Manitoba corn growers have long relied on weed-management research from Ontario or the U.S. Midwest, even though growing conditions rarely match what farmers see in their own fields.

A new set of trials by U of M researcher Loveleen Kaur Dhillon is set to change that.

WHY IT MATTERS: With most corn-based weed guidance borrowed from other regions, Manitoba growers need local research to fine-tune their spray timing.

Dhillon is in her first year as the university’s agronomist-in-residence (special crops), a five-year applied research role funded through the Manitoba Crop Alliance (MCA).

The position covers three “special crops” as defined by the program — corn, sunflower and flax — which are considered special because of their relatively low acres in the province, despite their potential.

Coming into the role with agronomy and plant breeding training, Dhillon said that aside from corn, which she had worked with during her master’s research in India, everything else was a fresh start.

She admitted she was nervous early on but settled in quickly once fieldwork began and she could see how producer-driven the program would be, allowing her to focus on basic, but essential, agronomy questions.

“I get to work on all those fun projects,” she said.

That farmer-facing element is central to how she sees her role.

Dhillon said the MCA partnership gives her a clear sense of grower priorities and helps her shape the work around what producers want studied.

Among this year’s work were two corn studies conducted at three Manitoba sites: Carman, Melita and Arborg.

In the first study, Dhillon used three widely grown hybrids and planted them on different dates to see whether adjusting seeding windows might influence how corn fits into the province’s shorter warm period.

The second study focused on the critical weed-free period, which is the window before early-season competition starts to cut into yield. Dhillon wanted to see how U.S. and Ontario recommendations hold up under Manitoba conditions.

She divided the work into two complementary approaches: one that let weeds grow for set periods before removal, and one that held plots weed-free for set periods before allowing weeds back in.

She said the work is also meant to help growers spray only when it matters most, making weed control more efficient, cost-effective and sustainable over the long term.

A season of contrasts

The three sites offered three distinct pictures of the growing season.

Melita had favourable weather, giving clean comparisons across weed-removal timings.

Carman had heavy weed pressure, which made the contrasts more obvious, even visible from the field edge and in drone images.

Arborg, however, was dry for much of the season, and the crop there looked very different from the other sites. Weed density and species composition also shifted under drought, which changed how the competition played out.

Dhillon said that although the conditions were challenging, the variation itself added value. Each site contributed a different piece of the puzzle, helping her understand how Manitoba’s range of environments might influence weed timing.

She hasn’t analyzed the data yet and won’t make recommendations until she has accumulated more site-years. Even so, based on differences seen in the field, Manitoba conditions don’t appear to mirror the conditions on which U.S. and Ontario recommendations are based.

Farmers who have managed corn here for years already know some of those discrepancies from experience; Dhillon’s first-year observations simply reinforce that Manitoba’s conditions deserve Manitoba-made research.

With more data coming next year, and with all three special crops under her long-term mandate, Dhillon said she hopes to give growers clear, locally grounded guidance they can use in their day-to-day decisions.

For now, she has something just as important: proof of concept that the province’s unique conditions behave differently enough to justify a made-in-Manitoba approach — and the beginnings of a program built to deliver it.

“The differences are quite clear,” said Dhillon.

“The protocol and the design of the experiment really worked.”

The post Corn research looks for Manitoba-based weed control appeared first on Grainews.

Recently a report published by the Propane Education and Research Council (PERC) in the U.S. caught our attention. It featured a field implement designed to be pulled by a tractor and inject steam into the soil to kill weed seeds where they’re lying in wait — a method similar to practices such as anhydrous ammonia application.

The report cited results from a project undertaken by two U.S. universities that PERC funded. The implement used propane as an energy source.

“The banded applicator injects steam along the seed line before planting,” it reads. “Researchers say heating the soil to 150 to 160 F for 15 to 20 minutes controls more than 90 per cent of certain troublesome weeds.”

That apparently led to a significant reduction in labour costs in weed control in the test field growing vegetables.

Other research reports, however, have been skeptical of the value of using a mobile steam application to kill weed seeds in the soil. Also, the idea isn’t new.

“It’s been around for a while,” says University of Saskatchewan professor Steve Shirtliffe. “We’ve done a little bit of research (on it) with a company that was starting up.”

That research effort found getting the soil up to a high enough temperature to kill weed seeds proved very difficult with a mobile implement.

“Even with going very slow, the temperature did not even get close to what it would have to be to kill weed seeds,” Shirtliffe adds.

“Seeds are harder to kill than microbes in most cases. Seeds are resistant to heat, sometimes even very high temperatures. There are two things with thermal injury: how high are you getting the temperature, and what’s the duration of that? It’slike cooking something.”

And even if the necessary temperature can be achieved to accomplish that, the effect isn’t limited to weed seeds and unhelpful microorganisms.

“It’s basically a scorched-earth policy,” Shirtliffe says. “You’re essentially sterilizing the soil. All the macrofauna in the soil will be killed, unless they’re deeper down than the part you’re heating up.”

In the trials Shirtliffe was involved in, the energy costs were so high as to be impractical. “To reach a high temperature in something as dense as soil that is moist takes a lot of energy.”

But there is a more practical way to use steam to control weeds, he suggests — namely, waiting until they emerge and hitting them then with a different type of applicator.

Steam applied to young green weeds can be very effective at killing them, according to a 2017 paper published in the New Zealand Journal of Agricultural Research.

That study looked at using a mobile implement to apply steam to young green weeds.

“At a tractor speed of three km/h, steam killed 100 per cent of 10-day-old mustard plants, sown as a surrogate weed,” the report says.

