Alternaria leaf blight disease of cucumber (Cucumis sativum L.), is an important foliar disease worldwide, especially under the protected cultivations (plastis tunnel and greenhouses) conditions. The causal fungus was identified as Alternaria cucumerina Ellis & Everh J.A. Elliott(Macrosprium cucumerinum), and its pathogenicity was confirmed on cotyledon and true leaves of cucumber Matrix cv. using detached leaf assay technique. Cucumber cultivar Matrix, Best and Beta alpha were susceptible to the infection with A. cucumerina. Cantaloupes, watermelon, muskmelons, pumpkins, loofa  and squash were  infected with A. cucumerina as a host range.  Squash and pumpkin were the most infected ones, while muskmelon and water melon were the lowest ones. Trichoderma sp., T. harzianum, T. viride and different Bacillus spp. (isolated from cucumber leaf surface)  and its culture filtrates significantly inhibited growth of A. cucumerina on PDA medium. Various concentrations of some plant oils and plant extracts reduced growth and spores germination of A. cucumerina, especially clove oil. Also, dithane M-45 was the most effective fungicide in reducing growth of A. cucumerina. Bacillus sp. (isolate 4),  T. harzianum, clove oil and Dithane M-45 were the most effect treatments in controlling cucumber leaf spot.