eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-02-04 4 2 717 720 6202 article Vinod Krishan 1 Jyoti Uikey 1 R.C. Saxena 1 Pest control and Ayurvedic drug Research Lab. S.S.L. Jain P.G. College Vidisha (India) Use of chemical pesticides for a longer period posed number of health problems to the non-target organisms including human beings. Moreover, mosquitoes have developed resistance to the pesticides. Plant products are considered quite effective owing to their target species specific activity as well as their eco-friendly nature. In this context Ocimum sanctum of family-Lamiaceae have been tried for the phytoecdysis like compounds and their effect on II and IV instar larvae of Culex quinquefasciatus. It was noticed that IV instar larvae are more susceptible than II instar. Ocimum sanctum which is known as Tulsi in Hindi is found plentifully in local area . Dried leaves powder was soxhleted for 48 hours duration in petroleum ether which yielded 2.76% green viscous crude substance. This yielded a crystalline substance b-ocimol - a phytoecdysone by spectral analysis. Its effect on larvicidal potential leading to delayed pupation and fall in population of the vector have been reported in the present paper. Therefore, it is suggested that plant products may be an alternative to the chemical pesticides provided they have this potentiality at low concentration. The LC50 and LC90 value for II and IV instar larvae of Culex quinquefasciatus recorded as 288.76 and 186.0 and 489.73 and 284.56 respectively. https://www.biotech-asia.org/vol4no2/mosquito-larvicidal-activity-of-ocimum-sanctum-on-culex-quinquefasciatus/ Ocimum; Culex; b-ocimol; Ecdysis; Larvicidal