The aim of this work was to investigate the influence of rutin, the main buckwheat flavonoid, on the growth and germination of selected phytopathogenic fungi — Alternaria alternata, Botrytis cinerea and Fusarium solani . Fungitoxicity of rutin was determined by the germination test using conidial suspensions of a fungi and the radial growth test using agar discs with the maternal fungus mycelium. Effects of rutin on tested fungus species were not toxic. Rutin stimulated formation of germ tubes and conidia of A. alternata and F solani . Inhibitory effects were found only on prolongation of germ tubes, secondary hyphal branching and the radial growth of Botrytis cinerea . The effect of rutin was dependent on the concentration especially by Fusarium solani .