[Podcast] The Big Picture of Glyphosate Resistance in The U.S. and The United Kingdom

“There is a lot of change in agriculture and those changes are changing the nature of weeds and how we handle weed management. But this is ultimately a really exciting time.”
— John Cussans, Weed Biology and Management Specialist, ADAS, United Kingdom

In today’s episode of the podcast, brought to you by Sound Agriculture, listen to a conversation with John Cussans, a UK based weed biology and management specialist with an organization called ADAS. Cussans addresses multiple confirmed cases of glyphosate resistance in the United Kingdom and how these cases differ and relate to confirmed cases of glyphosate resistance in the United States, as well as what role cover crops can play in cases of glyphosate resistance.

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Full Transcript

Mackane Vogel:

Welcome to the Cover Crop Strategies Podcast, brought to you by Sound Agriculture. I'm Mackane Vogel, associate Editor of Cover Crop Strategies. In today's episode, listen to a conversation with John Cousins, a UK-based weed biology and management specialist with an organization called ADAS. Cousins addresses multiple confirmed cases of glyphosate resistance in the United Kingdom and how these cases differ and relate to confirmed cases of glyphosate resistance in the United States, as well as what role cover crops can play in cases of glyphosate resistance.

John, thanks for for joining, but tell us a little bit about, you know, who you are, your background in agriculture, and I always like to start these conversations with you telling us about how you first got into agriculture, whether it's a family thing or something you just found your way to, what's, what's kind of your agriculture origin story?

John Cousins:

Oh, good question. Yeah, so I, I'm John Cousins and I work for an organization in the UK called ADAS. So ADAS was the, in the public sector, it was the extension service that the government ran. But, um, way back in the eighties, um, the government decided they weren't gonna be involved in the commercial activities on farms. So ADAS was privatized, and I've worked in, in weeds and weed science, um, since the eighties actually. My first job was at a place called Rothamsted Research, which is a big agricultural institute in the UK, and I've been in various roles, but right now, um, I've moved to ADAS. Um, I've got a team, a young team, so it's a really exciting time, um, as I'm sure we'll talk about later. There's a lot of change in agriculture, and that change is changing the nature of the weeds that we're trying to manage, and then the nature of weed management.

There are new challenges and there are also new opportunities. So it's, it's a really exciting time. In, in terms of how I got into agriculture, like I think so many people, it was entirely by accident. My dad actually randomly worked in weed science. I mean, you know, we're talking about in the fifties and the, the sixties. Um, and I really never had any interest in it at all. And then an opportunity arose and I just think it's, it's, uh, you know, working on weeds and weed management is the most, it's the most amazing job. The industry is a incredible industry. Um, farming, like it is all around the world, is filled with people who are, you know, innovators and forward thinkers.

Um, but they're also incredibly self-sufficient, you know, and that is a really fantastic combination. So you've got really incredible people you're working with, a real challenge, and you feel that you can contribute something, um, to people choosing sustainable paths for their, for their agriculture. And of course, we all love being in agriculture because agriculture is food and, you know, people do like to eat. So yeah, that, I mean, that's kind of how I've arrived here is entirely by random and random forces, and here we are.

Mackane Vogel:

I love that. Yeah, I think you're, you're spot on when you talk about sort of, um, especially, I mean, farmers in general are very creative people, but I think, um, I think when it comes to weed suppression, weed management, it really is, uh, something you have to think outside of the box with. And we're seeing that more and more as, um, as time progresses. And so, uh, that's a good segue into kind of the main discussion we're gonna have today about, uh, glyphosate resistance. So this, this topic came up based on an article that, that was talking about the first case of glyphosate resistance confirmed on a UK farm.

And so, uh, I want to talk a little bit about, I, I, you know, I think majority of our listeners are based in, in the US or Canada or North America. And so I think it'd be interesting to, to hear from you kind of the differences between what's going on in the UK with glyphosate resistance and what we're dealing with, um, in the US. So what, what can you tell us about this first case of, of, uh, glyphosate resistance being confirmed in the, in the UK?

