The objective of this study was to evaluate antifungal effect of essential oils (EO) from various Moroccan aromatic plants, namely: Artemisia herba alba, Origanum compactum, Rosmarinus officinalis, Thymus vulgaris, Lavandula stoechas, Mentha virdis, on Phytophthora citrophthora. Determination of oils antifungal activity was performed by measuring the diameter of mycelium.A growth model was established to evaluate fungal growth diameter as such: 1.834 * [Oil concentration in μL/20 mL PDA]2 – 6.166 * [Oil concentration in μL/20 mL] + 4.99. With correlation coefficient r2 = 0.999. The EO of O.compactum was then used for further chemical examination by gaseous chromatography coupled with mass spectrometry. The results showed that the most significant antifungal effect and the highest yield were obtained with O. compactum oil. The inhibition of Phytophthora was proportional to the dose of O. compactum EO applied. Total inhibition was at 2 μL/20 ml PDA, which may be due to the high level of Carvacol. Chemical analysis of Origanumcompactum EO, showed dominance of Carvacol (69%), followed in decreasing order by Cymene, Caryophyllene, Linalool and α-Pinene.