Acute Toxicity of Two Tropical Plant Extracts on the Fecundity and Fertility of Culex Quinquefasciatus Say

E Pushpalatha

doi:10.13189/azb.2015.030302

Abstract

Acute toxicity tests were conducted to determine the biological effects of partially purified extract of two tropical plants Croton hirtus L'Her., Pogostemon quadrifolius (Benth.) F.Muell on the juveniles of Culex quinquefasciatus Say. Rearing of C. quinquefasciatus larvae in water at concentration less than the critical concentrations for inhibition of adult emergence in 50% of treated larvae (EC50) of the ethyl acetate fraction of Croton hirtus and Pogostemon quadrifolius leaf extracts from hatching to emergence significantly decreased the fecundity of the C. quinquefasciatus and the hatchability of their eggs. At highest concentration of 50% EC50 of the extracts the decrease in the fecundity over the control ranged between 72.4 and 85.4 %.

Highlights

In view of the fact that mosquitoes develop genetic resistance to synthetic insecticides [1] and even to biopesticides such as Bacillus sphaericus [2,3] and the application of degradable botanicals for the control of mosquitoes is recommended [4]
The ethyl acetate (EA) fraction of Croton hirtus and Pogostemon quadrifolius leaf extract was very highly active with regard to its efficacy to inhibit adult emergence The lowest emergence in 50% of treated larvae (EC50) of the EA fraction is ranged between 8.79 ppm and 19.1 ppm against II instar larvae for Croton hirtus and Pogostemon quadrifolius respectively
Treatment of C. quinquefasciatus with 50% of the EC50 of I instar Culex of C. hirtus leaf extract decreased the fecundity by 85.4%

Summary

Introduction

In view of the fact that mosquitoes develop genetic resistance to synthetic insecticides [1] and even to biopesticides such as Bacillus sphaericus [2,3] and the application of degradable botanicals for the control of mosquitoes is recommended [4]. Thangam and Kathiresan [6 and 7] have reported that acetone extracts of several species of marine angiosperm and algae possess very high mosquito larvicidal activity with their critical lethal concentrations (LC50) ranging from 17.0 to 95.5 ppm. In an effort to increase the activity of plant extracts Pushpalatha and Muthukrishnan [8] purified the crude extracts in silica gel columns using solvents with a sharp polarity gradient and reported that 8.21 ppm of 3:1 petroleum ether (PE): ethyl acetate (EA) fraction of Vitex negundo leaf extract killed 50% of the treated II instar larvae of Culex quinquefasciatus. As a result of mosquitoes transmitting diseases, the critical concentrations of botanicals which inhibit 50% of the treated larval population from emerging as adults (EC50) are more meaningful than the LC50 [9,10]. The larvicidal activity of extracts from two tropical plants and the effect on fecundity and fertility against C. quinquefasciatus are reported in this paper

Methods

Results

Conclusion