“And it is so severe that if the conditions are bad, like if it’s humid or conditions are conducive for disease, it can completely wipe out a chickpea crop.”

The risky disease is typically managed through fungicide, crop rotation, using clean seed, resistant varieties and effective seeding rates. But Hubbard and other AAFC pulse scientists have been running trials on chickpea-flax intercropping since 2012.

The latest edition of the project was on display at this year’s Ag in Motion near Langham, Sask. It was featured at the AAFC booth alongside other research projects and crop plots.

Hubbard joined the project in 2018. She looked at various factors that could impact disease prevalence in a chickpea crop. Her team tested intercropping versus monocropping, adjusting seeding rates of flax while keeping chickpea constant. Without comparing rates, they looked at the impact of nitrogen fertilizer use. They placed the chickpea and flax in mixed rows.

“So, within a single row, there was both chickpea and flax mixed together or the alternative to that was alternating rows,” she explained.

The conclusion of the 2018-22 study was that intercropping was helpful in reducing disease. But there was a catch: the most effective rate of flax varied per year. Some years, the lowest rate was best; in others, higher rates performed better.

They also discovered that nitrogen tended to increase disease prevalence, and while both mixed and alternating rows helped reduce disease pressure, there was no notable difference between the two.

In 2023, Hubbard began another project to build on the research. This one integrates fungicide use and continues to compare intercropping versus monocropping. It is currently in its third year.

For fungicide application, there are four treatments: no fungicide; application once before flowering; application once during the flowering period; and application once before flowering as well as during for a total of two applications.

It also compares chickpea and flax varieties, which hadn’t been looked at in previous trials. They now have three flax and three chickpea varieties to make a total of nine combinations to compare.

So far, dry conditions have limited the usefulness of fungicide comparisons. Otherwise, the trend favouring intercropping has remained steady.

Why chickpeas and flax?

There is not yet a clear consensus on how flax helps to reduce ascochyta blight in chickpea crops. But the initial reasons for trying this intercrop mix were mainly logistics.

One factor was available herbicide and fungicide options. It was important that any products used were safe for both crops and registered for use on both.

“Some of the reasons you choose one thing or another is, is it within reason that you could seed them at the same time and harvest them at the same time?” Hubbard explained. “If one has a far longer growing season than the other, it’s not going to work.”

Another factor was how easily the two crops could be separated after harvest. If the goal is to grow them for grain rather than feed, separation becomes more important — and it’s typically done by size.

“So this works really well because chickpeas are big, and flax are small,” she said.

An additional benefit to the mix is that chickpeas help to thresh the flax bolls, breaking them apart for easier harvest. But harvest can get a little tricky because of the size discrepancy.

“Getting the combine settings such that you don’t either end up with so much non-seed material, like so much trash or so much residue, or that you don’t blow out your small seeds and not end up and lose a lot of yield (can be an issue),” she explained.

Working theories

Since the trial hasn’t yet concluded, there isn’t anything concrete. But Hubbard has a few working theories that are being considered and will be examined more critically.

Her first theory is that the intercrop changes the crop canopy microclimate in terms of temperature and humidity. However, there have been some holes in this idea.

The team checked the canopy every hour, recorded humidity and temperature, but didn’t find a significant difference when testing this between the monocrop and intercrop.

Another idea is that by planting the two crops beside each other, they engage in root-to-root, or arbuscular mycorrhizal fungi (AMF) communication. The communication may “prime” the chickpea defenses and encourage a stronger immune response.

Hubbard’s colleagues have tested this theory with plants in pots with a connecting tube, to create a shape like the letter “H.” But they didn’t see much impact whether it was flax or chickpea in the connected pot.

“In follow-up experiments, we found that just adding AMF, like just colonization by AMF, sometimes led to less disease,” she said. “And that wasn’t consistent. It depended on the severity of the disease or the experiment.”

Hubbard’s final theory is that flax causes a barrier or dilution effect to the chickpeas because it is typically a tall, slender plant.

“It’s a barrier between the chickpeas,” she explained. “And ascochyta blight is what we call a polycyclic disease, or a disease that can infect many times over the course of the season, so it can keep amplifying and spreading plant to plant. And having the flax there reduces the capacity for it to do that.”

By creating the physical barrier, it protects against wind, rain and other weather, limiting spore spread and direct contact.

Hubbard says this idea seems the most likely and relates best to results they’ve seen so far.

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At the Top Notch grower meeting in Moose Jaw sponsored by SaskCanola, SaskFlax, and the Saskatchewan Pulse Growers, Saskatchewan’s provincial plant pathologist, Barb Ziesman, talked about the preliminary seed test results from Saskatchewan seed tests this winter.

Seeding healthy seed is essential to getting your crop off to a good start. “You want to make sure you’re selecting healthy seed with low disease levels,” Ziesman said.

When you’re getting your pulse seed tested for germination, have the lab test for disease as well. “Pathogens on the seed can cause seedling blight, but also root rots,” Ziesman said. Disease will cause seedlings to be less vigorous. “And, if they’re less vigorous, they’re more stressed.”

