Group 14 herbicide-resistant kochia was confirmed in 2021 from a Saskatchewan sample submitted to Agriculture and Agri-Food Canada’s Prairie Resistance Research Lab at Lethbridge, Alta. If Group 14 resistance becomes common on the Prairies, the foundation of herbicide-resistant kochia control will crumble. As much as integrated weed management (IWM) is an often-used term and, perhaps seldom utilized, IWM is crucial to combatting this problem.
by Kaitlin Berger
This year has been designated the International Year of the Woman Farmer (IYWF 2026) by the United Nations. The goal for this designation is to highlight the essential roles women play across the agriculture and agri-food system throughout the world.
Because the next Census of Agriculture won’t begin until this May, we’re still looking back at data from the 2021 Census of Agriculture for insight on female farm operators in Canada. In 2021, that number increased by 2.3 per cent from 77,970 in 2016 to 79,795 in 2021.
While the 2021 Census of Agriculture determined that overall farm operator numbers have declined 32.9 per cent over the past 30 years, an article by Farm Credit Canada (FCC) - Breaking barriers: Women in Canadian agriculture - showed the percentage of Canadian female farm operators increased 25.7 per cent to 30.4 per cent over the same time period. The article predicts this upward trend will continue to 31.1 per cent by 2026. While there’s a lot of good news surrounding women in Canadian agriculture, women were still noting some barriers they faced in a survey interview by FCC in 2024. The FCC report also notes some key strategies to reduce these barriers, including enhancing mentorship and networking opportunities, improving access to resources, ensuring women have equal opportunity to leadership roles and increasing their visibility in the sector.
With this being the IYWF 2026, I was reflecting – specifically – on this last strategy.
One practical way Top Crop Manager, together with some of the other agriculture brands here at Annex Business Media, has been doing this is through the Influential Women in Canadian Agriculture (IWCA) program. Since 2020, this program has recognized Canadian women in all sectors of agriculture – from research to animal health and drainage. The IWCA year kick-off is a call for nominations of women who have made an impact within the agriculture sector in this country. Once the honourees of the IWCA award are chosen, we have the opportunity to highlight the stories and important work of these incredible people.
This year, we have some exciting changes coming for the IWCA program – and nominations are currently being accepted. Don’t hesitate to send your nominations – and highlight the women you see making a major impact in the industry. Visit agwomen.ca to make a nomination.
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“H-E-double hockey sticks, this stuff works great.”
The speed and performance of new Intruvix® II herbicide is so darn good, folks can hardly contain their excitement. By applying it with glyphosate before planting cereals, they’re saying goodbye and good riddance to narrow-leaved hawk’s-beard, volunteer canola, kochia and many other problem weeds. Enjoy cleaner fields, faster, while protecting your future glyphosate use. Cheese and crackers, how easy can you get?
Clean is good
Herbicide-resistant systems influence weed populations in canola.
BY JOEY SABLJIC
Since the 1970s, canola acreages have tripled to more than 21 million acres, fuelled in large part by major advancements in agronomy, herbicide-resistance technology and crop management practices.
At the same time, the ‘communities’ of weed species in Prairie fields have also been changing and adapting with the times. The question is how much the adoption of different herbicide-resistant canola genetics and other practices – like tighter rotations and no-till systems – has impacted weed populations over the decades.
A research team from the University of Saskatchewan (USask), University of Manitoba (U of M) and Agriculture and Agri-Food Canada (AAFC) may have a definitive answer.
Dilshan Benaragama, assistant professor at the U of M’s Department of Plant Science, has been working with the study’s principal investigator, Christian Willenborg, and Theodore Chatskoa – from the University of Saskatchewan, as well as Julia Leeson from AAFC.
Together, the researchers have analyzed 44 years of Saskatchewan Prairie Weed Survey data taken from canola fields between 1970 and 2014. To get the most accurate picture of shifting weed populations, they tracked species frequency – or the number of fields where specific weed species can be found, and species richness – the number of different weed species appearing in a field.
“Our hope was that, by performing a statistical analysis of all this available survey information, we could start to identify some more concrete trends, rather than something that may have been driven by the climatic conditions in any one season,” says Benaragama.
Within that 44-year span of weed survey data, Benaragama identifies two significant turning points, which have had an impact on species frequency and richness. The first took place in the early 1990s, when no-tillage systems became more widely adopted. The second turning point came when herbicide-resistant cropping systems, namely Roundup Ready canola, were first
ABOVE
Researchers explore how adoption of different herbicide-resistant canola genetics has impacted weed populations over the decades.
made commercially available in 1995.
What Benaragama and his fellow researchers eventually found was that several of the most historically important annual broadleaf weeds saw a considerable decline after herbicide-resistant canola came onto the scene. Species including wild mustard, stinkweed, lamb’s-quarters, flixweed and redroot pigweed all had lower average frequencies after 1995 compared to the previous 25 years from 1970 to 1995.
“What this tells us is that growers had access to more effective in-crop broad-spectrum herbicides in glyphosate and glufosinate,” says Benaragama. “The no-till
systems may have also had a positive effect as well.”
Some species, however, actually increased after 1995, including perennials and winter annuals like dandelion, shepherd’s-purse, narrow-leaved hawks-beard and volunteer canola. “These types of weeds are capable of emerging outside of the main in-crop spraying window and do well in cropping systems with minimal soil disturbance and where the same herbicide modes of action are frequently used,” says Benaragama.
Two species that showed a continuous, long-term increase, even after the introduction of herbicide-resistant canola in 1995, were cleavers and volunteer wheat. “The fact that we have wheat and canola often going together in crop rotations could be a big reason,” says Benaragama. “Plus, cleavers are a highly adaptable and biologically diverse species that allow it to be more persistent and adapt to many different cropping systems.”
THE BIGGER PICTURE OF CHANGING WEED POPULATIONS
In looking at the overall impact on weed populations, the survey data shows that herbicide-resistant canola helped reduce the abundance of broadleaf weeds but didn’t cut down on weed diversity. “Instead, what we’re seeing is that weed communities have shifted more towards species that can escape and survive in different herbicide-resistant and no-till systems,” says Benaragama. Species richness – or the number of different weed species in a field – did not show a steady decline year over year. In fact, the average number of species per field declined from the 1970s until about 2003. Then in 2012, the number of species spiked, likely due to it being an especially wet year. By 2014, the number of species dropped again. “This shows us that these patterns
are much more closely tied to climate events, like drought or wet years, than herbicide-resistant canola,” says Benaragama.
Another arm of the project involved conducting a field-scale study between 2008 and 2012 that looked more closely at the impact of different crop rotations and herbicide-resistance systems on weed populations.