“Plants of all the other species were killed when the treatments were applied soon after emergence (cotyledon stage), but as the plants increased in size, they became more resistant to heat, either because the terminal or axillary meristems were protected by soil, or because meristems were protected by thickened stems and leaves as the plants aged.”

“If you think about it, would it be easier to kill a little green plant or heat up the ground enough to kill a weed seed that’s in the ground?” says Shirtliffe.

Using steam to kill young, growing weeds has so far proven to be the most practical and cost-efficient way to use that technology for most applications, he says, and research around steam use in weed control continues to be discussed in academic circles as chemical control continues to draw unfavourable press.

The post Using steam as a weed control alternative to chemicals appeared first on Grainews.

While imports of other companies’ off-patent brands of glyphosate may buffer the immediate shock, the long-term implications could reshape weed management across the Prairies.

Hugh Beckie, a former Agriculture and Agri-Food Canada weed scientist, explored this very scenario in 2019. At the time, he was based at the University of Western Australia, so his modelling focused on Australian farming systems. But while the crops may differ, both Australia and Canada depend heavily on glyphosate-based weed control, making many of his findings relevant here.

Beckie’s work laid out not just the impacts of losing glyphosate, but the sweeping, system-wide changes farmers would need to adopt in its absence.

To understand what that shift might look like on the ground, Glacier FarmMedia spoke with Kim Brown, provincial weed extension specialist with Manitoba Agriculture, about the tools, trade-offs and decisions farmers may face if glyphosate were to disappear from the weed control toolbox.

Brown says Canadian farmers have already been working to reduce their reliance on glyphosate due to the rise of herbicide-resistant weeds.

“We’ve already been going down that road where glyphosate for certain weeds just has not been working,” Brown says.

“We’ve had to find alternative methods for weed control.”

That said, a full loss of glyphosate would escalate the challenge considerably, especially given that weed pressure is a constant in Prairie fields.

“There are weed seeds in the soil. The weed seed bank is vast,” she says.

“Every single year there will be weeds.”

That tracks with what Troy LaForge, who farms in the brown soil zone near Cadillac, Sask., about 65 km south of Swift Current, predicted when we asked him to consider what his fields would look like if glyphosate were to someday disappear from the market.

“What we would probably see is a progression in winter annual and perennial weeds, and from that perspective, we may have to change up to some different oilseeds where we can use actives like clopyralid (the Group 4 active in products such as Lontrel and Curtail) and some of the graminicides (Groups 1 and 2) that are more effective on perennial grasses like quackgrass and foxtail barley,” he says.

“We’d have to change to some different crops, and I honestly don’t know what those would be at this moment, but we may have to change because we just don’t have means of keeping weeds under control otherwise.”

Southwestern Saskatchewan is not generous with the rainfall and not typically canola country, but if glyphosate were to go away, “it might mean that we’ve got to start growing canola more continuously to use a product like glufosinate (the Group 10 active in Liberty) for example.”

Brown concurs there are other herbicide options, even in glyphosate-tolerant systems, thanks to stacked traits — but those alternatives likely won’t cover the same broad weed spectrum that glyphosate does.

“We will have alternatives,” she said.

“But it’s going to get a lot more complicated, and it’s definitely going to get more expensive.”

READ ALSO: Glyphosate class action moves forward in Canada

Farmers may also need to revisit herbicide products they aren’t currently using and some they haven’t used in years. Brown said some older chemistries may play a bigger role again, particularly in rotation or in tank mixes.

However, product availability, crop safety and regional fit will be key considerations.

“To me, as a no-tiller, the No. 1 issue is going to be what we replace it with, and at this point, the actives that are registered are going to increase our costs significantly,” LaForge says.

“And it’s probably going to mean that we’ve got to bring back some active ingredients that we haven’t had for a while and just have higher levels of toxicity at the end of the day.”

Losing glyphosate would also push integrated weed management (IWM) to the forefront.

“Those tools have always been there,” Brown says.

“In the past, we haven’t used those tools as effectively as we could. But we’re going to have to now because we won’t have a choice.”

Brown stresses the value of crop competition: adjusting seeding dates, seeding rates, row spacing and cultivar selection all help. But the biggest lever, she says, is crop rotation.

“Crop diversity is probably the single biggest thing we need to do when it comes to weed control.”

Life cycle diversity — mixing annuals and perennials, or at least spring and fall crops — can help break weed cycles and reduce reliance on any single product or practice.

Beckie’s paper indicates how Canadian farmers may have a leg up over their Australian counterparts when it comes to managing glyphosate resistance.

In Western Canada, about 40 per cent of canola acres are planted to herbicide-resistant varieties, but resistance hasn’t taken off the way it has in Australia. That’s largely thanks to the widespread use of glufosinate-tolerant cultivars and more diverse crop rotations.

Still, Beckie warns, losing glyphosate as a pre-harvest option would hit hard in pulse crops, where there are few good alternatives for controlling tough perennial weeds.

Harvest weed seed control (HWSC) is another tool Brown mentioned, and it also played a central role in Beckie’s post-glyphosate scenario. Originally developed in Australia — where herbicide resistance evolved faster and hit harder — HWSC focuses on capturing or destroying weed seeds at harvest to prevent them from replenishing the seed bank.

Beckie’s modelling leaned heavily on this strategy, especially in the absence of effective pre-harvest herbicides.

HWSC has also been gaining traction in Canada and could become more relevant as farmers look for non-chemical ways to keep weed populations in check.

“You want to destroy the weed seeds, or you want to move them, or take them off the field and not let them add to the weed seed bank,” Brown says.

Tillage remains an option, and Brown notes it’s something most farms already have the equipment to do — but bringing tillage back as a primary weed control tool comes with consequences.

