Abstract: The present invention is directed to methods and compositions for biological control of plant diseases using suppressive avirulent strains of Streptomyces spp. to control disease on a vegetable or other susceptible crop. The method includes applying one or more naturally occurring, suppressive avirulent strains of Streptonmces spp. to the crop to inhibit the growth of Streptomyces scabies or other plant pathogenic organisms that cause scab, wilt, or seedling blight disease. Preferably, at least two suppressive avirulent strains of Streptomyces spp. are applied to reduce the change of resistance from occurring. The suppressive avirulent strains ame compatible and will grow in the presence of one another and, when combined with the pathogenic organism, at least one of the suppressive avirulent strains preferably substantially outgrows the pathogen.