Evaluating the Insecticidal Potential of Selected Plant Extracts Found in Upper Brahmaputra Valley against the Dengue Vector Aedes aegypti Linn. (Dipter: Culicidae)

Mosquitoes act as vector for many pathogens that spread many diseases to human which causes millions of death every year. Dengue is one of the viral diseases transmitted by Aedes aegypti, with the fastest rate of growth across the globe. Control of mosquito relies primarily on synthetic insecticide. But synthetic insecticides have led us to emergence of insecticide resistance in mosquito and increase of their population over the years. Hence, in the past few years, major advances have been made in the area of biological mosquito control using bioactive compounds of plant secondary metabolites.

The present study assessed the larvicidal activity of different extracts of three plants Polygonum hydropiper L., Litsea salicifolia Roxb. (L.) and Clerodendrum indicum (L.) Kuntze found in upper Brahmaputra valley against larvae of Aedes aegypti. Petroleum ether, chloroform and methanolic extracts were prepared to check the mortality after 12 and 24 hours of exposure in all the extracts. Further, the adult inhibition assay was performed to check the growth period of the species with the most effective plant extract.

The highest mortality was recorded in the petroleum ether extract of P. hydropiper with LC₅₀ value 39.55 ppm and lowest mortality in chloroform extract of L. salicifolia with LC₅₀ value 148.21 ppm after 24 hours of exposure. Further, emergence inhibition assay was conducted with petroleum ether extract of P. hydropiper (most effective extract). Present study found that petroleum ether extract of P. hydropiper prolongs the developmental stages while significantly reduces the adult life span of A. aegypti. Hence, P. hydropiper can be used effectively as potential larvicide against A. aegypti larvae.