“What we have discovered very recently is that not only do these two pathogens cause disease, but they interact in such a way that the disease is increased, even when you grow a blackleg resistant canola variety,” University of Manitoba plant science professor Dilantha Fernando said. “It appears blackleg resistance cannot be maintained in the presence of the verticillium.”

The finding — first seen in greenhouse trials and now being tested in the field in plot at Carman, Man. — suggests that even varieties carrying strong blackleg resistance genes might suffer heavier damage if verticillium stripe is also present in the field.

WHY IT MATTERS: Manitoba is ground zero for canola’s verticillium stripe issues in Canada.

Fernando’s research suggests that interaction between the two diseases could hurt yields more than either disease alone.

“The work in the greenhouse has shown this interaction,” he said.

Other work has hinted at the same pattern. A recent study using blackleg-resistant hybrids (45H31 and CS2000) found that co-inoculation with the two disease pathogens increased blackleg severity and yield loss. In that case, the hybrids’ resistance mostly held. Fernando’s results point to a more complete breakdown.

Double trouble

Blackleg (Leptosphaeria maculans), a serious fungal disease of canola, has been spreading through the Prairies since it was first confirmed in northeast Saskatchewan in 1975. Genetics are a key tool keeping the disease in check, although experts in recent years have noted virulence changes complicating some of those resistance ratings.

Verticillium stripe (Verticillium longisporum) is newer. The stem-degrading, yield-reducing disease was first found in Manitoba in 2014 and has since spread into Saskatchewan. There are no varieties registered as resistant to verticillium, although seed companies are playing with varieties that seem more tolerant, and recent Manitoba research may have a line on a physical plant trait that may make infection more difficult.

Both diseases are common in Manitoba. Last year, the province’s canola disease survey found basal blackleg infections in 77 per cent of surveyed fields, stem blackleg infections in 58 per cent of fields and verticillium stripe in 60 per cent of fields.

Greenhouse to farm

While in the greenhouse, Fernando’s team was able to methodically test the disease interaction with blackleg resistance genes commonly used in Canadian canola,

So far, he said, his team hasn’t seen a single Canadian R gene that performs well when verticillium is also present. And while Fernando admits the number of R genes in his collection is limited, he’s certain about what he’s been observing.

“In a fairly confident way, I can say that the R genes that are available are not standing up well,” he said.

Still, greenhouse trials and the reality of the field are different things. Fernando wanted a real-world test.

He got the chance this year. Since 2014, Carman’s research station had enforced strict protocols to keep verticillium out — boot cleaning, washing equipment and avoiding suspect fields. “This was very well followed. But as a plant pathologist, I knew that that is not going to be clean forever,” Fernando said.

The tiny microsclerotia on verticillium are as small as dust particles, and he suspects they could easily bypass biocontrol protocols by riding in on the wind.

“All of a sudden last year, almost every field had verticillium,” he noted. “We went and took samples and also collected DNA from soil. We found that the pathogen was present.”

It was “the best thing that could happen, happened, where now we have natural verticillium inoculum, we have natural black leg inoculum, and we can put the varieties that carry different R genes and now test for the interaction,” the researcher noted.

It would have been nearly impossible to run the experiment in the field if they had to inoculate plants themselves, he added. That would have required separate treatments for blackleg first, verticillium first, and then both in sequence. That approach works in the greenhouse. In the field though, natural inoculant provides a much easier way to study the interactions without researcher interference and under normal exposure pressures from a mix of pathogen profiles.

The team proceeded to plant varieties with different R genes in plots where both pathogens occur naturally.

The Carman station already had a qPCR (quantitative polymerase chain reaction) testing method — a DNA-based tool that can detect specific pathogens in plant or soil samples — for both blackleg and verticillium. That let Fernando’s team quickly confirm that the two were often found in the same plant. They sent half the samples to an Alberta lab and kept half in Manitoba to further verify. They got identical results.

They’ll soon see official numbers from those field efforts. Fernando expects that by the end of August, when disease ratings are completed, they will learn whether any resistance genes were able to hold up under natural infection conditions.

Caution from the canola council

Chris Manchur, agronomy specialist with the Canola Council of Canada (CCC), was aware of Fernando’s preliminary results.

“It is too early to tell how significant of an impact this specific R-gene and verticillium interaction would have on yield in the field, but it underscores the importance of effective blackleg management to prevent any additive effects of both blackleg and verticillium stripe causing yield loss,” he said.

He added, however, that “these results are still early and I would look to waiting until results are replicated and verified through different tests before stating this as a significant development.”

Manchur advised farmers make sure they’ve brushed up on their disease identification skills. “Blackleg and verticillium can occur together, but the CCC has resources to help identify the diseases in the field. If you’re still unsure, there are options to send samples in for DNA testing,” he said.

While there are limited tools for verticillium, he said blackleg can still be managed with cultivar choice, seed treatments, and foliar fungicides at the two-leaf stage.

Looking ahead

Fernando’s work will continue through 2025 with more Carman trials, pathogen tracking and gene-expression studies. Assuming the team gets similar field results as their greenhouse trials, they face the future question of why the interaction is having such a result.

They’re already running tests in a controlled environment — inoculating with blackleg first, verticillium first, and both at once — and using fluorescently tagged strains to track how each pathogen moves inside the plant. They plan to use transcriptomic analysis (the study of all RNA messages a cell makes to see which genes are active at a given time) to see which plant genes are disrupted.

