Predicting the crop disease outlook for the Canadian Prairies is never easy. With the wild swings in temperatures and precipitation the region faced over the past couple of years, the task has become even more challenging.
“It’s always fun to speculate about what we might see,” says Michael Harding, a plant pathologist and crop health assurance lead with Alberta Agriculture and Irrigation. “In the end, though, the crystal ball gazing may or may not mean much depending on how the weather and climate actually play out.”
Grainews recently spoke with three Prairie provincial experts about crop disease pressures for the 2023 season and what can be done to reduce yield and quality loss as a result.
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Alberta
With respect to crop diseases, Harding says Alberta appears to be in good shape heading into the 2023 growing season. The province was relatively dry in 2021 and 2022, so there is slightly less disease-causing inoculum in the soil. Still, when preparing for this season, Harding cautions farmers not to get lulled into a false sense of security.
“We’re not in a trend where we’re seeing inoculum levels really building and disease situations getting ready to climax,” he explains.
“Having said that, a lot of the crop disease we have can bounce back pretty quick. We shouldn’t assume we’re going to have less disease in 2023 than a normal year. Scouting and doing risk assessments in crops are going to be just as important in 2023 as they are in any year. We shouldn’t assume diseases are or aren’t going to show up. We’re going to have to watch for them.”
Two of the diseases Alberta growers should be on the lookout for, according to Harding, are sclerotinia stem rot in canola and fusarium head blight (FHB) in wheat. Both have been present in many fields over the past three to four years and could be “back up at the front of mind” if Alberta receives significant rainfall in July, he adds.
Harding says two of the best weapons to fight sclerotinia stem rot and FHB are longer crop rotations and plant varieties with resistance or tolerance to the pathogens causing the diseases. Growers should also consider irrigation timing if applicable, and avoid irrigation during the flowering period for both crops, if possible, since that’s a critical time for disease initiation.
Alberta growers could see many of the “usual suspects” in this year’s disease outlook. That includes blackleg, sclerotinia, clubroot and some of the more common root diseases in canola. Alternaria pod spot and aster yellows remain relatively minor disease threats to canola while verticillium stripe is an emerging issue that bears watching, Harding says.
Fungal leaf spots, FHB and crown rot are some of the more common disease threats to cereal crops. Insect-vectored plant diseases remain a relatively low risk to cereals, but Harding says they are a concern because a recent increase in cover cropping has created a “green bridge” for both the vector and the virus to survive over the winter.
Root rots will likely remain the No. 1 disease concern in Alberta pulses, especially in peas and lentils. Root rots need to be successfully managed or growers could be faced with “extreme losses,” Harding explains.
In addition, chickpea growers should watch for ascochyta blight. Pea growers will also want to be prepared for ascochyta blight and mycosphaerella blight, which are both fungal diseases.
One of the emerging disease threats in cereals, especially wheat and barley, is bacterial leaf streak. Although it’s not a new disease, because it has been present in such low levels in the past it has generally gone unreported. This situation has changed over the past five years as the disease is becoming more common in the province. Harding says the seed-transmitted pathogen is difficult to manage because fungicides don’t control bacterial pathogens and there aren’t any bactericides registered for use against bacterial diseases in wheat. More research is needed to develop tools that will help producers manage the disease, he adds.
Saskatchewan
The 2022 growing season was a tale of two regions in Saskatchewan: much of the eastern segment received heavy amounts of rainfall while many areas to the west were bone dry. As a result, disease pressures were significantly higher in many fields in the eastern portion of the province than in the west. Alireza Akhavan, a provincial plant diseases specialist with the Saskatchewan Ministry of Agriculture, says it’s a trend that could continue in 2023.
Regardless of where you farm in Saskatchewan, blackleg in canola is a likely concern this season, since it is less affected by weather than many other diseases, according to Akhavan.
That’s especially true, he adds, if a field has a history of the disease and if a grower is using a tight rotation. The good news is SaskCanola now offers blackleg race testing, which Akhavan says will enable producers to make more informed decisions when choosing a variety.
A growing concern for many Saskatchewan canola growers, especially those on the eastern side of the province, is verticillium stripe, a soil-borne fungal disease that prevents moisture and nutrient uptake in plants.
The disease first appeared in the eastern portion of the province near the Manitoba border in 2021 and is now something all growers in the province should watch for, Akhavan says. The provincial ministry plans to conduct a post-harvest survey in all regions this year to better determine the disease’s foothold.
