Optimizing the application of Bacillus velezensis BAC03 in controlling the disease caused by Streptomyces scabies

BAC03 is a novel Bacillus velezensis strain previously studied for biological control of scabby diseases caused by Streptomyces scabies. To optimize its efficacy in disease control, different application strategies of BAC03 were investigated in this study, including timing, frequency, and concentrations of BAC03. BAC03 was either used for seed tuber treatment, foliar application or drenching in potting mix infested with S. scabies. Neither foliar application nor seed treatment affected disease severity. BAC03 applied five days before planting significantly reduced S. scabies population and completely suppressed radish scab, but the later BAC03 was applied the less effective it was. BAC03 at 105 CFU cm−3 potting mix or higher concentrations was effective in reducing radish scab. Increasing the frequency of BAC03 application did not increase the efficacy on disease reduction. BAC03 also increased the biomass of radish roots and leaves whether the pathogen was present or not.