Fernando is also interested in the potential of targeting what are known as susceptibility genes — plant genes that actually help pathogens infect. Knocking those out could make plants tougher, even without adding new resistance genes.

“It is going to be one step at a time,” he said, adding that, “by the end of July next year, we should have a very good handle on what’s going on.”

The post Verticillium may undermine canola blackleg resistance appeared first on Manitoba Co-operator.

Why it matters: Matching races of blackleg to resistant genes in canola varieties has been praised as a more precise way for growers to beat blackleg, but is it all it’s made out to be?

The fungal disease remains one of the most prevalent threats for canola, and got particular traction this year after a wet spring created friendly conditions for its development.

Management has typically involved variety choice and crop rotation, noted the Prairie Crop Disease Monitoring Network.

“However, over the past 10-20 years there have been concerns regarding observed shifts in blackleg pathogen virulence in response to the major gene resistance used in a number of varieties,” the organization said. Basically, that resistance might not be as strong as the farmer thinks.

“Changes in virulence patterns emphasize the critical need to stay on top of this disease,” the resource added.

Blackleg race testing is one of the tools pitched to stay ahead of the fungus. The hope is that a farmer can identify exactly which races are present in the field and match them with resistance genes in a canola cultivar.

The blackleg gene test has been available for years. The Manitoba Canola Growers Association includes it in its suite of free testing available to members.

Knowledge from those tests can be a powerful tool in choosing the canola variety that suits a farmer’s resistance needs, said Clint Jurke, an agronomy specialist with the Canola Council of Canada at the time of interview. So far, however, few canola growers have taken advantage.

“It is a new service, new technology, and so a lot of producers just don’t know that it is available,” said Jurke. “And it is a little tricky as well. Once you get that race test, it’ll give you some kind of crazy number … To take that to selecting the right variety, you might need a little bit of help.”

He added that the industry is developing training for agronomists.

Understanding resistance

Susceptible (S) through resistant (R) ratings applied to varieties upon registration can complicate variety selection. These ratings represent the average resistance or susceptibility of the variety to a given pathogen. In reality, the seed may have genes that are more resistant or less resistant than its rating suggests, Jurke said.

“We have seen every year, really, where there are varieties that are rated R that have done really poorly. They look completely susceptible in the field. So yes, there are cases where, if the grower is growing the wrong variety for that type of race in the fields, then they could have a pretty bad time with blackleg.”

It’s useful to differentiate the two types of resistance in plants and how blackleg races split off, said Jurke. Varieties include major resistance genes and quantitative resistance, also known as minor resistance genes.

With major gene resistance, blackleg starts to infect the canola plant but is stopped because the resistant gene allows the plant to recognize that pathogen and activate defences to kill it.

“It works really, really well, except that the pathogen doesn’t like to be recognized,” said Jurke. “And so there’s the pathogen, which is usually a population, and you’re going to have proportions of that population that the plant can recognize and portions that it can’t recognize.

“And that’s what we call different races. There might be one race that the major gene works against, but another race that’s in the field, it doesn’t work against.”

Minor gene resistance is more of a background immunity, comprised of genes in canola that work together against blackleg. These genes slow the disease, but the plant still becomes infected.

“And if environmental conditions are really conducive, like if you have a really wet spring in the early part of the season like we did this year, then you can get a lot of the fungus in and it can almost overwhelm that type of resistance,” said Jurke.

Major resistance genes are listed on some variety labels in Canada, depending on the seed company. There’s no system available for labelling minor resistance genes.

Making a match

Farmers can match a blackleg race to a major resistant gene in canola, but it can appear complex at first. Jurke recommends consulting the canola council’s online resources and then working with an expert.

The council’s Canola Encyclopedia is published every year with a comprehensive list of available canola varieties. It includes information on the type of blackleg resistance. Major resistance genes are not always listed on the variety label, said Jurke.

“In those cases, we do encourage farmers and agronomists to talk to their seed reps to help determine whether or not this is going to be the right variety for that particular field.”

BASF Canada has chosen not to list major resistance genes on its canola seed labels. Technical service manager Jared Veness said the main reason is that matching blackleg races to varieties can be inefficient.

“There’s over 80 different known races of blackleg with 10 to 15 causing the bulk of the issues in Western Canada,” he said.

“To accurately match up the appropriate major gene with what is in the field makes sense on paper, but probably very difficult to execute effectively.

“Most fields that have blackleg issues have two, three or more races within the field. And even if you have the appropriate major gene matched up with the race that you’ve identified, you can still get disease from the other races that are present.

“At that point, you can make the possible improper decision to rotate your major resistance genes to a different one.”

There could be anywhere from five to 50 minor genes contributing bits of resistance capacity “across all races of blackleg,” he said, and each one does something a little different. Often their mechanisms are unknown.

“Ideally, if we were to go in the direction of labelling in the future, we’d like to get to a place where we’re labelling what blackleg races the hybrid is resistant to and not get into the genes or mechanisms that infer that resistance.”

The company encourages canola growers to use integrated pest management practices such as crop rotations and seed treatments as much as possible. Listing resistance benefits may cause some farmers to think they’re protected and don’t need non-genetic solutions, said Veness.

“I’m generalizing here, but farmers, when they see resistance labels, often it can be viewed as a silver bullet. ‘I got resistance. I’m good. I can keep doing the things that I’m doing.’”