Brown points out that glyphosate was instrumental in the widespread adoption of minimum- or zero-till systems, and that if it’s no longer available, it could set things back significantly.

“There’s going to be many negative consequences with that,” she says, “including soil degradation, increased greenhouse gases and even just fuel consumption.”

Hence at LaForge’s farm, for example, tillage is just not an option.

“If we have to go back to tillage in this part of the world, we (would) probably decrease our yields instantly by 30 to 40 per cent,” given the amount of soil moisture that would be lost in the process, he says.

The availability of glyphosate has increased the diversity and productivity of the farm’s rotations and “created a whole new level of soil conservation in this area.”

There’s some hope on the horizon.

Brown points to emerging technologies such as laser weeding, electrocution, steam weeding and the potential for new herbicides or non-traditional weed control products. Much of this innovation, she said, is being driven by the urgency of the current situation.

“There’s a lot of research being done because of the very situation that we’re in right now,” she says.

Extension specialists such as Brown will play a key role in helping farmers adjust. She said the core message around integrated weed management isn’t changing, but the urgency and scope of that message are growing.

“We’re just going to have to get a lot more educated on some of these products that are out there that we need to be using,” she says.

“We have to raise that level of comfort, because that will be new territory for many farmers.”

The post What would happen if Roundup disappeared? appeared first on Grainews.

The pesky tumbleweed, which has become difficult to control in parts of Western Canada, doesn’t like to be buried. Research has shown the seeds of kochia are less likely to germinate when they’re buried in the soil.

For the last few years, AAFC scientists in Saskatoon have been studying methods to “artificially” bury kochia seeds in the soil as a possible way to control the tumbleweed.

The idea is founded on the principle that kochia typically appears in patches within a field, rather than across the entire field.

“Only treat kochia where it is found,” Shaun Sharpe, an AAFC weed scientist, told the Saskatchewan Agronomy Research Update in December in Saskatoon.

“The idea with patch management … (is) if we can pick out where it is and manage it heavily … we can apply a mulch or something to bury it.”

As Sharpe noted in his presentation, kochia has developed resistance to multiple herbicides and become a pernicious weed in parts of the Prairies.

In Canada, there are confirmed cases of kochia being resistant to Group 2, Group 9 (glyphosate), Group 4 and Group 14 herbicides.

Kochia’s resistance to herbicides is likely to get worse, so growers need alternative solutions to keep it in check.

Patches of kochia typically occur in areas near sloughs or in the marginal parts of the field.

“Wind is a major driver. Anywhere a tumbleweed can get caught… you may have a path where a tumbleweed travelled and get growth (of kochia) there. But rarely do I see a whole field infestation.”

A combine can also spread kochia seeds as it moves across the field.

Sharpe’s idea of “burying” kochia seed comes from a study done around 2005. Rene Van Acker, a former University of Manitoba weed scientist who’s now the interim president of the University of Guelph, was part of a project that looked at kochia seeds and germination.

“In growth room studies, kochia seed placed at the soil surface had greater emergence compared with seed burial to a 10-millimetre or greater depth,” the abstract for the study reports.

“Burying seed will greatly reduce future kochia populations.”

Previous studies have already established tillage is an effective way to bury kochia seed and control the weed. However, Sharpe wanted to study other methods because “we don’t want to go backwards” on tilling cropland.

“We’re in an environment where we don’t want to use tillage (because of) soil conservation,” Sharpe says.

From 2021 to 2023, Sharpe partnered with six farmers around Last Mountain Lake north of Regina for a real-world experiment.

At those six sites, AAFC scientists applied a layer of different materials to a patch of kochia, including black plastic; chaff; and hydro-mulch, a slurry of seeds, mulch and fibre that’s used in erosion control.

The researchers also mowed patches of kochia.

They did the experiment over three years and tracked the effectiveness of the different treatments.

The plastic mulch performed the best, providing 100 per cent control. However, spreading a layer of plastic on cropland isn’t a great idea.

However, the chaff was also effective. The level of control was 44-95 per cent, with higher levels in the first year of the study.

“The chaff treatment … we used whatever was in the field. We tried to get it six centimetres in depth,” Sharpe said.

“I’m very excited about this because chaff and straw is something that every farmer is going to have.”

Mowing was also effective — it controlled 50-95 per cent of the kochia population in the patch. However, it did require three to five cuttings per growing season.

The hydro-mulch was less effective.

Following his presentation, an audience member asked Sharpe about the risks associated with placing a layer of chaff on a patch of kochia. Wouldn’t that transport other weed seeds to the patch?

“Yes…. All the weeds in your field prior to harvest are coming out in the chaff,” he said.

“(But) if we’re going to seed a (weed) that’s not kochia, that’s OK with me too, just because you’re going to have additional competition in those patches.”

Sharpe’s research on “artificial” burial of kochia seeds is not yet published. At this writing he’s editing the paper and expected to submit it for publication early this year.

The post Get your kochia under control — by burying it appeared first on Grainews.

One of its strongest proponents is Josh Lade, a transplanted Aussie who’s been farming at Osler, Sask. since he moved to Canada in 2009.

Lade’s farm is all-in on a combine attachment called the Seed Terminator, on which he’s spent $400,000 over the past seven years to make sure the implement is utilized on every acre.

The Seed Terminator is an impact mill that churns weed seeds into innocuous chaff that’s blown out the back of the combine. Research has shown it, as well as other harvest weed seed control devices such as the Harrington Seed Destructor, Weed Hog and Redekop Seed Control Unit, can destroy up to 90 per cent of weed seeds.

READ MORE: What the weed seed smasher survey says

The Seed Terminator helps control weed populations by slashing the number of weed seeds going into the seed bank. Lade says it also prevents harvested weed seeds from being spread all over a field, which typically happens during combining.

