Larvicidal Potentials of Leaves and Bark Extracts of Eucalyptus camaldulensis (Schlect) and Eucalyptus citriodora (Hook) on Culex quinquefasciatus (Say) Larvae

Abstract

The larvicidal activity of leaf and bark extracts of Eucalyptus camaldulensis and Eucalyptus citriodora on juveniles of Culex quinquefasciatus was determined. Larvae were successfully bred in the laboratory in order to obtain a “pure” colony. 162 batches of 25 larvae each were treated with 3.90mg/l, 15.63mg/l, 62.50mg/l, 250mg/l and 1000mg/l of the plant extract in 3 replicates, for 24 hours to record mortalities, and for up to 96 hours to record feeding and fecundity of the larvae. There was increase in percentage mortality with increase in concentration of petroleum ether extracts. There was a statistically significant difference between extracts (P<0.05) used in the bioassay and mortality of larvae but there was no significant difference (P>0.05) between the two plant species used. Statistical analysis of average mortality figures using the Probit analysis for the leaf extracts of E. citriodora and E. camaldulensis gave the LC₅₀ of 245.47 (26.89 ± SE10.13) and 316.23 (22.89 ± SE8.95) for the crude extracts, the petroleum ether extract had LC₅₀ of 97.72 (44.95 ± SE12.89) and 223.87 (29.17 ± SE9.56). The methanol extract LC₅₀ was 162.18 (30.7 ± SE11.16) and 257.04 (26.47 ± SE9.28). The bark extracts LC₅₀ was 251.19 (27.78± SE8.39) and 398.11 (20.7± SE7.17) for methanol while the hexane extract had an LC₅₀ of 302.0 (21.56± SE8.11) and 630.96 (13.56± SE6.4) for E. citriodora and E. camaldulensis, respectively. Both plant species exhibited anti-feeding properties against larvae of Culex quinquefasciatus_.