Management

The first step commonly cited to manage blackleg is scouting, particularly at swathing time.

Verticillium stripe has complicated those operations. It is easy to mistake for blackleg, or vice versa, and is increasingly common in Western Canada. If uncertain or if blackleg is identified, take a sample to a lab, said Jurke.

“While you’re there, ask them to tell you what race you got. So with that, then you can take your blackleg diagnosis and then you can look for varieties that will manage that particular race.”

Both experts extolled “stacking” blackleg solutions to get the most bang for the buck.

“The ideal solution is to take one of those major resistance genes and have it stacked on top of that quantitative resistance … so you have a good major gene that kills a pathogen and then underneath that you still have good quantitative resistance,” Jurke said.

“And then, if you could throw that on top of a good fungicide seed treatment, you actually have a pretty good package that should deal with the majority of the disease.”

Veness also noted stacking can help protect the longevity of major resistance genes.

The post Gene testing for blackleg race: How useful is it to the farmer really? appeared first on Manitoba Co-operator.

Why it matters: A wet start to Manitoba’s growing season raised the risk profile for fungal diseases like sclerotinia and more producers applied fungicide.

Sclerotinia is typically one of the top canola diseases on the Prairies, although disease surveys found few infections in Manitoba last year. Early rainfall in 2024, with May and June posting well above average moisture, sparked concerns that the disease would return with a vengeance.

“It produces acids and all kinds of aggressive proteins that basically just go through the plant stem,” said Clinton Jurke, agronomy director with the canola council.

Those compounds eat away at plant cells. If it gets into the main stem and weather conditions include good moisture and relatively high humidity, the fungus prospers. The result is familiar to most producers: bleached, thin and brittle stems that shatter or shred easily when twisted and are spotted with black fungus.

“There’s nothing else that does that,” Jurke noted.

Scale of the problem

Infections on the main stem and branches have the highest impact on yield, according to the council.

When assessing sclerotinia stem rot levels, farmers are urged to look at a representative sample of plants throughout the field. The council suggests at least four to six sites per quarter section. At each site, 50 to 100 plants should be assessed.

Despite widespread worries, Jurke said it’s too early to predict infection levels.

“We expect sclerotinia numbers will be higher this year than what we’ve seen in the past few years, particularly in Saskatchewan and Manitoba,” he said, pointing to the higher precipitation in those provinces.

“Whenever the yield potential for canola is high, then the risk for sclerotinia is high. Usually that means there’s been good moisture.”

Managing sclerotinia is a prevention game. Fungicide is the best and most common solution touted by industry, but a farmer must forecast the risk of disease and apply the pesticide at the start of the infection cycle. There are a few varieties on the market with moderate levels of resistance, Jurke noted, but few farmers use them.

Back to blackleg

If there’s canola in Western Canada, there’s usually blackleg too.

“I guess it has been increasing over the past 10 years and gets a little bit worse every year. In Alberta, there’s been some pretty high levels of blackleg in the last couple of years,” Jurke said.

It is also one of the most common canola diseases in Manitoba. Last year’s provincial canola disease survey found blackleg in 86 per cent of surveyed fields, within which about 11 per cent of plants were infected.

Blackleg is not as dependent on weather conditions. It needs some moisture at the start of the season, but infection depends more on whether the pathogen can evade a plant’s built-in resistance, the canola council said.

It has been at the heart of a genetics arms race in recent decades after the pathogen began circumventing established resistant varieties on the market. Farmers and breeders have scrambled to stay ahead.

The fungus infects plants early in the season, at the cotyledon, one-leaf or two-leaf stage. It then travels through the plant to the base of the stem and top of the root, where it begins eating tissue. Producers will see cankering in the basal part of the stem. More cankers mean more yield loss.

Dry conditions near the end of the season, when the crop starts to dry, often result in worse cankers.

Despite the ongoing resistance fight, blackleg management remains largely about genetics and whether local blackleg races surpass chosen varietal resistance. There are tests to identify the blackleg race involved, but few growers opt for them.

Tight canola rotations also increase severity of blackleg.

“You need two years out of canola for the old canola residue to completely break down. Once that’s gone from the field, the pathogen is gone from the field,” Jurke said.

There are also new seed treatments that protect against blackleg infection. They promise protection up to the three- or four-leaf stage, dodging the plant’s most vulnerable window, but have yet to be commonly adopted.

Jurke also suggested that farmers send samples to a lab to determine if they’re dealing with blackleg or a newer problem on the Prairies: verticillium stripe.

The council singled out that disease threat earlier this year. A field can be infected with more than one of the canola fungal disease trifecta (sclerotinia, blackleg, verticillium) at the same time. If it is verticillium, producers will be wasting their money on fungicide or soil treatments and there are no resistant varieties yet.

The post Fall scouting for canola fungus appeared first on Manitoba Co-operator.

“Review the challenges you had last year and have a plan in place as to how you’re going to handle them this year,” said Warren Ward, agronomy specialist with the Canola Council of Canada.

“Maybe look back over a couple of years and see the challenges you dealt with on the farm and what you can do to make sure that they’re not going to be yield limiting in 2024.”

Why it matters: Issues like blackleg or herbicide-resistant weeds can be anticipated from last year’s field, but crop pests might be different year to year.

Trevor Herzog, Western Canada agronomy lead with Corteva Agriscience, said growers should be ready if it looks like another dry spring is in the works.

