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In the latest edition of the No-Till Farmer podcast, brought to you by NewFields Ag, Associate Editor Mackane Vogel talks with John Cussans, a weed biology and weed management specialist with the ADAS — provider of agricultural and environmental consultancy, policy advice, and research and development — based in the U.K. Cussans addresses multiple confirmed cases of glyphosate resistance in the U.K. and how these cases differ and relate to confirmed cases of glyphosate resistance in the U.S., as well as what role cover crops might play in cases of glyphosate resistance.

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Full Transcript

Hello, and welcome to the No-Till Farmer Podcast, brought to you by NewFields Ag. I'm John Dobberstein, senior editor of No-Till Farmer. Today we're going to hear a conversation between associate editor Mackane Vogel and John Cousins, a weed biology and weed management specialist with the crop consultant organization ADAS, based in the UK. Cousins addresses multiple confirmed cases of glyphosate resistance in the UK, and how these cases differ and relate to confirmed cases of glyphosate resistance in the US. As well as what role cover crops might play in cases of glyphosate resistance. Now let's join the conversation.

John, thanks for joining, but tell us a little bit about 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 your agriculture origin story?

Oh, good question. Yeah, I'm John Cousins, and I work for an organization in the UK called ADAS. ADAS was in the public sector, it was the extension service that the government ran. But way back in the 80s, the government decided they weren't going to be involved in the commercial activities on farms, so ADAS was privatized. And I've worked in weeds and weed science since the 80s, actually. My first job was at a place called Rothamsted Research, which is probably a big agricultural institute in the UK. And I've been in various roles.

But right now I've moved to ADAS. I've got a team, a young team. It's a really exciting time, 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 the nature of weed management. There are new challenges and there are also new opportunities, so it's a really exciting time. In terms of how I got into agriculture, like so many people, it was entirely by accident. My dad actually randomly worked in weed science, we're talking about in the 50s and the 60s. And I really never had any interest in it at all. And then an opportunity arose.

And I just think it's working on weeds and weed management is the most amazing job. The industry is an incredible industry. Farming, like it is all around the world, is filled with people who are innovators and forward thinkers, but also incredibly self-sufficient, and that is a really fantastic combination. You've got really incredible people you're working with, a real challenge, and you feel that you can contribute something to people choosing sustainable paths for their agriculture. And of course, we all love being in agriculture because agriculture is food, and people do like to eat. Yeah, that's how I've arrived here is entirely by random and random forces. And here we are.

I love that. Yeah, I think you're spot on when you talk about, especially farmers in general are very creative people. But I think when it comes to weed suppression, weed management, it really is something you have to think outside of the box with. And we're seeing that more and more as time progresses. That's a good segue into the main discussion we're going to have today about glyphosate resistance. This topic came up based on an article that was talking about the first case of glyphosate resistance confirmed on a UK farm. I want to talk a little bit about, I think majority of our listeners are based in the US or Canada or North America. And so, I think it'd be interesting to hear from you the differences between what's going on in the UK with glyphosate resistance and what we're dealing with in the US. What can you tell us about this first case of glyphosate resistance being confirmed in the UK?

Yeah, I'm in a almost live update. We have actually been working on three other locations. And whilst can't call them cases yet because there's a little bit more work to do, 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. Lolium multiflorum is one of our key arable weeds. And it's massively consequential in the UK. Although we don't have GM herbicide tolerant crops, we've got some conventionally bred tolerance to ALS herbicides in break crops, but we don't have GM herbicide tolerant crops. And I think it's fair to say that where the GM herbicide tolerant crops have been adopted, there's a little bit more glyphosate resistance 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, more cropping diversity, and people really trying to find a different way of farming, which I think comes under this umbrella of regenerative agriculture. Which is global concept, but applied differently in different places. But in the UK we've got challenges around that. Our farm size is tiny compared to in the US. And that means biosecurity is massive, where you've got a problem on one farm, you're talking about 10 hectare fields together, farms down sub thousand hectares sometimes. You've got a massively productive agricultural environment. 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. Spot yields higher than that.