John Cousins:

Yeah, so I mean, a almost live update, we have actually been working on three other, um, locations, and we, whilst we can't call 'em cases yet, 'cause there's a little bit more work to do, we, we think that we have one confirmed case and we now have three other farms where we've got real concerns about glyphosate tolerance in, all in Italian ryegrass. Um, so lolium multiflorum is our, one of our key arable weeds and it's massively consequential, uh, in the UK. So we, although we don't have GM herbicide tolerant crops, or we have, we've got some conventionally bred tolerance in two ALS herbicides in break crops, but we don't have GM herbicide tolerant crops. And, and that, I think, I think it's fair to say that where the GM herbicide tolerant crops been adopted, there's a little bit more glyphosate resistance or, or glyphosate resistance tends to come associated with that pattern of use.

But what we are seeing is a real shift towards reduced cultivation intensity and frequency, um, more cropping diversity, and, and people really trying to find a different way of farming, which I think comes under this umbrella of regenerative agriculture, um, which is kind of global concept, but applied differently in different places. Um, but in the UK we've got challenges around that. Our farm size is tiny compared to, I guess in the US. Uh, that means biosecurity is massive. Where you've got a problem on one farm, you're talking about kind of 10 hectare fields together, farms down sub-thousand hectares sometimes. You've got a massively productive agricultural environment. So our winter wheat, our autumn-sown wheats average, and you can imagine the average includes some fairly horrible crops. Average is nearly eight tons a hectare, but on farm it can be 10, can be 12, you know, spot yields higher than that.

And that really productive environment creates a really, a real challenge for weed management, 'cause obviously a, a failure of weed management in one year, massive seed returning of a problem in the next year. And although we don't have GM herbicide tolerant crops, which create that pressure, we are only one deep in non-selective herbicides. So we only have glyphosate authorized. We don't have glufosinate, we don't have diquat or paraquat or, or other total non-selective. So it's a real challenge. You can see how the selection scenario has changed around that reduction in mechanical weeding, reduction in inversion cultivation, but also secondary cultivations' reduction in alternatives. So now we're only glyphosate deep. Lots more crops, lots more trying to switch between different vegetation, cover crops, perhaps having an issue around sheltering weeds lower down against glyphosate. So it's a really challenging environment, and I think we all understand how we've got here. We just really wanna focus on sustainable use of glyphosate, facilitating people to make that change towards regenerative agriculture and supporting them while they're doing it.

Mackane Vogel:

Yeah. And, and to build off that, I, I'm also curious to hear you talk a little bit more about the, the specific climate that you guys are working in and what sort of, uh, role the, the weather patterns in that region are playing in, in this whole picture.

John Cousins:

Yeah, so our average rainfall, uh, will be about 500 and maybe 600 mils of rain. Most of our crops, so we have a very maritime climate, influenced obviously tiny islands stuck out in the Atlantic, sandwiched between the Atlantic and English Channel, and then the continent. A lot of rainfall, a lot of rainfall intensity. Um, soil moisture conservation is not an issue for UK farmers, but, um, working windows where, where you can travel, that's a real issue. So most of our cropping and certainly most of our productive cropping would be drilled in the, in our autumn, which would be kind of September, October, and grow through until the summer in August. There's a certain amount of spring cropping, um, particularly for break cropping, um, established around about now. So maybe February, March, a little bit later sometimes. But most of our productive cropping, taking advantage of all that rainfall, good soils.

So we're obviously, we were a glacial zone, so we have a lot of clays. We have a lot of really young soils, which obviously also bring, bring productive agriculture. And yeah, I mean, the, the world record for wheat production was obtained by a guy in the UK in, in Lincolnshire. It was over 14 tons. So yeah, it's a, it's a massively productive environment, and that means for weeds as a sort of, it's a truism that the more productive a crop is, the more productive the weed is. And that rate at which weed populations can accelerate is a real characteristic of our environment. So some work was done by an old colleague of mine called Steve Moss, um, some very early work on modeling population dynamics. In a non-plow system, to stand still for black grass, which is our major grass weed, you need 96% control in every crop. So that kind of tells you what the seed return potential and the potential rate of increase of grass weed populations is.

Mackane Vogel:

Yeah, that's, um, that's a big number for sure. And I, I think it's important too to point out annual ryegrass used as a cover crop in the US, kind of a different ball game than Italian ryegrass. What is it, uh, what is it about Italian ryegrass that has kind of maybe a higher risk of herbicide resistance?

