Italian Ryegrass Control with Ian Burke

Italian Ryegrass.

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Episode Transcription:

[ Music ]

Drew Lyon: Hello, and welcome to the WSU Wheat Beat Podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. We have weekly discussions with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production. If you enjoy the WSU Wheat Beat Podcast, do us a favor and subscribe on iTunes or your favorite podcasting app. And leave us a review while you’re there so others can find the show too.

[ Music ]

Drew Lyon: My guest today is Ian Burke. Ian is a professor of Weed Science at Washington State University. His research program is focused on basic aspects of weed biology and ecology with the goal of integrating such information into practical and economical methods of managing weeds in the environment. Ian teaches the undergraduate courses in Weed Science and Cropping Systems. Hello, Ian.

Ian Burke: Hi, Drew.

Drew Lyon: So, Ian, as I drive around eastern Washington, particularly the higher rainfall areas, I see an awful lot of Italian ryegrass. I know there’s a lot of growers out there pulling their hair out on this one. Can you give us a little update on the situation with Italian ryegrass?

Ian Burke: Sure. Italian ryegrass continues to be one of the few weeds that really scares me. It’s a weed that appears to be readily adaptable to anything we throw at it. It appears to germinate all throughout the spring. Once it gets established, it’s really hard to get rid of the seed bank. Because of that wide range of germination, that germination window is so broad, I think it escapes a lot of our inputs for managing it. It’s really competitive and really dense stands. So I think that’s a weed we’re stuck with and it’s one that growers should be prepared to pull out all the stops to manage.

Drew Lyon: I know one of the things that’s happened and I’ve seen since I came here in 2012, is just one after the other our herbicides are failing to work on this and they seem to fail fairly quickly after the introduction. Can you talk a little bit about why this weed is so resilient or so capable of developing herbicide resistance?

Ian Burke: You know, I believe there’s a couple of different reasons. It germinates in pretty high densities and so where we have ryegrass infestations, there’s a lot of ryegrass there. And this is a numbers game. And so, just like the plant breeders going out and selecting the best varieties, the growers are selecting the best ryegrass to escape their treatments. And the more plants that the ryegrass species can throw at our selection inputs, the more likely we’re going to see resistance develop. But it also has what we call a obligate outcrossing mode of crossing. So it only pollinates others around it. It doesn’t self-pollinate. And whenever that method of reproduction exists we see the, once the resistance develops, it usually spreads quite quickly through a population because it only takes a pollen grain instead of a seed. And so it’s wind pollinated. I suspect those pollen grains move many hundreds of feet. And I think it’s just really is very readily situated in a way to make it to select for resistance. And when I think about problems we’re having with herbicide resistance, all you have to do is look at the rigid ryegrass issues that Australia’s had for the last 40 years. And we’re on the same, we’re in the sort of same situation as they are. We’re just a little behind. We’re a little behind in developing the resistances that Australia has. We’re also a little behind in deploying the solutions that they’ve been able to deploy to at least manage around ryegrass. In many ways they’re essentially the same species and I suspect many of the same solutions for managing herbicide resistance will apply to our Italian ryegrass.

Drew Lyon: Okay. So is there hope? [ Laughter ] Is there something that you’ve been able to figure out a few techniques or methods for controlling–? Maybe you can tell us a little bit about the research you’ve been doing in the last few years with Italian ryegrass.

Ian Burke: You know, ryegrass, both of us have been working on ryegrass from a couple of different angles. There’s a couple of things that have cropped up that have made me think about integrative management strategies that would exist outside of the herbicides that we use. And clearly, you want to get the best possible wheat stand to compete with it. I think growers are already beginning to utilize alternative rotations. Growers see value in perhaps a glyphosate-resistant canola rotation, although that brings along a certain amount of problems on its own. But everyone needs to be thinking out of the box and that’s definitely an unusual rotation for us. I think that Italian ryegrass doesn’t compete as well with winter wheat as it does with spring wheat, and so spring wheat’s really been an area of emphasis for us to try and understand how to overcome it. I don’t know that I’ve found any particularly, truly effective one, name one solution, this does it. We haven’t found any tricks like that. Instead what we’ve been focused on, and I know that you’ve been focused on, is understanding the seed bank dynamics, understanding how much it shatters, to maybe be able to decide whether or not we can employ some sort of harvest weed seed management tool that’s, there are any number of those sorts of tools available. We’ve been thinking about how to make it germinate a little bit more in the field and there seems to be some promise even in that, in making the dormant weed seed, Italian ryegrass seed, germinate a little bit. But the reality is, you know, this is one of those weeds that has evolved resistance to multiple modes of action. And we know that herbicide resistance management, although it has to include non-chemical tools, when you do deploy those herbicides, it needs to be in sort of a ruthless, with a ruthless mindset that pull no punches. And so if you’re not using both pre-emergents and post-emergents inputs, we can’t mix the group one and the group two herbicides, but we can definitely put our pre-emergents group fifteen herbicide out and utilize a group one or a group two herbicide post-emergence. We’re also thinking in chickpea of strategically input there just before the ground cracks with something like a paraquat. That’s a variant of the double knock that the Australians use where we use glyphosate as a pre-plant input to clean things up that like volunteer and stuff. But then after you plant, really paying close attention to those crops as they come out of the ground and if you see anytime ryegrass patch that’s germinated well ahead of the crop, there’s a way you can even then drown that. Anecdotally I’ve put enough plots into both low grounds, and mid-slope and upper slope positions to know that if it’s in a wet area, that ryegrass, particularly if there’s still a lot of soil moisture, does not respond to herbicides in the same way it does in more upland sites. And so even something as simple as making sure your tile drain is working right could be viewed as an integrative weed management strategy for Italian ryegrass. So anything you can do, pull out the stops.

