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.
Ivoke, N., Okoye, I. C. and Ivoke, U. N. Department of Zoology, University of Nigeria, Nsukka, Enugu State, Nigeria
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