The researchers used canola crop rotation experiments in Lethbridge and Lacombe, Alta. conducted by Neil Harker at AAFC with LibertyLink, Roundup Ready canola and conventional (non-herbicide-resistant) canola in continuous, one-intwo, one-in-three and one-in-four rotations. “At that scale, we found that the rotation frequency and herbicide-resistance traits both play a major role when it comes to management and weed communities,” says Benaragama.
Continuous canola rotations using each of the herbicide-resistant systems all saw increases in chickweed and other winter annuals. But at the same time, wild oat, green foxtail and volunteer wheat were less of an issue.
Conventional and non-glyphosate systems with longer one-inthree or one-in-four rotations saw larger wild oat and green foxtail populations – showing the impact of less effective grass control when glyphosate was not used in-crop.
Roundup Ready systems also tended to suppress wild oats more effectively than LibertyLink systems but were still vulnerable to shifts in other weeds like chickweed, cleavers and volunteer canola.
Finally, the researchers found that volunteer wheat became more frequent in rotations where wheat was seeded in between canola crops
ABOVE Dilshan Benaragama and other researchers analyzed 44 years of Saskatchewan Prairie Weed Survey data.
under no-till conditions. Cleavers, meanwhile, increased across all herbicide-resistant systems and rotations, which pointed to their broad adaptability.
Both the 44-year weed survey study, as well as the farm-scale study, paint an interesting picture of weed populations over time, as well as where they could be headed in future seasons. The biggest management issue by far, according to Benaragama, is the emergence of an increasingly dominant, smaller set of harder-to-control species that are well adapted to no-till, herbicide-resistant systems and tighter canola rotations every one to two years.
That’s not to say herbicide-resistant systems haven’t played an important role for canola growers.
“While herbicide-resistant canola systems have helped to reduce weeds and simplify management for growers, they could also be selecting for a new, more challenging weed spectrum,” cautions Benaragama. “This demands integrated, rotation-based strategies, rather than looking to glyphosate or glufosinate-tolerant genetics alone.”
BY BRUCE BARKER
If you’re drawing water from a dugout, or a well with hard water, herbicide performance can be affected.
“It is crucial when we use pesticides to get maximum efficacy from each product used. Hard water can reduce herbicide performance. Anything that contributes to herbicides being less effective has long term implications for weed control,” says Kim Brown, provincial weed specialist with Manitoba Agriculture at Carman, Man. “When herbicides are not working as well as they are capable of, we see weedier fields, which increases the amount of weed seeds returning to the soil, and leads to more weed growth in the future. This is especially important when dealing with ever-increasing herbicide-resistant weeds.”
Dugout and well water are commonly used for spray water in Western Canada. They are cheap and often more convenient than hauling treated water. “Using dugout and well water can be a time- and cost-effective practice if done properly, but there are many factors to consider, including water hardness, pH, turbidity, alkalinity, salinity, and the herbicide product being used,” says Tyce Masich, crop extension specialist with the Saskatchewan Ministry of Agriculture at Moose Jaw, Sask. “I always recommended to annually test non-treated water sources used for spraying.”
‘Hard water’ mostly refers to the concentrations of
Dugout water is cheap to use for spray water, but it brings some challenges.
calcium and magnesium, although other cations (ions with a positive charge) - like sodium, potassium, aluminum and iron – contribute to hard water, says Brown. Total dissolved solids (TDS) or electrical conductivity (EC) is the first measure of water quality, and hard water is usually directly proportional to TDS or EC measurements. TDS is now mostly estimated by measuring the EC of water.
Masich says water hardness results are typically shown as the amount of calcium and magnesium, and is reported as calcium carbonate (CaCO3) equivalent in parts per million (ppm). He says water hardness under 300 ppm CaCO3 is safe for most herbicides. Anything over 1,000 ppm should be avoided.
The positively charged cations, specifically calcium and magnesium, can bind to negatively charged weak acid pesticides and reduce efficacy. These chemicals include glyphosate, 2,4-D amine, ‘dims’ herbicides (Group 1: tralkoxydim, sethoxydim, clethodium), bentazon and glufosinate. Generally, glyphosate and 2, 4-D amine solutions are most affected by hard water.
For glyphosate, the hardness level that impacts spray quality depends on the rate of glyphosate being used. For lower rates of glyphosate, 350 ppm CaCO3 equivalent is the maximum allowed water hardness. For higher rates of glyphosate, 700 ppm CaCO 3 is the maximum allowed hardness.
Nitrogen fertilizers like ammonium sulphate (AMS)
or Urea Ammonium Nitrate (UAN) can mitigate hard water, says Brown. AMS is more effective than UAN because AMS also contains sulphate. “It’s important to test your water and know how much AMS is needed to counteract the effects of whatever cations are tying up the herbicide and rendering it less effective,” she says.
Masich adds that AMS is only registered for glyphosate products and not 2,4-D amine. Another consideration when treating spray water is to add the AMS to the water before the herbicide. Specific instructions for mixing orders can be found in the Saskatchewan Provincial Guide to Crop Protection.
Negatively charged anions such as sulphate (SO42-), chloride (Cl-) and bicarbonate (HCO3-) also affect herbicide performance. Generally, bicarbonate levels in water greater than 500 ppm should be treated or avoided, and levels greater than 1,000 ppm are not recommended.
Bicarbonates can affect the dims as well as 2,4-D amine.
“For amine formulations, treating the water with a non-ionic surfactant can improve herbicide efficacy when bicarbonate levels are greater than 500 ppm. For dim herbicides, avoid using water with bicarbonate levels above 500 ppm,” Masich says. “Also, using the highest recommended herbicide rates (according to the product label) can help overcome bicarbonate antagonism. Maximum bicarbonate levels can vary depending on the herbicide and rate.”
There are other water quality factors to consider. Generally, water pH between 6 and 8 is acceptable for spray water, but pH greater than 8 can degrade pesticides. Buffering agents or surfactants can be used to bring down the pH of water. Masich recommends to always consult the
product label for water pH requirements. Turbidity, the presence of soil or organic matter in the water, also impacts herbicide effectiveness. Herbicide active ingredients, such as diquat, paraquat, glyphosate, dicamba and bromoxynil, can bind or be degraded by soil or organic matter. Salinity, with an EC of more than 500 µS/cm, can also be an issue.
“If dugout and well water falls outside recommended quality criteria, the first recommendation is to find a cleaner water source. Treated water is a good option but it can be time consuming and expensive for producers,” says Masich. “Using AMS or other water treatments can be used for certain herbicides to improve water quality, or herbicide rates can be adjusted, but careful consideration needs to be taken when using these strategies. And always look at the product label before use for specific water quality and herbicide rate information.”
Syngenta Canada introduced a nitrogen-fixing biological product called Envita Dry. It gives plants the ability to source additional nitrogen for the entire growing season, when needed – and it boosts yield.