While clubroot doesn’t yet have a large presence in Saskatchewan (one per cent of fields according to a recent survey), Akhavan says canola growers must remain vigilant. He says due diligence by farmers has helped keep the disease in check.
Two years ago, it was so dry in the province it was difficult to find any cases of FHB in cereals such as wheat and barley. It was a much different scenario last year, especially in eastern Saskatchewan, where disease prevalence was high, but its severity remained relatively low. Akhavan says growers must be on guard for FHB this year, especially if precipitation amounts are close to provincial averages.
“If the situation is conducive for fusarium head blight, especially on the east side of the province, producers should be very careful not to lose the narrow time window (to spray) for FHB,” he says.
Another potential concern for cereal growers in 2023 is bacterial leaf streak. Akhavan says there were several severe cases in the province’s southeast corner last year. This scenario could play out again this year, particularly if Saskatchewan has warm and humid conditions.
In terms of pulse crops, root rot remains a concern, especially for growers who plan on planting field peas or lentils. Anthracnose was the most important foliar disease in lentils last season and could be again if the province experiences a wet year, according to Akhavan.
Stemphylium is another leaf disease of lentils that is trending higher in Saskatchewan but is also a concern in alfalfa and quinoa crops.
Root rots are a big concern in pulses, particularly lentils and field peas, since both are susceptible to the pathogen causing aphanomyces.
Akhavan’s message to producers for the growing season is to stay vigilant and alert to crop diseases even though disease pressures were relatively low in the province over the last few years.
“Many of these pathogens have hard resilient structures that allow them to overwinter for multiple years,” he says.
“They stay there (in the soil) and wait for the right environment. One example is sclerotinia stem rot, which is heavily dependent on moisture, but if it’s dry those sclerotia or the resting body of the pathogen can stay in the soil very easily for three years and even up to five years or more. Then, as soon as the moisture comes, they are ready to germinate.”
Manitoba
Manitoba experienced a return to wetter or more normal moisture conditions in 2022, resulting in an increase in the incidence and severity of some field crop diseases.
What’s in store for 2023? While it’s still too early to know for sure, Manitoba Agriculture field crop pathologist David Kaminski did make some predictions during a presentation at the CropConnect conference, held Feb. 15-16 in Winnipeg.
Kaminski said he expects verticillium stripe in canola is going to be “increasing in both prevalence and severity” this year.
“You can see that it’s something that’s now on our radar. It has had a steady increase in prevalence over the last five years. It’s still not anywhere near the prevalence of blackleg, but it’s rising and that’s a concern,” he explained.
Kaminski added part of what makes fighting verticillium stripe so challenging is so much remains unknown, including the conditions in which it can thrive and what can be done to manage its spread and severity. His advice to growers who suspect they may have the disease in their fields is to contact the Pest Surveillance Initiative (PSI) crop pathology lab in Winnipeg and have the lab provide a diagnosis.
“It’s best to know what you’re dealing with when you’re going to try and do something about it,” he added.
Another concern, according to Kaminski, is FHB in cereals could return to pre-drought levels. While Manitoba didn’t experience the levels expected in 2022 following the province’s return to a wetter cycle, FHB did rebound from the previous year’s low levels, and that trend could continue.
In addition, Kaminski predicts the incidence of crown rust in oats will depend largely on producers’ management choices and varieties they grow. He said the spores that cause the disease can be carried great distances by the wind, sometimes from as far away as Minnesota and other parts of the United States.
Favourable conditions for crown rust development include late planting followed by warm, humid weather. The good news is many oat varieties grown in Manitoba have resistance to crown rust; however, that resistance can decline over time.
As far as leaf and root diseases in field peas and soybeans are concerned, Kaminski said it’s too tough to call at this time.
Clubroot was found in a Manitoba rural municipality where symptomatic canola had not previously been detected. Currently, there are no RMs in which 10 or more clubroot-infected fields have been documented. Kaminski said he expects clubroot might be found in new geographic areas this season.
Phytophthora root rot is one disease soybean growers should watch for. It’s caused by a fungal-like pathogen that can survive in the soil for up to 10 years. The pathogen is most active and damaging in wet soils.
The disease poses enough of a threat that it is now part of the province’s annual soybean survey for root, foliar and stem diseases. Kaminski added all producers must make an effort to protect and ensure the durability of the resistance genes present in disease-resistant varieties.
