Winter wheat leaf blotches development depending on fungicide treatment and nitrogen level in two contrasting years
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Tan spot (caused by Pyrenophora tritici-repentis) and Septoria tritici blotch (caused by Zymoseptoria tritici) are the most widespread winter wheat leaf diseases in Latvia. The aim of the present research was to clarify the development of leaf blotches on winter wheat depending on fungicide treatment schemes under four nitrogen rates. A two-factorial trial was conducted at the Research and Study farm “Pēterlauki” (Latvia) of Latvia University of Life Sciences and Technologies. For this study, data from the 2018/2019 and 2019/2020 growing seasons was used. Four schemes of fungicide application and an untreated variant, as well as four nitrogen rates (N120, N150, N180, and N210 kg ha-1 ) were used. The total disease impact during the vegetation period was estimated by calculating the area under the disease progress curve (AUDPC). The severity of leaf blotches in winter wheat leaves differed significantly during both vegetation seasons. Tan spot was the dominant disease in 2019 (18.7% in untreated variant). The development of tan spot was reduced by fungicide treatment; however, only in 2019, the influence of fungicide was significant. Septoria tritici blotch was the dominant disease in 2020 (11.4% in untreated variant), and its development was decreased by fungicides. Nitrogen fertilizer rate had no significant effect on the development of Septoria tritici blotches. Yield harvested in 2020 were significantly higher than those in 2019 (on average 5.23 t ha-1 in 2019, 8.40 t ha-1 in 2020). The using of fungicides provided significant increase of yield but there were no significant differences among fungicide treatment schemes.