John Cousins:

I mean, I think, so yeah, so we're lolium multiflorum, which is annual ryegrass. We do use perennial ryegrass a lot in, I, I guess as you do in fertility building phases, in environment schemes and so on. Italian ryegrass is, it's not the annual ryegrass which occurs in Australia, or no, there's a lot of glyphosate resistance. It's a kind of, as the name implies, pretty European arable weed. It does seem to be particularly prone to developing herbicide resistance at a very high rate. So we, aside from the glyphosate, when we look at in-crop selective herbicides, so we have our group ones and group twos as, as everyone does, but you know, it's a lot easier now what, now that Europeans aren't using the letters and the Americans are using numbers. We've actually, it's one of the few things where we've agreed to agree on something.

Mackane Vogel:

(laughs) Right.

John Cousins:

Um, yeah, so we have a lot of group ones, group twos. We have a lot of herbicide resistance to in-crop herbicides. And that's developed a lot faster in ryegrass than it, than it has in other grass weeds. We have, uh, resistance to flufenacet. So flufenacet would be our key North European, um, residual herbicide grass weeds, probably, I mean, we've overused it. So a few years ago, 60% of all, when cereal crops have flufenacet applied, quite a lot of it more than once. So yeah, but we've developed herbicide resistance in a residual herbicide, which is something you think, you know, you are in the end game when you're starting to develop resistance to residual herbicides. And now with glyphosate, we see issues with Italian ryegrass where we don't see the same problem with blackgrass, alopecurus, which will be our most widespread weed. We don't see the same problem in our brome species or wild oats or it, it really does seem that Italian ryegrass has this disproportionate propensity to develop herbicide resistance.

As to why that is, you know, all projects end with a requirement for more funding. That's where we'll, we'll finish, but I think one of the things that we're seeing with, as we begin to look a little bit more at ryegrass is just how incredibly genetically diverse the background is. So we have all sorts of types, we have all sorts of different levels of dormancy and germination patterns. We see differences in vernalization requirement in wild populations. So there's this massive genetic diversity and there's almost a kind of, a soup of lolium genetics in the landscape, 'cause we've got perennial, uh, you know, when living in the landscape, we've got lolium, we've got a certain amount of use of lolium multiflorum as a forage crop, and it's just the super genetics. And I think that gives you the raw ingredients to, to go on and select for herbicide resistance.

Mackane Vogel:

We'll come back to the episode in a moment, but first I'd like to thank our sponsor, Sound Agriculture, for supporting today's podcast. Did you know you can build a water and nutrient superhighway in your soil? You just need the Maximum Maker solution from Sound Agriculture, the easiest way to maximize your crop's access to nutrients all season long. First, source turns your soil into a nutrient factory, then Blueprint builds the delivery network by expanding the crop's reach beyond the roots. For the Maximum Maker solution that provides bigger or healthier crops, source it with Blueprint. Talk to your dealer or visit Sound.ag. And now let's get back to the discussion with John Cousins.

You touched on this earlier, but I wanna unpack it a little bit more just about how, you know, glyphosate resistance in the UK versus the US, it's kind of a bigger deal in, in Europe because the cropping systems are so different, and for other reasons. But I, I think that is an important part to, to really focus on. And, and so if you could talk a little more about just how different these cropping systems are and in what way?

John Cousins:

Yeah, so I mean the, the production, the productivity is a big issue. Um, we're very much dominated by, by, we have been historically dominated by winter cropping. So going from crop to crop with very little break between the crops, but actually we're seeing is adoption of conservation agriculture, regenerative agriculture, diversifying the rotation. Alongside the lack of mechanical weeding, we, we're seeing long periods between crops, maybe as a switch from winter crop into a spring crop, or you use a, um, like an environment scheme to support pollinators or create bird food over winter. You create these habitats almost outside of the productive crop where we're not trying to control the weed at all. And then you try and revert into maybe a late spring drill crop or maybe after a year, go back into a productive winter crop with no mechanical weeding, only glyphosate and a low disturbance drill.

And it's that kind of cocktail of, you know, you can imagine over winter, if you can grow a winter wheat crop that gives you 10, 12 tons of hectare, you imagine the vegetation you're developing on the stubble with natural regeneration and, and maybe a few cover crop species in there. Creates a real massive challenge 'cause you're trying to put the handbrake on and go from that back into a winter wheat crop. We don't want any of that vegetation. So I think we, I, i, I believe, and I suspect you, you do, and, and your listeners probably do that adoption of regenerative agriculture in the long term is gonna give you benefits for weed management, 'cause you've got your diversity, you're breaking weed life cycles and you are reducing your reliance on pesticides.

