Inhibition of growth of some plant pathogenic fungi by some antagonistic microorganisms isolated from soil

Actinomyces species I and II (tentatively identified awaiting confirmation) and Trichoderma harzianum were isolated from soils grown to cassava plants. The Actinomyces species inhibited the growth of five plant pathogenic fungi at a distance whereas T. harzianum was an active hyperparasite which attacked the mycelia of target organisms (plant pathogens) and prevented their continued growth. The three microorganisms compared favourably with two other established antagonists, Bacillus cereus and B. subtilis. But the species of Actinomyces were especially more active. Soil inoculation of the antagonists have prevented root and tuber rot of cassava plants in the field and are likely to be useful for preventing other soil‐borne diseases of plants.