In an interview with Grainews, Lade noted while farmers frequently use multiple tools and strategies to try and disrupt weeds cycles in their fields, “the reality is there’s always some weeds present at harvest.

“Those weeds at harvest time have survived all the agronomic practices that we’ve thrown at them and are the fittest weeds of the year,” he says.

“If you put them through the combine and spread the seeds back out over 40 feet, you’re just rewarding the survivors,” Lade adds. “With the Seed Terminator, we are stopping the combine from moving those weeds up and down the field.”

Return on investment

Lade, who spoke about the benefits of the Seed Terminator at the CropConnect conference in Winnipeg in February, estimates it costs about $120,000 to purchase.

Lade says his farm’s $400,000 investment in Seed Terminators has paid off in a number of respects. He pegged the overall return on the technology investment in the past four years at three to one, meaning it has paid for itself three times over.

The farm is less reliant on herbicides now, helping to produce costs savings associated the Seed Terminator that run at around $20 per acre, according to Lade. He estimates the cost for the Seed Terminator itself (for maintenance, repairs, et cetera) is about $5 per acre, making the net cost saving $15 per acre.

“We’ve been able to really cut back on double spraying our canola. To me, spraying your canola twice has been a bit of an industry standard, but we’ve found we can get away with just one spray at the higher rates and be done with it. There are definite savings on eliminating a sprayer pass,” he says.

He notes the farm’s move to Seed Terminators has enabled it to steer away from using some more expensive chemicals, and the reduced dependency on herbicides has also led to yield bumps in some crops that don’t tolerate certain chemicals that well.

“We’re not often spraying for wild oats or grasses in our cereal crops, for example, because it can be quite expensive and it can also have quite a metabolizing effect since you’re trying to kill a grass weed in a grass crop,” Lade says.

Lade doesn’t view harvest weed seed control technology such as the Seed Terminator as a replacement for herbicides, but rather as a complementary weed control partner.

“Residual herbicides are awesome at reducing pressures, but we still do need some in-crop sprays to try and get the escapees. That’s one spot where we’re cutting back, because I hate driving on the crop, I hate spraying my crop, but I know some weeds are present. Hence, we’ll use the Seed Terminator to just make sure that problem is not getting any worse,” he said.

“I just see the Seed Terminator as another herbicide mode of action. It’s not perfect. It’s got its flaws but a lot of chemicals do too. It’s really just that backstop. It’s there to keep in check anything that’s gotten through everything we’ve done all year to control weeds.”

Tips for potential buyers

Lade offers some suggestions for fellow Prairie farmers who might be considering purchasing a Seed Terminator.

One is to be mindful that the Seed Terminator, not unlike other combine attachments, requires additional horsepower.

“You need to make sure that you are not maxed out on your combine capacity,” he says. “If you are looking to get into this technology, it’s possible you might need a combine that’s a class size bigger than what you’re currently using.

“That’s because of the extra power that’s going to be used by these mills. They take 50, 60, 70 horsepower to run. So one thing I’d want to keep in mind is make sure you’ve got enough horsepower.”

Another important point to remember, he says, is that the Seed Terminator is best suited for chewing up dry — not green — material.

“Don’t think that you’re just going to be able to go and mill down all the green material. At the end of the day, it is a multi-stage hammer mill that works best on dry materials,” he says.

“Certainly, you can certainly take in a percentage of green material with it. What I find is as long as 75 per cent of the material going into the combine is dry, then the Seed Terminator can handle a fair amount of the green stuff. But just make sure that the majority of it is nice and dry and do proper burn downs to kill those green weeds, if there are lots of them.”

The post A Saskatchewan farmer is combining weed control with harvest appeared first on Grainews.

This advice came from Dr. Drew Lyon of Washington State University during his presentation at the Manitoba Agronomists’ Conference in December.

While Lyon’s discussion primarily focused on integrated weed management (IWM) in dryland wheat production systems in the Pacific Northwest, the strategies he discussed are equally relevant to Canadian farmers.

He zeroed in on three major principles of IWM: preventing weed problems before they start, choking out weeds and keeping weeds off balance.

Preventing problems before they start

Lyon highlighted the importance of clean seed and outlined strategies for avoiding the introduction of unwanted seeds. 

“You want to tarp grain loads going down the road,” Lyon advises. “A lot of weed infestations start along roadsides because the weed seeds sift to the top of the grain truck and then blow out and get started along roadsides.”

He also suggests cutting or removing weeds before they set seed. And for farmers using livestock manure, he recommends composting it thoroughly to kill any weed seeds.

While herbicide resistance was first discovered in the 1950s in the U.S., the problem escalated more quickly on fields in Australia, and as a result, farmers there have become leaders in the battle against herbicide resistance. In the early 2010s, Australians introduced the concept of harvest weed seed control.

When they looked at wheat harvests, they noticed weeds that developed resistance were rewarded by being spread throughout the field from the back of the combine. Harvest weed seed control attempts to address this issue.

“They started off with narrow windrow burning, which was highly effective but had issues with fire escaping and smoke-related health problems, so that approach has been slowing down,” Lyon says.

The industry is now shifting toward integrated impact mill systems, also known as weed seed destructors. These systems destroy a significant percentage of the seeds passing through the combine without leaving residue that needs to be burned or baled. But they are expensive.

Another issue is that the mature seed has to be in the head at the time of harvest; if it shatters out before that, the seeds are not going to go through the mill. But Lyon notes a suggestion from Australian weed specialist Michael Walsh — that if at least 30 per cent of the seed remains in the head at harvest, the process can still make headway.

