Diversification of cereal cropping systems with alternative crops, such as oilseed, pulse, and forage crops, furnishes producers with a range of agronomic and economic options. Crop diversification also improves management of plant diseases through manipulation of host factors such as crop and cultivar selection; interruption of disease cycles through crop rotation, fungicide application, and removal of weeds and volunteer crop plants; and modification of the microenvironment within the crop canopy using tillage practices and stand density. Management practices, such as seed treatment, date and rate of seeding, balanced fertility, control of weeds, field scouting, harvest management, and record keeping, can also be utilized to manage plant diseases. This review evaluates the risks to diversified crop production systems associated with the major plant diseases in the northern Great Plains and the influence of host, pathogen, and environmental factors on disease control. Principles to help producers reduce and manage the risk from plant diseases are presented, and discussion includes strategies for countering fusarium head blight (Fusarium spp.), commonly called scab; and leaf spot diseases in cereals; sclerotinia stem rot [Sclerotinia sclerotiorum (Lib.) De Bary] in oilseed and pulse crops; and ascochyta blight (Ascochyta lentis Vassil.; teleomorph: Didymella lentis Kaiser, Wang & Rogers) and anthracnose blight [Colletotrichum truncatum (Schwein.) Andrus & W.D. Moore] in pulse crops. Producers should not rely exclusively on a single management practice but rather integrate a combination of practices to develop a consistent long‐term strategy for disease management that is suited to their production system and location.

The malting barley (Hordeum vulgare L.) industry is often challenged by the availability of sufficient volume and quality to meet demand. Our objective was to evaluate the effects of agronomic practices on grain uniformity, protein concentration, yield, and yield components. Field experiments were conducted from 2005 to 2008 at eight rain‐fed locations in western Canada. The effects of two seeding rates (200 and 400 seeds m−2) and five N (0, 30, 60, 90, and 120 kg ha−1) rates on two two‐row barley cultivars (‘AC Metcalfe’ and ‘CDC Copeland’) were determined. Each experiment was conducted for 3 yr at each location (24 environments). CDC Copeland displayed some advantages over AC Metcalfe including higher grain yield, lower protein and more uniform kernels. For both cultivars, kernel weight, and plumpness were lower at the higher seeding rate; protein was also lower, maturity was earlier and kernels were more uniform. With increasing N rate, barley yield, kernel weight, and tillers plant−1 increased, but days to seed maturity and protein concentration also increased, and kernel plumpness and seed uniformity decreased. The increase in protein was less pronounced with CDC Copeland suggesting that there may be less risk with this cultivar of unacceptable protein levels at relatively high N rates. At many environments barley plant stand decreased while lodging increased with increasing N rates. To improve the likelihood that barley will be acceptable for malting growers should select low‐protein varieties, seed at relatively high rates and limit N application.

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Wild oat causes more crop yield losses and accounts for more herbicide expenditures than any other weed species on the Canadian Prairies. A study was conducted from 2001 to 2005 at four Canadian Prairie locations to determine the influence of repeated cultural and herbicidal management practices on wild oat population density, biomass, and seed production, and on barley biomass and seed yield. Short or tall cultivars of barley were combined with normal or double barley seeding rates in continuous barley or a barley–canola–barley–field-pea rotation under three herbicide rate regimes. The same herbicide rate regime was applied to the same plots in all crops each year. In barley, cultivar type and seeding rate were also repeated on the same plots year after year. Optimal cultural practices (tall cultivars, double seeding rates, and crop rotation) reduced wild oat emergence, biomass, and seed production, and increased barley biomass and seed yield, especially at low herbicide rates. Wild oat seed production at the quarter herbicide rate was reduced by 91, 95, and 97% in 2001, 2003, and 2005, respectively, when tall barley cultivars at double seeding rates were rotated with canola and field pea (high management) compared to short barley cultivars at normal seeding rates continuously planted to barley (low management). Combinations of favorable cultural practices interacted synergistically to reduce wild oat emergence, biomass and seed production, and to increase barley yield. For example, at the quarter herbicide rate, wild oat biomass was reduced 2- to 3-, 6- to 7-, or 19-fold when optimal single, double, or triple treatments were combined, respectively. Barley yield reductions in the low-management scenario were somewhat compensated for by full herbicide rates. However, high management at low herbicide rates often produced more barley than low management in higher herbicide rate regimes.

Clubroot, caused by Plasmodiophora brassicae, was detected for the first time on canola in Alberta. Galling, typical of the disease, was observed on the roots of canola (Brassica napus) plants in a dozen fields near St. Albert, Alberta. The presence of resting spores of the pathogen was confirmed by light and electron microscopy. Pathogen spores were isolated from diseased tissue and used to inoculate roots of B. napus 'Westar', on which they produced symptoms similar to those observed in the field. Resting spores were recovered from galls on inoculated plants. The identification of clubroot on the Alberta canola crop is a matter of concern, as the disease is associated with appreciable yield losses and can only be managed with extended intervals between host crops because other management strategies may be too expensive to implement or are of limited effectiveness. Further studies are underway to determine the extent of the problem.Résumé : La hernie, causée par le Plasmodiophora brassicae, a été trouvée pour la première fois sur le canola en Alberta. Typique de la maladie, la formation de galles a été observée sur des racines de canola (Brassica napus) dans une douzaine de champs près de St. Albert, Alberta. La présence de spores de conservation de l'agent pathogène a été confirmée par microscopies optique et électronique. Des spores de l'agent pathogène ont été isolées de tissus malades et utilisées pour inoculer des racines de B. napus 'Westar' sur lesquelles elles ont causé des symptômes semblables à ceux observés au champ. Des spores de conservation ont été retrouvées dans des galles de plantes inoculées. L'identification de la hernie dans les cultures de canola de l'Alberta est préoccupante puisque la maladie est associée à d'importantes pertes de rendement et ne peut être combattue que par de longs intervalles sans cultures sensibles, étant donné que les autres stratégies de lutte sont trop coûteuses ou d'efficacité restreinte. D'autres études sont en cours pour déterminer l'ampleur du problème.