Impacts of agronomic practices on the leaf spotting complex of common wheat in eastern Saskatchewan

Abstract

. 2009. Impacts of agronomic practices on the leaf spotting complex of common wheat in eastern Saskatchewan. Can. J. Plant Sci. 89: 717Á730. A survey of commercial common wheat crops was conducted in eastern Saskatchewan (2000Saskatchewan ( to 2002 to determine the effects of agronomic practices on the leaf spot (LS) disease complex and causal pathogens, and to determine the impact of LS on crop productivity. Leaf spots had a negative impact on grain yield, but did not affect market grade consistently. There was little effect of agronomic practices on LS severity, but cropping sequence and tillage system affected the mean percentage fungal isolation (MPI), whereas only tillage affected the percentage fungal occurrence. A previous noncereal crop, which had in most cases been preceded by a cereal, resulted in a higher MPI of Pyrenophora tritici-repentis (Ptr), the most common pathogen, and a lower MPI of the septoria leaf blotch fungi Mycosphaerella graminicola (Mg) and Phaeosphaeria nodorum (Pn). Levels of Ptr tended to be lower after 2 yr of noncereals, grown mostly under zero tillage. Overall, the MPI of Ptr increased with a reduction in tillage, being most common under zero tillage, whereas the septoria leaf blotch fungi were least common under zero tillage, and Cochliobolus sativus (Cs) was most prevalent under conventional tillage. The highest MPI of Cs occurred after summerfallow under conventional tillage. Tillage effects also varied with cropping sequence, being most pronounced after another cereal. Pyrenophora tritici-repentis was also associated with recommended or high seeding rates and with high N fertilizer input, although these factors might have been confounded by tillage system and cropping sequence, respectively. Overall, our findings indicate that in eastern Saskatchewan Ptr infection of common wheat prevailed in high-yielding and high N systems that included previously grown noncereals grown under zero tillage and seeded at recommended to high rates, whereas Pn, Mg and Cs occurred the most in lower-yielding and lower N systems preceded by another cereal crop or summerfallow under conventional tillage. However, LS severity was not significantly or consistently affected by any agronomic practice, which was attributed to the presence of all the most common LS pathogens in the region and years this study was conducted.Key words: Wheat, oilseed, pulse, summerfallow, leaf spots, tan spot Fernandez, M. R., Pearse, P. G., Holzgang, G., Basnyat, P. et Zentner, R. P. 2009. Impact des pratiques culturales sur la septoriose du ble´dans l'est de la Saskatchewan. Can. J. Plant Sci. 89: 717Á730. Les auteurs ont entrepris une enqueˆte sur le ble´cultive´dans l'est de la Saskatchewan (2000 a`2002) en vue de pre´ciser l'incidence des pratiques agricoles sur la septoriose et sur les agents pathoge`nes qui en sont la cause, ainsi que pour de´terminer l'impact de cette maladie sur le rendement des cultures. La septoriose diminue le rendement du ble´, mais n'a pas d'impact cohe´rent sur sa qualiteć ommerciale. Les ...

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

“…Pyrenophora tritici-repentis was the most widespread pathogen (present in 99% of all wheat samples plated), followed by P. nodorum (74%), C. sativus (61%), M. graminicola (60%), with P. avenaria being isolated from the lowest percentage of samples plated (28%). In general, the relative prevalence and occurrence of these LS pathogens agrees with a bread wheat survey conducted in 2000 to 2002 in the eastern region of Saskatchewan, in crop districts 1B and 5A (Fernandez et al, 2009). …”

“…For durum wheat, for the 139 crops with previous crop information, a previous year of summerfallow was more common (32%) than a previous pulse or oilseed crop (25-26%), while the least common previous crop was a cereal (18%). In the LS survey conducted by Fernandez et al (2009) in eastern Saskatchewan, the most frequent crop grown before the bread wheat sampled was also an oilseed (47%), while summerfallow preceded bread wheat in only 9% of the fields. The proportion of fields with a preceding cereal (24%) or pulse (20%) crop were somewhat higher than for bread wheat in the present study.…”

“…1) in the Black soil zone in southeastern Saskatchewan, Fernandez et al (2009) reported that isolations of LS pathogens from diseased leaves were affected by agronomic practices. They concluded that P. tritici-repentis was associated with previously-grown non-cereal crops under zero-till management, while P. nodorum, M. graminicola, and C. sativus were associated with previous cereal crops or summerfallow under conventional tillage.…”

The effects of soil tillage and crop rotation on the development of winter wheat leaf diseases

“…Bailey and Duczek (1996) noted the importance of variable meteorological conditions, which can minimise the differences in soil tillage systems. Also, Fernandez et al (2009) did not find a correlation between the level of leaf blotches and the soil tillage system or cropping sequence. A similar situation was observed in Canada, where wheat leaf spot diseases were not affected by soil tillage systems in any of the years during a fouryear study (Kutcher et al, 2011).…”

“…Wheat plots were categorised according to the previous crop and the soil tillage system. A similar method was used by Fernandez et al (2009). Data of disease development in 2010, 2012 and 2013 was used to evaluate different technologies.…”