Larvicidal & development retarding effects of hexane crude extract of Otostegia limbata on 3rd instar larvae of Drosophila melanogaster Meign (Diptera: Drosophilidae)

Abstract

The toxicological evaluation of Otostegia limbata was done against the third instar larvae of Drosophila melanogaster (Meigen) for 24hours of exposure. One ml of Otostegia limbata extract having concentrations of 2%, 3%, 4%, 5% and 6% was mixed with 1 gram of overripe banana fed to Drosophila melanogaster which caused 12%, 24.6%, 44%, 68%, 89% mortality and showed 100% death at higher concentration. While the percent pupation observed were 88%, 73.7%, 60.3%, 48%, and 23.3% respectively at 0.5%, 1%, 1.5%, 1.8% and 2%of extract. The Pupal inhibition and high mortality rate revealed that O. limbata has deleterious effects on insect growth. This is the first work to find the toxicological effects of O. limbata although the other members (plants) of the same species have been evaluated for toxicity, these findings provide the evidence that O. limbata is a good medicinal plant for further investigation against medically important insect pests.