Envita Dry is a convenient product to use, store and transport because it comes in a dry formulation that offers a two-year shelf life and low use rate due to Gluconacetobacter diazotrophicus (Gd) – a naturally occurring food-grade bacteria that enables nitrogen fixation. It has a broad application window, goes easily into suspension – and does not require pre-mixing. Each 200-gram pouch treats 40 acres and each 16 x 200 g case treats 640 ac.
The product is registered for use in potatoes, canola, cereals, corn, pulses, soybeans and forage crops in Canada. It’s recommended as a supplement to a growers’ existing fertilizer program.
“Envita Dry gives plants the ability to source additional nitrogen from the atmosphere and deliver it to the right place and at the right time when the plant needs it,” says Gustavo G Roelants, biologicals marketing lead for Syngenta Canada. “Soil-available nitrogen doesn’t necessarily equal plant-accessible nitrogen, and that’s where Envita Dry can add value by enabling nitrogen fixation to the crop for an additional supply of this essential nutrient. Envita Dry supports the nutrient use efficiency of the crop by fixing nitrogen inside cells throughout the plant’s leaves for a season-long nutrient supply.”
FMC Canada introduced Avireo herbicide, a pre-plant/pre-emergence co-pack that is the first to combine Group 27 (tolpyralate) and Group
14 (carfentrasone-ethyl) actives for managing weeds in Western Canada.
It provides control of annual broadleaf weeds such as Group 2-, 4- and 9-resistant kochia and Group 2- and 4-resistant cleavers and volunteer canola. Applied pre-seed or up to three days after planting, it can be tank mixed with glyphosate and Authority 480 herbicide. It’s best to apply to young, actively growing weeds during warm, moist conditions of 21 C or more. For ease of use, each case treats 80 acres. Re-entry interval is 12 hours.
“Initially registered for spring wheat, durum wheat and barley, Avireo herbicide also provides flexible application timing and a wide range of re-cropping options,” says a press release from FMC Canada.
LEFT Syngenta Canada introduced Envita Dry.
RIGHT This tractor was at the Farm Machine of the Year Awards at Agritechnica and shows a Europeanconfigured tractor.
FMC is continuing field trials for Avireo herbicide label expansion across major Western Canadian crops.
Case IH Optum 440 was introduced at Agritechnica 2025 and recognized as ‘Upper Medium Size Tractor’ category winner in the 2026 Farm Machine of the Year awards. One of three new 360 to 435hp Optum models, Optum 440 leads the group with 435hp featuring a compact, low-weight design that permits flexible operation.
Its compact design is combined with a long wheelbase at 3,190 mm, with a maximum operational weight of 18,000 kg.
LEFT FMC Canada is first to combine Group 27 and Group 14 actives for managing weeds in Western Canada.
Designed for heavy-duty operations, Optum 440 is equipped with a cursor 9 8.7-litre engine and a new CVXDrive transmission system – a technology that saves time allowing for 60 kph top speed and improved braking. The engine has a peak torque of 1,851 Nm at 1,400 rpm.
For ease of use, Optum 440 has optional centralized tire inflation and integrated precision technology with Connectivity Included, telematics, ISOBUS compatibility and Tractor Implement Management (TIM).
“It’s fantastic to see the design of the new Optum 440 recognized with this ‘Upper Medium Size Tractor’ Farm Machine of the Year award,” says Franz Josef Silber, global product marketing medium horsepower tractors at Case IH, in a press release. “This is a design created in direct response to farmers’ feedback on what they want in a high-hp yet light, compact and maneuverable tractor.”
Optum 440 will be available in North America in 2026.
BY KAITLIN BERGER
Editor’s note: Top Crop Manager published an article about this project on herbicide application timing on September 7, 2016 called ‘Dawn, noon or midnight: when to spray herbicides?’ and it continues to be one of the most viewed articles on our website. Given its popularity, we spoke with Ken Coles for an update.
When should you spray a herbicide? Dawn, noon or midnight? With the ever-growing challenge of herbicide resistance across the Prairies, this question continues to be as important as it was when Ken Coles - executive director at Farming Smarter in Lethbridge, Alta. - first conducted a project on herbicide application timing between 2012-2014.
No matter how small, decisions that could impact herbicide efficacy on troublesome weeds are important. “You almost have to do everything right when you start getting into those really troubled fields,” says Coles. “All those little extra things that you can do compound and make a huge difference.”
One of the reasons Coles originally started looking into conducting research on herbicide application timing is because autosteer started to take off and nighttime spraying became a possibility. “Before GPS and guidance, spraying at night was just not possible as the operator could not see the markers and would result in a crazy amount of overlap,” Coles says. “But now, it can be done and expands the already tight spray window.”
Funded by the Alberta Canola Producers Commission and Alberta Barley Commission, Coles led a threeyear small-plot, replicated research project that compared herbicide application timing during early morning (4 a.m. to 5 a.m.), midday (noon to 1 p.m.) and night (midnight to 1 a.m.).
There were two components to the trial – a pre-seed burndown and in-crop herbicide application. The preseed burndown application treatments included
systemic and contact herbicides, as well as multiple different groups, including Group 4, Group 9 and Group 14.
ABOVE The two components to the trial included a pre-seed burndown and in-crop herbicide application.
Technicians applied in-crop herbicides on multiple crops, including peas, wheat, LibertyLink canola and Roundup Ready canola. They also seeded tame mustard and tame oats to simulate both broadleaf and grassy weeds in the plots. They used Group 1 and Group 2 on peas, Group 1, 2, 4, 6 and 27 on wheat and Group 10 on canola.
The most effective spray timing was midday, and spraying at midnight was the second-best option. “Definitely to me the biggest shocking result was how poor early morning ones did overall,” says Coles. Where he lives in southern Alberta, it was assumed that it was best to get up early and spray to beat the wind. “That dawn early morning treatment, really
LEFT The three-year small-plot, replicated research project compared herbicide application timing during early morning, midday and night.
early morning treatment, I think we saw at the time upwards of 30 per cent decreased efficacy,” he adds. There were differences in efficacy based on each crop, too. Wheat does better early in the morning, canola in the middle of the day and peas at night. “If you want to take advantage of the improved efficacy that you can get spraying in the day for canola, and spray your wheat in the morning, then that’s a really easy thing to be able to change your schedule and kind of play to the advantages that you know might happen.”
At the time of the project, Coles was really interested in Delta T – a measurement of the difference between the wet bulb and dry bulb temperature. Similar to when you jump out of a pool and it’s windy and you feel cold, as water changes from liquid to vapour, the process or evaporative cooling sucks heat from the plant and could cause stress. While he originally thought Delta T could be a tool growers could use to measure when to spray, he now thinks it’s situational dependent. “Whenever you try to come up with simple solutions in agriculture, you realize it’s way too complicated to
do that,” he says.