Drew Lyon: Yeah. It’s proving to be quite a difficult species to control. And I think, you know, we’ve been trained to kind of look at just one answer and this is not a one trick pony sort of thing. You have to pull out just every different method you can. And I believe it’s the one that’s going to force growers to switch up the rotations. I think we’re going to run out of the few chemistries that worked well today fairly quickly. I don’t know what’s coming down the line. What about some of these tools that the Australians are using? The harvest weed seed control, the, you know, there’s a number of different things there. Have you taken a look at much of that? I know I’ve done a little bit of work but have you thought about how to integrate something like that into the system that we have?

Ian Burke: It should be doable. There’s a couple of different approaches we can take. I’ve watched a few growers experiment. I don’t have any direct experience but, you know, you could do something as simple as making sure you get that chaff coming out of the back of the combine that would contain weed seed into a nice tight windrow and perhaps even burning it if that’s allowed. You could potentially try and get one of the, what they call the Harrington Seed Destructors, which is a relatively new innovation that involves a really large industrial hammer mill mounted up underneath the combine. And there’s a series of separators that separate the seed out from the chaff and then all that seed goes through the hammer mill and is turned into dust and that’s what comes out the back of the combine. Unfortunately, as I understand it, those have been somewhat to difficult to import. There’s also what they call chaff carts and that’s sort of a halfway between windrow burning and actually producing some sort of grain bale or chaff bale where the cart catches all the chaff and then periodically just simply dumps it into a pile on the field. The growers in Australia would just burn that and hopefully a lot of the weed seed. And then there’s sort of the last step would be to actually have something you tow behind the combine that produces, turns that chaff into a bale that you then haul away. And there’s positives and negatives that come along with that but I have to think that however much nutrients we’re removing in the process of baling that the weed seed leaving the farm as well would be really important. And then on the other end, obviously there’s going to be weed seed that gets into the ground. My thoughts have been turning to the duration of the seed in the soil, how long that lives there. And there’s evidence from other areas that are not Mediterranean in climate that the Italian ryegrass seed bank maybe might last at most three or four years, particularly in a no-till situation where all that seed’s sitting on the surface. But here in the inland PNW, where we don’t have a lot of moisture during the summer to really keep that seed wet and perhaps expose it to disease and then, you know, our winters are when we have all our moisture, the ground’s quite frozen. And I suspect that our weed seed lasts longer as a consequence. So I’m going to try and figure that out. But either way, I’d view it as sort of if you have ryegrass, it’s a five to eight-year proposition to really get out of the infestation you have if we can do it. And it’s going to involve as many different strategies as we can possibly throw at it to get rid of it.

Drew Lyon: I know I’ve had some people talk to me about would this be a weed species we might want to copy the zero-tolerance program that we see in Arkansas against Palmer amaranth where they basically for a large geographic area, I think, almost a county basis, they just, all the growers agree they’re not going to let the stuff go to seed. Do you see something like that ever working for Italian ryegrass? Do we need something that aggressive to get on top of this do you think?

Ian Burke: I see value in that for this one particular species. And the primary reason is, unlike some of our other grass species that primarily self-pollinate, this species, because it outcrosses because that pollen can move so far. It’s sort of everyone’s problem. Like if your neighbor evolves a resistance, it’s going to move, probably through the pollen, into your Italian ryegrass, too. So whenever you have a plant like that, a weed like that, that can spread its genes in that very efficient manner, I think it behooves all of us to get organized around being really aggressive in its solution. And, you know, maybe there’s some mechanisms we can engage, not necessarily a regulatory environment or anything like that, but maybe provide some structure around a unifying approach to managing it would be a proactive thing for us to be doing.

Drew Lyon: I know. I think in Arkansas it’s pretty much a voluntary, the growers had to agree that they were going to do it and it was such a bad problem they basically ran out of ways of controlling Palmer amaranth. So they went to it. And we’re not quite there yet with Italian ryegrass but I think we might get there at some point. So that might be something worth exploring. Anything else you’d like to tell us about your program or where people might go to find some information on your work in Italian ryegrass if they’re interested?

Ian Burke: You know, all of this appears in our annual reports in the website and I encourage people to go peruse there. And as always, we’re always anxious to hear by email. Go ahead and ask us what we know, any time.

Drew Lyon: And your email address for those people who might be interested?

Ian Burke: Yeah. That’s easy. It’s

Drew Lyon: All right. Thanks, Ian.

[ Music ]

Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat Podcast. If you like what you hear, you can subscribe on iTunes or your favorite podcasting app so you never miss an episode. And leave us a review while you’re there. If you have questions for us that you’d like to hear addressed on future episodes, please email me at You can find us online at You can also reach out on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat Podcast is a production of CAHNRS communications in the College of Agricultural, Human, and Natural Resource Sciences at Washington State University. I’m Drew Lyon. We’ll see you next week.