And that really productive environment creates a real challenge for weed management. Because obviously a failure of weed management in one year, massive seed return 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. We only have glyphosate authorized. We don't have glufosinate, we don't have diquat or paraquat or other total non-selective. 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. It's a really challenging environment. And I think we all understand how we got here, we just really want to focus on sustainable use of glyphosate, facilitating people to make that change towards regenerative agriculture, and supporting them while they're doing it.

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

Our average rainfall will be about 500, maybe 600 mils of rain. Most of our crops... We have a very maritime climate. Obviously tiny island stuck out in the Atlantic, sandwiched between the Atlantic and the English Channel, and then [inaudible 00:08:16]. A lot of rainfall, a lot of rainfall intensity. Soil moisture conservation is not an issue for UK farmers. But working windows where you can travel, that's a real issue. Most of our cropping, and certainly most of our productive cropping, would be drilled in the autumn, which would be September/October, and grow through until the summer in August.

There's a certain amount of spring cropping, particularly for break cropping, established around about now. Maybe February/March, and a bit later sometimes. But most of our productive cropping, taking advantage of all that rainfall. Good soils. Obviously, we're a glacial zone, so we have a lot of clays, we have a lot of really young soils. Which obviously also bring productive agriculture. The world record for wheat production was obtained by a guy in the UK in Lincolnshire, over 14 tons.

Yeah, 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. Some work was done by an old colleague of mine called Steve Moss, some very early work on modeling population dynamics in a non-plow system to stand still for blackgrass, which is our major grass weed. You need 96% control in every crop. That tells you what the seed return potential and the potential rate of increase of grass weed populations is.

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

Lolium multiflorum, which is annual ryegrass. We do use perennial ryegrass a lot in... I guess as you do in fertility building phases, in environment schemes, and so on. Italian ryegrass, it's not the annual ryegrass which occurs in Australia. I know 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. Aside from the glyphosate, when we look at in-crop selective herbicides, so we have our group ones and group twos, as everyone does. It's a lot easier now the Europeans aren't using the letters and the Americans are using numbers. It's one of the few things where we've agreed to agree on something.

Right.

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 has in other grass weeds. We have resistance to flufenacet. Flufenacet would be our key North European residual herbicide grass weeds probably. We've overused it. A few years ago, 60% of all winter cereal crops had flufenacet applied quite a lot of it more than once. But we've developed herbicide resistance in a residual herbicide, which is something you think you're 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 would be our most widespread weed. We don't see the same problem in our brome species or wild oats. It really does seem that Italian ryegrass has this disproportionate propensity to develop herbicide resistance. As to why that is, all projects end with a requirement for more funding. That's where we'll finish.

I think one of the things that we're seeing as we begin to look a little bit more at ryegrass, is just how incredibly genetically diverse the background is. 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. There's this massive genetic diversity, and there's almost a a soup of Lolium genetics in the landscape. Because we've got perennial, we're 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 a super genetics. And I think that gives you the raw ingredients to go on and select the herbicide resistance.

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

Yeah. The productivity is big issue. We're very much dominated by... We have been historically dominated by winter cropping, so going from crop to crop with very little break between the crops. But actually, what we're seeing is adoption of conservation agriculture, regenerative agriculture, diversifying the rotation. Alongside the lack of mechanical weeding, we're seeing long periods between crops, maybe as a switch from winter crop into a spring crop. Or you use 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 cocktail of... You can imagine over winter, if you can grow a winter wheat crop that gives you 10, 12 tons a hectare. You imagine the vegetation you're developing on the stubble with natural regeneration and maybe a few cover crop species in there. Creates a real massive challenge because 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. I believe, and I suspect you do, and your listeners probably do, that adoption of regenerative agriculture in the long-term is going to give you benefits for weed management.

Because you've got your diversity, you're breaking weed life cycles, and you're 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 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. We're really talking about a transition, talking about not really being clear, and saying that finding glyphosate resistance in the UK is not a barrier to adopting regenerative agriculture. But if we're going to see that transition, my God, it's got to be associated with a real focus on glyphosate.

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

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

With that, you mentioned that while that is true, it shouldn't necessarily discourage you from making that transition now if you're still thinking about it. For somebody listening who's maybe thinking they're ready to start implementing cover crops, or stop tillage or reduce tillage, what's something that you think, 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?

