Larvicidal and Insect Growth Regulatory (IGR) Activities of Leaf-extract of Carica papaya against the Filariasis Vector Mosquito, Culex pipiens pipiens (Diptera: Culicidae)

Abstract

This study evaluated the potentials of the leaf-extract of Carica papaya as a larvicide and Insect Growth Regulator (IGR) against Culex pipiens pipiens mosquitoes. Extract of the plant material was obtained by solvent extraction and bio-assayed against 4th instar larvae of the mosquito species, using extract-test concentrations ranging from 5.00 – 60.00 mg/l, and following World Health Organisation’s protocols. The results indicated larvicidal activity 24 hours post-exposure, with LC50 and LC90 of 25.49 and 49.68 mg/l, respectively. Sub-lethal concentration of the extract elicited significant (P<0.05) growth regulatory effects against the mosquitoes; as the duration of immature stages was more than doubled (9.97±0.74 days in the untreated, as against 21.78±7.72 days in the test mosquitoes); and survival rate was reduced by >80%. The treated mosquitoes were significantly (P<0.05) smaller (wing length = 3.12±0.40 mm) than their untreated counterpart (wing length = 3.81±0.17 mm). Likewise, daily survival rate and longevity of the adult mosquitoes were significantly reduced in the treated group. The sub-lethal concentration of the extract, however, had no significant (P>0.05) effect on wing symmetry. The findings of this study suggest that C. papaya is a promising source of lead compounds for sustainable mosquito vector control.