Conservative soil tillage is considered as the main tool to preserve soil fertility, to reduce gas emissions, and to save financial and labour resources. However, majority of researchers have found that different systems of reduced soil tillage increase the occurrence of slugs, weeds and diseases, including wheat diseases. The aim of the present study was to determine the impact of reduced soil tillage on the severity of winter wheat leaf blotches. The influence of different soil tillage systems and crop rotation on the severity of winter wheat disease was evaluated in a two-factorial experiment: A – soil tillage system (A1 – traditional soil tillage with ploughing at the depth of 22–24 cm); A2 – reduced soil tillage with disc harrowing up to the depth of 10 cm); and B – different crop rotations (B1 – continuous winter wheat; B2 – winter wheat and oilseed rape were grown; B3 – crop rotation). The severity of diseases was determined approximately every 10 days during the whole vegetation season, the total disease impact was estimated by calculating the area under the disease progress curve. Tan spot, caused by Pyrenophora tritici-repentis and Septoria tritici blotch, caused by Zymoseptoria tritici dominated in trials during the entire research period. Soil tillage is the most important factor promoting the development of tan spot, continuous wheat sowings also increased the severity of tan spot. The development of Septoria tritici blotch did not depend on the agronomic practice applied.