That’s the message from Dan Undersander, forage agronomist and professor emeritus at the University of Wisconsin. He spoke during a three-day intensive forage workshop hosted by the Canadian Forage and Grassland Association at the University of Manitoba in March.

While many growers are aware of winterkill and stand thinning, they might not realize just how many diseases are chipping away at their yields — or when those issues can start.

“If you don’t know what you’re looking for, you won’t see it,” Undersander says. “And you’ll think that everything is just fine when it isn’t.”

Black stem

Black stem is caused by the fungus phoma medicaginis and is one of the most common alfalfa diseases across Canada’s Prairies. It tends to show up in cool, wet conditions and often appears early in the season.

According to the Manitoba Agriculture website, the disease can be identified in early spring by numerous dark spots on the lower leaves, petioles, and stems. These may expand into large black areas. Infected leaves often turn yellow and fall prematurely, and lesions that girdle the stem can cause wilting above the damage.

“If it causes complete girdling of the stem, then the stems will die,” Undersander says. “If you have enough of that, then your plant will die.”

Early cutting can help reduce losses, as can rotating with non-legumes for a few years before reseeding alfalfa.

Crown rot, root rots

A wide range of fungi — including fusarium, rhizoctonia, and phoma — cause crown and root rot, especially in older stands or those affected by winter injury. Symptoms include stunted growth, yellowing, and poor vigour.

“If crown rot is less than 50 per cent of the crown’s diameter, it’s probably worth keeping the stand,” Undersander says. “But if it exceeds 50 per cent, you should think about turning it over, because there’s a good chance it won’t survive.”

Winter crown rot, also known as snow mould, is another threat to alfalfa and other legumes. It’s caused by several soil-borne fungi that are most active during late fall and early spring when plants are dormant and soil temperatures are near freezing. Once the soil warms above 0 C, these fungi become inactive, and alfalfa is no longer at risk for this disease.

Aphanomyces

Aphanomyces is another type of root rot, caused by the oomycete aphanomyces euteiches, and has become a significant disease in alfalfa production, particularly in wet or poorly drained soils.

“If the seedlings are coming up and the cotyledon dies, but the seedling stays erect — that’s probably aphanomyces,” Undersander says.

It often appears on slopes rather than in low-lying areas, and its biggest effect is on root development. Undersander explained that aphanomyces causes root pruning, which weakens the alfalfa’s root system. As a result, the plants become less competitive, creating opportunities for weeds to invade the field.

Verticillium wilt

This cold-weather vascular disease was introduced from Europe and has been causing problems in British Columbia since the 1970s. It was first detected on the Prairies in 1998, in Manitoba, but has since spread to Saskatchewan and Alberta.

Undersander says it can be identified by what he calls a “thumbprint” on the leaf — irregular, pale or yellowish patches that appear on the leaves, which can resemble the shape or impression of a thumb.

“This is a disease that causes dead leaves on a green stem,” he says. “It causes problems because it’s attacking the vascular system.”

Symptoms are worst in spring and fall. Infected stands may die out in a few years, especially under irrigation. Rotating with cereals or grasses — and avoiding potatoes, sunflowers and sweet clover — is recommended.

Common leaf spot

Caused by the fungus pseudopeziza trifolii, this disease shows up as tiny black or brown circular spots on leaflets, with a lighter brown raised disc in the centre. As the infection spreads, leaves will yellow and drop early, reducing yield potential. It thrives in moist weather and overwinters in crop residue.

Manitoba Agriculture recommends cutting before leaves begin to fall, and using resistant varieties such as Rambler.

Downy mildew

This foliar disease shows up as pale blotches on the top of leaves and a violet, downy growth underneath. Plants may appear bunched or twisted at the top. It’s most active in spring and fall under wet, humid conditions but usually doesn’t cause serious damage.

Undersander points out that downy mildew can be a concern in both spring and fall. “Depending on the time of year, different organisms can be a problem,” he says.

According to Manitoba Agriculture, resistant cultivars such as Algonquin can be used for control, and rotating with cereals or grasses can help reduce infection.

Phytophthora

Phytophthora root rot is especially problematic in poorly drained areas and spreads through standing water in warm weather.

Even if phytophthora doesn’t kill the plant right away, Undersander says, it can severely damage the root. The plant may appear healthy for a while, but when dry conditions hit, it often can’t access enough moisture and will die as a result. He advises digging about six inches to check root health.

“You might keep the alfalfa for the current season,” he says, “but if the root is rotted off, you should plan on turning it over.”

Anthracnose

Though it’s often associated with lentils and dry beans, anthracnose can also be a yield thief in alfalfa — and it frequently goes unnoticed, Undersander says. The disease is identifiable by diamond-shaped lesions on the stem and sudden dieback at the top of the plant.

“There has been good resistance to it,” he says. “And we should think about taking advantage of that, because it will cause as much as a 20 or 30 per cent yield loss if you’re not paying attention.”

Timing matters

The appearance and impact of alfalfa diseases often depend on both the age of the stand and the time of year. Diseases such as phytophthora, pythium and black stem typically show up in new seedings, while bacterial wilt, fusarium wilt, crown rot and verticillium wilt are more common in older stands.

“You wouldn’t expect to see them in the first year or two, but you would maybe see them in the third or fourth year,” Undersander says.

Seasonal conditions also influence disease expression. Some pathogens thrive in cool, wet weather: downy mildew and verticillium wilt, for example, are often seen in spring and fall. Others, such as spring black stem and pythium, emerge early in the season, while summer black stem appears later.

Understanding when a disease is likely to appear can help with diagnosis and inform decisions about cutting, rotation and stand management.

Management tips

Undersander offers several general tips for alfalfa growers aiming to manage disease risk.