The charts below and further down show the numbers reported by three Saskatchewan labs, showing their preliminary test results.

The first column for each disease shows the percentage of PFS: pathogen-free samples. That is, the percentage of samples submitted to labs that were not infected. The higher this number the better. As Ziesman explained, “This means that 20 per cent of the lentil samples that were submitted had levels of anthracnose.”

The second column for each disease shows the mean (average) percentage of infection. In this case, 0.9 per cent. In the case of anthracnose, if the mean infection is above 10 per cent, “you should be thinking about using a seed treatment.”

For field peas, ascochyta could be a big problem this year. Seed infected with ascochyta can develop seedling blight. As shown in the table, only 21 per cent of the samples submitted were free of the ascochyta pathogen. “That means 80 per cent of the samples had some level of ascochyta species on the seed.” (For the math fanatics out there, this means you have a four in five chance of having an infected seed lot, based on these preliminary results.)

The ascochyta infection levels are also high, with a mean (average) preliminary level of 4.9 per cent, as shown in the table. This means many farmers will be in that grey area where you can still use the seed, but you should probably use a seed treatment. “Our general rule of thumb is that you should be using a seed treatment between five and 10 per cent,” Ziesman said. If your field pea seed has an infection level above 10 per cent, “maybe look for another seed lot.”

These high levels of infection are not surprising, as root rot symptoms were observed in 59 per cent of lentils last year, and 53 per cent of peas.

It’s complex

Ziesman pointed out that we often refer to root rot as “root rot complex” because there’s often more than one organism involved. While we focus on aphanomyces, fusarium species can be involved too. “These two groups of organisms work together synergistically,” Ziesman said. This means that if both problems are present, you’ll see more disease and higher severity than if there was just one of them present.

Having both fusarium and aphanomyces does not mean you just have more of the same. You have two different biologies working against you. Fusarium species are true fungi. “This means that some of our fungicides are going to be effective against them.” But aphanomyces are not fungi at all. They’re actually oomyces, or water moulds. A lot of fungicides are not effective against these organisms.

Because there are two different types of organisms, there are two host ranges. Fusarium has a wide range of hosts, from pulses to canola. Aphanomyces has a much narrower range of potential hosts.

“Having root rot does not mean you’re going to have more fusarium head blight, but if you have a cereal crop that has a lot of fusarium head blight, it might mean you have a higher risk of root rot.

“We used to talk about fusarium root rot versus aphanomyces root rot,” Ziesman said. The two diseases have different symptoms, and the results can look very different in the field. But it’s not usually that easy to tell the two types of infections apart. Even experienced pathologists can have difficulty differentiating the two diseases in the field, Ziesman said, because there is often more than one pathogen involved. If you want to identify your particular problem so you know exactly how to best deal with it, you are going to have to send your plants to a lab for testing. “You might want to know if it is aphanomyces, because management changes with aphanomyces.”

Why us? Why now?

Why are root rots causing so much trouble in recent years?

There are a couple of factors at work. First, we’ve been growing peas and lentils on the Prairies for a long time. This has given spores a chance to build up. If you’ve been growing lentils and peas in your fields for 40 years, you’ll have a higher chance of getting root rots.

Second, we’ve had a lot of wet years in the recent past, which also gives infection a chance to shine. Both peas and lentils are stressed under wet conditions. And when plants are stressed, they’re more likely to become infected. “Anything that stresses the plant is going to increase its risk of infection,” Ziesman says. This results in a higher likelihood of infection.

Crop rotations will affect your chances of having root rots. If you’ve been growing that crop only every four years, the spores will have had less opportunity to build up in the soil.

Compaction is also an issue. “We see higher severity and more root rot in areas of the field that are compacted. Compaction is going to hold more moisture, but it’s also, again, going to cause more stress for that plant.” Compaction creates a zone where root rot can thrive.

Choosing the right field

One way to lower your risk of developing root rot is to choose the right field. “Make sure that you choose fields that are lighter, or drier fields,” Ziesman said. Choose fields that have good drainage, and coarser soil. Ideally, choose fields that have no history of root rots.

“If you have a field that has aphanomyces, the recommended crop rotation is six to eight years away from peas and lentils. In heavily infested fields, we’re looking at closer to that eight years.”

But don’t be alarmed. Ziesman is not saying you can’t put a pulse crop in your rotation. “We’re not talking about all pulses. We’re really talking about peas and lentils,” she said. Peas and lentils are the most susceptible, and produce the most oospheres when infected. But as shown in Table 3, pulse crops like soybeans or fababeans are not susceptible to aphanomyces. You can still grow a pulse crop on fields where you may have had root rot in peas and lentils in the past. GN

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The disease that is perhaps most concerning, most visible and most likely to cause yield loss is ascochyta, or mycosphaerella blight, said Holly Derksen, former field crop pathologist at Manitoba Agriculture. (Derksen has since moved on to Arysta LifeScience where she works as a technical support special.)

