Repellent Effect of Ethanolic Extract of Scent Leaf ( Ocimum gratissimum ) and Neem Leaf ( Azadirachta indica ) on Adult Culex Mosquitoes

Abstract

Mosquitoes control through the use of synthetic chemical compounds have been discovered to have toxic residual effect as it gets accumulated into the food chain, thus, there is a need for environmental friendly compounds such as botanicals. This study was carried out to determine the repellent effect of ethanolic extract of Scent leaf ( Ocimum gratissimum ) and Neem leaf ( Azadirachta indica ) on adult Culex mosquitoes. Mosquito larvae were acquired from stagnant pool of water around and within the Federal University of Technology, Akure. Leaves extract of O. gratissimum and A. indica was extracted using absolute ethanol as solvent. Different concentrations of the oil extract were prepared (5 ml, 10 ml, 15 ml, and 20 ml) and adult culex mosquitoes were exposed to these concentrations for a period of 2 hours. The results showed complete protections time of 80 minutes at 20% concentration for O. gratissimum and 12 hours at 20% concentration for A. indica . It was observed that A. indica have higher protection time than O. gratissimum . The results from the bioassay of the extracts on the mosquitoes revealed that both leaf extracts have repellent effect on the Culex mosquitoes. The four different concentrations of the extract showed significant difference in their repellent effect (p<0.05). It is apparent that both O. gratissimum and A. indica oil extract have repellent activity against Culex mosquitoes.