In order to control the clubroot of brassica vegetables which is settled-planted in a farm field, it is necessary to previously treat the seedling with a chemical before settled planting or treat the soil with a chemical, but the clubroot is sometimes not controlled depending on the weather or soil conditions. In addition, the treatment with a fungicidal compound at a high concentration causes a problem of phytotoxicity or crop persistence. An object of the present invention is to solve these problems and provide a method for easily and simply controlling clubroot without causing a problem of phytotoxicity or crop persistence. The present invention provides a method for controlling clubroot, comprising applying cyazofamid to brassica vegetables after seeding or settled planting in a farm field.
