Black scurf and dry rot diseases caused by Rhizoctonia solani and Fusarium sambucinum are the most limiting factors for potato production. In laboratory trials, Trichoderma harzianum isolate 3 and T.viride isolate 1 showed highly antagonistic effect against all tested pathogenic isolates of R. solani and F. sambucinum. All bio compost extracts inhibited linear growth of R. solani and F.sambucinum, bio compost 3 at 50% concentration provided highest reduction in linear growth. Drenching soil with tested bio composts before sowing potato tuber significantly reduce Fusarium dry rot and Rhizoctonia Black scurf diseases during two cultivation seasons. Bio-compost 3 followed by bio compost 1 and 2 were the most effective soil treatments in control of both diseases during two seasons. Moreover, such treatments resulted highest records of plant growth parameter as well as quantity and quality of potato tuber yield. The highest records of potato total tuber yield, nutritional values, and total carbohydrates were observed in bio compost 3 followed by bio compost 1 and bio compost 2 soil treatments if compared with compost 4 and control treatments during 1st and 2nd seasons. It could be stated that, field application of composted agricultural wastes fortified with bio control agents could be suggested as easily soil biologically soil treatment for controlling fungal soil borne pathogens of potato especially under organic farming system.
 

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