INVESTIGATIONS ON THE OVIPOSITION DETERRENCE AND OVICIDAL POTENTIAL OF THE LEAF EXTRACTS OF ARGEMONE MEXICANA AGAINST AN INDIAN STRAIN OF DENGUE VECTOR, AEDES AEGYPTI (DIPTERA: CULICIDAE)

Current study was conducted to evaluate the oviposition deterrent and ovicidal potential of A. mexicana extracts against laboratory-reared A. aegypti. The leaf extracts of A. mexicana were prepared in five differentsolvents selected based on their polarity; petroleum ether, hexane, benzene,acetone and ethanol. The studies concluded that the deterrence potential of all the leaf extracts gradually increased with increasing concentrations revealing a positive correlation between the two. The results showed the maximum oviposition deterrent potential of the petroleum ether extractsagainst A. aegypti with 31% effective deterrence at 200 ppm which rose by 66% at 400 ppm. The hexane leaf extract was found to be the least effectivedeterrent amongst the other extracts displaying an ED% range of 61.5% to 2.68%. Exposure of freshly laid eggs of A. aegypti with different leafextracts for 24 h resulted in a significant increase in the ovicidal potential of each extract with increasing concentration. Remarkably, the acetone leafextract of A. mexicana was found to exhibit the highest ovicidal potential against A. aegypti with a significantly reduced egg hatch of 27.32% when exposed to 400 ppm extract as compared to control treatment; this extract causing the lowest percent hatch of 18.35% at 1000 ppm which was 0.1-2.1 folds lesser than that obtained with other leaf extracts. The petroleum ether and benzene leaf extracts were also found to show noticeable ovicidalefficacy while the remaining leaf extracts were found to be poor ovicidal agents as they were not significantly effective even at higher concentrations.Our results clearly indicate the appreciable oviposition deterrence andovicidal potential of various extracts prepared from the leaves of A. mexicana against A. aegypti. However, the mechanism causing these impacts is still not known and needs to be explored.

Keywords:

Argemone , oviposition deterrence , ovicidal , oviposition activity index , egg hatchability , effective deterrence