He recommends starting with good-quality seed and avoiding planting alfalfa after another legume. Where possible, he says, farmers should stick to planting in well-drained fields to help prevent root rot diseases and avoid wet spots that can foster pathogen growth. Maintaining good pH and nutrient levels is important, he adds, because vigorous plants are more disease-resistant. He suggests controlling insects, since they also introduce pathogens to a crop.

READ MORE: Alfalfa aptitude: five things to consider when selecting varieties

Farmers should also mow new seedlings before old stands, and try to mow clean fields before infected ones, to reduce disease spread.

“Wait till the dew is off before mowing,” Undersander advises. “I don’t recommend expecting all the dew to be gone, but at least a high portion of it.”

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It’s not a huge amount of additional resistance, but some are marginally better.

“Based on the field results, it doesn’t look like massive differences, but I think there are some differences,” says Tom Warkentin, a field pea and soybean breeder at the University of Saskatchewan.

A couple of years ago, University of Saskatchewan experts learned that certain pea varieties may have stronger resistance to root rot.

Indoor testing showed that several varieties on the market, including AAC Ardill, AAC Aberdeen, CDC Amarillo, CDC Lewochko and AAC Profit, can better withstand aphanomyces and the other pathogens in the root rot complex.

Field pea and lentil growers have been struggling to cope with aphanomyces root rot — a complicated soil disease — since it was discovered in Saskatchewan in 2012 and Alberta in 2013.

The disease thrives in wet soil conditions and hinders nodule development on pea roots, “which further exacerbates symptoms, as plants will not be able to fix nitrogen needed for growth,” the Manitoba Pulse and Soybean Growers website notes.

“As a result of both root infection and nodule loss, infected plants produce fewer pods, a reduced number of seeds per pod or may even die before pod development.”

However, the root rot complex is more than just aphanomyces, the SaskPulse website adds.

“In fact, it is usually aphanomyces and fusarium together that are the most devastating. Therefore, it is not only about managing aphanomyces but fusarium as well.”

To test the indoor results, scientists conducted plot trials in root rot nurseries at Lethbridge, Saskatoon and Morden, Man., in 2024.

It’s hard to draw firm conclusions from one growing season, so more research is needed to determine which pea varieties are more resistant.

“We’re going to run it (the trial) again next year: three locations in 2024 and three locations in 2025,” said Warkentin, who spoke at the Manitoba Agronomists Conference in mid-December in Winnipeg.

“I think we’ll shake out … that these are more resistant than those…. We should be able to pick out high, medium and low.”

To be clear, a pea variety with more resistance doesn’t mean it can be grown in a field with a high level of aphanomyces in the soil, but it could provide some short-term help for growers.

Right now, farmers with fields infected with root rot pathogens must wait six to eight years before seeding peas and lentils again.

In the long run, farmers need more tangible solutions, including new varieties with improved resistance to aphanomyces.

In January, the pulse industry and the provincial government of Saskatchewan announced $4.2 million in funding to accelerate research and identify solutions to root rot.

“I think it is a very big deal,” Sabine Banniza, a University of Saskatchewan plant pathologist, said in January.

“It’s the first time a concentration of funding (has been) put to this issue.”

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On the good news side, there are management options that help reduce the risk, research is narrowing in on some treatments that may help control the disease, and plant breeding is making progress on resistance.

That’s the update from Michelle Hubbard, a research scientist at Agriculture and Agri-Food Canada’s Swift Current Research and Development Centre and a plant pathologist specializing in pulse crop diseases.

As Hubbard told producers attending the recent Western Applied Research Corporation (WARC) crop conference, being aware of the potential risk of aphanomyces root rot is an important first step in dealing with the disease.

“Unfortunately there are no in-crop rescue treatments that work for controlling aphanomyces,” Hubbard says. “But the best approach is first to be aware that the disease is out there and avoid fields that are at high risk of disease development.”

She recommends having soil or pulse crop roots tested for signs of the disease. There is good information online about collecting samples; growers can also consult one of the provincial pulse crop associations or ask a crop consultant how to collect samples and where to have materials tested.

Aphanomyces euteiches is a root rot pathogen that thrives under wet conditions. It was first detected on the Prairies about a dozen years ago, but it’s suspected to have been around for much longer. Field peas and lentils are the pulses most affected by aphanomyces, while other crops such as chickpea, faba bean and soybean appear to have resistance.

Infected pea and lentil plants will appear wilted and yellow and symptoms are often first detected in low spots or the perimeter of drowned-out areas.

“At times aphanomyces can be very patchy in a field,” Hubbard says, “although whole fields can be affected” and infection levels can range from relatively mild to severe.

She says if producers suspect a production issue, they should have soil and/or root samples tested. Infected roots will become mushy and may have a caramel discolouration, but this can be masked by other root rots. The best way to confirm an aphanomyces infection is by submitting a soil or root sample to a lab.

If you’re planning to grow peas or lentils in fields where pulse crops have not been grown for several years, she says to have soil tested to make sure the field is disease free.

What doesn’t work

Hubbard says research at seven different sites across Western Canada over the past six years is helping to sort the wheat from the chaff in terms of which treatments don’t work and which show some promise.

In the what-doesn’t-work column, intercropping peas with canola, mustard, camelina or oats doesn’t appear to be of any value in controlling the disease. The thinking with intercropping peas with brassicas has been that the glucosinolates in oilseeds would break down in the soil, producing an antifungal or biofumigant compound that might check the aphanomyces pathogen — but so far they have seen no effect.

Hubbard cautions not to throw out the intercropping idea completely. While it didn’t have any effect on the root rot disease, they did observe the pea/mustard and pea/canola intercropping showed a yield benefit at some sites, some years.