Although ascochyta likes moisture, Derksen says the disease also occurs in dry years. “It may not be at economical levels in a dry year, but it always shows up,” she said.

Ascochyta shows up in the leaves as centric lesions. When it starts on the leaves, Derksen says it’s an indication that growers need to get out there and scout before it moves to the stem. Peas already have lodging issues, which can be exacerbated by disease issues.

“Once it moves to the stem, it girdles the stem, preventing water and nutrients through the plant,” she said.

Timing is important with ascochyta. Symptoms can be show up in the lower leaves, but may not move into the canopy.

“If you start to see symptoms, but then the weather turns dry, they’ll probably just stay on the leaves in the lower canopy, and again, won’t be a huge yield issue,” said Derksen.

If you do need to spray, do so at early bloom, and then again seven to 10 days later, if conditions are conducive to disease. But if disease symptoms show up after that early bloom, she recommends watching the weather forecast closely before taking action.

“If disease only moves in at late bloom, you might be able to see quite a few symptoms, but it won’t necessarily affect the yield,” she said. “Because once that seed pod is getting in there and the peas are forming, there’s not a lot that’s going to change your yield after that point.”

Aphanomyces root rot

While ascochyta is the disease that most concerns farmers, aphanomyces root rot should be on your radar.

Currently, aphanomyces is not widespread in Manitoba, but growers do need to be concerned about it in the long term, said Derksen.

Aphanomyces first showed up in Canada around 2012. “It’s one of those fun diseases that produces those long-lived spores in the soil,” said Derksen sarcastically. “Once you have it and it’s at a level where it’s causing economic damage, there isn’t really a rotation that keeps peas in the rotation that we can recommend that will manage the problem.”

Aphanomyces is an aggressive disease, a water mould that moves easily through the soil, which makes it a bigger concern in wet years. Soybean growers familiar with phytophthora root rot will already know how to manage for aphanomyces, since the way one manages the two diseases is very similar.

No matter which disease is present, aboveground, root rot symptoms look similar. The reality is that it’s unlikely you have just one pathogen when aphanomyces is present. If only aphanomyces is present, the roots will have a caramel colour.

“But chances are you have both aphanomyces and fusarium,” said Derksen, who recommends having soil tested for the presence of pathogens. If aphanomyces is present, avoid planting peas in those fields and limit soil movement. As far as rotation goes, wait six to eight years before adding peas back to the rotation.

Currently there is just one active ingredient available that targets causal agents, and that’s ethaboxam. Researchers are looking for other solutions.

While peas struggle in wet years, Derksen thinks they are a good fit for Manitoba growers.

“Peas do not do well in wet years, which is why they kind of fell off the radar for a while in Manitoba,” said Derksen. “In dry years, they definitely thrive.”

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Fungicide resistance shares some fundamentals with herbicides, says Jared Veness, field marketing manager at Bayer Crop Science. By applying fungicide, farmers are applying selection pressure to a pest. Within that pest’s population, there are likely individuals with mutations that allow them to survive the fungicide.

The survivors will pass on those mutations to their progeny. It’s a process common to any type of resistance, Veness says.

Resistance risk is a combination of agronomic practices, pathogen biology, and the chemical group. Veness says most western Canadian diseases are low risk.

However, septoria and ascochyta are considered medium risk by the Fungicide Resistance Action Committee (FRAC), a group of industry and academics that reviews resistance risk globally. Botrytis (grey mould/blossom blight) and powdery mildew are considered high risk, Veness says.

As for fungicides, Group 11 (strobilurins) has the highest risk of being overcome by resistance, Veness says. A single gene can confer 100 per cent resistance to strobilurins. Farmers can get good control in one application, and no control the next.

“And that has been shown through a lot of pathogens, globally,” says Veness.

Chickpeas provide an example of strobilurin resistance close to home. As chickpea acres ramped up in the early 2000s, resistant cultivars weren’t on the market. And farmers needed to control ascochyta.

“You combine your highest-risk fungicide with a medium- to high-risk pathogen, and you’re spraying it four or five times a year — that’s how you get a problem,” says Veness.

Still, not every pathogen is at risk of evolving resistance to strobilurins. For example, the mutation that confers strobilurin resistance to rust is lethal to the pathogen, Veness says.

Group 7 (SDHIs) are medium to high risk, and Group 3 (triazoles) are medium risk. Multiple genes are needed to confer resistance to a triazole, Veness says, so farmers would see an erosion of control over time.

Multiple mutations often come with a fitness penalty, Veness adds. That means that once the fungicide applications stop, the resistant pathogens won’t be able to compete with their non-resistant cousins.

But resistance can persist in other populations. Agriculture and Agri-Food Canada researchers have found that strobilurin-resistant ascochyta don’t incur a fitness penalty. Veness doubts that strobilurins would effectively control ascochyta to this day in areas with past problems.

Graham Collier, technical services manager for Nufarm, says seed treatment resistance is a bit easier to wrap one’s head around. He compares it to variety resistance to diseases such as clubroot. A clubroot-resistant canola variety can drop the infection level in a field drastically.

