Culicidae). The larval mortality was recorded after each 12 h of 2 d continuous exposure. All extracts indicated moderate larvicidal activities; however, M. Piperita ethanolic extract inhibited larvae growth and signified higher toxicity, as compared to O. basilicum. LC50 and LC90 of 2nd, 3rd and 4th instars larvae were 301.90, 276.60 and 198.02 ppm in water and 238.84, 156.46 and 146.24 ppm in ethanol extract of M. piperita respectively. Whereas, LC50 of O. basilicum was 588.13, 512.22 and 490.92 ppm in water and 413.75, 396.29 and 302.78 ppm in ethanol extract against 2nd, 3rd and 4th instar larvae respectively. Biochemical analysis of extract treated larvae revealed a significant decrease in proteins, carbohydrates and lipids of larvae. Among the two plants tested, M. Piperita (p=0.01) showed significantly higher toxicity, as compared to O. basilicum (p=0.02). Biochemical analysis of extract treated larvae revealed a significant decrease in proteins, carbohydrates and lipids. Phytochemical analysis of M. piperita in ethanol revealed the presence of alkaloids, anthraquinone, carbohydrates, flavonoids, phenols, saponins and steroids whereas, water extract added, cardiacglyosides, instead of phenols, anthroquinone and saponins. In further studies, these chemicals can be isolated and evaluated individually for their toxicity to use in preparing environment friendly larvicides.