The effect of salicylic acid (SA) individually or/and in combinations with three standard fungicides named Flutolanil (Moncut WP 30%), Telcolofos-methyl/thiram (Rhizolex 50%WP) and Carboxin-Thiram (Vitavax 200 WP) was studied for the field control of damping-off and root rot diseases of cantaloupe (Cucumis melo var. cantaloupensis) and squash (Cucurbita pepo), cvs Askandarany and Mera, respectively. The experiments were carried out in the years 2012 and 2013. In vitro studies the effect of the aforementioned fungicides and salicylic acid on growth of Rhizoctonia solani and Fusarium solani was determined. The effective concentration was found to range from 50 to 200 ppm, and the higher concentration the greater inhibitory effect. The combination of salicylic and vitavax 200 and salicylic acid and Rizolex at 200 ppm showed the highest effect on R. solani and F. solani with the averages of 84.75, 86.79, 71.25 and 87.13%, respectively.  In field trials, soaking seeds in salicylic acid, either single or in combination with the fungicides in concern, significantly decreased both damping-off and root rot of squash and cantaloupe. In addition to increasing the numbers of survived plants, the used treatments increased shoot length as well as fresh and dry weights. The results showed that mixed salicylic acid application with fungicides to seeds of squash and cantaloupe significantly decreased disease symptoms by 70.32 and 64.07% for vitavax 200 and rhizolex treatments, respectively, for squash. The corresponding figures for cantaloupe were 62.89 and 55.90%, respectively in the second season 2013. Moreover, the treatments in concern increased the activities of peroxidase and polyphenoloxidase. It is noticed, however, a negative correlation between disease incidence and activities of both peroxidase and polyphenoloxidase in either squash or cantaloupe plants. Meanwhile, the treatments in concern increased the contents of Mn and Fe but decreased Zn of both tested crops In general, the results indicated that especially the combined SA and standard fungicides showed a better response to fight damping-off and root rot diseases than the treatment alone. Thus the present study shows that the induction of defense related enzymes may be enhance resistance in squash and cantaloupe plants.