What hasn’t changed since the time of the project is Coles’ understanding that the “little things” can make a big difference when it comes to timing your herbicide application. “When you think about humidity and plant stress, temperature, you really notice right off the bat that there’s what’s called a diurnal effect between humidity and temperature, so as the temperature goes down, the relative humidity goes up and that really changes the conditions that the plants are under.”
It’s worth being attentive to how this impacts the stomata opening and closing, how some plants will point their leaves differently at night. “You’re thinking about all these factors, and it gives you a better perspective on all the things that are going on that might change efficacy.”
While Delta T is not a one-size-fits-all, recognizing when plants are under stress still plays a big role in deciding when to spray. “Herbicides work best when plants are actively growing and if they’re under stress for a long time, they shut down,” says Coles. “So middle of the day when it’s too hot, they shut down; they’re not uptaking herbicide, you’re not getting as good of a kill.” Realize your potential.
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It’s best to avoid spraying a herbicide early in the morning if it’s cold – especially a pre-seed herbicide –because the plant needs time to come out of stress from the night. Likewise, avoid spraying a herbicide during the late afternoon – after 2 or 3 PM and before evening – on a hot summer day because the plant has likely been under stress for too long. “It is a very complicated dynamic, so it’s hard to really share rules of thumb with people, but when they start to understand those differences, they can kind of make better decisions,” says Coles.
It’s still as important as ever to avoid spraying during an inversion - when the air is cooler near the ground and warmer as you get higher. Inversions cause smaller particles or droplets to be suspended in the air and increase the chance of off-site targets. They are more of a risk when spraying at night or early in the morning.
Over the past decade since this project’s completion, several things changed the decision-making process for herbicide applications. There’s greater urgency now, with the growing problem of herbicide resistance and weeds like kochia. “We have to now take the steps to put all of these tools that we have together and herbicide layering and all of this other stuff to steward the products that we have because eventually they’re becoming useless and it’s not a scenario we want to be in,” says Coles.
The good news is that there’s also been progress in the past decade. Technology has improved, specifically nozzle technology. “Nozzle technology’s developed so that they can spray in windier conditions now,” Coles says. Sprayers also have onboard weather stations that allow you to evaluate wind conditions better.
Herbicide providers continue to develop new formulations, raising the question of whether different additives could allow the products to work better in more
Liberty herbicide was applied during early morning, day and night.
conditions. Coles also looked into how water quality could impact spraying and saw some big impacts. “I think there’s still room to fine tune and improve,” says Coles. “We need to do a better job and maybe this is good timing to start talking about time of day, but now let’s layer it with spray additives, water quality and whatever other tool we have because we just don’t have a choice if we want to get these things under control.”
Since 2014, Coles conducted other projects around spray applications. He did a trial across three locations in Alberta on fungicide application timing. The results showed some benefits of spraying in the morning and evening. However, fungicide efficacy is not as dependent on when you spray. “Fungicides are always tough because if you don’t get disease incidence, then you don’t get a lot of results whereas herbicides are guaranteed a result every time.”
While Coles hasn’t investigated insecticide timing, he says they will spray certain crops at night to avoid the pollinators. “That’s sort of an interesting dynamic that hasn’t really been explored,” he adds. He’s also done demos on desiccating – and discovered that time of day certainly plays a role in desiccant effectiveness. The weather following the applications also matters. “There’s definite improvements to spraying in the evening than in the heat of the day because that’s more of a contact herbicide,” he says.
It’s best to avoid spraying a herbicide early in the morning if it’s cold – especially a preseed herbicide – because the plant needs time to come out of stress from the night.
Coles still sees the project on herbicide application timing as one of his favourite projects – and a major reason is because farmers drove it. They came to him to ask for the research and were eager to see the results. He even saw them adopt the research results on their farms after only the first year. “Most scientists would say that’s the worst thing that could possibly ever happen. We always presented it as such: you’re the owner and operator of your farm. You’re going to take the risk based on you. But at the same time, they could see right away, spraying first thing in the morning came at a cost.”
The project changed the way he approaches extension. “Farmers that engaged with us and were curious saw the benefits right off the bat instead of waiting four years.”
It was also extremely helpful in providing a better understanding of what might impact the efficacy of a herbicide application. “It’s an important project that makes you think about all these little things that can make a difference.”
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Bunyamin Tar’an is developing freeze-tolerant chickpeas.
Wild species are key to enhancing a crop’s genetic diversity.
BY VANESSA FARNSWORTH
With Statistics Canada reporting that chickpea acres jumped 12.5 per cent to 541,000 in 2025 — the largest number of acres for many years — it’s no wonder scientists are looking to breed varieties better adapted to tolerate those notoriously cold prairie temperatures.“We would like to give more farmers in Western Canada the opportunity to grow chickpeas as part of a four-year rotation for long-term sustainability,” says Bunyamin Tar’an, the Saskatchewan Ministry of Agriculture Strategic Research Program (SRP) chair in chickpea and flax breeding. “We have peas, lentils, faba beans, common beans and now soybean heading west from Manitoba, but we also need chickpeas, which are better adapted to drier areas, including the vast majority of southwestern Saskatchewan from Swift Current south.”
Chickpeas may be an important pulse crop for growers in Western Canada, especially in areas where farmers are faced with the root rot Aphanomyces in peas and lentils. However, Tar’an notes that the short growing season combined with the crop’s intolerance to cold weather means that subzero temperatures can and do have adverse impact on chickpeas, hampering growth, reducing yields and lowering overall quality.
“With that short growing season, we are often hit with problems at two times of the year,” says Tar’an. “When we seed in early May, sometimes the temperature drops just when the plants are poking up from the ground, and they die or don’t recover. And because chickpea is a long growing season crop, sometimes when we have an early frost at the end of the season, the immature watery pods become frozen, and that reduces the quality.”
These things make it crucial for scientists to develop chickpea varieties that can withstand low temperatures, particularly at the seedling stage. However, the narrow genetic base of existing cultivated chickpeas hinders crop improvement efforts, something that led Tar’an to look at crop wild relatives (CWR) as a way to enhance the genetic diversity of cultivated species.
“Initially, just out of curiosity, we asked if there was anything within the germplasm of the cultivated and wild species that we have in our collection that can withstand low temperatures,” Tar’an says.
One wild species, Cicer reticulatum, stood out for
several reasons; its genetics are closely related to the cultivated species, it tolerates suboptimal environments, it’s genetically and phenotypically diverse and it’s fully cross-compatible. All these things make it an excellent genetic resource for a breeding program looking to improve cultivated chickpeas.
