Assessing Effects of Climatic Change, Region and Agronomic Practices on Leaf Spotting of Bread and Durum Wheat in the Western Canadian Prairies, from 2001 to 2012

Abstract

The leaf spotting (LS) complex is a widespread wheat (Triticum spp.) disease across the Canadian Prairies. A 12‐yr survey (2001–2012) was conducted in commercial fields across Saskatchewan, Canada to quantify LS and pathogen prevalence by wheat species, soil zone, latitude, longitude, previous crop/tillage, and climate. Leaf spotting severity was greater in durum than bread wheat. Pyrenophora tritici‐repentis had the greatest percentage occurrence and frequency of isolation. Percentage isolation of this pathogen and Cochliobolus sativus was greater in durum than bread wheat, while the reverse was true for Phaeosphaeria nodorum. Responses of wheat species to previous crop/tillage were not consistent. Bread wheat in the Brown soil zone had lower LS, and C. sativus levels, than in the other two soil zones, no other pathogen was significantly affected by soil zone. For bread wheat, going northward and eastward increased LS severity, going eastward decreased P. tritici‐repentis levels, going northward and eastward increased P. nodorum, while going south, and to a lesser extent east, increased C. sativus. Wet and warm conditions, particularly in the last years of this survey, and the presence of P. nodorum and C. sativus, were responsible for greater LS severity. Overall, P. tritici‐repentis was associated with warmer and drier conditions, and could not explain LS severity. Greater precipitation and temperature, especially in the last 3 yr (2010–2012), coincided with greater LS and C. sativus levels. Therefore, under higher precipitation and temperatures, C. sativus can become an important leaf pathogen in the western Prairies, especially in durum wheat. Long‐term survey assessed climate impacts on leaf spot levels and pathogen prevalence. Used climate data in a zone around each field for accurate assessment of its effects. Large‐scale assessment of soil impacts on leaf spot severity and pathogen prevalence. Identification of leaf spot pathogens most associated with disease severity in wheat.