PUPAL EMERGENCE INHIBITION ACTIVITY OF ACALYPHA INDICA LEAF EXTRACT AGAINST DENGUE VECTOR, AEDES ALBOPICTUS MOSQUITO

Abstract

Objective: To investigate the larvicidal activities of six varying extracts of Acalypha indica (A. indica) leaves from family Euphorbiaceae against the dengue mosquito vector, Aedesalbopictus (Ae. albopictus) in laboratory.Methods: Leaves from the study plants were separated, air dried in room temperature, grounded and extracted with different solvents (petroleum ether, chloroform, ethyl acetate, n-butanol, ethanol and aqueous) by solvent apparatus and aqueous extract by maceration method. The extra solvents were evaporated to obtain crude extracts by using rotary evaporator. The crude extracts of six different solvents were dissolved in dimethyl sulphoxide (DMSO) to prepare test dosages of 1000, 2000, 3000, 4000 and 5000 ppm. Third instar larvae of Ae. albopictus were exposed to 1000, 2000, 3000, 4000 and 5000 ppm concentrations of petroleum ether, chloroform, ethyl acetate, n-butanol, ethanol and aqueous extracts of A. indica and compared with control to determine the larvicidal effects. Larval bioassays were carriedout according to World Health Organisation (WHO) procedures. The rate of larval mortality was recorded after 24h and 48 h of time exposure. Three duplicate trials were made for each tested dosage. IC50 and IC90 values were calculated by using probit analysis.Results: Based on probit analysis result the 24h and 48h LC50 and LC90 of petroleum ether extract of A. indica against Ae. albopictus was found to be 2805.43 ppm and 2376.11 ppm, 3825.14 ppm and 3327.8 ppm, respectively. An LC50 and LC90 value of chloroform extracts of A. indicaa gainst third instar larvae was found to be 2276.5 ppm and 4015.8 ppm (24h), 2213.36 ppm and 3430.43 ppm (48h), respectively. An LC50 value of 4472.17 ppm and 2469.61 ppm, and LC90 value of 4215.84 ppm was obtained on ethylacetate extract treatment against Ae. albopictus for 24h and 48h exposure, respectively. The 24h and 48 h LC50 and LC90 values of n-butanol extracts of A. indica was found to be 2777.88 ppm and 3628.19 ppm, 2225.61 ppm and 2518.86 ppm, respectively. In the present study, the larvicidal bioassays demonstrated that the n-butanolextract was most effective with 100% mortality against larvae of Ae. albopictus at 3000, 4000 and 5000 ppm compared to other extracts. All other extracts (petroleum ether, chloroform and ethyl acetate) of A. indica at high concentration (4000 ppm and 5000 ppm) manifested a significant (P<0.01 and 0.05) knock down effect of 100% moratality after 24h and 48h exposure. While the third instar lavae of Ae. albopictus were found to be most susceptabile and produced no mortality to ethanol and aqueous extract at varying parts per million. Conclusion: A. indica leaf extract was tested for the first time against dengue vector Ae. albopictus and the results revealed that A. indica can be used to control dengue vector. Further this extract needs to be evaluated under field conditions for proper exploitation of Ae. albopictus mosquito larvae. Thus, the present study provided a first report on A. indica as a prompting mosquito larvicidal activity and can be considered for further investiagtions such as formulation of bioinsecticides to control Ae. albopictus populations