Applying herbicides also didn’t reduce disease levels on the pulse crop — but again, there are pros and cons. Hubbard says on the “con” side, herbicides can actually be a stress on the crop and weaken plants, making the crop more susceptible to disease injury. On the “pro” side, however, a herbicide application can control weeds such as shepherd’s purse, chickweed, vetches and others that are also hosts for aphanomyces pathogens.

Other treatments that so far also appear ineffective in controlling aphanomyces are biocontrol and natural products, including arbuscular mycorrhizal fungi (AMF) which can be effective in controlling other pathogens.

Treatments that might work

Results have been a bit sporadic, but Hubbard says research has shown some benefit from some treatments at some sites, “so it is worth looking at those practices further.”

Practices which appeared to produce some benefit in some locations included liming and applying gypsum, both of which can increase soil calcium.

“There are certain liming products such as spent lime from sugar beet processing, which helps to increase soil pH and calcium levels, which may have a benefit,” Hubbard says.

In looking at liming and gypsum treatments at the Swift Current site in 2022, for example, gypsum didn’t reduce the disease load, but it did appear to have a real benefit in increasing yields.

“That was in 2022, and then to add to the confusion in 2023 at the Swift Current site, gypsum appeared to have an effect in reducing root rot infection, but it had no effect on yield,” Hubbard says. “So this is telling us that gypsum and liming can have an effect — we just need to figure out how and why.”

WATCH: AgGronomy TV: Avoiding root rot in pulse crops

While biocontrol products so far haven’t been effective, Hubbard says new products are still in development which could reduce disease load or strengthen crops against the disease.

One natural product being evaluated, is under development by MustGrow Biological Corp. in Saskatoon. The company uses extracted and concentrated molecules from mustard plants, with the goal of commercializing them as natural, organic biopesticides, biofumigants and bioherbcides.

Hubbard is also looking at whether increasing rates of nitrogen fertilizer with pulse crops might be an effective treatment in reducing yield losses due to root rot.

And, of course, plant breeding is another important tool in developing crops with disease resistance. She says the University of Saskatchewan is getting close to releasing a field pea variety with some measure of resistance to aphanomyces.

Developing a lentil variety with disease resistance, however, appears to be a longer-term breeding project.

Take-home message for 2024

With research rolling along in the background, producers are advised to follow the best management practices for producing pulse crops this coming year.

• Be watchful for signs of root rot disease and have soil and plant roots tested to determine if the disease is present.
• Assess your disease risk, avoid fields with known issues, or sites with high moisture which may be prone to disease development.
• Follow a proper crop rotation, avoiding back-to-back pulse crops on the same field, and, if possible, produce pulse crops in a four-year rotation, which helps reduce the risk of disease development.
• If the disease is detected it may require a seven- or eight-year break in rotation before peas and lentils are seeded again.
• Grow other types of pulse crops, such as chickpea, faba bean or soybean, which are resistant to aphanomyces.
• Use good-quality seed, which helps to produce seedlings with high vigour.
• Use seed treatments that provide some measure of protection against root rot and other diseases.
• Select varieties with disease resistance — such as a pea variety with moderate resistance to fusarium — again, to produce a healthy crop stand.
• Make sure the pulse crop has proper nutrition.
• Keep good records on how pea and lentil crops perform during the growing season.

“Research continues to evaluate best management practices and also to better understand the disease complex which affects peas and lentil crops,” Hubbard says. “And when we do have new varieties with disease resistance, we will need to take care of it. Pathogens are always looking to adapt to and overcome genetic resistance, so it is important to apply proper management to protect that resistance as best and for as long as we can.”

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Dyrland, who crops about 16,000 acres of pulses, grains and oilseeds southwest of Kyle, says many farmers are caught between a rock and a hard place when it comes to growing pulse crops. Obviously, rain is needed to help crops grow, but it doesn’t take a great deal of moisture to trigger an outbreak of the soil-borne disease, which can quickly reduce or wipe out yield in lentil and pea crops.

“It is just a devastating situation for ourselves and many other farmers,” says Dyrland. “Lentils have been the most profitable, best-returning crop on our farm, but now aphanomyces is forcing us to reduce acres, extend rotations as best we can and look at alternative crops.

“We manage it the best we can, but I really don’t see any solution until we get varieties with genetic resistance to the disease and/or seed treatments that are also effective against the pathogen.”

And until some type of a silver bullet (if it even exists) is developed, Agriculture and Agri-Food Canada researcher and plant pathologist Syama Chatterton says the best approach is, first, to manage rotations to hopefully prevent the disease from appearing on your farm and if it is already present to apply management practices that reduce the effects of the disease. There is no quick fix — it’s about making the best of a complicated situation.

Cropping rotation near Kyle

Dyrland, who farms with family members, crops a total of 16,000 acres including about 2,000 acres under irrigation and 14,000 acres of dryland. Crop rotation includes pulse crops on about 50 per cent of their dryland acres — large green and red lentils, yellow peas and, more recently, Kabuli chickpeas. The rest of the farm is seeded to canola, durum and barley.

Dyrland says it was about 25 years after growing the first pulse crops — Laird lentils in the late 1990s — that serious disease issues showed up on the farm. Aphanomyces wasn’t identified until the 2016 growing season, and then it hit with a vengeance.

“According to local weather records, we had about 40 inches of rain that year,” says Dyrland. “Everything was saturated, crops were lost, but we learned the underlying issue with the pulse crops was aphanomyces.

“Up until then, there might be a low spot on the field where the crop died out, but we figured it was just too much moisture. We’ve come to realize probably that was a patch of field infected with aphanomyces and now it has spread.”

Dyrland, who is also the chair of Saskatchewan Pulse Growers, says on his farm the lentils appear to be more susceptible to the disease — yield can be wiped out — whereas yellow peas are not as seriously affected.