I think you see it as a package. You've got your crop diversity and you're reducing your cultivation intensity, and maybe you've got low disturbance drilling. Leaving weed seed on the surface is a positive, because you're feeding other trophic groups in farmland. You don't necessarily want to bury all these weed seeds and create a long-term seed bank. You really want to manage them then and there. The crop diversity in and of itself, you're breaking life cycles.

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 cycle's problematic weeds with later drilled spring crops, break crops alongside cereal crops, nitrogen fixing crops with lower inputs. The more you're disrupting and breaking up those life cycles and changing the niches for weeds, the more balanced the system is in terms of weed management in the long-term.

But that's not to say that transition isn't really challenging. It requires more management, that's what we're seeing. It requires a higher level of technical ability. Yeah, we don't want to discourage that because that's where we want to be 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. It's important that we get the messaging right, that people don't hear the headline and are discouraged. But we talk about exactly what we're seeing, where we're seeing it, and what the real implications are.

Absolutely. Yeah, I couldn't agree more. And I think our audience is... If you've made it this far listening to the Cover Crop Strategies podcast, you probably know that you're in agreement with that sentiment.

I guess to wrap up this preliminary discussion, you mentioned at the beginning that there could be a couple more cases that you guys are looking at. I guess, talk a little bit about where the research is headed and what updates and next steps might be ahead in the coming months.

Yeah, it's important to say, whilst the locations probably won't mean anything to listeners outside the UK, but what we are seeing is populations completely independently. We have 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 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. 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. We're seeing that.

Right now as people begin to drill spring crops, we've seen going into a spring crop in a no-till system is one of the places where the resistance is most visual, let's put it that way. We're running some free glyphosate resistance testing, a plant-based rapid turnaround testing supported by Bayer Crop Science, I have to say. And they've been really supportive in, as I know they are globally, around glyphosate sustainability, glyphosate use. There'll be some live updates.

We have a weed resistance action group in the UK, and globally there's a herbicide resistance action group. There's a European herbicide resistance action group. In the UK, we have something called RAG. We're reporting back as soon as we see these samples, we'll report back on a summary of all the samples that we test in the spring. Obviously, there's research going on in the background trying to look at mitigation. Can we use tank mixing with alternative modes of action in extremis where we've got confirmed resistance? Can we look at modes of action? Will that give us a bit of a clue as to how we can mitigate the problem where it occurs?

And really, resistance management is weed management. Key plan of sustainable use of glyphosate. It 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? Do we need to think about targeted mechanical weeding? Can we use companion cropping to make more competitive crops?

Yeah, we mustn't become herbicide resistance junkies. It's a symptom, not a cause. Glyphosate resistance or herbicide resistance is a symptom of an overreliance on a particular herbicide or a particular family of herbicides. It's not the 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 weed management in the round.

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

Absolutely.

Well, thanks, John. Like I said, we'll be sure to get you back on for an update sometime soon.

Cool. Really good to talk to you. And we'll come back and update you. It'll be fine. Everything will be fine. It's a difficult time in agriculture in the UK more broadly. I don't know if you are, probably not aware, big, big changes. We had a change of administration in the UK, and they're making big changes to the way that agriculture is supported. And some of these approaches to support other trophic levels on farmland have 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. And obviously that's not good. But the government has taken away the 100% inheritance tax rebate, but not fixed the problem about farms not making any money. So, you can see the wall, you can feel that we're moving at speed, but I can't see the solution yet. It's a really difficult time, and I know there are people in UK listening, this is not the end of the world. To my certain knowledge, no one has been badly injured as a result of herbicide resistance occurring on their farm. 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 a particular issue. As I say, Bayer has been supporting this free testing work, you can contact their representative. And we'll be okay.

Well, as we talked about at the beginning, farmers are a creative and a resilient bunch. I think the sentiment is absolutely true.

Well, that's it for this episode of the No-Till Farmer Podcast. We'd like to thank John Cousins from ADAS in the UK for his invaluable insights into glyphosate resistance. We also want to thank our sponsor, NewFields Ag, for making this podcast possible. A transcript of this episode and our archive of previous podcast episodes are both available at no-tillfarmer.com/podcasts. For John Cousins, Mackane Vogel, and our entire staff here at No-Till Farmer, I'm John Dobberstein. Thanks for listening, keep on no-tilling, and have a great day.