The paper summarizes the results of observations on the occurence of diseases on hybrid rye Marder F1 and a traditional rye cv. Motto. Observations were performed in field conditions, on plots treated with fungicides, and untreated control plots. Powdery mildew (Erysiphe graminis), leaf scald (Rhynchosporium secalis), leaf rust (Puccinia dispersa), and stem rust (P. graminis) were the most commonly occuring diseases, although leaf spot caused by Fusarium spp. was also observed. Hybrid rye studied, Marder F1 was characterized by high susceptibility to fungal diseases. The paper also presents data on the quantity of grain yield as related to chemical control.