Insecticidal Efficacy of Selected Botanicals on three species of Adult Mosquitoes in Osogbo, Osun State, Nigeria

Abstract

The present study investigated the insecticidal potency of phytochemicals from three indigenous botanicals namely Moringa oleifera (Drumstick tree), Vernonia amygdalina (Bitter leaf) and Ocimum gratissimum (Scent leaf) against adult mosquitoes of the Anopheles species, Aedes species and Culex species cum their larval habitats. Collection of the mosquito larval was made after scouting and identifying their breeding sites using scoops, plastic containers, sieves etc. Larva collection was done in the wet season (April to October) while the collected larva were conveyed to the laboratory and reared until they emerged into adults. A bioassay comprising twenty five adult mosquitoes from each of the three adult mosquito species were exposed to the botanicals at three different concentrations (5g/10ml, 10g/10ml and 15g/10ml) to assess their insecticidal potency which was measured through their knockdown rate (kdr) and mortality rate. The kdr were recorded at intervals for an hour while the mortality rates were recorded after 24hours of exposure. A total of 400 mosquito larva were collected and five larval habitat encountered. The three botanicals showed insecticidal potency against the adult mosquito species. However, O. gratissimum had the highest potency at 15g/10ml against Anopheles (46%) and Culex (34%) species respectively (p {square} 0.05). Aedes spp was resistant to the botanicals which may be due to a resistance barrier mechanism in Aedes spp that the botanicals lack the ability to break. The botanicals could be adopted in the control of adult mosquitoes as they are biodegradable, eco-friendly and economical in contrast to synthetic insecticides with a view to consolidating global efforts on mosquito-borne diseases control and elimination with little or no human or environmental hazard.