Effect of Root Extracts of Lantana camara (Verbenaceae) on Larvae of Aedes aegypti (Diptera: Culicidae)
Larvicidal activity of three solvent root (bark and wood) extracts of Lantana camara Linn. was investigated against first and fourth instars of Aedes aegypti larvae after 24 and 48 h post-treatment exposure to serial concentrations (0.1, 0.05, 0.01, 0.005, 0.001 %) of aqueous, ethanolic and acetone crude extracts. All extracts showed varying degrees of larvicidal activity reported as LC50 and LC90 values. At 24 h post-treatment exposure of first instar larvae, larvicidal activities of acetone extract (LC50=0.011%; LC90=0.017%) was similar to the ethanolic extract (LC50=0.011%; LC90=0.023%) but differed from the aqueous extract (LC50=0.047%; LC90=0.056%). After 48 h treatment exposure of first instar larvae, acetone extracts (LC50=102 ppm or 0.0102%; LC90=162 ppm or 0.0162%) was significantly more toxic than either the ethanolic extract (LC50=107 ppm or 0.0107% ; LC90=216 ppm or 0.0216%) or aqueous extract (LC50=428 ppm or 0.0428%; LC90=548 ppm or 0.0548%). After 48 h treatment exposure of fourth instar larvae, acetone extracts (LC50=181 ppm or 0.0181%; LC90= 192 ppm or 0.0192%) exerted the most lethal effects, followed by ethanolic extract (LC50=225 ppm or 0.0225%) and aqueous extract (LC50=605 ppm or 0.0605% ; LC90= 710 ppm or 0.0710%). Sensitivity / susceptibility of larval instars to extracts appeared to be dose and developmental stage-dependent. Factorial analysis showed that extracts (F=0.044; df =2,36 ; p<0.001) treatment rate (F= 19.83; df=5, 36; p<0.001) and exposure time ( F=2.23 ; df=1, 36; p<0.001) significantly affected mortality of the first and fourth larval instars (F= 9.13; df=1, 36; p< 0.001). The results indicate that root extracts of L. camara may be effective in controlling the vector of urban yellow fever, Ae. aegypti especially at the immature stages of development.
N Ivoke, IC Okoye, UN Ivoke