Potato (Solanum tuberosum L.) is one of the most important vegetable crops in the
world as well as in Egypt. The cultivated area of potato was increased for exportation
and local consumption. About 3.7 million tonnes of potato were yielded from about
318,214 feddans (FAO 2010).Potato plants are attacked by many pathogenic fungal, viral and bacterial diseases. Among all potato bacterial diseases, Streptomyces scabies (Thaxter) Lambert and Loria (syn. S. scabies) is the main causal agent of common scab, a widely distributed disease which causes major economic losses in potato production (Lambert & Loria 1989;Goyer et al. 1996). Plant-pathogenic Streptomyces spp. can survive in soil or plant debris for over a decade (Kritzman & Grinstein 1991). Several methods were used for controlling the disease including chemical treatments of seed potato tubers (Davis et al.1976), irrigation (Adams & Lapwood 1978), changing soil pH (Pavlista 1992; Waterer 2002), rotation strategies (Li et al. 1999), use of a tolerant cultivar (Bouchek-Mechiche et al. 2000) and biological control with non-pathogenic streptomycetes (Liu et al. 1995;Ryan & Kinkel 1997; Agbessi et al. 2003). Applied chemical control is generally the most effective for controlling the disease; however, no effective chemical product is available for common scab disease.