“Keep an eye on forecasts and weather. … If the forecast does look dry, then a farmer may decide to start seeding a little sooner just to try to take advantage of the existing moisture before it blows away in the wind or starts to disappear from that ideal seeding depth for the crop they’re considering.”

Herzog also reminded farmers to have seed treatment and weed control plans in place. In particular, he noted seed treatments that target flea beetles, cutworms and seedling blackleg.

“If you have patches of weeds that seem to get an early start and they are taking advantage of the early season moisture, make sure you have a weed control plan figured out to take away that early season pressure on the crop that’s trying to grow through a stressful environment,” he added.

After applying a tank mix with glyphosate, producers should “monitor those weeds as they get the odd shower here or there. And then maybe [apply] an early season in-crop application of some herbicides to keep the weeds at bay and allow that crop to get established.”

Flea beetles and grasshoppers

Although flea beetles have become a commonly cursed scourge of canola in the early growing season, 2023 was not the worst beetle pressure Western Canada has seen. Last year was relatively quiet on the insect pest front from a Prairie-wide perspective, said Ward.

That doesn’t mean this year will be the same.

“Even if you had a good year with [flea beetles] last year, don’t be lulled into a false sense of security.”

The same goes for grasshoppers.

“If it remains dry in the spring, that will be something to watch out for into the new year,” Ward said.

Flea beetles and grasshoppers were noted pests in Manitoba in 2023. Last year’s insect pest summary, put out by Manitoba Agriculture entomologist John Gavloski, noted that “use of seed treatments to manage early-season flea beetle populations continues to be the norm.

“Protection from seed treatments was not long enough in many instances and feeding damage to young plants at or above threshold levels, and additional use of foliar insecticides, occurred in many fields, although not to the same extent as last year.”

Gavloski credited that improvement to good spring growing conditions and warm soil.

Manitoba’s flea beetle issue was not limited to spring. Some fields in central and northwest Manitoba were sprayed in late July and August due to prevalence of the pest on flowering or podded crops. In the east, some fields in late summer were also sprayed for flea beetles, lygus bugs or diamondback moths.

Other insect pests

Aside from localized populations in Alberta, diamondback moths were not out in force in 2023, said Ward, though the Manitoba pest report noted spraying in all regions except the southwest and counts up to 60 per square foot.

Looking to 2024, the moth is always a pest species to look out for, Ward said.

“They come up with the wind currents from the United States. Keep an eye on the monitoring maps and the traps that are out there to predict where and when they might become an issue.”

Trap counts in Manitoba are reported through the province’s weekly pest updates.

Manitoba dodged issues with alfalfa looper, though the pest was reported in other parts of the Prairies.

Loopers were not a species of note in the season’s pest summary, although Ward noted the green caterpillar confounded other western Canadian producers and agronomists.

“It looks a little bit like bertha armyworm but greener,” he said, noting alfalfa loopers appear earlier.

Ward urged producers to brush up on pest identification knowledge so they manage the right problem when it appears.

“In some cases, [species] may look similar but don’t do similar damage or, in some cases, they do similar damage. So, it’s a matter of knowing what you’re dealing with and that’ll give you the options that are available.”

The disease usuals

Verticillium stripe is under the microscope of agronomists and researchers, and is specifically a disease of note in Manitoba.

The pathogen was the second-biggest threat identified by Manitoba Agriculture’s 2023 Canola Disease Survey in terms of prevalence. One in every four surveyed fields was infected. Blackleg was found in 86 per cent of fields.

Those numbers are down from the year before, Manitoba Agriculture plant pathologist David Kaminski noted during a September webinar.

Last year was the first time since verticillium stripe was noted in the survey that prevalence decreased in Manitoba.

While Manitoba is the Prairie hotbed for verticillium stripe, Ward said symptoms have been found in eastern and central Saskatchewan as well, and it’s not likely to stop there.

There are few management strategies, but there’s at least one identified condition that seems to exacerbate the issue.

“Dry, stressed conditions later on in the growing season is where it seems to show up worse,” said Ward.

“You can’t really scout for it until later in the season. Even at swathing time, it’s tough to distinguish. The best time to scout for it is after harvest when you can go out there and identify it on stubble.”

Manitoba’s easy sclerotinia year was echoed through the rest of the Prairies, but Ward urged producers to remember that good growing conditions for canola are often friendly to sclerotinia.

“Looking at what conditions are during the growing season is really going to be the number one factor as to whether we see that disease developing next year.”

Producers should be “thinking about it and going through the risk assessment for sclerotinia as we get into that flowering time of year,” he added.

If there was blackleg in the field in 2023, assume it will also be there this year and plan accordingly, said Ward.

“If you know you had higher blackleg levels last year, especially if you sent some samples away for race identification to a lab, you’ve got some more information where you can start looking at finding a variety that is resistant to that race.”

Aster yellows

Last year was also the worst year since 2012 for aster yellows on the Prairies, particularly in areas of western Saskatchewan and into Alberta, said Ward.

Manitoba didn’t escape the disease either. The 2023 Canola Disease Survey found aster yellows symptoms in 20 per cent of the 100 fields monitored. Between 2018 and 2022, the survey found prevalence of the disease at 10 per cent or below.

Manitoba Agriculture pathologists also noted the surge in aster leafhoppers observed earlier in the season. A vector for aster yellows, the insects tipped surveyors that 2023 might be a bad aster yellows year.