But if a farmer reseeds that variety to the same field every two years for six or so years, he would select for clubroot races that weren’t deterred by the resistance gene.

“So they went from being a very small percentage of the population in the soil to the only ones that were successfully reproducing,” says Collier.

Collier says the same type of thing happens with Metalaxyl seed treatments controlling pythium. Pythium includes several pathogen species. Metalaxyl controls some pythium species very well. But it doesn’t control all of them well, and the seed treatment selects for those insensitive species.

“And then if you have a year where that species is favoured, you have a whole ton of pythium infections, despite the fact that you treated,” says Collier.

“We don’t have any documented resistance in Western Canada yet, but it’s kind of one of those things that’s a safe assumption because we’ve used so much for so long.”

Some disagreement over resistance management

There is a fair bit of debate around resistance management in fungicides, says Collier.

Collier sees similarities between managing foliar fungicide and herbicide resistance. He suggests rotating modes of action when possible. Collier also suggests using products with multiple modes of action. As in herbicides, it’s important to make sure both active ingredients target the pest, although Collier says this is generally the case with fungicides.

But Collier acknowledges that it’s not easy to rotate modes of action, given the limited number of chemical groups in Western Canada. And Veness doesn’t see rotating chemical groups as necessary in most western Canadian farming situations.

Veness points out that not all pathogens overwinter. And those that do will need a host the following year to cause problems in that crop. For example, he says, a farmer who’s growing canola on wheat stubble doesn’t need to worry about using a Group 3 fungicide, even if she applied a Group 3 the previous year. The sclerotinia she is targeting in canola doesn’t infect wheat.

“So you’re not placing selection pressure on that pathogen multiple years in a row,” says Veness.

Collier acknowledges Veness’ point about a pathogen’s need for a host. However, he points out, resting spores can linger on stubble or in the soil.

Collier says academic research is finding that using a fungicide that is less effective puts less selection pressure on the disease population. The fungicide brings the disease under threshold level. “But you don’t go for 99 per cent control because that will erase your fungicide mode of action so quickly.”

That may seem counterintuitive. But disease populations are much higher than weeds, Collier says. “So if you’re controlling 95 per cent, that five per cent that’s left over is still millions of individuals.”

But although Collier is leaning towards this approach himself, he’s quick to point out the concept isn’t agreed upon. FRAC focuses more on the idea of using a high rate, to maximize control, and rotating chemical groups or using multiple modes of action. And there is research to support both concepts, he says.

What farmers can do

Veness says Western Canada is “in good shape relative to other areas” around the world for fungicide resistance. That’s partly due to the short growing window, which suppresses inoculum levels.

Still, both Veness and Collier agree farmers can take practical steps to cut their fungicide resistance risk.

Understand the pathogen you’re targeting and what the relative resistance risk is, says Veness. And don’t spray products with the same mode of action several times in one year.

Application timing also plays into resistance risk. It’s always better to apply fungicides sooner than later, Veness says. “And that’s because if you can apply early, there are fewer spores.”

Spraying when there are fewer spores protects the plant and yield. It also decreases the chances of resistance developing, Veness explains.

Cultural practices are important as well. Rotate crops, says Collier, to reduce inoculum. Less inoculum means a smaller disease population to deal with in future years. Tillage can also help, says Veness.

“Good rotations and good cultural practices will help prolong a fungicide for sure,” says Collier.

Both Collier and Vanier recommend using resistant cultivars. Resistant cultivars don’t guarantee that a farmer won’t have to apply fungicide. But resistant cultivars reduce the inoculum levels. That reduces the likelihood of resistance development.

“Likewise the selection pressure on the resistance genes can be reduced with a fungicide application — a layering of controls type approach,” says Collier.

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“Without a doubt there were some good quality lentils produced in 2016, but the percentage of high quality lentils produced would be much lower than what we typically see in Western Canada,” says Trevor Glas, marketing development specialist with Bayer CropScience.

High disease pressure took its toll on lentil quality as well. “White and grey mould were the major culprits this year,” says Glas.

Mother Nature holds all the cards when it comes to weather. But farmers have a few tricks up their sleeves to help them manage disease.

Know your diseases

Glas says there are four major lentil diseases to watch for; ascochyta blight, anthracnose, sclerotinia (white mould), and botrytis (grey mould).

Ascochyta blight can be seed- or residue-borne. Lesions are tan or grey with dark borders, and may have little black spots (fruiting bodies) in the middle, according to the Saskatchewan Pulse Growers.

Lentils infected with anthracnose will have grey to cream coloured lesions on stems and leaves. Lower leaflets will yellow or brown before dropping, and lower stems will canker, killing the plant.

Botrytis (grey mould) shows up as fuzzy grey growth. On young plants, it appears near the soil surface, according to Alberta Pulse Growers. Botrytis grows on pods, flowers, or lower stems on older plants, Alberta Pulse notes.

