Six strains of Dothichiza populea Sacc. et Br. which originate from different clones of poplar were selected for research of their vegetative compatibility. Growth and morphology were previously studied in vitro conditions. The strains showed significant differences in all of the above mentioned parameters. Micelial pairings of the strains were incompatible in all combinations on carrota agar. These results showed that morphology and growth intensity of colonies of strains, as well as vegetative compatibility pointed out to the possibility of existence of different physiological races of this pathogen.