The use of bacteriophages to control the development of different bacterioses, including those caused by bacterium Xanthomonas campestris is one of the most promising areas of development in the field of plant protection. At the same time, the selection of the most active bacteriophages and the determination of parameters of their use remains one of the most urgent tasks of this direction. The use of phage preparations with low initial concentration of phage particles may not only prevent the development of bacterial disease, but also lead to the emergence of phage-resistant bacterial strains. In this paper, the influence of bacteriophages in various concentrations on bacterial strains and the possibility of latter infecting the host plant is analyzed. It was established that the treatment of bacterial suspensions by bacteriophages with a titer of 107-108 PFU/ml excluded the development of disease in plants inoculated with this bacterial suspension. In case of a decrease in the initial titer of bacteriophage, in some cases, symptoms of the development of the disease began to appear, down to the point that after treatment of bacterial suspensions by phages with a titer of 103 PFU/ml, the development of bacterial disease in host plants inoculated with this bacterial suspension was noted in all the studied cases.