Lentils with white mould on stems, leaves, pods, and flowers are infected with sclerotinia (white mould). Alberta Pulse notes that the first signs are “light-brown, water-soaked discolourations” on stems, leaves, or pods. A cottony thread will show up around the collar if humidity and temperatures stay high, Alberta Pulse says.

Both botrytis and sclerotinia are late-season diseases. Farmers dealing with grey mould should use dust masks during harvest, as spores can cause breathing problems, according to Sask Pulse.

Forecasting disease

“It’s all about preventative disease management. In lentils, you cannot wait for disease to show up,” says Glas.

Predicting disease presence is difficult, says Glas. He suggests farmers take a look at their crop when deciding whether to spray. A crop with good or extremely high yield potential is worth protecting, he says.

Cropping history also plays a role.

“Looking at your rotation or your neighbour’s crop rotation can help predict the presence of diseases like sclerotinia, for example,” says Glas. Sclerotinia also hits canola, peas, and sunflowers.

“So if canola’s in your rotation, there’s a very good chance–especially if you’re in a tight rotation — that sclerotinia could be a problem in your lentils,” says Glas. Sask Pulse also recommends a four-year crop rotation to manage anthracnose. And ascochyta blight overwinters on lentil stubble, so Sask Pulse advises farmers to avoid growing lentils on lentil stubble.

Sask Pulse notes that while botrytis inoculum lurks in the soil of every field, it generally only rears its mouldy head when heavy stands lodge during wet, cool summers.

Farmers also need to consider genetic resistance within the variety, stand density, moisture conditions in the soil and crop canopy, and rain forecast, says Glas.

Application tips

“A single application in lentils is extremely common in the majority of the lentil-growing area,” says Glas. In higher input lentil growing areas, it’s common to apply fungicides twice, he adds.

Usually agronomists recommend applying fungicide at flowering, for the first pass. “But this year, the… vegetative growth was so dense in the lentils that the rows were closing prior to flowering.”

That’s why it’s important to look at row closure as well when timing the first pass, Glas says. Because of the moisture and growing conditions in June, many lentil growers applied fungicide earlier than if they’d looked at flowering alone.

Farmers trying to prevent late-season diseases such as sclerotinia or botrytis will spray again 10 to 14 days later, Glas says.

Sclerotinia and botrytis are challenging diseases to manage, partly because farmers need to apply fungicides before the disease shows up.

“If you wait for the disease to show up, it’s too late and the damage is going to be done. You’ll get some control but it’s not going to be satisfactory,” says Glas. Farmers who applied fungicide before row closure, and did a second pass later, saw better yields and quality, says Glas.

But getting the second pass right is tricky with botrytis and sclerotinia. “When you make that second application you’re really trying to drive the fungicide down into the canopy,” says Glas. That can be difficult, he says, especially in a year like 2016 when the canopies are very dense.

To improve coverage, Glas suggests making sure boom height is set to 18 to 20 inches above the target. Higher water volumes also help. Glas says 10 gallons of water is the minimum with a ground application. But growers will apply up to 15 gallons of water to push more spray solution down into the canopy. Slowing down also helps.

Farmers should also double check the labels for rates, and to make sure the product is registered for the diseases they’re planning to hit. Glas says Bayer’s product, Delaro, does provide protection for all the major lentil diseases, but not all fungicides do.

Environmental conditions are important, too. Avoid windy days, Glas says. And he doesn’t recommend spraying in extreme heat — 30 C or higher. Glas adds that the closer the mercury gets to 30 C, the more water is needed.

For more information on lentil disease, visit saskpulse.com or pulse.ab.ca.

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Some farmers are opting for less susceptible pulses, including fababeans in moist areas.

Of course, fababeans could be vulnerable to disease as well. Here are the foliar diseases fababean growers should watch for, along with management strategies.

Diseases to watch

Chocolate spot is known as botrytis grey mould in other crops. But, Dr. Sabine Banniza, plant pathologist with the Crop Development Centre at the University of Saskatchewan, said, “fababean has its own special species.”

The disease can be “very devastating” if conditions are wet, said Banniza, and develop very quickly. Fababean growers will initially see tiny reddish lesions, said Banniza. Those lesions grow, coalesce, and eventually turn the entire leaf blackish-brown. Sask Pulse notes the disease can be residue- or seed-borne. Chocolate spot can cause defoliation and even lodging if stems are affected.

• Read more: How crop diseases become resistant to fungicides

Fababeans can suffer from other leaf diseases as well. Rust can be a very destructive disease in other countries, Sask Pulse notes. But, in Western Canada, leaf rust is “probably a bit rare,” Banniza said. It’s easily identified by the orange-brown pustules on the upper and lower leaf surfaces.

Alternaria leaf spot is more common than rust in fababeans, Banniza said. It’s often a secondary infection, following ascochyta blight.

If the weather is really wet, sclerotinia white mould is a risk in fababeans, said Banniza. Farmers will see cottony white mycelium on the plant’s surface.

Fababeans are susceptible to the same pathogen that causes anthracnose in lentils and field peas. Sclerotinia can also infect fababeans, but so far it is less common in fababeans than it is in other crops.