To manage the disease risk, Dyrland says he extends the rotation between susceptible pulse crops as much as possible and for the past four years that has involved bringing Kabuli chickpeas into the rotation. They grow reasonably well in his area and chickpeas show resistance to aphanomyces.

Faba beans and soybeans are also pulse/legume crops less susceptible to root rot disease, but because they are later maturing, they really don’t have a fit in Dyrland’s rotation.

Dyrland says the persistence of the pathogen that causes root rot disease, Aphanomyces euteiches, poses a particular challenge. The recommendations are to extend rotations between pulse crops by four, six or, even, eight years. “Yet we have some fields where we haven’t grown a pulse crop for 10 to 15 years and when we did plant peas or lentils, the disease was still active,” he says. “It is extremely long lived.”

As of early April, Dyrland shakes his head thinking about cropping decisions for the 2022 season — they may not be made until the last minute. It has been a low snowfall (dry) winter in his area and he didn’t expect to be in the field until the soil warms up in early May.

“We have a few things to consider,” he says. “The 2021 growing season was a major drought in this area and we are still dry. Soil testing shows we have high residual fertility in the soil. The tests are also showing, in some fields, we have a high risk of Group 2 herbicide carryover (there just wasn’t enough moisture to dissipate chemical in the soil profile). And then there is also the risk of what happens if we do get moisture, which could mean a serious outbreak of aphanomyces.

“We have a pretty good idea of what we’d like to do this year, but there are a lot of variables to affect cropping decisions. It will probably come down to what the conditions are like as we are about to head out to the field.”

And on the research front

Chatterton, who is based at the Lethbridge Research and Development Centre, says trying to manage pulse crop root rots — aphanomyces in particular — is a complex business.

These naturally occurring pathogens are like a nightmare visitor who arrives at your doorstep and never wants to leave.

There are several pathogens that fall into the category of root rot diseases, which include Pythium spp., Botrytis spp., Fusarium spp. and Rhizoctonia solani. All of these pathogens can be damaging to pea and lentil yields in varying degrees of severity. However, all can be controlled to some extent with seed treatments and all seem to have a more limited resting spore lifespan than the aphanomyces-causing pathogen, A. euteiches.

“Aphanomyces euteiches is the most damaging to peas and lentils of all the root rots. There is no effective control, and we really have no good handle on how long it will persist in the soil,” says Chatterton. “Some of the older literature and recommendations say it can persist for 10 to 20 years. More current recommendations are to extend rotation to six to eight years between susceptible crops, but even that doesn’t work in every situation. I think it really comes down to the soil type and the moisture regime in any given area.”

Chatterton says with 2021 being a very dry year in many parts of Western Canada, root rot severity was relatively low, “but that doesn’t mean that farmers should be complacent,” she says. “It is still out there. So don’t use 2021 as an indicator. Think back to the last time you grew peas or lentils in a more normal or higher-moisture growing season — how did your crops perform?”

If pulse crops are infected with root rot disease, she says it is important to determine which pathogen it is. She recommends having the soil or, better yet, root samples tested to determine which pathogen is present. None of the diseases are great, but crop rotation and seed treatments might be more effective if you’re only dealing with Fusarium spp., for example. A different management approach might be required if the pathogen is A. euteiches.

“My recommendation is, during the growing season, send samples of infected roots to a lab for proper testing,” she says. “That’s more certain than testing a soil sample. Then a farmer knows for sure what they are dealing with.”

Chatterton’s research looks at root rot from a couple of different perspectives. First, what is the proper rotation interval between susceptible pulse crops if you don’t have aphanomyces on the farm? Also, what is an appropriate interval if the disease pathogen is already there? In another research project she is looking at some other cultural practices, which might help to reduce the effects of the disease.

In terms of rotation and cropping intervals, Chatterton says if there is no aphanomyces in a field or on the farm, aim for at least a one-in-four-year rotation between pulse crops. “The longer the interval between susceptible pulse crops, the lower the risk of the disease developing on your farm,” she says.

If root rot pathogens are present on the farm, a longer interval of perhaps six to eight years between susceptible pulse crops is recommended, but again there is no guarantee. She says a lot will depend on the soil type and moisture regime.

A look at cultural practices

Research involving cultural practices hasn’t arrived at any firm conclusions, but it’s showing some promise at helping reduce the effects of the disease.

One area of research is looking at the use of certain preceding crops to reduce the effects of root rot the following year. Crops such as mustard, oats and even faba beans are known to produce biofumigants, meaning they release chemical compounds that naturally control root rot pathogens.

“The idea is to seed one of these crops on a field, then plow it under as green manure and the following season seed peas or lentils on that field,” says Chatterton. “Chemicals released in the green manure may help control the severity of the root rot.”

Preliminary findings in research trials at Lacombe, in the black soil zone, show faba beans and oats used as green manure appeared to benefit pea yields the following year. However, there was no apparent benefit when the trial was carried out on plots within the brown and dark brown soil zones.

To Chatterton, that suggests the effect is biomass dependent. In the black soil zone, there was more green manure biomass plowed into the soil producing a greater chemical effect on the pathogen, compared with, perhaps, a lighter or thinner green manure crop in the drier growing areas.

Non-host crops

In one other area of research, Chatterton is using root rot-resistant or non-host pulse crops in rotation with susceptible pulse crops to see if the non-host crops can be used to reduce the rotation interval for susceptible pulse crops.

Pulse crops such as faba beans, chickpeas and soybeans are resistant or even considered as non-host pulse crops when it comes to aphanomyces. Could these crops be used in rotation with peas, for example, to help reduce disease levels and the pea crop interval — grow peas one year then plant a resistant pulse crop for one or more years following?

