Effect of Extracts of Ocimum Gratissmum L. (Scent Leaves) on Some Mosquitoe Genera in Makurdi Metropolis, Benue Nigeria

Ocimum gratisimum is a plant with so many uses-culinary, medicinal, pesticidal, insecticidal, aesthetic. This research was designed to find out repellence, knockdown and knock-dead activity of hot and cold aqueous and ethanol crude extracts against mosquitoes of three genera-Culex, Aedes and Anopheles sp. Ocimum gratisimum leaves were harvested from different locations in Makurdi. Leaves were picked, washed, and dried crispy for seven (7) days under shade. Crispy dried leaves were grinded into fine powder. The powdered was weighed and divided into four equal parts. Each part was subjected to hot and cold aqueous and ethanol extraction. Extracts were concentrated with rotatory evaporator. Concentrates where allowed to dry in the open at room temperature. 2, 3 and 5g of extracts were weighed and used to make different concentrates; each in 5ml of Absolute ethanol. These concentrates were tested against lab bred mosquitoes for repellency, knockdown and mortality, using the World Health Organization Pesticide Evaluation Scheme. The results showed complete repellence to all extract types, increased knock down with increased concentration and variable mortalities to the different extract methods. Based on these, Ocimum gratissimum extracts can be used locally and as an alternative to synthetic chemicals in the production biodegradable and eco-friendly mosquito repellent, and “mosquitocidal” formulations.