You're really thinking holistically about cropping systems and maybe being a little bit more adaptive and thinking more outside the box in terms of how you go from crop to crop and, and how your system looks. But in the short term, to make the transition, we really, really, really need the glyphosate to make those abrupt changes. And that's where the pressure is. So we're really talking about a transition, talking about not, you know, really being clear and saying that finding glyphosate resistance in the UK is not a barrier to adopting regenerative agriculture. But if we're gonna see that transition, my god, it's gotta be associated with a real focus on glyphosate.

Mackane Vogel:

Yeah. So to clarify, I mean, I guess what you're getting at is that farms that maybe adopted regenerative agricultural practices long ago might in a better position to be able to handle this now.

John Cousins:

Yeah, I, I think so. It, it is very much in the transition we're that we're seeing a problem. Um, maybe not adopting all the different elements, but kind of, you know, maybe losing the mechanical weeding, cultivation, you know, um, you say cultivation, I say mechanical weeding, but losing that element and maybe not thinking about all the, all the other tools and elements in regenerative agriculture, um, which do tend to come along as the system matures. So yeah, it, it, I know we'll get bored of the transition narrative, you know, we'll, it's like people, everyone wants, seems to, seems to want to be on a journey these days. But it really is in that, those first steps into a system that we really need to focus, I think.

Mackane Vogel:

So with that, you kind of mentioned that while that is true, it shouldn't necessarily discourage you from making that transition now if, if you're still thinking about it. I guess for somebody listening who's maybe thinking, you know, they're ready to start implementing cover crops or, or stop tillage or reduce tillage, what's, um, what's something that you think, you know, maybe a word of advice of why it's still a good idea, even though we've got things like glyphosate resistance occurring more often?

John Cousins:

I mean, I think the, you see, you see it as a package. So you've got your crop diversity and your, you know, you are reducing your cultivation intensity and maybe you've got low disturbance drilling. You know, leaving weed seeds on a surface is a positive because you are feeding other trophic groups in farmland. You know, you don't necessarily want to bury all these weed seeds and create a long-term seed bank. You really wanna manage them then and there. The crop diversity in and of itself, you are breaking life cycles. So we've got, we had a system dominated by winter cropping. We had a weed floor dominated by winter annuals. It's just that the crops select the weeds, and the more you're breaking up the life cycles of problematic weeds with later-drilled spring crops, break crops alongside cereal crops, you know, or nitrogen-fixing crops with lower inputs, the more you are disrupting and breaking up those life cycles and changing the niches for weeds, the more balanced the system is for, in terms of weed management in the long term.

But that's not to say that transition isn't really challenging, requires more management. That's what we're seeing, requires a higher level of technical ability. So, but yeah, we don't want to discourage that, because that's, that's where we wanna be, I think as an industry and also the public want that. It's a big part of public policy in the UK as it is right across Europe. So it's important that we get the messaging right, that people don't hear the headline and they're discouraged, but we talk, talk about exactly what we're seeing, where we're seeing it, and what the real implications are.

Mackane Vogel:

Absolutely. Yeah. I, I couldn't agree more. And I think our, our audience is, is, you know, if you're, if you've made it this far listening to the Cover Crop Strategies podcast, you probably know that you're, uh, in agreement with that sentiment. So I guess to, to kind of wrap up this, this preliminary discussion, you mentioned at the beginning that, you know, there could be a couple more cases that you guys are looking at. I guess talk a little bit about, you know, where the research is headed and, and what kind of and next steps might be, uh, ahead in the, in the coming months.

John Cousins:

Yeah, so, um, it's important to say, um, whilst it, the locations probably won't mean anything to, to listeners outside the UK, but what we're we're seeing is populations completely independently. So we have a, the first population was in the county of Kent, which is right down in the south in the UK. We're following up on three other populations. One is in Essex, which is kind of right to the east of London. One is in North Yorkshire, which is much further north up the center of the country, and one is in Somerset over to the west. So they're all being selected for in situ independently, which is a real theme of herbicide resistance. Everyone worries about seed spreading, but what they need to worry about is their own practice in their own fields. So we're seeing that right now as people begin to drill spring crops.