Wild oats come pretty close to reaching, and sometimes exceed, that 30 per cent shatter threshold. But even though wild oats aren’t the ideal candidate for impact mills, Lyon points out that destroying some of the seed is better than nothing.

“Over time, the less viable seed you put in the seed bank, the less you have to deal with,” he says.

Choking out weeds

When he says farmers need to choke out weeds, Lyon essentially means they need to grow a crop that out-competes the weeds.

“I’ve put out hundreds of herbicide trials in my 30-plus-year career. And herbicides always look better in a good stand of a crop than they look in a poor stand,” he explains. “Herbicides rely on crop competition.”

Prior to the introduction of very effective herbicides, this method was one of the principal strategies for weed control.

“I think we need to get back to looking at doing everything we can to grow a good, competitive crop and getting it out of the ground as quickly as possible,” he says. “A lot of competition occurs early, so the quicker you can get your crop out of the ground and growing and competing, the better.”

He advises using quality seed that emerges early and competes better early on. He also suggests narrowing row spacing to get shading more quickly.

“In my mind, this is one of your best weed control strategies you have, even if you’re using herbicides.”

Keeping weeds off balance

Don’t give weeds an opportunity to adapt.

“The idea here is, don’t keep doing the same thing over and over again,” Lyon says. “Don’t use the same herbicide or herbicide modes of action; don’t use the same crop rotation; and don’t use the same tillage practices over and over again, or you will develop resistance.”

For crop rotations, Lyon recommends selecting crops with varied seeding dates: winter crops, early and late spring crops, and even summer crops — essentially, crops with different life cycles.

One thing the Australians do is work perennial crops into their system.

“They’ll do annual cropping for several cycles, and then they’ll plant a pasture crop for a cycle (three or four years),” Lyon says. “They’re able to drive that weed seed bank down on the weeds that are problematic.”

Farmers in the Pacific Northwest do something similar, he adds. They have a lot of Italian ryegrass problems, and farmers — especially those in low-lying, wetter areas — will plant alfalfa.

“As long as you cut that alfalfa before the Italian ryegrass sets seed, no seed goes into the seed bank for several years, and then you come back and annual-crop it again.”

Lyon also recommends choosing crops with varied competitive abilities and extended rotation cycles to manage weeds. He discussed how the length of time you stay out of a particular crop plays a crucial role in reducing weed populations — and points to a study he did in western Nebraska on jointed goatgrass with some compelling results.

“Jointed goatgrass was a big problem in our winter wheat-fallow production areas in western Nebraska,” he says. “It shares a common genome with wheat, so they can hybridize. Fortunately, most of this seed is sterile and won’t produce a plant, but a low percentage can produce and backcross.”

The results showed excluding wheat from the rotation for one year, similar to a winter wheat-fallow situation, would reduce the weed seed bank by about 15 per cent, leaving around 85 per cent of the seed still viable.

However, if the break extends to two or three years, it can reduce the seed bank to about 35 per cent, and after three years, less than 10 per cent of the seed would remain viable.

“This is true of a lot of annual grasses, which is why a crop rotation can be quite effective if you can stay out and prevent new weed seeds from being produced for two, three or four years,” he said. “You can drive down the seed bank fairly quickly.”

Another way to keep weeds off balance is to rotate or combine herbicides to get more than one mode of action working against the weeds.

“We’ve tended to throw one mechanism of action at a time at this, and when we burn that one out, then we go to the next one until we burn that one out,” Lyon says. “It’s gotten us to the position where we have fewer and fewer herbicides that now work.”

The same principle can be applied to mechanical control methods. He recommends no-till growers introduce a little tillage every once in a while, and those constantly tilling should introduce some no-till.

“You want to use cultural, mechanical and chemical rotation to keep your weed infestations low,” said Lyon. “The fewer plants you spray with herbicides, the less chance you have of developing herbicide resistance.”

The post Rethinking weed management appeared first on Grainews.

For decades, the pace of discovery of new modes of action — that is, how a herbicide interferes with the plant’s normal functions — was robust. From the 1950s through the 1980s, an average of one new mode of action every two years was registered. Since then, aside from a smattering of new active ingredients, major herbicide innovations have become rare.

Dr. Franck Dayan, a professor in the department of agricultural biology at Colorado State University, pointed to several reasons for the decline, including increasing costs of research and development programs and commercialization. But Dayan, speaking at the Manitoba Agronomists’ Conference in Winnipeg, said one of the biggest reasons for the slowing pace of innovation is hubris.

“For many years, we saw about 100 patents a year. Then, when glyphosate-resistant crops were introduced, that number suddenly dropped,” said Dayan. “We were told that glyphosate would solve all of our problems, so we stopped doing research in that area.”

The good news is, the slowed pace of discovery isn’t because researchers are running out of target sites for herbicides.

While it’s true that much of the low-hanging fruit has been picked, Dayan said scientists are still finding new target sites and new ways to exploit them more effectively.

Researchers are turning to new approaches — strategies that focus on previously overlooked biological pathways or that harness natural processes — to develop more effective herbicide solutions.

Targeting proteins for destruction

One exciting approach comes from a North Carolina company called Oerth Bio, exploring the use of PROTAC (proteolysis targeting chimera) molecules in herbicide development. A PROTAC molecule is a special type of molecule that helps an organism get rid of unwanted or harmful proteins — but they can also be fooled into targeting proteins the plant needs.

Traditional herbicides, Dayan explains, work by attaching to a specific protein in the plant, blocking its function, and killing the plant. Oerth Bio’s method is different: it uses the plant’s own systems to break down the target proteins.

