Turkington, T. K., O'Donovan, J. T., Edney, M. J., Juskiw, P. E., McKenzie, R. H., Harker, K. N., Clayton, G. W., Xi, K., Lafond, G. P., Irvine, R. B., Brandt, S., Johnson, E. N., May, W. E. and Smith, E. 2012. Effect of crop residue, nitrogen rate and fungicide application on malting barley productivity, quality, and foliar disease severity. Can. J. Plant Sci. 92: 577–588. The productivity and quality of the malting barley cultivar AC Metcalfe and leaf disease severity were evaluated under three residue types [barley (Hordeum vulgare L.), canola (Brassica napus L.), field pea (Pisum sativum L.)], two nitrogen (N) fertilizer rates (50 or 100% of soil test recommendation for N), and two fungicide treatments (no fungicide or fungicide applied) at seven sites across western Canada from 2006 to 2009. Residue type had a significant effect on leaf disease severity, which was increased when barley was the previous crop compared with canola and field peas. In general, emergence, head counts, grain yield, kernel weight, test weight, kernel plumpness were lowest for barley grown on barley residue compared with canola and field pea residue. Fungicide application reduced leaf disease severity and increased yield, kernel weight, test weight, and kernel plumpness, while decreasing dockage and thins. However, the magnitude of the impact of fungicide on one or more of these parameters was lower compared with planting barley on field pea or canola residue. Overall, increasing the N rate from 50 to 100% had no effect on leaf disease levels and only increased yields slightly compared with not planting barley on barley residue. However, the 100% rate of N did significantly increase grain protein levels. In contrast, planting barley on field pea residue did not result in a consistent increase in grain protein.

May, W. E., Ames, N., Irvine, R. B., Kutcher, H. R., Lafond, G. P. and Shirtliffe, S. J. 2014. Are fungicide applications to control crown rust of oat beneficial? Can. J. Plant Sci. 94: 911–922. Crown rust (Puccinia coronata Corda f. sp. avenae Eriks.) negatively impacts seed quality and yield in oat (Avena sativa L.) in rust-prone areas of eastern Saskatchewan, Manitoba, Ontario, and Quebec. Genetic resistance is the primary means for controlling this disease, but early seeding and fungicide applications have been suggested to reduce yield losses. Trials were conducted in six locations in Saskatchewan and Manitoba in 2009–2011 to determine the interactions between cultivar, fungicide application, crown rust and seeding date. The cultivars were chosen to represent a range of resistance to the current races of crown rust: AC Morgan, very susceptible; CDC Orrin, susceptible; CDC Boyer, partially resistant; and Leggett, resistant. Crown rust severity varied among locations and cultivars. The sprayed flag and penultimate leaves of AC Morgan tended to have similar amounts of crown rust as the unsprayed leaves of CDC Boyer and CDC Orrin regardless of the level of crown rust infection. Leggett's yield and quality did not respond to fungicide application. Only AC Morgan consistently benefited from a fungicide application. At high crown rust sites fungicide application improved AC Morgan's yield by 17 to 27% (690 kg ha−1 to 781 kg ha−1). Delayed seeding reduced grain yield from 8 to 26% with 8% occurring at low crown rust sites and the largest reductions occurring at high crown rust sites in susceptible cultivars. The test weight of AC Morgan increased from 242 g 0.5 L−1 to 255 g 0.5 L−1 when fungicide was applied at high crown rust sites seeded in mid-May. Fungicide application did not change the test weight of Leggett. The β-glucan level was affected more by seeding date (0.4%) and cultivar (0.4%) than fungicide application (0.1%). Seeding a cultivar with better crown rust resistance than AC Morgan in mid-May eliminated most of the benefits derived from fungicide application. These results indicate that prophylactic fungicide applications are unlikely to provide yield improvement when early planting is combined with even a moderately disease-resistant cultivar.

Harker, K. N., O'Donovan, J. T., Turkington, T. K., Blackshaw, R. E., Lupwayi, N. Z., Smith, E. G., Dosdall, L. M., Hall, L. M., Kutcher, H. R., Willenborg, C. J., Peng, G., Irvine, R. B. and Mohr, R. 2015. Canola cultivar mixtures and rotations do not mitigate the negative impacts of continuous canola. Can. J. Plant Sci. 95: 1085–1099. High-frequency canola (Brassica napus L.) rotations increase canola production risks. From 2008 to 2013, direct-seeded experiments involving several variations of continuous canola were compared with wheat (Triticum aestivum L.) and field pea (Pisum sativum L.) rotated with canola at five western Canada locations. Continuous canola rotations involved sequences of different herbicide-resistant canola and two-cultivar mixtures of herbicide-resistant canola from different sources in the same year. Fertilizers, herbicides, and insecticides were applied as required for optimal production of all crops. Rotating herbicide-resistant canola types over years or mixing two cultivars of the same herbicide-resistant type provided no pest management, yield or seed quality advantages compared with planting the same herbicide-resistant cultivar type each year. In 2013, weed biomass was lower in canola preceded by other crops than most continuous canola treatments. Compared with continuous canola, when 1 or 2 yr of wheat or field pea and wheat were inserted into 3-yr rotation cycles, 2010 root maggot damage was reduced 6% and 2013 blackleg [Leptosphaeria maculans (Desmaz.) Ces. & De Not.] incidence and severity were reduced 53 and 54%, respectively. Furthermore, yields were 22% higher when canola was grown only once in 3 yr compared with continuous canola and the wheat–canola–canola rotation. The most important mitigation strategy to ensure long-term sustainable canola production is to rotate canola with other crops.

