The effective agent in the biological plant pesticide Mycostop is  Streptomyces ray bacteria, which have been isolated from Finnish Sphagnum peat. Mycostop’s antagonistic effect is based on several mechanisms. When Mycostop is added to the substrate, the ray bacteria it contains populate the roots of plants and thereby exclude disease-causing microbes.Ray bacteria also prevent the spread of disease-causing microbes by means of their antifungal compounds. Moreover, Streptomyces bacteria produce other metabolic compounds, which promote plant growth.

Streptomyces mycelium on the surface of a fungus species belonging to the genus Alternaria.

An example of the impact of Streptomyces bacteria in preventing the growth of the fungus Alternaria brassicicola, which causes damping-off. This is the result of antifungal metabolic compounds generated by Streptomyces.

On the left Mycostop and Alternaria, on the right just Alternaria.