Essentially, researchers identify a protein in the plant to target, then use parts of the PROTAC molecule to guide the plant’s natural protein breakdown system (E3 ligase) to tag the protein for destruction. The ligase attaches a small molecule called ubiquitin to the protein, marking it for destruction by the plant’s proteasome (a cellular “clean-up crew” that breaks down unwanted proteins).

“The beauty of this method is that it uses the plant’s own waste disposal system to remove targeted proteins,” Dayan says.

While Oerth Bio’s research is still in the early stages and not yet available commercially, it shows promise as a new way to target weeds by messing with their biological processes at the protein level.

Disrupting protein-to-protein interactions

Another promising strategy comes from the Israeli company Projini, which is tackling the challenge of what are known as “undruggable proteins.”

An “undruggable protein” refers to a protein in a plant that is difficult to target or affect with herbicide treatments because they lack the binding sites to which herbicides typically bind.

To overcome these challenges, instead of looking to disrupt traditional sites where a single protein completes a task, Projini targets biological processes in plants where two proteins must interact to complete a task.

Dayan pointed to an example where they identified compounds that prevent the two proteins involved in the synthesis of cysteine, a critical amino acid, from interacting. By disrupting these interactions, it’s possible to block entire biochemical pathways in the plant, preventing the production of critical compounds and ultimately killing the plant.

Doubling down on phosphonates

Another company pushing the envelope in herbicide development is MicroMGX, which focuses on discovering new phosphonates — chemical compounds with strong potential as herbicides. Glufosinate and glyphosate are both derived from naturally occurring phosphonates.

Phosphonates work by mimicking natural substances that plants need and disrupting their ability to process nutrients. For example, glufosinate mimics glutamate, a molecule that affects plant growth by interfering with an enzyme called glutamine synthetase.

To find new phosphonates, MicroMGX looks at the genomes of microbes to identify enzymes involved in producing these natural compounds. By screening a wide range of microbial strains, they’ve pinpointed a gene cluster in Pantoea ananatis, a type of bacteria.

Dayan says the Chicago company was able to retro-engineer this gene cluster, identify the structure of the phosphonate, and figure out how to grow the microbe to produce large amounts of a powerful, natural herbicide called pentafos.

Built-in resistance gene

Along similar lines, Dayan referenced a 2018 study published in Nature that uncovered some intriguing findings. The researchers focused on a compound called aspterric acid, produced by the aspergillus fungus, which has herbicidal properties. The researchers sequenced the fungus’s genome to identify the genes responsible for producing the herbicide compound.

The key point with this study is that, in addition to finding the genes for the herbicide, the researchers discovered another gene that gave the fungus resistance against its own toxic compound, allowing it to protect itself from the herbicide it produces.

“So you basically get a new herbicide and a new resistance target for that herbicide,” Dayan explains.

While these new technologies and approaches have led to a commercially available herbicide, they could become fruitful in the coming decades, and they could provide an abundance of new herbicides. But Dayan said the industry has learned from the overconfidence that surrounded the development of glyphosate-tolerant crops.

“Integrated weed management is still where we need to go,” he said. “If we keep doing the same thing we’ve been doing, we’re going to have the same problems over and over.”

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“I’m not going to say that herbicides don’t work because there are quite a few herbicide options still to manage volunteer canola,” says Charles Geddes, a research scientist for Agriculture and Agri-Food Canada at Lethbridge. “But when we talk about weed management, it’s really all about integrating those herbicide programs with other cultural factors.” 

Geddes speaks from experience: he currently leads the AAFC Weed Ecology and Cropping Systems Research program, which monitors herbicide-resistant weeds across the Prairies. And in the early 2010s, his PhD work at the University of Manitoba was specifically focused on controlling volunteer canola in soybeans. 

Volunteer canola was a big issue at the time — especially in Manitoba, where soybean acres were on the rise because short-season cultivars had emerged that could thrive in the province. The challenge arose because these new soybean varieties, like canola, were genetically modified to be resistant to the same herbicides. 

“Farmers who had already been growing canola were starting to adopt soybeans, and volunteer canola was coming back as a difficult-to-control weed in those soybean crops,” Geddes says. 

As a result, a lot of emphasis was placed on developing strategies to manage the problem — and one of the strategies Geddes looked at was targeting the seed bank. 

“The easiest way to do that is through some form of physical disturbance, whether it’s tillage or harrowing,” he says. 

Anyone who grows canola knows there will be a certain amount of seed loss. Whether it’s seed being lost ahead of the combine, at the header, or being blown out of the back of the combine because of the way the combine is set, some seed loss is to be expected. 

Geddes notes surveys on the Prairies revealed seed losses of up to 5,000 seeds per square metre. Canola seeds have a unique ability to enter ‘secondary dormancy’ under the right conditions, such as warmer temperatures and dry soil. This dormancy allows the seeds to persist longer in the soil seed bank. 

“We can typically see volunteer canola sticking around for at least two to three years,” he says. 

Fall harrowing 

So, beginning in 2013, Geddes, along with his research partner and study co-author Rob Gulden, set up research plots across southern Manitoba, at Carman, Howden and Melita, to test the effectiveness of soil disturbance on the volunteer canola seed bank. 

They studied how both the timing and type of soil disturbance impacted the seed bank. In terms of soil disturbance, they looked at harrowing and tandem disc compared to a zero-till control. In terms of timing, they ran the two soil disturbance methods immediately following harvest, one month after harvest, and the following year, just before spring seeding. 

“What we found was that if you can disturb that soil as soon after canola harvest as possible, it goes a long way to helping to deplete the seed bank going into the next growing season,” Geddes says. 

The research found early soil disturbance enhanced seed-to-soil contact for seeds lost during harvest. With sufficient moisture, the seeds germinated, and winterkill did the rest. The results were a little less pronounced a month after harvest, and negligible pre-seeding. 