Ascochyta blight is a seed-borne disease or residue-borne disease in western Canadian fababeans, according to Sask Pulse. It is a different species from ascochyta pathogens that infect other pulses.

In fababeans, ascochyta lesions are tan or grey, with dark margins. Often tiny black fruiting bodies are in the centre. The disease is most severe when it infects the pod, which can happen if fields see wet weather in July or August, according to Sask Pulse.

Diseases such as ascochyta can be mixed up with herbicide damage, Banniza said. Reviewing recent weather helps diagnose the problem. Farmers can also send tissue samples to labs, said Banniza.

Managing disease

Crop rotation is the first line of defence in disease management. Banniza explained farmers can manage residue, which harbours disease, by rotating crops.

Farmers dealing with chocolate spot should leave four years between fababean crops, according to Sask Pulse. The same pathogen also infects lentils, so farmers shouldn’t grow fababeans after lentils. Sask Pulse also suggests skipping buckwheat if chocolate spot is a problem.

Fababean growers should also make sure they don’t plant fababeans adjacent to last year’s fababean, pea, or lentil fields, Sask Pulse notes. Planting them in close proximity to those pulses increases the risk of anthracnose infection.

Using disease-free seed is also a good practice. Sask Pulse recommends having seed tested for seed-borne diseases such as anthracnose, ascochyta, botrytis, sclerotinia, and fusarium. Farmers should consider seed treatments if disease is detected, if there’s a history of soil-borne diseases, or if they’re seeding into cool, moist soil.

Fungicide application is “an important tool,” said Banniza. The recommendation is to apply fungicide at flowering if disease symptoms are present in the lower canopy and conditions favour disease.

Fababeans produce clusters of flowers, and the number of flowers in each cluster increase after the fourth node, said Banniza, and then decline later. The middle part of the plant holds the most yield potential, so that’s what farmers should protect, she added.

Depending on weather conditions, fababeans might require a second fungicide application to control leaf disease, Banniza added.

By the time sclerotinia disease symptoms are visible, it’s too late to treat, Sask Pulse notes. If sclerotinia is likely to develop, Sask Pulse suggests spraying at 20 to 50 per cent flowering. Sask Pulse recommends spraying no more than twice per season. †

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Almost all pulse leaf diseases are triggered by rain and moisture in the canopy, said Dr. Sabine Banniza, plant pathologist with the Crop Development Centre. “Many need the rain in order to spread.”

So which diseases should farmers be guarding against in their lentils? Banniza outlined the top leaf diseases she sees in Saskatchewan during a Saskatchewan Pulse Growers webinar.

Anthracnose

“The number one lentil disease we have in the province these days is anthracnose,” said Banniza.

Anthracnose causes beige or brown lesions. Those lesions are not very conspicuous, Banniza said, and so farmers and agronomists would have to look closely to see them. Once the disease is established, farmers will likely see leaf drop.

Those stem lesions can also girdle the stem, killing the plant above the girdle, she said. “And when this happens, you all of a sudden start seeing these dead patches in your lentil crop.”

There is anthracnose resistance in lentils, but that resistance covers Race One, the less aggressive strain. Race Zero is more aggressive and more common, and there is currently no resistance to it in cultivated lentil varieties.

Ascochyta blight

Ascochyta blight used to be the top lentil disease in Saskatchewan. But the last serious outbreak was in 2005, said Banniza. That drop is a success story of lentil breeding program, she said.

“We’ve bred quite good resistance into almost all the lentil cultivars that are available now,” said Banniza. As a result, the ascochyta blight population “has just imploded and hasn’t really been able to come back.”

Stemphylium blight

Stemphylium blight starts out as light beige lesions that coalesce. The whole leaf eventually turns brown. Farmers will also see leaf drop.

Spores are airborne, making it difficult to do field research on the pathogen, Banniza said. But the research they’ve done indicates that early to mid-flower infections may cause yield loss, seed stain, and seed infection.

However, stemphylium blight often rolls in late in the season. Those late infections probably don’t cause much damage, Banniza said. “And if it’s really late, it may actually work like a natural desiccant because it defoliates the leaves.”

White and grey mould

Sclerotinia white mould and botrytis grey mould are two different organisms. But they are “like sister and brother,” said Banniza. “They often show up together because they both thrive in the same conditions.”

These diseases are very recognizable because they grow on the outside of the plants, said Banniza. Cottony white mould on stems, leaves, flowers, and pods is sclerotinia, while fuzzy grey growth indicates botrytis.

Both diseases show up late in the season when canopies are dense and moist. Tall, lush lentil crops are more likely to suffer an infection. Lentils tend to lodge in those conditions, creating an even denser mat of biomass that doesn’t dry.

“And that’s when these two diseases really get going,” said Banniza.

Managing leaf diseases

Banniza recommends a four-year rotation to control leaf disease. Tightening the rotation raises the risk of building disease inoculum in the fields.

