Background: Saprolegniasis is an important aquatic fungal disease that causes severe damages at different growth stages of aquatic animals. Saprolegnia parasitica has been identified as an important pathogen in aquaculture. This study was investigated the activity of antifungal methanolic extracts of Foeniculum vulgare, Achillea millefolium, Satureja hortensis, Cinnamomum zeylanicum, as well as Artemisia annua essential oil against S. parasitica in comparison with formalin.

Materials and Methods: In this descriptive study, Saprolegnia parasitica originated from rainbow trout’s farm effluent. Phenotypic identification was performed and amplification of ITS rDNA region was adjusted by using of two general primers like ITS1 and ITS4, subsequently sequencing by use of internal primer were performed. The antifungal effects of the plants were investigated based on broth microdilution method and compared by formalin.

Results: The results of sequencing verified the obtained fungus is S. parasitica. In broth microdilution method, the essential herb Artemisia inhibited the growth of S. parasitica at a concentration of 128 &mug/ml (MIC = 128 &mug/ml). At the same concentration, however, it did not show any fungicidal activity (MFC &ge 2048 &mug/ml). Methanolic extracts of the plants fennel, yarrow, Savory, and cinnamon displayed no direct effects on S. parasitica.

Conclusion: Based on the results obtained in the present study, Artemisia can be classified as a powerful antifungal essential plant. The essence of Artemisia performed more effectively compared to formalin for the growth inhibition of S. parasitica.