Abstract: A field experiment was carried out to investigate the biological control of R. solani by different organisms including bacteria and fungi. Three methods of application were used during the study. Control results differed with the method of application used. The present study indicated that all the antagonists tested inhibited infection by R. solani and that the efficacy of prevention depended on the application method used. Coating sugarbeet seeds with antagonists was produced results for applying the antagonist to control R. solani. A soil preinoculation that contained the antagonist was better than treating them with extracts of antagonists although antimicrobial compounds in the extracts have been found to control the disease to the same extent. The most effective biocontrol agent was Trichoderma harzianum. Hyphal interactions between T. harzianum and R. solani were observed by scanning electron microscopy. T. harzianum attached to the host by hyphal coils.