In laboratory tests, the effectiveness of water plant extracts obtained from 20 species of herbal plants on the degree of contamination of white mustard seeds (Sinapis alba L.) by fungal and bacterial pathogens was evaluated. The analysis showed that the contamination of the tested seed material was statistically significantly influenced by the plant species from which the biopreparations were obtained. However, there were no significant differences in the method of preparation of extracts for the examined traits. The tested natural preparations had a different effect on limiting the superficial growth of bacteria and fungi on seeds. However, infusion and macerate obtained from the bark of Salix alba L. were the most effective in limiting the contamination with both bacterial and fungal pathogens. The number of seeds infected with fungi after the application of these preparations was 24.25% on average, whereas in the case of bacterial colonization of the tested material, the value of this indicator was 1.00% on average