“We looked at growing these non-host pulse crops in a rotation with two-, three-, four- and five-year intervals between pea crops and, basically, we found you’re going to have to wait a long time before you see an effect,” says Chatterton.

“And it may depend on where you farm,” she adds. “At Taber (east of Lethbridge), the resistant crops were grown as part of an eight-year rotation cycle between pea crops and there was still no reduction in disease level. However, at Redvers, in southeastern Saskatchewan, there appeared to be some benefit after four years. So, there was no conclusive recommendation. It may depend on the soil type and moisture regime.”

Chatterton says even though there is no effective registered seed treatment for aphanomyces, she recommends using the products on all pulse crop seeds, just to help the seedlings get off to a good start. One of the issues with A. euteiches is it can infect the pulse crop at any time, not just at the seedling stage.

For more information on dealing with pulse crop diseases, the provincial pulse growers’ associations along with the University of Saskatchewan have produced an excellent fact sheet called, Root Rot in Peas and Lentils in Western Canada (opens as a PDF). It is available online.

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Pulse growers are being urged to go up to eight years between plantings of either peas or lentils, which dominate pulse acres in the province.

“Our susceptible crops are pea and lentil and, to a lesser extent, dry bean. The disease is pretty widely spread, pretty much all the way across Alberta,” said Jenn Walker, research manager with the Alberta Pulse Growers Commission.

The commission, like other pulse organizations, recommends growing pulses every four years, both to meet growing demand and to break up disease cycles.

“It’s important for us to communicate that rotation is important and if growers pull out the pulse because of fear of aphanomyces, they are actually intensifying the potential for disease in canola and cereals,” said Walker.

And growing pulses every four years is definitely doable, she added.

The good news is there are aphanomyces-resistant pulse crops such as soybeans (an oilseed, but one that fixes nitrogen), fababeans and lupins.

“Really what we’re seeing now is that a producer can grow a faba or soybean where it is appropriate, with good potential for lupins as we learn more,” said Walker.

Favourites under siege

Aphanomyces, a soil-borne pathogen that attacks roots of infected plants, has been a nightmare for many growers.

It can spread across fields, particularly in wet years and while there may not be clear signs of an infestation initially, yields can be slashed with wide swaths of the crop looking like they’ve been drowned out. When pulled, the roots of severely affected plants may be little more than a wisp. Growers report that pea fields seem more susceptible than lentils, but scientists say both can suffer severe yield loss.

And they say it can take many years for spore loads to decrease to the point where you can safely grow peas or lentils again.

“In some locations, we’ve found some recovery after four years, whereas in other locations, we’re pushing six to seven years and we haven’t seen recovery yet,” said Syama Chatterton, an Agriculture Canada plant pathologist in Lethbridge.

But shifting to something other than peas and lentils would be a huge change.

In the past five growing seasons, those two crops have accounted for anywhere from 91 to 96 per cent of Alberta pulse acres, according to Statistics Canada data. In contrast, fabas have been around two per cent of acres during that time (2016-20) while soybeans barely make the StatsCan report and lupins don’t show up at all.

But the federal agency’s estimate for this year also shows a significant drop in pea acreage. While Alberta growers have grown 1.8 million acres of peas in three of the last five years, this year’s total has dropped to just over 1.4 million acres. (However, wheat acres have also gone down with canola and barley acres grabbing the land that had gone to wheat and peas last year.)

Fababeans have seen an uptick in acres this year (nearly 60,000 acres versus 35,000 or less in the past four years) but they “are quite different from other pulses,” said Walker.

“They are a very long-season crop, so they require a lot of days to complete their life cycle,” she said. “They need to be planted early, and they will be one of the last things harvested.”

The markets for fababeans — both for human food and feed — are expanding, she added.

A staple food in North Africa and the Middle East, they are the highest-protein pulse grown in Alberta, which makes them very attractive for poultry and swine rations. They can be used in cattle rations as well.

Fababeans offer lots of options, since they can be grown in high-tannin or low-tannin varieties.

“We have a lot of research going on to support the basic agronomy,” said Walker. “Pulse growers themselves have really done a lot of work on the agronomy side. That makes them a plausible, unique, attractive option.”

Former provincial pulse agronomist Mark Olson agrees.

“Fababeans make good sense because they have been researched in Alberta for quite some time,” said Olson, who now works in the private sector. “It’s definitely a good crop to look at.”

A different sort of pulse

Olson has also been helping investigate the use of lupins in the province.

Two varieties of lupin are being tested in Canada; one in Manitoba and one in Alberta. Both varieties have resistance to aphanomyces.

“There are 280 species of lupin, but there are only a few that are agriculturally important,” he said. “One is the narrow leaf blue lupin, and the other is the white lupin.”

The narrow leaf blue lupin is more suited to Alberta, and the white to Manitoba. Koralta Agri-Business has started growing narrow leaf blue lupin of the Boregine variety in Alberta and growing contracts will be awarded in August 2021, he said. AgCall, another Calgary-based company, is assisting with the commercialization and research of lupin.

Narrow leaf blue lupin is grown extensively in Australia and is used primarily in feed applications. However, it can also be used in food applications. Companies in Europe use the narrow leaf blue lupin in plant protein applications such as yogurt, ice cream, salad dressings, and mayonnaise, said Olson.

“The narrow leaf blue lupin likes soil pH below 7.2 so it rules out a lot of the brown and dark-brown soil zones because their pHs are quite a bit higher,” he said. “The Europeans and the Australians I checked with are pretty adamant that soil pH has a huge impact on the narrow leaf blue lupin.”

Provincial research found narrow leaf blue lupin are earlier maturing than white lupin — somewhere between late pea and early fababean, said Olson. (White lupin maturity is similar to soybean, which is why it’s being looked at for Manitoba.)

