<p>In this study, biocontrol of <i>Acidovorax citrulli</i>, a bacterial fruit blotch agent causing significant yield and quality loss in melon, was investigated in pot and field experiments, using bacterial strains isolated from different sources. For this purpose the antibacterial activity of 17 bacteria was determined in pot and field experiments. At the same time siderophore and hydrogen cyanide production and the enzyme activity (chitinase, cellulase and protease) of the strains with antibacterial activity were determined. In the pot experiment, the plant group to which <i>Pseudomonas fluorescens</i> strain IT 188 was applied had no disease symptoms. In the field experiment, it was determined that the disease severity of 77.8%, determined as the average of both years in the positive control group, decreased to 30% as a result of the application of the same strain. It was found that 5 of the strains produced hydrogen cyanide, all had protease activity, and 8 had cellulase activity. The results of the study show that antagonist bacterial strains applied as preventive treatments have significant potential in the biological control of bacterial fruit spot disease, with IT 188 being the most promising strain. The inclusion of strain IT 188, which significantly reduces disease severity by inhibiting the growth of <i>Acidovorax citrulli</i>, in the integrated management program contributes to the success of disease control.</p>