So we've seen drillings going into a spring crop, um, in a no-till system is one of the places where the resistance is most visual, let's put it that way. Um, so we're running some free glyphosate resistance testing, a kind of plant-based rapid turnaround testing supported by Bayer Crop Science, I have to say. And they've been really supportive in, in, um, as I know they are globally around glyphosate sustainability and glyphosate use. So there'll be some live updates. Uh, we have a weed resistance action group in the UK and a, globally, there's a herbicide resistance action group. There's a European herbicide resistance actually. But in the UK, we have something called RAG. Um, we're reporting back, um, as soon as we see these samples, we'll report back on a summary of all the samples that we test in the spring. Um, I mean obviously there's research going on in the background trying to look at mitigation.

Can we use tank mixing with alternative modes of action, um, in extremis? Where we've got confirmed resistance, can we look at modes of action? Will that give us a bit of a, a clue as to how we can mitigate the problem where it occurs? And really, resistance management is weed management. So key plank of sustainable use of glyphosate has nothing to do with glyphosate. It's seed capture tools. Can we adopt those? It's thinking about non-chemical control in crop and out of the crop. Can we have inter-row hoeing on the scale that we need for broad acre crops? Um, do we need to think about targeted mechanical weeding? Can we use companion cropping to make more competitive crops?

So yeah, we, we, we mustn't lose, become herbicide resistance junkies. It's a symptom, not a cause. You know, glyphosate resistance or herbicide resistance is a symptom of an over-reliance on particular kind of herbicide or a particular family of herbicides. It's not cause of your problem. Your problem is much more deep-rooted than that. And we mustn't lose track of that and stop talking about integrated we management in the round.

Mackane Vogel:

Well, I think that's really well said and an important thing to remember. So, um, obviously this, this isn't the, the end of the discussion, but, uh, we'll, we'll continue to provide updates as, as, uh, they become available and something to, uh, to definitely keep our eye on moving forward into the, uh, into the summertime here. So-

John Cousins:

Absolutely.

Mackane Vogel:

Uh, well, thanks John. And, uh, we'll, uh, like I said, we'll be, be sure to get you back on for an update sometime soon.

John Cousins:

Cool. Really good to talk to you and, uh, yeah, um, we'll, we'll come back and update you. Uh, it'll be fine. Everything will be fine. You know, no one, it's a difficult time in agriculture in the UK more broadly, I dunno if you're-

Mackane Vogel:

Yeah.

John Cousins:

Probably not aware, you know, big, big changes around the change of administration in the UK and that they're making big changes to the way that, um, agriculture is supported. And some of these approaches to support other trophic levels on farmland had been subject to payment support. That all seems to have been suspended. In the UK, we've got into the trap of a lot of farms don't actually make a profit, but that was okay because there was no inheritance tax.

Mackane Vogel:

Right.

John Cousins:

And obviously that's, that's not good. But, you know, a government has taken away the, the 100% inheritance tax rebate, but not fix the problem about farms not making any money. So you can see the wall.

Mackane Vogel:

Yeah.

John Cousins:

You can feel that we're moving at speed, but I can't see the solution yet. So it's a really difficult time, and, and I know that people in the UK are listening. You know, this is not the end of the world, you know, to my certain knowledge, no one has been badly injured as a result of herbicide resistance occurring on their farm.

Mackane Vogel:

Right.

John Cousins:

We can deal with this and we'll do everything we can at ADAS. You can email weeds@adas.co.uk if you've got particular issue. Um, as I said, Bayer has been supporting this free testing work. You can contact Bayer representative, and we'll, we'll be okay.

Mackane Vogel:

Well, as we talked about at the beginning, farmers are, uh, a creative and a resilient bunch. So, uh-

John Cousins:

Absolutely.

Mackane Vogel:

I think the sentiment is absolutely true.

That's it for this episode of the Cover Crop Strategies Podcast. Thanks to today's guest, John Cousins, and thanks as always to our sponsor, Sound Agriculture, for helping to make this podcast possible. A transcript of this episode and our archive of previous podcast episodes are both available at covercropstrategies.com/podcasts. And for our entire staff here at Cover Crop Strategies, I'm Mackane Vogel. Thanks for listening, and have a great day.