Managing scab diseases of potato and radish caused by Streptomyces spp. using Bacillus amyloliquefaciens BAC03 and other biomaterials

Streptomyces spp. cause scab in plants like potato and radish. To effectively control this disease, biologically based materials were examined for their efficacies. In greenhouse or growth chamber tests, potting mix was infested with Streptomyces scabies (10(6) CFU cm(-3)), followed by applying different products. Bacillus amyloliquefaciens strain BAC03 (10(5) CFU cm(-3)) reduced disease severity and potentially enhanced growth of radish; chestnut tissues at 50% in volume, oregano and clove essential oils (0.1 mu g cm(-3)), and ground horseradish (>0.18 g m(-3)) significantly reduced the severity of common scab in potato and/or radish. In two Michigan fields in 2011 and 2012, chestnut tissues (1.15 kg m(-2)), oregano essential oil (1.5 ml m(-2)), and ground horseradish (0.38 g m(-2)) were incorporated into the soil 2 weeks before planting. BAC03 (10(6) CFU ml(-1), 1 L m(-2)) was drenched into the root zone soil 4 times at 2 week intervals starting 1 month after planting. BAC03 significantly reduced disease severity by 17-57% relative to control in two locations over 2 years. BAC03 also enhanced potato tuber weight by 33% and 26% in 2011 in two locations. The rest of the treatments caused significant disease reduction, but were less effective compared to BAC03, and efficacy varied depending on location and year. Therefore, BAC03 can be a good biological control agent for potato common scab management. (C) 2013 Elsevier Inc. All rights reserved.