Clubroot disease was found on wasabi (Eutrema wasabi Maxim.) growing in drained paddy fields in Yamaguchi Prefecture. The clubroot incidence was high in wasabi plants transplanted from one of two nursery beds set in drained paddy fields, where the occurrence of clubroot on Cardamine flexuosa With., a cruciferous weed, was more frequently observed. In the inoculation test, the clubroot fungus from the weed showed high pathogenicity to wasabi as well as that from Chinese cabbage. It is suggested that the fungus from the weed affects wasabi in fields.