The type of soil disturbance didn’t seem to matter. Both methods performed equally well compared with the no-till control.

READ MORE: How to keep last year’s canola out of your beans

“What that means is that even if we’re in more of a no-till or a min-till environment, we can get away with a bit of a lighter disturbance,” said Geddes. “It’s just enough to promote that seed-to-soil contact in the fall.” 

Published in 2017, Geddes’ work was one of the earlier studies to look down these paths for control of volunteer canola in soybeans — but its findings still stand today as farmers continue to grapple with volunteers. 

The changing face of volunteer management 

For the past 20 years, volunteer canola has risen in the rankings of problem weeds. Geddes says recent surveys have placed volunteer canola in the top two or three most abundant weeds in the Prairie provinces. 

“It’s different than some of the other herbicide-resistant weeds because volunteer canola resistance was actually purposefully selected through genetic modification,” he says. And while those genetics have improved weed management in canola production, because its seeds can persist in the soil for so long, they tend to come back to haunt farmers. 

Crop rotation and sequencing 

As a result, Geddes says crop rotation has become a critical tool in volunteer canola management. 

“If we’re growing tight crop rotations that are only two to three years in length, it’s not a surprise that voluntary canola will be one of the more abundant weeds to manage,” he says. “So having enough of those crops between canola rotations to manage those volunteer canola populations is quite important.” 

As mentioned, few, if any, farmers think chemistry alone will help them control volunteer canola. 

“With a herbicide-only program, combined with short or non-diverse rotations, it’s pretty difficult to keep the issue under control,” Geddes says. “If they are practicing tight rotations, they quickly learn that the issue can show up, and you really do need those break crops in there to manage it effectively.” 

The order in which to plant rotations is also important. For example, with voluntary canola being particularly difficult to manage in soybeans, it would make sense to put a cereal between canola and soybean crops, so you have at least a one-year break. 

“Those volunteers will be reduced going into your soybean crop already, because you’ve had enough time since your last canola crop.” 

Crowd it out 

Because canola was bred to be a relatively competitive crop, voluntary canola acts as a relatively competitive weed. So, in terms of cultural weed management, it makes the most sense to apply those strategies early in the growing season. 

“It does get up and out of the ground quickly,” Geddes says. “So it’s really that early season they want to target to get as competitive a crop as early as possible.” 

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“I think the best management practice that someone could do for weed resistance is the one you’re not currently doing on your farm,” says Rory Cranston, technical strategy lead with Bayer. “Weeds figure out habits. They don’t figure out different system approaches.”

Cranston spoke on a panel about herbicide-resistant weed management at the Bayer CropScience booth during July’s Ag in Motion show at Langham, Sask.

Shaun Sharpe, a weed ecology research scientist with Agriculture and Agri-Food Canada (AAFC), who was also on the panel, said afterward that using novel approaches to weed management doesn’t mean throwing the baby out with the bathwater.

Chemical control is the backbone of weed management strategies, he says, but the backbone is breaking — and farmers will have to adapt.

In conventional terms, spraying is timed to optimize yield, which seems like sound logic. The problem is that weeds that emerge later are often ignored because they don’t affect yield.

“Conventionally, we’ve just been leaving those alone. But, of course, those weeds produce seeds that go back into the seed bank,” Sharpe says. “Something like wild oat that emerges later has more potential to grow and produce seeds later in the season.”

The pillars of any weed management strategy are chemical control (herbicides), cultural control (crop rotation, cover crops), mechanical control (mowing, hand weeding) and, to a lesser extent, biological control.

Sharpe says farmers should focus on cultural strategies to reduce weed populations.

“We want to get canopy closure quickly, and we want to have a very competitive crop. So we want to pick crops that are going to be competitive against weeds, and we want to plant them in a way that we’re going to get good canopy coverage quickly.”

Those strategies could include higher seeding rates, using cover crops or introducing intercropping.

While none of these techniques are new, Sharpe says there is more interest in intercropping as a weed control method.

“When I was at AIM, I spent a lot of time at the intercropping plots for AAFC. I found that there is a lot of good feedback from the growers. They’re interested in how you seed it, how you harvest it, whether you can spray anything in it, and how it does against disease and weeds.”

AAFC is focusing on intercropping as a management strategy to combat herbicide resistance.

“I think that that system is going to grow. It’s just going to take some time, because it’s a new way to farm for a lot of folks who are doing monocultures,” Sharpe says.

“There’s still a lot of agronomic questions to answer, but I think it does have a lot of potential, and there was definitely a lot of interest from farmers.”

One thing is certain, he says: no one is under the illusion that herbicide chemistries will be the saviour of agriculture as they once were.

“With herbicide resistance, we’re not going to spray our way out of it. That’s been the message for a few years now.”

Emerging technologies are helping farmers be more efficient with spraying. Targeted use of chemicals can extend their effectiveness and prevent emergence of herbicide resistance.

Optical spot sprayers are one tool in the fight. Boom-mounted cameras can detect a weed and spray it. The sprayers have been around for a while and the technology has recently been adapted for spray drones.

One company is taking the precision spraying concept beyond the seek-and-destroy approach of optical spot sprayers. Geco Agriculture’s predictive weed control system promises to pinpoint the location of weeds before they emerge.

It will even predict patches of herbicide-resistant weeds and it’s relatively inexpensive.

“They don’t need any new equipment, and they don’t need to adopt any new practices on the farm,” Geco Agriculture CEO and founder Greg Stewart says. “Really, what they’re buying from us is the analysis.”

The company pulls farm data (crop rotations, spraying records, et cetera) from the past five years and sources imagery data from satellite providers.