There aren’t many control options for aster yellows, Ward noted. The best producers can do is watch for reports of aster leafhoppers moving in from the U.S.

“It’s not something you can really plan around [aside from] looking for it. The chances of it being really bad two years in a row are low but not inconceivable.”

Weeds

Winter is also a good time for growers to assess options for herbicide-resistant weed management, Ward said.

“If you know you have resistance on your farm, look at planning right now what you can do. A herbicide system would be one [strategy]. Give yourself the most options to be able to deal with those weeds.”

Resources

In-depth information on insects, diseases and weeds common in canola, including management strategies, is available on the Canola Council of Canada website. Information on a number of crop pests is also available on the Prairie Pest Monitoring Network website.

The post Prepping for the 2024 canola crop appeared first on Manitoba Co-operator.

Stem striping

When the crop is full height, but still green, infected canola plants will often have a two-toned stem — half healthy and green and half discoloured and drying down. This is where the disease gets its name.

Leaves can show similar symptoms: healthy on one side, diseased on the other.

This is one way to differentiate verticillium stripe, since farmers will not see stem or leaf striping with blackleg or sclerotinia stem rot. Sclerotinia will cause stem discolouration but it will not stripe half the stem.

Stem cross-section discolouration

Verticillium stripe infects roots and enters the plant’s vascular system. Verticillium hyphae (branching filaments that make up the mycelium of a fungus) and conidia (asexual spores) fill up the vascular system, giving the stem cross-section a greyish colour.

This is easily confused with blackleg. There are two main tips to distinguish the pathogens. With blackleg, stem tissue infections tend to be darker and cause distinct wedge shapes of black. Verticillium is lighter grey and more general throughout the cross-section.

Blackleg stem discolouration is confined to the crown area at the base of the stem. Verticillium darkening can extend well up the stem.

Black specks

As the verticillium infection advances, microsclerotia will start to form on the underside of the peeling stem skin. These can be found all the way up the stem.

Verticillium specks may seem similar to blackleg pycnidia, but they’re much smaller – more like powdery pepper. In some cases, blackleg pycnidia will have a purple-pinkish ooze of pycnidiospores around them. Blackleg pycnidia are also confined to a lesion no more than a few centimetres in size. If you see pink and specks confined to a lesion, it’s blackleg.

Stem peeling and weakening

Peeling stem skin is a symptom of verticillium stripe. Under that peeled outer layer will be the microsclerotia, often taking the shape of faint black vertical striping.

Severely diseased stems may break off and can be confused with lodging.

Sclerotinia stem rot will also cause weakened, brittle stems, but sclerotinia will not have the stripy, speckly microsclerotia. Sclerotinia stem rot will cause the entire stem tissue to shred, not just the outer layer.

Inside the stem, sclerotinia will form sclerotia bodies – the canola-seed-sized resting bodies. Verticillium stripe does not produce sclerotia bodies.

The post Verticillium stripe symptoms appeared first on Manitoba Co-operator.

The national group, drawing on data from the 2022 Manitoba Canola Disease Survey, has summed up the most significant disease threats growers faced last year.

Posted through the council’s Canola Research Hub, the information also covers 2022 summaries from the rest of the Prairies and has links to scouting guides, digital planning tools, lab contacts for disease testing, production blog posts and climate maps.

WHY IT MATTERS: Last year’s disease woes may impact how producers want to approach 2023.

Manitoba data shows that lodging, caused by high winds during canola’s bloom period last year, may have contributed to 2022 disease rates.

Both blackleg and sclerotinia stem rot were flagged for their spread in the province. Results from the 115 surveyed fields found blackleg in 85 per cent of them. Sclerotinia was found in 41 per cent. Incidence rates in the field were found at 13 and three per cent, respectively.

“Sclerotinia is a very destructive disease, in that it kills plants. It doesn’t just weaken them or reduce their seed production,” said Manitoba Agriculture plant pathologist David Kaminski.

“Resistance breeding for sclerotinia has been far less successful than resistance breeding for something like blackleg.”

While blackleg is also destructive, Kaminski said, most herbicide-tolerant crops today have been bred with blackleg resistance in mind.

“We cut through the stem to see how much blackleg is evident and what we’re generally seeing is the levels are quite low. The severity of blackleg has not been high even though the prevalence has been quite high.”

The 2022 survey rated both sclerotinia and blackleg severity as 1.2 on a five-point scale.

However, severity results for both diseases were calculated using the entire pool of surveyed crops, not just infected fields. Many more fields dodged sclerotinia completely compared to blackleg.

Eyes on verticillium stripe

Verticillium stripe remained the imminent concern. The soil-borne fungal disease was found in 38 per cent of surveyed fields. Within those, the disease had infected 23 per cent of plants.

Incidence rates for verticillium stripe were based only on infected fields, while incidence data for blackleg and sclerotinia was calculated using all surveyed crops.

The disease is a relative newcomer, first confirmed in Western Canada in 2014. Because of that short history, it’s also a disease with significant gaps in agronomic knowledge.

What Kaminski does know, however, is that the percentage of fields reporting the fungus is rising.

“We have seen that the crop is more likely to lodge when the stem is weakened by verticillium and, with these pod-shatter-resistant varieties that are left to stand longer, you might have parts of the crop lying down,” Kaminski said.

“That makes it difficult, if not impossible, to harvest. You might be leaving a lot of the yield behind in the field.”

