One of the factors affecting winter wheat grain yields are leaf blotches. The two-factorial trial was conducted in the Research and Study farm ‘Pēterlauki’ in 2017/2018 and 2018/2019 (Latvia). Four nitrogen rates and five fungicide treatment schemes were used. The aim was to clarify the impact of leaf blotches on the winter wheat yield. In winter wheat plots, the tan spot (caused by Pyrenophora tritici-repentis) dominated but also Septoria leaf blotch (caused by Zymoseptoria tritici) was found. The severity of leaf blotches in winter wheat was low in both years due to dry and warm weather. The development of leaf blotches was influenced by fungicide application schemes, but not by nitrogen fertilizer rate. The total disease impact during the vegetation period was estimated by calculation the area under the disease progress curve (AUDPC). AUDPC for both diseases were significantly higher in the variant without fungicides (F0) and in the variant, where half of dose of fungicides at the growth stage (GS) 55–59 (F1) was used. The using of full dose of fungicide at the GS 55–59 (F2) as well as using of fungicides two (F3) or three (F4) times in growing season significantly decreased the values of AUDPC for both diseases, but differences among AUDPC values in mentioned three variants were not significant. Results showed that the nitrogen fertilization significantly increased the average per both years grain yield until the nitrogen rate N180. Fungicide treatment schemes had no significant effect on the average grain yield.

Winter wheat (Triticum aestivum L.) leaf diseases are an important risk factor that influences the productivity and quality of wheat production. The aim of the present study was to review published scientific literature about the possibilities for integrated control of winter wheat leaf diseases. The most common and economically important wheat leaf diseases are Septoria leaf blotch (caused by Zymoseptoria tritici), tan spot (caused by Pyrenophora triticirepentis), yellow rust (caused by Puccinia striiformis), and powdery mildew (caused by Blumeria graminis). The severity of winter wheat diseases has varied significantly over the years and depended on meteorological conditions, variety resistance to pathogen, and tillage system. The crop rotation and an efficient residue management significantly decrease the development of tan spot. The development of Septoria leaf blotch mainly depends on meteorological conditions, but agronomic practice is less important. The use of disease-resistant varieties is the most economical, safe, and effective way to prevent and control wheat leaf diseases. Many European countries have a number of decision support systems for optimizing and minimizing the use of fungicides. Decision support systems are based on control thresholds and meteorological observations. Most used parameters are: air temperature, relative air humidity, and precipitation. These systems have been developed in the countries with a milder climate and a longer vegetation period than Latvia, and systems need to be adapted to Latvian conditions. The main groups of fungicides for disease control in winter wheat are azoles, strobilurin, and carboxamides. The results of many studies about the effectiveness of fungicide groups show that the obtained results differ and further research is needed.