This work aims to test the antifungal effect of essential oils of Corymbia citriodora, Mentha spicata and Mentha arvensis in vitro. The study was carried out in a completely randomized block design, with a factorial scheme of three essential oils (Corymbia citriodora, Mentha spicata e Mentha arvensis) and five concentrations, of 0, 50, 100, 500 and 1000 mg ml -1 . It was possible to conclude that the tested oils have compounds effective in inhibiting the mycelial growth of Pythium sp., suggesting the possibility of use for the formulation of biofumigants for soil treatment.