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The effects of 2 species of Trichoderma as T. vride and T. harzianum on reducing the potato black dot disease caused by Colletotrichum coccodes on two cultivars (Aula and Draga) in factoriel experiment completly randomized design was tested in open air condition. The data on Fresh weight of plants from different treatments showed that the noninfested control treatment was significantly different from the others ( ci. = 5%). Adding ! viride isolate of Shahriar in soil infested with C. coccodes with cultivar Draga had shown that this treatment was signifiDantly different. This isolate of Trichoderma was able to reduce the disease and had more ability antagonistic effect than T. harzianum of Ahvaz on the disease caused by C. coccodes in this test.