EFFECT OF ETHANOLIC EXTRACTS OF Hyptis suaveolens, Curcuma longa AND Ixora coccinea AGAINST 3RD INSTAR LARVAE OF Culex quinque fasciatus

Abstract

Most mosquito species have been implicated to be vectors of lots of debilitating diseases of humans and livestock. While there are over 3500 mosquito species that have been identified, Culex quinquefasciatus stands out because they are hardy and can survive different environmental conditions compare to Aedes and Anopheles species. Culex quinquefasciatus transmitts pathogens like bacteria, fungi, protozoans and helminths. The aim of this research is to assess the larvicidal potential of ethanol solvent extract of the leaves of Hyptis suaveolens, Curcuma longa and Ixora coccinea against 3rd instar larva of Culex quinquefasciatus. Adult Culex quinquefasciatus were collected blood fed, reared in an entomological cage. The resulting 3rd instar of F1 generation were assayed using serial concentrations of 10% stock solutions of the leaves extracts while feeding ad libitum. The result obtained revealed that aqueous extracts of the three plants at different concentrations (10 mg/L, 20 mg/L, 30 mg/L, 40 mg/L and 50 mg/L) caused varying mortality in C. quinquefasciatus third (3rd) instar larvae after exposure. Extract of Ixora coccinea recorded significantly higher mortality (20.33 ± 0.57) at 50 mg/L concentration than H. suaveolens (16.67 ± 0.57) and C. longa (14.33 ± 0.57) in similar concentrations. Lethal dosage studies required to yield 50% and 90% mortality for larvae was found to be smaller (LD 50 = 38.3 mg/L and LD 90 = 74.1 mg/L) with extract of Ixora coccinea. The individual or synergistic effect of some phytochemicals such alkaloids, phenols, terpenoids, and flavonoids that were observed could be responsible for mortality of larvae since they can stop larva feeding and chitin synthesis. Other plants and solvents should be tested on different mosquito species in a bid to obtain more plants that can control the vector.