Tehran University of Medical Sciences Journal of Arthropod-Borne Diseases 2322-1984 15 4 2022 09 04 380 388 Sara Sabzalizade Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Amir Amani Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran AND Medical Biomaterials Research Center (MBRC), Tehran University of Medical Sciences, Tehran, Iran Hassan Vatandoost Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran AND4Department of Chemical Pollutants and Pesticides, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran Fatemeh Hosseini Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Roya Najafi-Taher Medical Biomaterials Research Center (MBRC), Tehran University of Medical Sciences, Tehran, Iran Hamid Reza Basseri Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 2021 08 31 2022 09 04 Objectives Due to undesired environmental impact of insecticides as well as resistant of vectors to them, development of organic and natural insecticides have been more considered. In the current study, we developed nanoemulsion of eucalyptus and investigated lavicidal activity of it against malaria vector, Anopheles stephensi and Culex pipiens under  laboratory as well as semi field conditions.  Materials and Methods: An optimized nanoemulsion was prepared by mixing Eucalyptus oil, Tween 80 and ethanol at ratio of 1:2:1.5 in distilled water, then, stirred for 20 minute at room temperature. The product was then used for bioassay tests against 3-4th instar larvae of Anopheles stephensi as well as Culex pipiens.  Furthermore, semi field trial was carried out to evaluate larvicidal activity of nanoemulsion of eucalyptus. Results: Nanoemulsion of eucalyptus showed significantly high lavicidal activity comparing with bulk eucalyptus essential oil. The LC50 and LC90 value of nanoemulsion against An. stephensi were 111.0 and 180.8 ppm respectively and 29.5 and 73.7 ppm for Cx.  pipiens, respectively. In the semi field condition, the Nanoemulsion of eucalyptus decreased 1-2nd instar larval density of Culicines and Anophelines to 90.1%  and 85.2%, respectively. Conclusion: The nano formulation of eucalyptus oil showed high larvicidal activity.  Therefore, nanoemulsion of eucalyptus oil can be used as an eco-friendly larvicide against mosquitoes. https://jad.tums.ac.ir/index.php/jad/article/view/1481 https://jad.tums.ac.ir/index.php/jad/article/download/1481/574