Clubroot is also monitored, said Kaminski, “however, it’s been very rare that we have found it in one of those fields. Clubroot-infected fields are usually brought to our attention by agronomists or farmers themselves.”

Joining the team

Growers might consider volunteering their fields for this year’s survey.

“We always like to have co-operators, especially new co-operators who haven’t been involved before,” Kaminski said.

Manitoba’s canola survey began in 1971 and has been used to track the spread and severity of a number of diseases. The data contributes to agronomy, management and future breeding priorities.

Kaminski and his crew like to survey 100 to 150 fields each year. Sampling was historically later in the season when crop was mature and ready for swathing. With the rise of shatter-resistant varieties and straight cutting, however, they’re using a different maturity indicator.

“We use the seed colour change in the lower pods,” Kaminski said. “The crop is done flowering; it’s produced most of its seed and the ones in the lower pods are starting to get some colour in the seed coat.”

After arranging a time to visit the farm, Kaminski’s team heads into the field beyond the headlands, where there’s a possibility of double seeding and accidental extra fertilizer, so they can get a representative sample of the crop.

“We pull 20 plants at five different sites using a ‘W’ pattern to pace off those sites,” he said. “You’ll end up some distance from where you started, but you’ll have a bundle of canola plants from each of those sites, and then we determine how much blackleg is there, how much sclerotinia there might be, and now we’re beginning to look at verticillium stripe.”

Canola pathogens are highly adaptable, making continued surveys even more important.

There are also immediate agronomic benefits for those who volunteer their fields to be surveyed.

“They do get information back,” Kaminski said. “It’s after the fact, but you can plan for subsequent years. If you saw a lot of blackleg, you would try to be much more conservative with your rotation or look for a variety that had better resistance to the races of the pathogen that you’ve got in your soil.”

Farmers who would like to participate in disease surveys may contact Kaminski at 204-750-4248.

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The fungal infection that has a yield-destroying effect on canola crops was first discovered in Saskatchewan in 1975 and eventually spread across the country.

Blackleg is the result of the interaction between two closely related fungal species, Leptosphaeria maculans and the less virulent Leptosphaeria biglobosa.

In the 1990s, resistant strains were developed that did a good job of controlling the disease, but with blackleg yield losses once again on the rise, researchers are looking at new and creative approaches to fight it.

A recently published paper by University of Manitoba plant pathologist Dilantha Fernando, co-authored by Rasanine Padmathilake, flips the script on how these two fungal species interact.

“The L. maculans, which is the virulent strain, is predominantly found early in the season,” Fernando says. “L. bigloboso, which is the less virulent strain, comes along later in the season.”

It’s similar to Robert Jenner’s suspicion, in the 1790s, that less-virulent cowpox protected milk maids from the more-virulent small pox, leading to the first immunizations against disease.

[RELATED] Grainews: Blackleg is still a threat for canola

Research done at the University of Manitoba in the early 2000s showed inoculation with the less virulent strain can boost the resistance of canola plants against the highly virulent strain. Fernando’s team set up lab and greenhouse trials to confirm the effectiveness of L. biglobosa as a biocontrol agent against L. maculans.

The trials began by creating isolates of both fungal species in the lab. In the greenhouse, they had several plants at the cotyledon stage. They infected those plants with the two strains at different intervals and compared the results four days after infection. Those results were promising. Plants first treated with the L. bigloboso species showed resistance to L. maculans, and it happened quickly.

“The triggering of defence genes takes place within hours,” says Fernando. “And it is not the isolate itself that is doing the work. The plant’s defence mechanisms are being triggered by the less virulent strains.”

In other words, the less virulent isolate immunizes the plant against the more virulent strain, similar to the way a vaccine works.

“The defence pathways are expressed because of the resistant gene, and it’s the same principle here,” says Fernando. But instead of resistance being created in a lab, the plant creates its own.

The trick is to develop a product and delivery technique that are practical for use on the farm.

Timing of the application is critical. Blackleg is basically in the stubble of every canola field so beating the L. maculans to the punch is not easy.

“On the applied side, the farmer must be able to capture and inoculate with the less virulent strain at those very early stages of the crop,” Fernando says.

That’s one more thing on the farmer’s to-do list, and it has a hard deadline, which could stymie farmer uptake. Further development will require investment from the private sector, which could also be a roadblock to development.

But Fernando says there is hope because of recent seed treatments. Products like Syngenta’s Saltro protect against blackleg and slow the infection in its initial stages. Fernando says using a seed treatment like that could buy the farmer some much-needed time to apply an L. bigloboso treatment before L. maculans starts to dominate.

[VIDEO] Below, Dane Froese with Manitoba Agriculture offers a quick explainer on why ‘matching the puzzle piece’ is essential to keeping blackleg in check and reveals how growers can unearth the canola genes that will offer the best blackleg resistance in their fields.

Fernando says he can’t speculate on what a farm-ready product might look like, but he did say certain characteristics would have to be considered. One of the tricky aspects of dealing with a biological entity is keeping it alive.

“You would need the inoculum to have a fairly good shelf life so the spores do not disintegrate and become non-viable,” says Fernando.

Companies might consider an adjuvant or a mechanism that would make the inoculant stick to the plant more effectively than a regular spore, he added.

But the most crucial consideration is timing.

“We already know the timing of L. maculans, but what is required is to see whether we can beat that period by enough to trigger the defence genes,” says Fernando. “Then the plant will take care of itself.”

