Bactericidal activity of copper-containing fungicide Ridomil Gold R (WDG) was tested in framework of potato black leg control. Three strains of bacteria causing potato black leg were employed in the trials: Dickeya chrysanthemi (DSM 4610, Germany), Pectobacterium carotovorum subsp. brasiliensis (Russia, Omsk region), Pectobacterium wasabiae (Russia, Kemerovo reg.). The activity was estimated in vitro by counting colony number on PDA agar with 0.1, 0.2, 0.4, 0.6, and 1.0% of the fungicide. According to the results, for all the tested bacteria Ridomil Gold R had LD100 = 0.2%. Additional test has been done by potato leafprint method, after spraying leaves by bacterial suspension. The leaves were imprinted on PDA agar with 1% fungicide. No viable bacteria were found after incubation.