Some aspects of wheat leaf diseases epidemiology in Latvia, 1998-2000.
Field experiments were carried out at the Research and Training Farm "Peterlauki" of Latvia University of Agriculture in the central part of Latvia, during 1998-2000. Assessments were made on the upper three leaves every week from the start of stem elongation to full ripening. Incidence and severity of diseases were determined. Tan spot (Pyrenophora tritici-repentis) was the most harmful and economically important wheat disease. Incidence and severity were 100 and 70% in 1998, 100 and 5% in 1999, and 100 and 4-18% in 2000, respectively. Septoria leaf blotch (Septoria tritici, teleomorph Mycosphaerella graminicola) and glume blotch (Stagonospora nodorum, teleomorph Phaeosphaeria nodorum) were observed on the lower leaves each spring, because infections started in autumn. Further spreading was not observed in this period and disease development was not remarkable. Spreading of mildew (Erysiphe graminis) depended on the cultivar, circumstances of growing and meteorological conditions. Yellow rust (Puccinia striiformis) and brown rust (Puccinia tritici [Puccinia striiformis]) were observed only on the several cultivars during the experimental period.