Social Science Research Network | 2021
Efficacy of Some Selected Indigenous Plant Extracts against Two Urban Mosquitoes Culex quinquefasciatus Say and Aedes aegypti L. (Diptera: Culicidea): An Update
Abstract
Efficacies of the chloroform and aqueous extracts of the leaf, stem and root of three indigenous plants viz. Calotropis procera, Polygonum hydropiper and Thevetia neriifolia against the larval mortality and reproductive potential of two urban mosquitoes Culex quinquefasciatus Say and Aedes aegypti L. are reported here. Results show that the chloroform extracts of C. procera leaf (LC50 = 167.48 ppm), P. hydropiper stem (LC50 = 341.79 ppm) and T. neriifolia leaf (LC50 = 209.45 ppm) had excellent larvicidal effect on Cx. quinquefasciatus. The aqueous extracts of C. procera stem (LC50 = 207.18 ppm), P. hydropiper stem (LC50 = 634.92 ppm) and T. neriifolia leaf (LC50 = 453.34 ppm), however, had relatively milder larvicidal effect on the mosquitoes under study. Both the extracts significantly reduced percentage of egg-hatch and adult emergence per raft, lengthened immature duration and increased immature mortality in all the treatment groups. The chloroform extracts had a significantly negative effect on the number of eggs per raft, but both chloroform and aqueous extracts failed to induce any appreciable effect on the female ratio. Compared to the aqueous extracts, chloroform extracts are much more efficient against Cx. quinquefasciatus productivity. Results on Ae. aegypti indicated that the leaf extracts of C. procera (LC50 =696.14 ppm), the stem extract of P. hydropiper (LC50 =1164.36 ppm), and the leaf extract of T. neriifolia (LC50 =872.91 ppm) had significant larvicidal effects compared to the respective controls. In general, the extracts significantly reduced egg-laying, decreased egg-hatch, lengthened immature duration, and increased immature mortality culminating in reduced adult emergence. A comparison of the larvicidal efficacy of the extracts against the two mosquito species reveals that Cx. quinquefasciatus is more sensitive to the plant extracts than Ae. aegypti. However, further research is solicited to evaluate the impact, persistence and effectiveness of these extracts against the vector mosquitoes under indoor and field conditions.