A few years ago, Tar’an and his team at the University of Saskatchewan subjected eleven cold-tolerant wild C. reticulatum accessions, two cold-sensitive cultivated species (CDC Leader and CDC Consul) and a cold-sensitive check to freezing temperatures at the early vegetative growth stage for up to 24 hours under controlled conditions. After a two-week recovery period, they compared the responses.
“We were focusing on the seedling stage because once plants are hit by low temperatures during that stage, some won’t recover, which then requires farmers to reseed. If they don’t, they’ll get patchy fields and that will be a problem. The crop won’t be uniform, and weeds will move in.”
None of the plants from the commercial varieties survived that initial experiment. The four most cold-tolerant wild species and both cultivated species were further evaluated by subjecting them to a cold acclimation period, then both sets of plants (acclimatized and non-acclimatized) were exposed to freezing temperatures, then returned to control conditions for recovery and assessed after two and three weeks.
“We initially subjected the plants to normal growing conditions, then reduced the temperature from 22 C during daylight down to 4 C for one week, which led the plants to acclimatize,” says Tar’an. “Then, we reduced
the temperature to -6 C for 24 hours. After that, we returned it to normal conditions and then looked at the regrowth of the plant.”
Only the acclimatized wild species survived the freezing temperatures, and two of those (CudiA_152, Kesen_075) had the highest degree of cold tolerance, not only surviving but also developing new roots. Selected plants from an F2 population developed from a cross between CDC Consul and Kesen_075 also proved to be cold tolerant. Further analysis provided insights into potential freezing stress response mechanisms.
“During that time period, from the acclimatization and the cold reaction, we collected the RNA — so we could examine what genes are being expressed — and we compared those with plants grown under normal conditions,” Tar’an says. “What were the differences? What triggered this response? From there, we made some hypotheticals based on pathways that are well known in other species. Was there any similarity to what we have in chickpeas?”
A BALANCE
Tar’an’s team identified ten significant quantitative trait
CONTINUED ON PAGE 21
New tools and genes for detection and resistance.
BY MATT MCINTOSH
Pea seed-borne mosaic virus (PSbMV) is one of – if not the top – viral threat to peas on the Canadian prairies. To help limit its spread, and to support in-field control, researchers at the University of Saskatchewan (USask) have developed effective means of detecting PSbMV in pea plants, pea seeds and the insect vectors by which the virus spreads.
PSbMV is a pathogen affecting chickpeas, lentils, peas and faba beans. Alfalfa can act as a host for the virus as well, although it will not show symptoms of the infection. “The difficulty with viruses is, in many cases, they’re not distinct, and it’s hard to know what you’re looking at,” says Sean Prager, associate professor in the USask Department of Plant Sciences. “You might see what looks like herbicide damage, but it’s really viruses, nutrients, things like that.”
Specific signs growers can watch for when scouting for physiological impacts of PSbMV include stunted and malformed plants, with delayed or uneven maturity. They can also check the leaves for the mosaic leaf pattern, clearing and swelling of leaf veins, as well as molting, curling and necrosis. Another sign of damage is stunted shoots with reduced internode length, and internode malformation, as well as deformed pods or aborted seeds. On peas and chickpeas, it’s important to look for brown rings and spots on seeds, shrivelled seeds or a split coating.
“When you get the mosaic pattern, it’s very distinct if you know what you’re looking at. But if you don’t get that severity, you don’t necessarily know what you have,” adds Prager. “Not doing anything about it eventually translates to yield loss.”
PSbMV spreads when aphids carrying the virus damage pea plants, or when infected seeds or plants are disbursed. The virus has a high seed-to-plant
transmission rate. Infected seeds can also be asymptomatic but still pass on the virus, making efficient and timely identification a greater challenge. Controlling the virus necessitates planting virus-free seed, controlling aphids and fostering genetic resistance in the crop when possible.
ABOVE PSbMV infection on pea (CDC Meadow) two weeks after inoculation (one month old plant).
Prager and his colleagues have been investigating how PSbMV spreads for eight years. While the pathogen has not historically been common in Saskatchewan, the number of cases and its geographical spread have started increasing.
“It’s been more common in the Idaho and Washington State area. The same can be said in Montana and North Dakota,” says Prager. “The assumption has been it’s largely an aphid-related issue and, in the Prairies over the last decade or so, we didn’t have as much of a problem with pea aphids. Now that we have pea aphids more often, our guess is that we are getting the virus more often.”
Prager is currently pursuing several objectives to help
loci (QTLs) distributed across five chromosomes in wild chickpea, all of which are associated with tolerance to freezing stress. They also identified functional candidate genes within these QTL regions that are believed to play vital roles in mechanisms related to cold tolerance. These findings paved the way for the targeted breeding strategies now being used to make the crosses and selections with the goal of developing chickpeas that are cold tolerant without sacrificing yield, seed quality or other factors necessary for commercialization.
“When we make a cross with a wild variety, the seed quality and how it looks isn’t necessarily appealing to consumers,” Tar’an says. “So then I have to bring back that desirable characteristic while maintaining the plant’s tolerance to cool temperatures.”
Tar’an and his team are making significant progress. On the material they’ve tested so far, the recovery rate following that critical 20- to 24-hour freezing period has been 100 per cent, a huge improvement compared to currently available commercial varieties, most of which fail at six hours. The goal now is to identify new lines that strike a balance between improved cold tolerance and other desirable characteristics.
“It’s about compromise. That’s how the biology works,” says Tar’an. “For me, as a researcher, it’s about how this one factor and the others are interconnected within the plants. Where is that connection between two factors at the genetic level? Is the same gene controlling both components or are they controlled by separate genes that are close together? And if they are close together, can we separate them?”
While initial scientific studies were conducted indoors in a controlled environment designed to mimic typical growing conditions in Saskatchewan, largescale breeding takes place in the field where temperatures can be unpredictable.
“That’s been a challenge. The larger breeding scale can’t be done indoors. We have to do the growing in the field, so we seed early and record the temperatures, but for the past few years we’ve been seeing warmer early seasons,” says Tar’an, noting this has slowed down progress. “Although it has not been as fast as I would have expected, we’re making definite progress crossing the wild material with the cultivated lines.”
Tar’an estimates it will take several more years of field testing to ensure those promising varieties perform stably at low temperatures before they’re ready for commercialization. He’s optimistic that, once that happens, farmers will be able to breathe a little easier.
“It’s not like chickpeas will ever become cold tolerant down to -20 C, but at least the crop will be able to withstand -6 C for 20 hours and be able to regrow,” he says. “That may set growers back a little, but their fields aren’t going to need reseeding.”
get ahead of the PSbMV on the Prairies. The first involves examining how the virus adapts to Saskatchewan legume crops after repeated infection cycles.
