The common control method of leaf blotches is the application of fungicides; however, the results of trials are inconsistent. The aim of the present study was to evaluate the impact of the fungicide treatment intensity on the severity of leaf blotches and to assess the correlation between the development of diseases and winter wheat (Triticum aestivum) yield in 2018–2021. The development of diseases was evaluated regularly. In this study, the severity of leaf blotches at the medium milk ripening (GS 75–77) was used. Tan spot dominated in 2018, 2019, and 2021, but Septoria tritici blotch dominated in 2020. Fungicides significantly decreased the severity of tan spot and Septoria tritici blotch, but the efficacy of used fungicide treatment schemes differed during trial years – it was more pronounced under higher pressures of leaf blotches. In the year with a high severity of Septoria tritici blotch, the best efficacy was obtained when fungicide was used two times (at GS 32–33 and GS 55–59), but for tan spot – when the dose of fungicide was done in two or three applications. Usage of fungicides increased wheat yield only under high pressure of diseases. A strong significant correlation between the severity of Septoria tritici blotch at GS 75–77 and grain yields was established only in 2020, when the severity of the disease was higher.