Use is expanding — an eastern Canadian company is making a lupin hummus and the pulse is also used for products such as the high-protein Blue Menu pancake mix (a Loblaws’ President’s Choice label).

In addition to high protein (34 to 40 per cent), lupins have very low starch levels (less than two per cent).

“It falls in between fababean and soybean in terms of its protein, but it has very little starch,” said Olson. “The oddity is it has an oil to it. A lot of pulse crops have one to 1.5 per cent oil. They are quite low in oil. But lupin will have, depending on the species and variety, between six to eight per cent oil and fat.

“There’s a possibility of utilizing the oil in products like salad dressing and stuff.”

Lupin will grow best in the black and thin black soil zones, where there are enough frost-free days with lots of moisture and high organic matter.

Olson said that researchers are also looking at winter pulses in the far south, and there has been new variety development in winter pea and winter lentil.

Alexis Kienlen is a reporter with the Alberta Farmer Express. Her article appeared in the June 14, 2021 issue.

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“Pulses got off to a pretty good start. Moisture levels in the soil were pretty good. Most of the pulses were up and growing rapidly,” Risula said, noting pulse acres in Saskatchewan this year are roughly the same as in 2019.

The weekly crop report stated that pulses were at 82 per cent normal development as of July 14, with five per cent ahead and 13 per cent behind. The southeast region led the way with pulses at 88 per cent normal; the southwest, at 71 per cent, was farthest behind the curve.

“Peas are quite tall and are starting to pod,” Risula said. “Lentils are flowering and are going to begin podding pretty quickly. In some areas, lentils might be already.”

Along with the good soil moisture levels, most of Saskatchewan received a significant amount of rain that was quite time timely, Risula said.

In some regions, such as low-lying areas, that has led to root rot in pulse crops. As for other foliar diseases, those have been minimal this year.

“We don’t seem to having any problems with insects,” Risula added.

— Glen Hallick reports for MarketsFarm from Winnipeg.

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The 2018 canola disease surveys for Saskatchewan and Manitoba reported root rots in six per cent of fields, says Clint Jurke, Canola Council of Canada (CCC) agronomy director. Manitoba estimated the percentage of infected plants to be around 0.3 per cent and Saskatchewan did not estimate the percentage of infected plants. Alberta has not surveyed for root rots in the last seven years.

One of the difficulties of root rot is it’s not really understood how prevalent it is, or how much damage it causes overall. “Where we do know that root rot is causing a bigger problem is often as a secondary pathogen, particularly if you have blackleg,” says Jurke. “Root rot seems to be worse in blackleg-infected plants, especially if the plants are really heavily infected.

The pathogens that cause root rot can severely affect yields, especially if infection occurs early in the season.

“Likely what happens is the plant’s defence systems are compromised by the blackleg fungus, so now the root rot pathogen has the ability to cause a lot more damage,” he adds. “It exacerbates the whole blackleg issue. It’s one of those diseases that makes sick plants even worse.”

Agronomists also note that interactions with insects, such as cabbage flies, can further exacerbate root rot. Cabbage flies produce root maggots, and when those maggots tunnel around canola roots, they open wounds where infection can set in.

Varied symptoms

Root rot complex is caused by soil-borne fungi that affect the roots of mature canola plants. The primary pathogens involved in root rot complex include Fusarium species, Rhizoctonia solani, and Pythium species. The root rot complex itself includes foot rot, late rot, root rot and brown girdling root rot. Of the four, brown girdling root rot is the most serious. In many cases, root rot diseases are initiated by infection early in the plant’s life.

Root rot is a serious issue in Western Canada. Losses are highest when wet soil conditions occur around early flowering and followed by dry weather later in the season. In some fields, infection levels reach as high as 80–100 per cent, causing as much as 50 per cent yield loss.

Identifying root rot can be tricky since the disease complex manifests in several different ways. Seedling diseases exhibit symptoms during the germination and emergence phase of the plant’s life. Adult root rots exhibit their symptoms at the two-leaf stage and later, and are mostly evident near the end of the plant’s life.

“The infection process may have started during the seedling stage for both types of diseases, but when the symptoms manifest determines which type of disease it will be,” says Jurke.

Early symptoms of brown girdling root rot, for instance, manifest as light-brown lesions on the taproot or main lateral roots. The roots will expand and merge, and the taproot will look as if it’s wearing a belt that’s fastened too tightly. In some cases, only a short stub of the taproot remains. In the field, plants affected by brown girdling root rot will ripen prematurely, often before any seed has been set.

Brown girdling root rot is most prevalent in the Peace River region of Alberta. Jurke says this is likely due to the region’s environmental conditions, cold soils and the frequency at which canola is grown.

Foot rot symptoms include hard, brown lesions at the base of the stem. Salmon-coloured masses will often be present in the lesions. Since the lesions develop late in the season, yield loss as a result of foot rot tends to be minor. When lesions occur earlier in the growing season, they can cause premature ripening and reduced yield.

Root rot symptoms are more variable in both colour and shape. According to CCC resource material, symptoms can be grouped into four types: a light-grey, oval lesion on the upper taproot; a dark-grey discolouration of the lower taproot and internal tissue (this will later turn black); a light-brown, soft, widely spread taproot lesion; or a dark-brown, sunken, sharply defined taproot lesion.

In canola-growing regions symptoms will occur sporadically. Generally speaking, Brassica rapa varieties tend to be more susceptible to root rot. Brown girdling root rot is not commonly seen outside of the Peace River region. A test should be conducted in order to confirm the disease’s presence.

Root rot prevention

Preventing root rot starts with crop rotation, as the risk of root disease tends to increase when rotations are shorter. Jurke says growers should consider including peas or other pulse crops in the rotation to reduce disease severity. Not only will they help lengthen the rotation, but they’ll also improve nitrogen levels in the soil.