The post An inoculation against blackleg appeared first on Manitoba Co-operator.

Blackleg (Leptosphaeria maculans) is a severe fungal disease of canola plants, and with canola generating about one-quarter of all farm crop receipts in Canada, it is a serious threat to producers.

The new research was led by AAFC’s Dr. Fengqun Yu and her team of scientists at AAFC’s research and development centre in Saskatoon. The team recently completed the first large-scale resequencing of the blackleg pathogen.

Blackleg was first discovered in northeast Saskatchewan in 1975. The first sequencing was done by French and Australian scientists more than a decade ago. But while those efforts created a useful reference genome, they focused only on islolates collected in France.

“Our work focuses on sequencing Canadian isolates,” says Yu. “We collected isolates from Manitoba, Saskatchewan and Alberta over about two decades. We really wanted to look at the whole picture; at the genetic variation in the isolates across the Prairies.”

Canadian strains have been previously characterized by relatively few molecular markers, which has made it difficult to detect the variation responsible for the pathogen’s ability to adapt. But with the cost of DNA sequencing rapidly dropping, Yu’s team was able to select 162 strains taken from Western Canada. This allowed the team to get a clearer view of Canadian populations than ever before.

“It’s very exciting,” says Yu. “We found quite a few new variations and the isolates from Manitoba look highly diverse.”

The results showed the pathogen populations were composed of three distinct sub-groups — and that strains collected from 2012 to 2014 were more genetically diverse than those collected approximately five years earlier.

The sampled populations from Saskatchewan and Alberta were of similar genetic composition, while the Manitoba strains were highly diversified, which makes managing the disease more complicated. The difference in population structure among the provinces may be associated with precipitation, as fungal diseases like blackleg thrive in moist conditions.

Dane Froese, provincial oilseed specialist with Manitoba Agriculture, says he’s not surprised that genetic variation looks greater in Manitoba.

“We tend to have conditions that are more favourable for the disease,” he says. “Just based on our environmental patterns, we have a longer growing season, and we generally have more heat and more moisture – all things that favour disease development.”

That’s the kind of data that will lead to better management of the disease.

“This research is really exciting, because now we have the information we need to really understand the unique genetics and variations of blackleg-causing pathogen strains across Canada,” says Yu. “Armed with this knowledge, we can develop modern disease-resistant cultivars and discover new solutions to better help growers protect their crops from this serious disease.”

Froese agrees.

“For managing blackleg, it’s a positive step forward,” he says. “Understanding which gene populations are present and which ones are more dominant in different geographies in Manitoba makes breeding efforts more focused and more precise. A more precise tool is always what we need to manage a changing and ever-evolving disease.”

It’s also important research because blackleg is not easy to manage with fungicides, so developing resistant strains is an important way to combat the disease. Most strains available in Western Canada already have some level of blackleg resistance.

“Resistance is a combination of minor and major genes,” Froese says. “As pathogens shift, it becomes more and more critical for growers to be able to match their major resistance genes, in addition to their minor resistance genes, in their canola rotations.”

Yu says it is a constant battle between the pathogen and plant resistance, noting her research aims to be predictive and stay ahead of the disease. She says this new data is a major victory in the battle against blackleg.

“We are very excited to see it applied in the near future.”

However, farmers won’t see new resistant varieties for a while due to the way new discoveries wend their way through approval processes.

“My guess is the earliest some of these new findings will work their way into new crop breeding practices is five years down the road. It takes a year or two to make those crosses, to go through the co-op testing and then to hit registration,” he says. “But long term, it’s a positive story.”

The post Getting a leg up on blackleg appeared first on Manitoba Co-operator.

That’s a question canola growers may find themselves asking more in the future, as verticillium stripe (VS) gains a stronger foothold on North American farms, a recent webinar hosted by the Prairie provinces’ canola associations heard.

It was first discovered in Manitoba in 2014 and is caused by the fungal species verticillium longisporum. The pathogen has a longer history in Europe, dating back to the 1960s in Sweden and subsequently spreading through the rest of north-central Europe.

Justine Cornelsen, an agronomy specialist with the Canola Council of Canada said the first step in managing the problem is going to be getting out and scouting the field and identifying it.

“You’ve got to get into your fields and know what you’re working with,” she said.

The VS infections “snuck up on” the canola sector, she said, due to undiagnosis or misdiagnosis as it’s been confused with blackleg. Some of the symptoms can be similar and the two pathogens can even at times be found in the same plant at the same time. It also has similar symptoms to fusarium wilt (another fungal infection). And because the symptoms typically occur later in the season, it may get missed entirely.

“We’re not going out in the field and looking for that old residue and that’s where verticillium is very obvious,” she said. So, what should you look for?

“What we are seeing as an early symptom was half-stem senescing: half of the stem still being green, healthy and mature and the other half starting to prematurely ripen.”

Another cue is that a cross-section of the stem has a greyish hue to it. Later in the season, the microsclerotia begin to appear.

“That is the real key diagnostic feature when we are looking for verticillium,” she said.

For blackleg, the best time to scout is just prior to swathing or around that 60 per cent seed colour change.

“When the plant starts to die off, it becomes very confusing to know what you’re working with,” said Cornelsen.

“Ideally, you pull up plants that well represent the field,” she said. For best results, you need to snip through the root tissue right at the base of the stem.

