Bacterial leaf spots (Xanthomonas spp.) on roses cause great losses to farming. In vitro, the survey of antagonistic density was tested by using three antagonistic isolates (BR16, BR37, BR88) against Xanthomonas spp. (XR13, XR9, XR18 strains). These antagonists and pathogens were diluted separately at 10, 100, 1000 &10000 fold. Results showed that the inhibition abilities were increased with diminishing the population of the pathogen. In which, the antagonists with populations less than 10⁶ CFU/mL are not sufficiently or low effective in forming the inhibitory zone against the pathogen. Therefore, a density of about 10⁷ CFU/mL was selected in the trials on rose under net-house conditions. From that, with the foliar application, three isolates (BR16, BR37, BR88) were tested against the three mentioned pathogenic strains. Results showed that pretreating with antagonistic bacteria achieved high disease control efficiency. In which, BR88 has the highest disease reduction efficiency reaching 70.1%, 72.4%, and 73.3%, when infecting the XR13, XR9, or XR18, respectively. Furthermore, treatments from applying separately three antagonistic isolates all have AUDPC lower than the treatment with only disease inoculation from 2.4 to 4.7 times. In which, the AUDPC of treatment of BR88 was similar to BR16 when infecting XR13,...