“Pulse crops are infected by different pathogens, and so the opportunities for those canola-infecting pathogen strains to increase is diminished,” says Jurke.

Likewise, it’s also important to maintain recommended fertility levels in the soil, particularly nitrogen, phosphorus, potassium and sulphur. Nitrogen, in particular, decreases disease severity.

“When plants are stressed, then their ability to fight off root infections is diminished,” says Jurke.

Disease management starts at planting — even before farmers get out in the field. To keep disease at bay, choose certified seed, which will have a fungicide package, says Jurke.

“Risk goes up dramatically if the seed is not treated,” he says.

Note that no economical chemical controls are available for brown girdling root rot or any of the adult-plant root rot diseases.

At planting, good stand establishment — so a vigorous, uniform crop — is crucial for preventing disease. Pay attention to soil temperature, planting depth and uniformity, and make sure seeds are planted into a firmly packed seedbed, says Jurke.

“The longer seeds are sitting in an ungerminated or slow-growing state below the soil’s surface, the greater the risk,” says Jurke.

Other management tips include practicing good weed control. Any weeds that are in the Brassica family are potential hosts, says Jurke. Problematic weeds include shepherd’s purse, stinkweed, volunteer canola and flixweed.

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Peas, dried peas in particular, were a major part of the diet in the U.K. in the 19th and early part of the 20th century. Surprisingly to some, the major supplier of dried peas to the U.K. in those years was the province of Ontario. Peas (green types) were grown in Ontario, sometimes staked, were harvested, and exported across the Atlantic. Green boiled mushy peas were a staple diet of the less affluent British.

Peas were also played a major part in the dawn of genetics when the Austrian, Gregor Mendel, in the mid-19th century preformed breeding experiments with green and yellow peas and tall and dwarf cultivars.

Peas as a Canadian crop

Why did peas suddenly emerge as a major Canadian crop?

It all began with the discovery by plant breeders in California that they had bred leafless or semi-leafless peas. These peas, unlike the tall lanky or short leafy pea cultivars, could intertwine with each other and stand up in the field or row. In the late 1950s, these leafless peas were acquired by the National Vegetable Research Station at Wellesbourne in the U.K. with great enthusiasm. They immediately put the leafless genotypes to work developing field and table leafless varieties of peas.

In the early 70s I did some work with regular leafy peas while I was at the University of Guelph in Ontario. I used a popular variety called Trapper. Trapper growth and yield had good potential but prior to harvest this leafy pea would lodge badly under field conditions causing most of the pods, peas included, to rot before harvest. Trapper and other leafy peas behaved likewise in my plots on the western Prairies.

By the time the 80s came around the leafless pea varieties arrived in the Prairie provinces and pea production was again off and running in Canada. There seems to be no visible difference between leafless and semi-leafless as far as I can tell.

Now there are dozens of semi-leafless pea varieties, both green and yellow types, all with good to excellent resistance to lodging, the real key to Prairie pea production, something that we now take for granted. In 2018 around five million acres of peas were planted in Western Canada.

Peas, like the rest of the legume family, such as bean, alfalfa, clover, soybean, caragana, peanuts, lupins and legume species often fix some, if not most of their nitrogen requirements. To do this they must be root inoculated with specific species and strains of rhizobic bacteria to effectively fix or manufacture their own nitrogen. There are distinct species of rhizobic bacteria for example for peas and soybeans. In peas and beans specific stains of one species of rhizobia are are better on peas or on faba beans. Other families of plants on the Canadian Prairies also fix nitrogen, such as Russian olive, wolf willow and buffalo berry, but these fix nitrogen in association with actinomycete bacteria. Alder trees, common in the west, also fix nitrogen in association with specific kinds of filamentous actinomycete bacteria.

No added nitrogen needed

The nitrogen-fixing ability of peas, other legumes and non-legumes gives them the ability to out-compete other non-nitrogen fixing plants growing under nitrogen-poor soil conditions. So, applying nitrogen to peas, beans or alfalfa is generally, but not always, a thorough waste of time and money. You could call it “gilding the lily.”

Dry peas, on average are 25 per cent by weight protein or four per cent nitrogen. When they germinate in nitrogen-deficient soils in the presence of suitable rhizobia species, the pea roots very quickly allow the rhizobial bacteria to invade the roots to form root nodules. If soils are high in nitrogen, the pea roots will reject the nodule-forming rhizobia and take up the free nitrogen. Free nitrogen also means lots of weeds also picking up this available nitrogen.

In nature, peas and all other nitrogen-fixing plant species, particularly legumes in agriculture, have this giant advantage in nitrogen-deficient soils. Nitrogen-fixing peas can grow rapidly with their own nitrogen-fixing supply, while the competing weeds are nitrogen starved. Therefore, all legumes should be planted on your most nitrogen-deficient cropland, and please resist the temptation to add nitrogen. Do not waste money!

Seed and fertilizer

Peas can be seeded early in the season in mid-April to May when the soil temperature in the top two inches (5 cm) reaches 4 C. They grow best in moist, well-drained soils and do poorly in wet water-logged soils. Recommended inoculum should be added during the pea seeding process, preferably in pelletized peat. Ensure that the rhizobial bacteria are fresh and viable. Most soils contain wild rhizobia but not usually in sufficient quantity to optimally inoculate the roots of the pea crop. Nitrogen fixation by peas is a high energy consuming process by the plant, needing lots of photosynthetic sugar to fix the nitrogen.

In addition to the sugars needed in the root nodule by the bacteria, the nodules need phosphate, cobalt, iron, molybdenum, manganese and zinc to accomplish this process. Pink interiors of the healthy nitrogen-fixing nodules indicate the presence of leghaemoglobin, a relative of blood haemoglobin in animals.