“And if you run into a year when conditions are conducive, you’ll see an earlier outbreak and a much more severe outbreak which is more difficult to control,” said Banniza.

However, that longer rotation is unlikely to reduce stemphylium blight because the spores are airborne, she added.

Farmers should also choose resistant cultivars when they can, she said.

Scouting is very important, said Banniza. The eight- to 10-node stage is the best time to apply fungicide, so scouting needs to be done before then.

Banniza said the management strategy is the same for several of the leaf diseases.

“So if you see lesions early on in your crop, and conditions are conducive to infection, it doesn’t matter whether it’s an anthracnose lesion or an ascochyta blight lesion or a stemphylium blight lesion.”

However, it’s a “different story” for sclerotinia white mould and botrytis grey mould, she said. Because those diseases develop in thick lentil stands, usually after canopy closure, fungicides don’t penetrate the canopy.

If a farmer is lucky, the fungicide will reach the top third of the canopy in those cases, Banniza said, but the disease is usually at the bottom. “So for these two diseases unfortunately fungicide is not a very good option.”

In fact, there are no great control options for sclerotinia white and botrytis grey moulds, she said.

“The best option is to manage your canopy. But that’s obviously very tricky because when you seed it, you don’t know what the growing season will look like,” said Banniza.

“If you knew it was going to be a wet year, you would probably try to seed at a slightly lower rate just to make sure the canopy is a little bit more open.”

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That’s certainly been the case in Saskatchewan, where farmers in most regions are actively scouting for, or in some cases spraying for, crop diseases, according to the provincial crop report.

So which leaf diseases should pulse growers watch for? And what are the management options? Dr. Sabine Banniza, plant pathologist with the University of Saskatchewan, reviewed the major pulse diseases in a recent Saskatchewan Pulse Growers webinar.

Anthracnose — Anthracnose is the number one disease for lentil growers in Saskatchewan these days, Banniza said. Lentil growers should look closely for brown or beige lesions. Once the disease is more established, farmers are likely to see leaf drop. Lesions can eventually girdle the plant, killing it, she added.

Resistant lentil varieties are available; however, she said, they are only resistant to race one. Race zero, the more aggressive and common anthracnose strain, can overcome those resistant varieties. Lentil breeders hope to have race zero resistance “in a short period of time,” she said.

Ascochyta blight — “Of all the pulse crops, I would say ascochyta blight in chickpeas is the most aggressive. It spreads very, very fast and you really have to be on top of managing that disease,” said Banniza.

The disease can also infect faba beans and lentils. Mycosphaerella blight, an ascochyta disease, hits peas, too. Although each crop species is susceptible to a different ascochyta species, they look similar, said Banniza. Farmers should watch for lesions with a darker border and spots in the centre.

In faba beans and chickpeas, the disease can look similar to herbicide damage, so farmers should think about field history and recent weather when trying to diagnose the problem.

Stemphylium blight — In lentils, stemphylium blight starts out as light beige lesions. Those lesions eventually merge, turning the entire leaf brown. Leaf drop also occurs.

Conducting field research on this disease is difficult because spores are airborne. But Banniza said their research shows early to mid-flower infections may cause yield loss, seed stain, and seed infection in lentils.

Often stemphylium blight shows up late in the season. Late infections probably don’t do much damage, Banniza said. In fact, very late infections may work as a natural desiccant, defoliating lentil leaves, she added.

Sclerotinia and botrytis — Sclerotinia white mould and botrytis grey mould are relatively easy to diagnose. As their names suggest, they cause a “cottony white” or “fuzzy grey” mould on the plants stems, leaves, flowers, and pods, Banniza said.

Very wet conditions favour these moulds. Lentil growers with very thick, lush stands are more likely to see these diseases late in the season, especially if the crop lodges. Faba beans and chickpeas can also be infected by sclerotinia white mould.

Chocolate spot — Faba beans are susceptible to a specific species of botrytis grey mould, known as chocolate spot in this crop. Banniza said the disease can be “very devastating” if conditions are wet.

Chocolate spot can develop very quickly, causing defoliation and even lodging. Initial symptoms are tiny reddish lesions. Those lesions enlarge, coalesce, and turn the entire leaf brownish-black.

Banniza cautioned the disease can be confused with herbicide damage. Farmers need to think about weather patterns when diagnosing the problem, as it’s a rain-driven disease. They can also send tissue samples to a lab, she added.

Tips for managing disease

A four-year rotation is an effective way to reduce most of the leaf diseases, as it reduces the inoculum in the fields, Banniza said. However, airborne diseases such as stemphylium blight can’t be managed through rotation, she added.

Scouting is also crucial. Foliar diseases tend to start at the bottom of the plant, Banniza said, so it’s not good enough to glance across the field. Banniza also recommended paying more attention to high-risk fields — for example, wet fields, as well as fields with dense canopies or lodging crops.

Because ascochyta blight is so aggressive in chickpeas, Banniza recommended a preventive fungicide application very early in the season. Whether or not chickpea growers will need to spray again will depend on weather and disease symptoms. Banniza suggested reviewing the SaskPulse fungicide application checklist.