. 2015. The impact of fungicide and herbicide timing on foliar disease severity, and barley productivity and quality. Can. J. Plant Sci. 95: 525Á537. There is interest in mixing herbicides with a half-rate of fungicide at herbicide timings for barley in western Canada. At six sites across the Canadian prairies from 2010 to 2012 combinations of herbicide and the fungicide Tilt † (propiconazole) were applied to barley at the two-to three-leaf stage (herbicide and half-rate fungicide), five-to six-leaf stage (herbicide and half-rate fungicide), and/or the flag leaf stage (full or half-rate fungicide only). Each plot area was cross-seeded with tame oat as a model weed prior to seeding. Upper canopy leaf samples were collected for leaf disease assessment at the early dough growth stage. Weed biomass, and grain yield and quality were determined. Total leaf area diseased (a combination of scald, both forms of net blotch and spot blotch) was greater for the two-to three-or five-to six-leaf stage herbicide-only treatments and the combination herbicide and half-rate fungicide treatments compared with fungicide at the flag leaf stage. Yield, 1000-kernel weight, kernel plumpness and test weight were greatest and kernel thins lowest for treatments with a flag leaf stage fungicide application. Split applications of fungicide at the time of herbicide application and at flag leaf emergence did not improve disease management and crop productivity compared with a single full rate fungicide application at the flag leaf stage. Weed biomass was generally not influenced by the treatments because weed control was excellent at all sites. However, yield was lower when herbicide was applied at the five-to six-leaf versus the two-to three-leaf stage. For improved leaf disease management and yield in barley, fungicide applications should include a flag leaf stage timing for adequate protection of upper canopy leaves, which are key contributors to yield and grain filling. Delaying herbicide application to the five-to six-leaf stage in an attempt to accommodate a fungicide application reduces barley yield due to early-season weed interference.Key words: Fungicide, herbicide, timing, leaf disease, barley Turkington, T. K., O'Donovan, J. T., Harker, K. N., Xi, K., Blackshaw, R. E., Johnson, E. N., Peng, G., Kutcher, H. R., May, W. E., Lafond, G. P., Mohr, R. M., Irvine, R. B. et Stevenson, C. 2015. Impact du moment d'application des fongicides et des herbicides sur la gravite´des maladies foliaires ainsi que sur la productivite´et la qualite´de l'orge. Can. J. Plant Sci. 95: 525Á537. Les producteurs d'orge de l'Ouest canadien souhaiteraient ajouter un fongicide, a`la moitie´du taux recommande´, au moment de l'application des herbicides. De 2010 a`2012, a`six sites des Prairies canadiennes, les auteurs ont applique´des me´langes d'herbicide et du fongicide Tilt † (propiconazole) a`de l'orge parvenu au stade de la deuxie`me ou de la troisie`me feuille (fongicide a`la moitie´du taux recommande´et herbicide), a`celui de la cinquie`me ou de la sixi...

Vera, C. L., Irvine, R. B., Duguid, S. D., Rashid, K. Y., Clarke, F. R. and Slaski, J. J. 2014. Pasmo disease and lodging in flax as affected by pyraclostrobin fungicide, N fertility and year. Can. J. Plant Sci. 94: 119–126. Severe infection of the fungal disease known as pasmo, caused by Septoria linicola (Speg.) Garassini, reduces seed yield of flax (Linum usitatissimum L.) in western Canada. Pasmo may also indirectly affect seed yield by predisposing flax plants, under favorable weather and soil fertility conditions, to lodge. With the objective of studying the possible association of this disease with the occurrence of lodging and their effect on seed yield, a study was conducted at Melfort, Saskatchewan, Canada, during 4 consecutive years (2009, 2010, 2011 and 2012), with two fungicide regimes (application and no application) and five rates of nitrogen (N) fertilization (0, 33, 66, 100 and 133% of recommended). The application of pyraclostrobin fungicide reduced disease severity and increased seed yield of flax in the 3 yr (2010, 2011 and 2012) that pasmo infection was detected, and prevented or reduced the occurrence of lodging in the 2 yr (2010 and 2012) with favorable weather conditions for the occurrence of lodging. Increasing rates of N resulted in increased seed yield in 2009 and 2012, regardless of whether fungicide was used or not. Increasing rates of N also increased the severity of pasmo disease in 2010, 2011 and 2012, and of lodging severity in 2010 and 2012. The increase in disease severity due to N occurred in the absence of fungicide in 2011 and when fungicide was applied in 2012, while in 2010 just the effect of N on the two fungicide treatments combined was significant. Only low levels of disease severity (near 20%) were observed when fungicide was applied in 2011, while extreme disease severity (near 100%) occurred in 2012 at all levels of N when fungicide was not applied. The increase in lodging, as N rates increased, was observed only in the absence of fungicide, in both years. The occurrence of lodging took place late in the development of flax.