Biological control of clubroot on cauliflower with Trichoderma and Streptomyces spp.
The effectiveness of Trichoderma and Streptomyces spp. in suppressing clubroot of brassicas, which is caused by Plasmodiophora brassicae, was tested on cauliflower seedlings in glasshouse and field crops. The glasshouse experiment showed that of fifteen isolates of Trichoderma spp. and one Streptomyces sp. tested, six of these reduced (P<0.05) disease severity compared to the untreated control. In further testing of these six isolates, three isolates of Trichoderma spp. and one isolate of Streptomyces sp. significantly reduced disease severity. A field trial was carried out on clubroot-infested land. Crushed maize colonized with Trichoderma and Streptomyces was spread onto the plots and rotary-hoed into the soil. Results showed that three Trichoderma isolates (TC32, TC45 and TC63) and one Streptomyces isolate (S99) reduced (P<0.05) disease severity on the root systems, but did not increase the top weights of the plants (P>0.05).