Lentil growers can manage many of the leaf diseases the same way, Banniza said.

“If you see lesions early on in your (lentil) crop, and conditions are conducive to infection, it doesn’t matter whether it’s an anthracnose lesion or an ascochyta blight lesion or a stemphylium blight lesion. You will follow the same disease management categories.”

Lentil growers should be scouting early, and if a fungicide application is warranted, spraying at the eight- to 10-node stage, she said. Sask Pulse has a fungicide application checklist available online.

If lentil growers see more wet weather, they should consider a second fungicide application in three weeks, says Banniza. The application efficacy from the first application will decline in two or three weeks. New growth will also be unprotected, she says.

Fungicide efficacy for mycosphaerella blight in peas is variable, according to several field trials done by various research groups, Banniza said. “You can’t predict, it appears, whether a fungicide application really translates into a yield gain.”

For pea growers facing a mycosphaerella blight infection, spraying may be more of an economic decision, she said.

Banniza doesn’t recommend fungicide applications for sclerotinia white and botrytis grey mould in lentils, either. Because the diseases infect thick lentil stands late in the season, the fungicide is unlikely to penetrate enough of the crop canopy to make a difference, she explained.

“The best option is to manage your (lentil) canopy. But that’s obviously very tricky because when you seed it, you don’t know what the growing season will look like,” said Banniza.

As for faba beans, fungicide application is “an important tool,” Banniza said. If farmers see disease symptoms during flowering in the lower canopy and weather conditions favour disease, application is warranted, she says. The most yield potential is in the middle of the faba bean plant, so farmers should try to protect that area, she said.

A free version of the Crop Protection Book is available through Alberta Agriculture’s website.

— Lisa Guenther is a field editor for Grainews and Country Guide at Livelong, Sask. Follow her at @LtoG on Twitter.

CORRECTION, Aug. 2 2016: A previous version of this article incorrectly stated ascochyta blight looks similar to herbicide damage in chickpeas as well as faba beans.

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This is the advice Bobbie Bratrud, who farms near Weyburn, Sask., offers to first-time lentil growers.

“Because they’re so valuable this year my advice would be to spray on time, and don’t wait to look for the disease. If you’re starting to see signs of the disease you’ve lost yield potential already,” she says.

This year, the Bratruds seeded 2,000 acres of CDC Dazil CL red lentils, alongside canola, wheat, barley and soybeans. Over the last couple of years, they’ve had issues with ascochyta blight and anthracnose in their area, depending on the weather.

“Our approach for fungicide in lentils is that we generally plan on spraying. We try to do this at the first flower just before the rows close up,” she says. The Bratruds use Priaxor, and effectiveness lasts about seven to 14 days.

According to Dale Risula, the provincial specialist in special crops for Saskatchewan, the three most typical diseases of lentil are ascochyta blight, anthracnose and stemphylium blight. Lesser diseases include sclerotinia and botrytis.

All five diseases are dependent on moisture and can be controlled with timely fungicide applications. So far, Saskatchewan hasn’t seen much rain, but regardless, farmers have to plan for the worst-case scenario. “You want to be prepared for any potential problems that might come up. It’s not an easy decision to make with regard to controlling disease,” says Risula.

But overuse of fungicides means the risk of creating resistance. “You don’t want to use anything and risk creating insensitivity among disease organisms, but you want to protect your plants at the same time. It’s a matter of field scouting, knowing your history, and choosing the right products,” he says.

Clean seed

Risula says disease management starts with buying clean seed, but this might not have been an option for some growers this year as demand has skyrocketed.

“Some seed treatments can affect spores on the seed if you can’t obtain clean seed,” he says. “In some years this is an issue, when the demand is high, and lentil demand this year is super high with a lot of acres going in.”

He says disease pressure is more likely to be a problem on fields that have been seeded to lentil for multiple years running, and treated with the same modes of action. “If they’re overused, you’re creating more and more multiplications of the disease, and there are so many possible outcomes of disease that can come from each generation because they morph so rapidly and can change and become more aggressive,” says Risula.

He echoes Bratrud in recommending spraying at early flowering, on average the third week of June. However, he cautions growers that spraying without signs of disease can be costly and unnecessary.

“If you’re scouting and there’s an absence of any signs of disease and you’re watching the weather forecast, if it’s wet and rainy and the forecast is calling for more rain, the probability is that you’ll have disease. If the forecast is dry, you’re wasting dollars on fungicide,” he says.

If growers are using resistant cultivars and spot just a few lesions, and the weather is shaping up to be wet, “you’re not taking that big of a risk by not applying fungicide,” Risula says.

As far as fungicide application goes, Risula recommends spraying using adequate water volumes, depending on the crop stand and thickness of the canopy. “If it’s really dense and a heavy canopy, apply using a higher water volume to ensure you penetrate the canopy and get better coverage,” he says.

“Chances are you won’t have that heavy of a canopy, but even so having adequate water volume will ensure better coverage.” †

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