eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-04-27 6 1 509 512 8647 article Kh. M. S. Al-Ghamdi 1 M. S. Saleh 2 J. A. Mahyoub 1 Z. I. Al-Fifi 1 Department of Biological Sciences, Faculty of Science, King Abdul-Aziz University, Jeddah (KSA). Mosquito Research Lab., Jeddah (Kigndom of Saudi Arabia). The biological effects of the insect growth regulator (IGR) , Dudim and the plant extract Neem oil on the developmental stages of Culex pipiens, the dominant mosquito species in Jeddah,Saudi Arabia, were evaluated. The records showed that the response of Cx. pipiens to the test compounds depends on the differential mode of action of the compounds and its effective concentrations. According to IC50 values (concentration which to inhibit the emergence of 50% of mosquito adults emergence), the IGR Dudim (0.0003 ppm) proved to be more effective against Cx. pipiens than the Neem oil (70 ppm). On the other hands, treatment whit IC90 values (concentration which to inhibit the emergence of 90% of mosquito adults emergence) of Dudim (0.0032 ppm) and Neem oil (140 ppm) did not exhibit any market effect on nontarget organisms (naiads Odonata, aquatic hemipterans, aquatic coleopterans) associated with mosquito breeding sites. https://www.biotech-asia.org/vol6no2/laboratory-evaluation-of-the-insect-growth-regulator-dudim-and-the-plant-extract-neem-oil-against-culex-pipiens-mosquitoes-with-reference-to-its-side-effects-on-aquatic-nontarget-organisms/ Insect growth regulator; Culex pipiens; neem oil; aquatic organisms