The aim of this research was to find an alternative to synthetic fungicides currently used in the control of plants damping-off diseases caused by Phytophthora species. The study was carried out to evaluate the antifungal efficacy of garlic extracts (Allium sativum L.) and Metalaxyl fungicide against Phytophthora melonis, P. drechsleri and P. capsici causal agent damping- off in plants of Pepper, Melon and Cucumber in in vitro and greenhouse conditions [1]. Fungal radial growth for each concentration of garlic extracts on Phytophthora species was measured. Also, the median effective concentration (EC50) values (μl/ml) of garlic extracts measured [2]. The chemical composition of the essential oils was determined by gas chromatography-mass spectrometry (GC-MS). Results of in vitro indicated that plant extract of garlic caused a significant decrease in the mycelial growth of phytophthora species and it had Fungistat properties. The maximum and minimum inhibitory effect of plant extract was observed for P. capsici (EC50 = 43.293 ppm) and P. drechsleri (EC50 = 286.465 ppm), respectively. EC50 of fungicide of Metalaxyl on mycelial growth of P. capsici, P. drechsleri and P. melonis were 20. 869, 20.055 and 17.702, respectively. The profile of the extract components of Allium sativum showed that Diallyl tetra sulphide (31.32%), Allyl disulphide (26.78%), Nitrosothymol (8.64%), 1H-1,2,4-Triazole, 3-thiol-5-methyl (8.4%) and Allyl sulphide (6.15%) were the main compounds. Microscopic observation shown morphological changes in hyphal cell of Phytophthora species as discoloration, hyphal swelling and lyses of hyphe. The results of greenhouse showed that plant extract significantly increased growth factors in plants of Pepper, Melon and Cucumber as dry weight of stem and root, length of stem and root compared to control (P 0.05). This results shows that the antifungal activity of plant extract of Allium sativum on Phytophthora species. Garlic extract was found to be fungicida