“The premise is the virus has strains that adapt to host plant and location. The most common strain appears specific to Saskatchewan, which means it’s likely been here for a while. What we want to know is the extent to which the virus will adapt to different host plants,” says Prager. “We keep infecting plants over generations, and sequence the virus to see if it changes genetically. It’s essentially the same technology we use for COVID-19.”
Objective two is to determine the mechanisms and durability of resistance against PSbMV in legumes, which involves identifying what genetic material could improve resistance. Currently, Prager says all peas “don’t stand up well” to PSbMV, barring those which carry the resistance gene.
“There is a known gene that conveys resistance to PSbMV in peas. Some breeding programs will breed that gene into peas, but it has not been done in any of our Saskatchewan pea lines yet. If it is part of one of those lines, it happened by sheer chance,” says Prager, adding a previous lack of focus on PSbMV resistance stemmed from the fact it was historically not a major threat in the province.
The range of PSbMV severity has also been analyzed. “All of the legume varieties that don’t have the resistance gene show something unpleasant. Chickpeas are the hardest hit, but pea and fava beans are all symptomatic,” says Prager. “We also looked at other wild legumes – such as purple prairie clover, rugged alfalfa, and fenugreek – to see how they avoid infection or are not systemically infected and symptomatic.”
“What we do is basically make a slurry of plant tissue and other things, and rub the plant and make the plant get sick without needing the aphid. In some cases, the leaf that you rub gets sick, but you don’t see it anywhere else in the plant. Native legumes sometimes have resistance genes, which could be alternative sources of resistance for breeding programs … I used seeds from one wild collection of purple prairie clover, and one variety of each fenugreek and alfalfa. There is a possibility that the other varieties or collections are susceptible to the virus.”
While investigating sources of resistance is meant to support legume breeders and growers long-term, the development of an efficient tool for the detection and prediction of severe PSbMV variants is meant to provide an interim stop-gap solution.
“We’ve done a lot of work on that. We have the ability to detect the virus in aphids, plants, and in many ways are able to for doing so to whomever needs them,” says Prager. His lab has developed polymerase chain reaction (PCR)-based virus detection protocols and assays which can be used in a wide range of platforms, including conventional PCR, quantitative polymerase chain reaction (qPCR) and digital PCRs. These can be used to detect the virus from aphids, seeds, as well as fresh or dried plant tissues.
A simple field tool based on visible symptoms was also developed to show how disease symptoms appear at different growth stages in pea, chickpea and faba bean. This provided growers the capacity to detect problems early in the field. Efforts to help familiarize growers with PSbMV symptoms are ongoing, and include field days and workshops throughout the growing season. “We hope these tools will become part of our provisional survey programs to get a feel of how problematic PSbMV is,” says Prager. “Because right now, we don’t really know.”
He again reiterates, however, that improved genetic resistance will ultimately prove to be the most effective response. “We’re getting to the point where we’ve identified sources of resistance. If we can get those into varieties people grow, hopefully by the time PSbMV becomes a massive problem, you’ll have that resistance.”
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It’s not a disease.
BY BRUCE BARKER
Some sharp-eyed plant pathologists identified physiological leaf spot in a few winter wheat fields in southern Alberta in 2025. It’s somewhat rare in Western Canada, but it is increasingly common and has caused yield losses in Montana in spring and winter wheat.
“It’s a difficult disorder to diagnose and so it probably gets missed a lot, but we haven’t seen or heard many cases over the past five years,” says Michael Harding, a plant pathologist with Alberta Agriculture and Irrigation at Brooks, Alta. “It is a physiological response to environmental stress and/or chloride deficiency.”
Harding says physiological leaf spot is typically observed in the upper canopy during the flag emergence to boot stage of wheat, while symptoms can be missing or rare on lower leaves. He points to a Montana State University AgAlert extension bulletin in May 15, 2025 by Uta McKelvy, extension plant pathologist, and Clain Jones, soil fertility specialist, that further describes the symptoms.
“Physiological leaf spot appears as circular to oblong, dark brown or chlorotic lesions, and the tissue in the center looks bleached, white to gray in color. The lesions are often surrounded by narrow chlorotic (yellow) halos and tend to be more numerous toward the tip of the leaf blade. PLS lesions have more discrete margins compared to fungal leaf spots, which are more diffuse and continue to expand over time. Most importantly, unlike tan spot, it does not develop small black spots in the center of the lesion when kept in a humid environment for 24 to 48 hours,” says McKelvy.
Harding says that physiological leaf spot development due to environmental stress occurs “in wheat when we have cool, cloudy weather followed by a sudden burst of bright sunlight and warm days – or alternating between very cloudy and very intense sunlight. This environmental trigger for physiological leaf spot is usually a factor when we see it, and is more likely to occur in May or June.”
It’s worth noting that Harding says there is no fungal pathogen causing this disorder. In other words, it is
ABOVE
Physiological leaf spot appears as circular to oblong, dark brown or chlorotic lesions.
not a disease. “A fungicide will not be effective and should not be considered if physiological leaf spot is the only leaf spot issue on a crop,” he says.
Jones says that MT researchers two decades ago observed severe physiological leaf spot in durum wheat in Montana that caused yield losses, and it has been observed on spring and winter wheat as well.
CHLORIDE DEFICIENCY MAY BE A COMPOUNDING PROBLEM
Physiological leaf spot can be linked to chloride (Cl) deficiency, says Jones. He says that low chloride uptake
by the plants can occur in sandy soil with high rainfall because the chloride has leached, but also in droughty soils where root growth is reduced. “If you want to rule out or rule in chloride deficiency, we suggest you do a tissue test for chloride concentration. The suggested critical level in plant material (entire plant) is between 0.1 and 0.4 per cent, with large yield increases and leaf spot decreases when chloride was applied at tissue chloride concentrations below 0.1 per cent.”
Chloride deficiencies have gone up dramatically in Montana in the past
25 years, says Jones. He cites soil test data from AGVISE Laboratories since 2000, where the percentage of soil tests with less than 45 kg Cl/ha (40 lb/ac) in the top two feet is trending upwards. The majority of the soils now have soil test levels less than 40 lb/ac, and some areas have as high as 80 per cent of samples testing low in Cl. Fields fertilized with potash which is 50 per cent Cl should have less potential to have Cl deficiency.
In Western Canada, data from AGVISE also shows that Cl fertility may be a concern as well. Notably, Cl levels were below 40 lb Cl/ac in more than 50 per cent of soils from many regions in 2025, especially in Saskatchewan.
Harding says supplementing deficient areas with Cl fertilizers can help prevent the disorder but may not provide a yield benefit. Chloride levels in soil of more than 34 kg/ha (>30 lb/ac) in the top 60 cm (24 inches) are generally sufficient in Alberta.