In recent years, LiDAR (light detection and radar) and NDVI (normalized difference vegetative index) technology have exploded in terms of accuracy and scope, and they’re having a massive impact on agriculture.

But despite the resolution these satellite images can provide, it’s the scope rather than individual images that interests Stewart.

“What we really do is take a step back and try to understand how the weed population is evolving dynamically over several months and then over several years,” he said.

“You can get somewhere between two and four satellite images per week, depending a bit on cloud cover. We’re actually trying to leverage all of that data.”

New tools to bear

With crop and spraying data collected from the farm, combined with the satellite data, Geco runs an analysis that produces several tools to manage weed pressure.

The first one is a five-year history of weeds in the field. An analysis produced today would go back to 2019 and indicate what weed patches looked like in each of those years, whether they’re getting better or worse, and the crops in which they appeared.

The next tool is a map that shows areas of potential herbicide-resistant weed patches in the field.

Stewart said farmers can use this as a preliminary indicator of potential resistance areas before the patches reach the size at which humans typically detect them.

The third tool is a prediction model, which estimates where the weeds will be in the coming season. The predictions aren’t infallible, but Geco has been conducting tests at a research farm run by the Winnipeg-based agricultural tech accelerator EMILI (Enterprise Machine Intelligence and Learning Initiative), and their predictions are close to the mark.

“Last year, we made predictions for 2024. We were usually in around the 90 per cent hit rate using the prediction,” Stewart says.

The final tool is a prescription map.

“The prescription map is just a file that a farmer will typically upload into their sprayer or granular applicator,” Stewart says.

“They’ll use the map to direct these actions towards the weediest hotspots, which will allow them to beat down the weeds before the season comes on.”

Ability to spray more efficiently will lower input costs.

“All of a sudden, it makes that more economically digestible to a farm and they may be willing to incorporate that into the rest of their weed protection program. So, you get an affordable way of introducing this mode of action into your strategy, and you get to focus it on where the weeds are the worst.”

Over time, “mother patches” of weeds reveal themselves.

“These mother patches of weeds that are out there tend to be your worst actors, and they will tend to donate weed seeds to the rest of the field. So, if you are able to start suppressing them, you can suppress weed emergence more generally, throughout the field,” Stewart said.

That’s just the chemical side of things. Geco’s predictive weed control system can also contribute on the cultural side of weed management.

“We’re getting people who are inputting our prescriptions into a seed drill,” said Stewart. “So what they’ll do is up the rate of seeding into the areas that are predicted to be the weediest, and that gives you some crop competition to fight the weeds. It’s just another tool in the toolbox.”

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Throughout the growing season, as interesting plants pop up in ditches, fields and pastures, I get texts, tweets and messages with photos of mystery plants from friends requesting identification. “Is this a good plant? Is it a weed? Does it grow here often? Is it toxic?”

My interest in plant identification started young with my mom, a former ag rep and agrologist, who is the original plant ID matriarch of the family.

As a kid, I remember neighbours and even strangers dropping by with puzzling plants for her to look at. I learned from her that the right plants can add beauty and bucks, but the wrong ones can cost you money and a lot of grief.

When I got older, I gravitated toward summer jobs that leveled up my weed, forage and rangeland plant identification. I quickly learned there are a lot of identity-obsessed plant experts, and I’m fortunate to have an inner circle of plant gurus to lean on for more information.

Whether a plant is welcome or not will differ according to region, soil type and goals; what might be a preferred plant on one farm is a weed on another.

Farmers and ranchers spend a lot more time identifying plants than perhaps they realize. Plants provide us with many clues about what is happening on our land. For example, we use weed identification in our annual crops to determine potential problems, including herbicide resistance. Being aware of common weeds helps us decide which crop protection products to use.

The threat of invasive weeds has many farmers vigilant and on the lookout for infestations of leafy spurge, toadflax or scentless chamomile. Risks like the movement of feed, the use of equipment between “contaminated” sites and clean fields, and industrial development and construction can all lead to a productivity-sucking invasion. In this sense, accurate plant identification can be the difference between swift eradication and a costly, multi-generational fight against invasive weeds.

Of course, there are plenty of good plants to take note of, too. For example, some plants only grow in moist habitats and their presence can indicate pockets of sub-irrigation, making them helpful in deciding where to potentially source a new well or dugout. These riparian plants can also filter out sediment and nutrients, helping to improve standing water quality.

Plants are also a part of our culture, and we look to them to signal the beginning or end of seasons. The familiar ritual of seeking out a prairie crocus confirms the arrival of spring; the ripening of saskatoon berries is a summertime staple; and the turning of leaves on a dogwood or Manitoba maple is a beacon of colder weather.

My favourite group of plants are those that are native to our Prairie grasslands. These plants have spent the past 10,000 years (give or take) adapting to be resilient against whatever disturbance is thrown at them.

Range plants each occupy a different, valuable niche on the landscape. In addition to providing benefits such as forage, carbon sequestration and biodiversity, many range plants fix nitrogen, like one of our many native milkvetch species.

Other species, such as creeping juniper, reduce hillside erosion. Shrubs such as buckbrush and silver sagebrush help trap snow and provide habitat for songbirds. Winterfat, a beloved prairie shrub, looks similar to sagebrush but lacks the smell. It’s known as the “ice cream” species because it’s preferred by both livestock and wildlife, and its robust presence can be an indicator of a healthy prairie pasture.

There are several regional plant ID books and you can also find answers to plant questions at your local extension office. There is also a wonderful website that helpfully categorizes wildflowers according to colour.

The next time you see a plant that piques your interest, ask yourself why it might be there. What are our plants telling us about our environment?

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