Larvicidal Activity of Nelumbo nucifera Gaertn. (Nymphaeaceae) against Anopheles stephensi (Liston 1901) and Its Effect on Non-target Organisms

Abstract

Background and objective : Control of mosquito vector is of paramount significance to reduce disease incidences as proper vaccines against mosquito borne diseases are yet to develop. Standard amalgamation of cost effective, target specific and bio-degradable insecticides is necessary owing to vector resistance, an evolutionary phenomenon and intoxication of nature through indiscriminate use of chemical insecticides. The present study projected larvicidal activities of the crude and solvent extracts of Nelumbo nucifera seed coats against the malarial vector Anopheles stephensi under laboratory conditions. Methods : Crude extracts of N. nucifera seed coats were scrutinized for larvicidal activity against 1 st to 4 th instars larvae of A. stephensi . Solvent extractions of the same material fractions were carried out by means of petroleum ether, ethyl acetate and water. Dose dependent mortality assay was performed by graded concentrations (from 60 ppm to 180 ppm) of the solvent extracts. Quantifications of LC 50 and LC 90 values were consummated through log-probit analyses. ANOVA analyses were performed for statistical justifications of the larvicidal property. Impacts of the extracts on a non-target water fauna were evaluated under laboratory conditions. Result: The highest mortality was recorded in 0.5% concentration of crude extracts after 72 hours of post exposure. Ethyl acetate extract was found to be the most potent larvicidal agent exerting efficient larvicidal activity amongst all the three solvent extracts. Following introduction of ethyl acetate extracts, 1 st and 2 nd instars larvae exhibited 100 per cent mortality within 72 hours of post-exposure. The mortality rates for 3 rd and 4 th instars were 96 and 72 per cent respectively with the same observation period. The rate of mortality (Y) was found to be positively correlated with the concentration (X) through regression analyses. ANOVA analyses established the statistical significance of the larvicidal activity of the seed coat extractives. However, the non-target populations were entirely non-responsive to extracts under study. Conclusion: Seed coat extracts of N. nucifera is effective against A. stephensi larvae . It is non-toxic to non-target organisms and environment-friendly.