The fungal growth inhibition induced by essential oils, as determined by the disc diffusion assay, was dependent mostly on the volume (varying from 5 µL to 60 µL) and nature of the essential oils. According to the results presented in Figure 5, it can be noticed that the essential oils tested had antifungal activity against Fusarium graminearum G87, but their efficacy is different. Thyme essential oil was the most effective, with an inhibition rate of over 80% at the lowest volume of essential oil used for the growth inhibition of this fungus, namely, 87.04% for 7 µL. Clove oil was also effective against the tested fungus, with an inhibition rate of 81.64% when using 40 µL. It is assumed that the high antifungal potential of clove essential oil is due to its active principle, eugenol (85.7%). The results are in accordance with the study of Abbaszadeh et al. [46] regarding the effectiveness of eugenol against pathogenic fungi, which demonstrated that this phenylpropanoide had antifungal activity against all tested fungi. The antifungal activity was in direct ratio with the concentration of eugenol added to the media. In a study made by Marin et al. [47] who tested the efficacy of cinnamon, clove, oregano, palmarosa, and lemongrass oils against the mycotoxines produced by Fusarium graminearum, it was shown that clove essential oils was the most efficient against zearalenone and deoxynivalenol release.