Bacterial fruit blotch (BFB) caused by Acidovorax citrulli is a serious disease of cucurbit crops. Despite the economically important bacterial disease of cucurbits in the world, there are no commercial cultivars with effective BFB resistance or bactericidal chemicals. In this study, nanomaterials (Ni nanoparticles, Ni-graphites, and graphites) for antibacterial activity against A. citrulli were prepared by Radio Frequency (RF)-thermal plasma which is the most widely used and is applied to a broad spectrum of industrial, medical and agriculture applications. Morphology and composition of nanomaterials synthesized by RF-thermal plasma were characterized by scanning electron microscopy, energy dispersive X-ray spectrometer and X-ray powder diffraction analyses. In order to verify the antibacterial effect of nanomaterials, fifteen strains of A. citrulli were used. The result of antibacterial activity tests showed that Ni nanoparticles were the most efficient antibacterial agent with 100% inhibition rate to all fifteen A. citrulli strains. When the inhibition rate of Ni-graphite was compared with that of graphite, Ni-graphite was more efficient to inhibit A. citrulli. Graphite also showed inhibition rate of more than 50% to most of A. citrulli strains except stratins 2, 3,and 35. These findings suggest that nanomaterials, especially Ni-nanoparticles synthesized by RF-thermal plasma system could be one of the best alternatives for development of new antibacterial agents.