To mitigate physiological leaf spot, Jones says that applying 11 to 22 kg/ha (10 to 20 lb/ac) potash (0-0-60) should be sufficient (5 to 10 lb Cl/ac) to supplement Cl already in the soil, although it doesn’t always provide
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Best management practices outlined.
BY BRUCE BARKER
Tired and unproductive, a forage field that has been neglected can be brought back to life with a good fertility program.
“Removal of all above-ground material with haying over time removes a lot of nutrients, and production declines due to lack of fertility,” says Jeff Schoenau, soil scientist with the College of Agriculture and Bioresources at the University of Saskatchewan (USask). “A tired forage stand can be brought back to life with the addition of fertilizer or manure.”
Forage stands remove a large amount of nutrients from the soil each year. A five ton/acre alfalfa crop removes 260 to 320 pounds of nitrogen (N) per acre, 60 to 80 lb P 2 O5/ac, 270 to 330 lb K2O/ac and 25 to 35 lb/ac sulphur (S). With a forage legume like alfalfa, most of the N can come from the air through biological nitrogen fixation, but the other nutrients come from the soil.
A three ton/ac grass stand removes 90 to 120 lb N/ ac, 25 to 35 lb P2O5 /ac, 120 to 140 lb K2O/ac and 10 to 15 lb S/ac. For pure grass stands, all the nutrients
ABOVE Research projects at USask have developed fertility strategies for forages.
including N must come from the soil. In mixed legume-grass stands, some of the N the legumes fix from the air gets transferred to the roots of the companion grass.
Schoenau says that forage producers can capitalize on biological N fixation with legumes in the forage stand. A research project by Gazali Issah in the Department of Soil Science at USask found that greater than 90 per cent of the N found in alfalfa was derived from biological N fixation. Of that, a significant proportion of fixed N could be transferred to a grass companion.
“The actual amount of nitrogen fixed depends on nodulation, environmental conditions, soil available N and other nutrients that influence N-fixation such as phosphorus (P),” says Schoenau. “For example, rhizobia don’t like acidic soils.”
An advantage of having a legume mix in a forage grass stand is that they can also contribute non-N benefits to subsequent crops. Schoenau says that legumes are reported to have the ability to solubilize P from less soluble forms in the soil. Additionally, they have deep root systems that can mobilize parent material P reserves at depth and bring them to the soil surface for recycling.
a yield benefit. Dry fertilizer applications can be applied at any time through the late jointing stage, depending on sufficient rain (or irrigation) he says. Alternatively, a similar amount of chloride can be applied as a liquid (for example, calcium chloride or ammonium chloride). Liquid formulations can be applied to the foliage up to the time of flag-leaf emergence, but earlier is better.
Research work conducted in Montana has also found that some winter wheat varieties are more susceptible to physiological leaf spot. Older wheat varieties like Accipiter, Buteo, Falcon and Redwin were found to be very susceptible to the disorder. McKelvy notes that over the past few years, the newer variety Bobcat has repeatedly developed physiological leaf spot. “Please note that Bobcat has been performing very well throughout its development process at MSU, even in the presence of physiological leaf spot,” says McKelvy. Overall, wheat growers should be aware of the issue and learn to identify the disorder. McKelvey encourages readers to consult with a specialist/diagnostic lab if they see leaf spots and wonder if it is physiological or fungal. “I find them really very difficult to tell apart and, in my opinion, it is really the best course of action to have it properly diagnosed before making management decisions.”
Should physiological leaf spot be identified, the recommendation is to investigate whether Cl deficiency is a contributing cause.
Research has also found that there is a non-N yield benefit to cereals when grown on a legume stubble compared to a cereal stubble. This can be attributed to improved soil tilth and soil fertility, and a break in the pest cycle. “That’s the magic of legumes,” says Schoenau.
For forage stands that are primarily grasses, a recent Living Labs study at Touchwood Hills Ranch Demonstration Site in 2024 by M.Sc. student Mason Plews looked at sod-seeding with a no-till disc drill into grass forage stands to establish legumes into the field. He compared purple alfalfa, sainfoin and yellow alfalfa seeded in the spring or fall, with or without glyphosate application for grass stand suppression.
The best legume stand establishment was when a pre-seed glyphosate application was applied, reducing competition from the grass for the emerging legume seedlings. However, this significantly reduced forage yield in the application year and may leave the soil susceptible to erosion. Late fall seeding when the stand is dormant did significantly increase plant counts compared to spring seeding without suppression.
Schoenau says that hayed grass stands such as brome grass are frequently deficient in N and P, but also sometimes deficient in K and S. Many forage fields test in the single digit parts per million (ppm) for extractable P while the critical level above which no responses generally occur is approximately 30 ppm. He says that mixed stands containing legumes often respond better to applied P than pure grass stands alone because legumes have high P requirements, needed for the biological N fixation.
“A good strategy to ensure good P fertility throughout the duration of a forage stand is to start out with good P fertility to begin with, adding enough banded P at establishment or pre-plant banded P to last for the duration of a stand, rather than trying to
Sod
seeding to introduce forage legumes
broadcast P later and have the P hung up at the surface,” says Schoenau.
On the other hand, a mixed grass-legume stand with more than 50 per cent legume will often show little yield response to added N fertilizer. The legume will fix N if the nutrient is not available in the soil.
Building soil P fertility is possible with annual applications of P fertilizer, but it is a slow process. A general rule of thumb attributed to retired soil scientists Cindy Grant and Don Flaten is that the rate of fertilizer P required to raise soil test P by 1 ppm ranges from 20 to 40 lb P2O5/ac over and above the amount of P removed at harvest.
Balanced nutrition is also important. A three-year Saskatchewan research project from 2005 through 2007 near Star City, Sask. showed that the highest timothy forage yield was obtained when N, P, and S fertilizer were applied together rather than individually.
“Removal of all aboveground material with haying over time removes a lot of nutrients, and production declines due to lack of fertility.”
Applying the right rate in the right place with the right source with best timing applies as much to fertilizing forages as it does to annual crops. Late fall and early spring are good times to apply N fertilizer to reduce volatilization losses, and snowmelt/rain will help move broadcast N into the soil. Broadcast urea (46-00) treated with a urease inhibitor will also help reduce volatile ammonia losses.
Surface dribble banding of Urea Ammonium Nitrate (UAN) solution (28-0-0) is also effective, especially if rain follows application. A research study at Meacham, Sask. in 2004 demonstrated that surface
dribble band of UAN can be as effective as banding UAN through a coulter opener. Applications of 50 and 100 lb N/ac dribble banded versus coultered in produced similar yields of around 4,000 lb/ac dry matter at 50 lb and around 4,500 lb at 100 lb. These compared to the unfertilized yields of around 2,500 lb/ac.
