The purpose of the three-year-long field experiment was to identify the effect of the UGmax soil fertilizer (microbiological preparation) on the presence of Streptomyces scabies on tubers of two edible potato cultivars. The experiment was established using the randomized split-block method, in three replications, in central Poland (52°03’N; 22°3’E), on the soil consisting of loamy sands, slightly acidic and acidic. The examined factors included: 1st factor: edible potato cultivars (Satina and Typhoon), 2nd factor: doses and dates of application of the UGmax soil fertilizer (1. control object without UGmax; 2. UGmax applied to soil before planting tubers at a dose of 1.0 dm3∙ha-1; 3. UGmax applied to soil before planting tubers at a dose of 0.5 dm3∙ha-1, when the height of plants is about 10–15 cm, and in the flower buds making phase at a dose of 0.25 dm3∙ha-1; 4. UGmax before planting tubers at a dose of 1.0 dm3∙ha-1 and when the height of plants is about 10–15 cm, and in the flower buds making phase at a dose of 0.5 dm3∙ha-1; 5. UGmax when the height of plants is about 10–15 cm, and in the flower buds making phase at a dose of 0.5 dm3∙ha-1). Symptoms of common scab were assessed on a 9-point scale on 100 tubers randomly collected from different experiment objects. As a result of the study, it was demonstrated that treatments with the use of the UGmax soil fertilizer limited the occurrence of common scab on potato tubers and affected the average level of infestation of the sample and the average level of infestation of infested tubers.