Pea plants are very good scavengers of soil nutrients and, unlike wheat or flax, rarely suffer from micronutrient deficiency. As far as macronutrients are concerned, peas can pick up enough phosphorus in soils considered to be deficient for wheat or canola. Nonetheless, peas cropland should have good to adequate levels of phosphorus, potassium, and sulphur very low to minimal levels of nitrogen. Nitrogen levels below 10 or 15 pounds per acre would be most suitable.

A 50-bushel pea crop should produce most of the 150 pounds of the nitrogen it requires via the root nodules but it also needs over 40 lbs. of P, 140 lbs. of K and 15 lbs. of available S. Growers should also ensure that the pea cropland is free from soil residues of atrazine, clopyralid and flucarbazone highly damaging to the pea crop.

Diseases of Peas

In the last 30 or so years pea breeders have given us excellent crop stability with leafless varieties, powdery mildew resistance, fusarium wilt resistance, and moderate to early maturity. Mycosphaerella blight is a major problem but problems with sclerotinia, seedling root rots, septoria blotch, downy mildew and bacterial blight also occur. All of these diseases including pink seed, brown spot and virus diseases can be managed.

The big exception: aphanomyces root rot. This root rotting soil-borne fungus disease has previously wiped out peas-growing industries in France, New Zealand and Wisconsin in the United States.

Aphanomyces euteiches is a soil-borne resting spore, forming zoospores that are highly destructive to legumes and pulse crops particularly in wet or waterlogged soils. Stains of this fungus affect a wide range of legumes including peas, beans, faba beans, lentils and alfalfa to name a few.

This destructive root rot disease can best be described as the “clubroot disease of peas.” It’s OK if you disagree with me — I cannot force you to be right.

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The root rot fungus has only one disease cycle per year but masses of water-moving zoospore can be devastating to the pea crop. You will see small to very large areas, especially along drainage channels or wet spots of yellow dead to dying pea plants with brown coloured rotten roots.

To prevent aphanomyces in your fields:
1. Check every field growing peas for root rot, paying particular attention to field entrances.
2. Remember, there are no resistant pea varieties.
3. Ensure that any custom seeding or harvesting equipment is steam cleaned before access to your aphanomyces-free cropland. Any utility or oil service equipment that has access to your cropland must also be steam cleaned. Hold this equipment to rigid soil cleanliness.

Does this not sound like clubroot control in canola? Yes, because the disease life cycles of root rot and clubroot are very, very similar. Both diseases move very rapidly via motile zoospores in wet soils.

Controlling aphanomyces root rot:

1. Repeat: there are no resistant varieties.
2. Follow the above prevention procedures and avoid planting peas in heavy soil prone to flooding.
3. Surprisingly, canola crop residue breaks down in the soil to produce soil fumigating isothiocyanates and thiocyanate compounds that are toxic to aphanomyces root rot spores. Peas following canola may do better that peas following cereals if your cropland is infested with aphanomyces root rot.
4. Follow as-long-as-possible pea crop rotations on badly infested land.
5. Be aware of aphanomyces in your area or your own cropland. Avoid moving equipment of any kind from infested cropland to uninfested areas. If possible, seed infested cropland last of all.

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Some of this trend is attributable to single-mode-of-action products and a reliance on one or two chemistries or technologies — but the adaptability of weed, disease and insect species can’t be underestimated. Their respective abilities to select for resistance and evolve beyond an active ingredient or single mode of action is well-documented.

That’s why the move to multiple modes of action (MMOA) is gaining popularity. According to Glen Forster, technical development manager with BASF, growers are well aware of the impacts of herbicide resistance, particularly since they’re dealing with it at greater frequencies. That’s why many newer fungicides launched in the past four or five years are taking the multiple-mode-of-action approach, he said.

“With fungicides, there’s a lot of education going on in the marketplace to help producers become more aware, and that it’s important to think about resistance management before resistance occurs,” Forster said. “Growers are well-versed in herbicides but the knowledge base on resistance management in fungicides is becoming stronger on a yearly basis.”

One of the primary challenges in sharing that message comes from the frequency and intensity of herbicides versus fungicides. Growers must manage different weed species on an annual basis, whether it’s Canada fleabane or lamb’s quarters. But diseases are different: in any year, the right environmental conditions must be present, the host species must be at the right stage and there have to be sufficient amounts of the pathogen present — all at the same time.

“Even though you may spray the same mode of action on a wheat plant and then the next year, spray the same mode of action on a soybean crop, since the diseases may not be affecting that crop, you don’t have a selection pressure on an annual basis,” Forster said. “If the disease isn’t present in the field or the weather conditions aren’t conducive for that disease, you won’t have selection pressure.”

Advances in breeding technology have also helped growers, with resistance “packages” for diseases such as phytophthora root rot in soybeans and fusarium head blight in wheat. In some years, such breeding enhancements might negate the need for a fungicide application in wheat fields, or at least reduce their number.

But not every disease package is perfect, hence the industry’s move to MMOAs. No matter how sporadic a disease incidence might be, or whether its intensity is low, the key with MMOAs is to be proactive — to reduce the potential for the selection of resistance before it has a chance to start the selection process.

“The chance of having a population that’s resistant to both a strobilurin and a succinate dehydrogenase inhibitor (SDHI) in a field with a multiple mode of action is extremely rare,” Forster said.

“Although fungicides may not need to be MMOA today, it’s always a better strategy to use those prior to resistance selection, to prevent losing one of those tools you have. Diseases will adapt and we need to make sure that we constantly preserve the tools that we have from a fungicide performance perspective, and prevent disease from occurring.”

— Ralph Pearce is a field editor for Country Guide at St. Marys, Ont. Follow him at @arpee_AG on Twitter.

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