Liquid manure is ideally injected into the soil to reduce odor, reduce nutrient loss and increase nutrient recovery by the forage crop. A research project in 2000 at Engelfeld, Sask. assessed the response of crested wheatgrass to injected swine effluent at 3,300 gallons per acre (GPA) (37,000 L/ha; 100 N, 15 P2O5, 50 K2O) and 6,600 GPA (74,000 L/ha; 200 N, 30 P2O5 and 100 K2O). The unfertilized check yielded 1 t/ha, compared to 2.4 t/ha for the low application rate and 4.4 t/ha for the 6,600 GPA rate.
Solid cattle penning manure is more difficult to achieve high nutrient recovery when broadcast on pasture since incorporation by tillage is not possible. Solid manures are slow-release sources of nutrients, and surface application further slows nutrient release, says Schoenau. Significant amounts of nutrient may also be lost in the pen prior to transfer to the field. In a study in east-central Saskatchewan near Lanigan at the Western Beef Development Centre, in the year of application, nutrient recovery in forage grass from spread manure hauled from pens was only five to nine per cent of N and three to five per cent of P that was originally present in the hay and straw bedding used for the cattle in the pens.
A better solution for capturing the nutrients and benefits of cattle manure is in-field feeding. About 10 per cent of nitrogen consumed by a cow is retained in the cow with the rest excreted mainly in urine. Similarly, only about 20 per cent of P is retained in the cow with the rest excreted mostly in dung. In the Lanigan study, feeding cattle in the forage field via bale grazing or bale processing captured and recycled much more N and P contained in feed and bedding than pen feeding, hauling and spreading manure. It was calculated that the forage crop recovered 30 to 45 per cent of added N and 21 to 32 per cent of P with in-field feeding.
“There is more efficient conservation and recycling of feed nutrients with in-field feeding systems,” says Schoenau. He cautions, though, that in-field overwintering feeding sites need to be carefully located to avoid run-off of water into sensitive water bodies.
Schoenau says a good starting point in forage fertility management is to soil or tissue test to analyze for nutrient deficiencies, and to develop a fertility strategy that will provide nutrient to meet short- and long-term requirements and obtain maximum benefit and longevity from perennial forage stands.
by Bruce Barker, P.Ag |
Kochia herbicide resistance has become widespread on the Canadian Prairies. Kochia populations have now been identified as having resistance to Groups 2, 4, 9 and 14, with some Group 2+4+9 stacked resistant populations identified.
With the declining usefulness of herbicide control, research led by Shaun Sharpe, weed scientist at Agriculture and Agri-Food Canada (AAFC), evaluated alternate, physical management strategies for controlling kochia patches. This strategy, if implemented for three years, takes advantage of the short, two-year seedbank persistence of kochia seeds. The objective of the three-year study was to evaluate physical patch management strategies of mowing or single applications of black plastic, hydro-mulch and chaff on kochia densities.
Six farm fields with kochia patches in the rural municipality of Last Mountain Valley, Sask. were used in the study. The six treatments included an untreated control, black plastic mulch, overseeding with green wheatgrass ‘AC Saltlander’, field chaff, a coconut-based hydro-mulch referred to as coco mulch, and mowing using a string trimmer with clipping removal. The treatments were applied only in the spring of 2021 except for mowing which was conducted four times each year.
Black plastic mulch was applied in the spring and required some repairs in 2022. Coco mulch was applied at 3,026 lb/ac (3,400 kg/ha). Wheat chaff at a depth of 2.75 inches (7 cm) was applied on four sites, and canola chaff on one site. Site 4 had minimal chaff availability, so cattail leaves cut six inches (15 cm) above the soil surface were applied as a chaff treatment. Mowing was conducted when kochia reached 4 in (10 cm) in height and was conducted four times per year. Broadcast seeding of AC Saltlander was conducted in the spring and fall of 2021, but it did not establish.
Kochia densities were measured five times throughout the spring and summer. Warm and dry environmental conditions favoured kochia development.
Kochia density in the untreated control reached a maximum of 60 plants ft2 (600 plants/m2) in 2021, 1,000 plants/ft2 (10,000 plants/m2) in 2022 and 230 plants/ft2 (2,300 plants/m2) in 2023. The researchers observed that in 2022 and 2023, kochia
establishment was high and there was evidence of ‘self-thinning’ of the stands between May and June measurements.
The black plastic mulch was the most successful in controlling kochia. In fact, kochia failed to emerge through the mulch in each treatment year. However, it had degraded by the end of 2022 and had to be replaced.
The next most successful was the chaff treatment with the lowest kochia density in 2021 and 2022, and the second best compared to mowing at the early July measurement date in 2023. Chaff mulch reduced kochia densities to five to 14 per cent of the untreated control in 2021, five to 22 per cent in 2022, and 22 to 56 per cent in 2023. The reduced kochia control in 2023 was attributed to degradation of the chaff by two-thirds of its original depth. The researchers indicated that further research should be conducted to see if heavy harrowing could help restore the chaff depth, and if field crops are able to establish and grow through the chaff.
Mowing had the lowest kochia densities in 2023. In 2021, mowing reduced kochia densities to seven per cent of the untreated control, and to two per cent of the untreated control in 2023. In 2022, kochia plants were very short, which limited the effectiveness of the treatment with final treatment densities similar to the untreated control. The mowing treatment had several drawbacks, including the need for multiple mowing passes in the absence of crop competition, and the patches would need to be in accessible areas of the field. Further research into the effectiveness of commercial flail mowers would help to understand if mowing a few inches higher would be effective.
Coco mulch applied once during the spring of 2021 also helped to reduce kochia densities over the three years but was not as effective as the other chaff treatment or mowing. In 2021, coco mulch reduced kochia densities to 16 to 28 per cent of the untreated control, and by 37 to 73 per cent in 2022, and 22 to 64 per cent in 2023.
An economic analysis was conducted to compare the cost of the treatments. This included equipment, materials, labour and gas.
Considering all costs over three years, mowing was the least costly at $416/ac followed by chaff/straw mulch bales at $517/ac and chaff/straw mulch collected with a chaff cart at $1,077/ac. Coco mulch came in at $6,000/ac, and plastic mulch at $7,028/ac.
These costs are high – some prohibitively – but a pre-harvest agricultural weed survey in 2019/20 found that herbicide-resistant weeds cost Saskatchewan grain farmers $343 million per year. Therefore, farmers on the Prairies must determine what kochia infestations cost them, and what it’s worth to control patches with alternative practices when herbicides are no longer effective.
Bruce Barker divides his time between CanadianAgronomist.ca and as Western Field Editor for Top CropManager. CanadianAgronomist.ca translates research into agronomic knowledge that agronomists and farmers can use to grow better crops. Read the full research insight at CanadianAgronomist.ca.
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