Polyamine biosynthesis inhibitors, DL-α-difluromethylornithine (DFMO) and DL-α-difluromethylarginine (DFMA) at concentrations of 1.0 and 3.0 mM greatly inhibited mycelial growth of Phyllosticta antirrhini on Czapek Dox Agar (CDA). Putrescine at the concentration of 1.0 mM completely reversed the inhibitory effect of DFMO but only partially that of DFMA. Both polyamine biosynthesis inhibitors at concentrations 1.0 and 3.0 mM applied preventively and curatively strongly inhibited the development of the pathogen on snapdragon leaves.