Equally important in managing these diseases is crop rotation. Research has shown that it is possible that verticillium lasts in the soil for 10 to 15 years. So, planting canola every year is just going to increase the level of infection year after year. Crop rotation is important for both verticillium and blackleg.

Because there is more known about blackleg, the best management practices are better defined than for verticillium stripe. So beyond scouting and crop rotation, there are some standard practices that are well established, such as choosing the hybrid with the right resistance.

Foliar fungicide applications have been available for a long time but aren’t commonly used because the treatment is preventive and has to be done very early (two- to four-leaf stage). It also provides no benefit if your resistant hybrid is functioning.

“If it’s not acting like a resistant hybrid, if a major gene is being overcome, that’s where an application pays off,” Cornelsen said.

All canola seed is treated with a fungicide that acts to prevent transference of blackleg within hybrid seed bags or from the field, but until now, seed treatments haven’t been available that provide in-field protection. “This will be the first year where canola growers can access or buy a seed treatment to protect the plants when they’re growing,” said Cornelsen.

Because VS is so new to Canada, beyond scouting and crop rotation, management practices are not well defined.

“We’ve taken a lot of work and research out of Europe but even there, they are still struggling to manage this particular disease,” said Cornelsen. However, it can help to control the brassica weeds and canola volunteers.

“If you can get rid of the hosts, you’re not going to allow that inoculant to build.”

One of the challenges for managing the disease is because it is a soil-borne pathogen that can survive in the soil for 10 to 15 years. However, steps can be taken to help mitigate the spread of the disease. These steps include equipment sanitation and developing an on-farm biosecurity plan.

Sheau-Fang Hwang of the University of Alberta also spoke to the webinar, detailing current research into VS, both in the greenhouse and field.

Because it’s a new disease in Canada, little is known about yield loss, but European estimates range between 10 to 50 per cent yield loss.

To help strengthen the knowledge base of the disease in Canada, a ‘Verticillium Stripe Management’ project was established through the Canola Agronomic Research Program (CARP) in 2019. The final results of the four-year study won’t be available until 2023, but Hwang discussed some of the early results in her presentation.

In 2020, Hwang’s team was involved in field testing to evaluate VS severity and impacts under different inoculum levels.

The results of those field tests indicate that VS:

• Reduces seed germination rate;
• Reduces plant height; and that
• Disease severity increased as inoculums level increased.

“Yield losses were observed in all the treatments,” she said.

Hwang was also involved in three greenhouse studies. The first compared the effects of verticillium longsporium with that of verticillium dahliae (another species of verticillium fungus). These experiments determined that VL was significantly more virulent. In the second greenhouse study higher mortality rates were observed when plants were inoculated with higher concentrations of the disease. And the third greenhouse study looked at the timing of when the pathogen was introduced. That study discovered disease symptoms increased, plant height decreased and plant mortality increased when plants were inoculated at three weeks, compared to plants inoculated at one week.

Dilantha Fernando of the University of Manitoba also made a presentation on his work on blackleg.

First detected in northeastern Saskatchewan in 1975, it’s a widespread canola disease throughout the Prairies, and could be a blueprint for how to combat the looming VS threat.

In 2011, Fernando was involved in the first gene study of blackleg to determine what resistant genes (r-genes) were available in canola.

“We were able to successfully show that there are several r-genes that are available, but the predominant one was the Rlm3 gene,” said Fernando.

Further research determined that this particular gene had become quite susceptible to blackleg infection.

The work that Fernando and his team did back in 2011 resulted in the establishment of r-gene labelling for canola seeds which now plays an important role in the management of the disease.

Hybrids are now labelled as R (resistant), MR (mostly resistant), MS (mostly susceptible) and S (susceptible).

The blackleg research Fernando is currently doing is drilling down deeper into the r-gene ratings through a systematic r-gene rotation study.

The post Canola foes the same — but different appeared first on Manitoba Co-operator.

DeKalb’s DKTF 92 SC and DKTF 94 CR will not be available for 2020, Bayer said. Canola growers who have already booked those seeds for this spring are now asked to talk to their local sales reps or retailers about suitable replacements.

“Last season proved to be a challenging environment for Canadian growers across the board,” Bayer said in a release Wednesday. “Some expressed concerns about the performance of these two hybrids in particular, while others saw these hybrids perform as expected.

“Ultimately this inconsistent performance did not meet Bayer’s expectations.”

The company said it ran side-by-side trials with other DeKalb TruFlex canolas and confirmed “the inconsistent yield results were limited to these two hybrids,” while “all other TruFlex canola, straight cut and clubroot hybrids performed to expectation.”

Separately on Twitter, the company said it would recommend DKTF 96 or 75-65 RR to replace DKTF 92 SC, while a TruFlex canola clubroot hybrid is “an alternative” for DKTF 94 CR.

DKTF 92 SC was announced in 2018 for use in the 2019 growing season, and was billed as having “improved pod strength for straight cutting” plus “very good combining ease and multigenic, R-rated blackleg resistance.”

DKTF 94 CR was also first made available to growers for the 2019 season and was billed as having resistance to five clubroot pathotypes (3, 2, 5, 6 and 8) plus an R rating for blackleg.

DeKalb promoted both TruFlex varieties as offering growers “a wider (herbicide) application window, with up to as many as 14 more days, without sacrificing yield potential.”

The two varieties’ herbicide tolerance packages were also marketed as allowing growers to control 51 weed species, “24 more than the Genuity Roundup Ready canola system.” — Glacier FarmMedia Network

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