Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 7 1 2015 10 13 31 37 EN Ali Mohammadi Department of Microbiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, Iran. Maryam Hashemi Microbial Biotechnology and Biosafety Department, Agricultural iotechnology Research Institute of Iran (ABRII), Karaj, Iran. Seyed Masoud Hosseini Microbial Biotechnology and Biosafety Department, Agricultural iotechnologyResearch Institute of Iran (ABRII), Karaj, Iran. 2015 10 12 2015 10 12 Background and Objectives: The efficacy of Mentha piperita L, Zataria multiflora Boiss and Thymus vulgaris L essential oils (EOs) was evaluated for controlling the growth of Phytophthora drechsleri, the causative agent of damage to many crops that is consumed directly by humans. Materials and Methods: The EOs used in this study was purchased from Magnolia Co, Iran. The pour plate method in petri dishes containing Potato Dextrose Agar (PDA) was used to evaluate the antifungal properties of EOs. The minimal inhibitory concentrations (MIC), minimum fungicidal concentration (MFC) as well as mycelial growth inhibition (MGI) were measured. The IC50 value (the concentration inhibited 50% of the mycelium growth) was calculated by probit analysis. Results and Conclusion: The fungal growth was significantly reduced by increasing concentrations of tested EOs. The complete reduction was obtained with Shirazi thyme at all concentrations, whereas the complete reduction for peppermint and thyme was observed at 0.4% and 0.8% (v/v) concentrations, respectively. Meanwhile, the minimum inhibition was observed when 0.1% peppermint (MGI values of 9.37%) was used. The IC50, MIC and MFC values of Shirazi thyme was 0.053, 0.1% and 0.2%, respectively. Similarly, MIC and MFC values of peppermint and thyme were recorded 0.4% and 0.8%, respectively. The results obtained from this study may contribute to the development of new antifungal agents to protect the crops from this pathogenic fungus and many agricultural plant pathogens causing drastic crop losses. https://ijm.tums.ac.ir/index.php/ijm/article/view/139 https://ijm.tums.ac.ir/index.php/ijm/article/download/139/121