In vitro, B. subtilis, T. harzianum, T. viride, T. spirale and C. minitans isolates showed different inhibitory
effects against the growth of S. cepivorum. T. harzianu. While T. spirale showed the greatest antagonistic
effect to the pathogen, followed by T. viride and B. subtilis isolates. However, isolates of C. minitans showed a
slight antagonistic effect. In greenhouse experiments, the application of the tested powder formulations of
bacteria and fungi to infested soil at the time of planting and two weeks before transplanting, significantly
reduced the incidence of white rot on Giza 6 onion cultivars. The application of bacterial antagonists two
weeks before transplanting resulted in the highest reduction of disease incidence. However, a similar
reduction in disease severity was detected when the tested fungal antagonists were applied at the time of
transplanting or two weeks later. The use of these bioagents in the form of powder formulations as soil
treatment could be recommended for the control of white rot in onion.