Evaluation the efficacy of bio-agents, application as foliar spray against vegetables foliar diseases incidence was carried out in open greenhouse conditions. The tested bio-agents were Trichoderma harzianum, T. Viride, Bacillus subtilis, Pseudomonas fluorescens and Saccharomyces cerevisiae were evaluated. The recorded foliar diseases, i.e. Powdery, Downy mildews of Cucumber, Cantaloupe and Pepper as well as Early, Late blights of Tomato were significantly reduced at all treatments either alone or in combinations comparing with untreated plants. Application with either T. harzianum and B. subtilis showed significant reduction in diseases incidence comparing with the other applied bio-agents. The other bio-agent treatments, T. viride, P. fluorescens and S. cerevisiae recorded moderate reduction in this concern. On the light of the present study it could be suggested that the usage of bio-agents might be used as easily applied, safely and cost effective control methods against such foliar plant diseases.