Burcucumber (Sicyos angluatus) is a representative ecosystem-disturbing plant in Korea and currently widely spread throughout the country. A sclerotia-forming fungus with moderate host selectivity, Sclerotinia trifoliorum BWC98-105, was tested in the laboratory, green house and natural habitat for its pathogenicity to burcucumber. When mycelial culture fragment was inoculated to burcucumber seedlings under the green house condition, mycelial growth was observed in the following day, and then resulted in the onset of wilting from 5 days after inoculation (DAI). Its characteristic sclerotia as a sign was observed from 7 DAI, and thus plants turned into dark-brown color at the bottom of stem of burcucumber that was eventually blighted at 14 DAI. Similar visible symptoms were observed in natural habitat. Based on the results of showing typical blight symptom to burcucumber and the sign of sclerotia, we report S. trifoliorum BWC98-105 causing stem blight against burcucumber. Its globular pellet was considered of having quite potential as a bioherbicide to control burcucumber in Korea.