Beschreibung:
<jats:title>Abstract</jats:title><jats:p><jats:italic>Actinomyces</jats:italic> species I and II (tentatively identified awaiting confirmation) and <jats:italic>Trichoderma harzianum</jats:italic> were isolated from soils grown to cassava plants. The <jats:italic>Actinomyces</jats:italic> species inhibited the growth of five plant pathogenic fungi at a distance whereas <jats:italic>T. harzianum</jats:italic> 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, <jats:italic>Bacillus cereus</jats:italic> and <jats:italic>B. subtilis.</jats:italic> But the species of <jats:italic>Actinomyces</jats:italic> 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.</jats:p>