Control of Plasmodiophora brassicae by combining antagonists, organic amendments, and cultivation practices

Abstract: Plasmodiophora brassicae is a common threat to vegetables of the Brassicaceae family. Recent research has shown that Trichoderma ssp. are potential antagonists of P. brassicae. Furthermore, ridge cultivation and the use of chitin-based fertilizers are potentially able to reduce the disease. In order to control the disease different control measures and their combination were evaluated in a pot and a field experiment. In a first step different biocontrol agents (Trichoderma spp., and Bacillus spp.) were tested alone and in combination with Biosol (chitin) in a pot experiment in the greenhouse using naturally clubroot infested soil. In this experiment, a synergistic effect between antagonists and chitin-based fertilizer was observed. Of the best performing biocontrol strain, one strain was selected for the field experiment. The field experiment was conducted in a naturally heavily clubroot infested soil. The application of antagonists, application of a chitin-based fertilizer, and the cultivation on ridges were tested alone and in all possible combinations. All control measures reduced the disease, where ridge cultivation had the most disease suppressive effects. Additional disease suppression by combined measures was observed. To control clubroot it is worthwhile to combine different preventive control measures.