LARVICIDAL POTENTIAL OF BOTANICAL EXTRACTS OF Syzygium aromaticum, Sida acuta AND Codiaeum variegatum AGAINST Anopheles gambiae s.l. AND Aedes aegypti IN IKORODU AND ALIMOSHO LGAs, LAGOS STATE, NIGERIA
Authors
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Joshua, I.
Department of Zoology (Applied Entomology and Pest Management unit)
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Kemabonta, K. A.
Department of Zoology (Applied Entomology and Pest Management unit)
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Odimegwu, J. I.
Department of Pharmacognosy, University of Lagos, Akoka, Lagos, Nigeria
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Ajibade, Peace
Department of Zoology (Applied Entomology and Pest Management unit)
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Adetoro, F.
Department of Zoology (Applied Entomology and Pest Management unit)
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Adeniran, J. T.
Department of Zoology (Applied Entomology and Pest Management unit)
Abstract
Botanical larvicides are becoming popular due to development of resistance to insecticides used for larviciding. This study characterised the chemical constituents and evaluated the larvicidal activity of botanical extracts of Syzygium aromaticum (clove), Sida acuta (wire weed) and Codiaeum variegatum (variegated croton) against third-instar larvae of Anopheles gambiae s.l. and Aedes aegypti collected from Ikorodu and Alimosho Local Government Areas, Lagos State, Nigeria. Leaves of S. acuta and C. variegatum were extracted with n-hexane in a Soxhlet apparatus, clove buds were hydrodistilled in a Clevenger-type apparatus, and the chemical constituents were profiled by gas chromatography–mass spectrometry (GC-MS). Larvae were exposed to 200, 400 and 600 ppm of each extract following the World Health Organization larval susceptibility protocol, mortality was recorded at 24, 48 and 72h, and lethal concentrations were estimated by probit analysis. Eugenol (55.26%), eugenyl acetate (18.00%) and caryophyllene (12.09%) were the main constituents of clove oil, whereas the extracts of S. acuta and C. variegatum were dominated by fatty acids and their esters. Clove oil was the most toxic to An. gambiae larvae (72-h LC50 = 284.1 ppm; LC90 = 1,723.8 ppm), followed by S. acuta (LC50 = 2,138.0 ppm), while no lethal concentrations could be estimated for C. variegatum. Against Ae. aegypti, only clove oil yielded estimable values (LC50 = 568.7 ppm; LC90 = 1,062.6 ppm). Larval mortality increased with concentration and exposure time. These findings identify clove essential oil as a promising botanical larvicide for the management of malaria and yellow fever vectors in Lagos and support its evaluation in semi-field and field trials.
Keywords: Anopheles Gambiae, Aedes Aegypti, Larvicidal Activity, Clove, Wire Weed, Variegated Croton, Botanical Extracts, Essential Oils, GC-MS, Vector Control