What's New In Weed Science with Dr. Ian Burke

May 12, 2021

Show Notes & Resources Mentioned:

Contact Information:

Contact Dr. Ian Burke via email at icburke@wsu.edu.

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Episode Transcription:

Drew Lyon: Hello. 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. In each episode, I speak 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 Dr. Ian Burke. Ian is a Professor and R.J. Cook Endowed Chair of Wheat Research and 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.

Dr. Ian Burke: Hello, Drew.

Drew Lyon: So I thought we’d just have a “what’s new in weed science” discussion today. 2021 is definitely different than 2020. Some new things have come along. Let’s talk about it. One of the things I think we’ve both worked a little bit on is this new weed-sensing spray, the Weed-It system. I wonder if you can talk a little bit about what you’ve been doing with that system.

Dr. Ian Burke: Sure. I’ll weigh in. I think it’s an amazing technology that I think we still have a lot to learn about how to use. You know, in a couple of years, we’ve had opportunity to use a piece of equipment. It’s been clear to us that it is easy to misjudge rate, to not have a clear sense of the weed density you’re going to treat, and when you put those two things together, you could spend a whole lot more money than you had intended to, and so you really do have to be strategic about how you mix up your herbicides to go treat a fallow system when you maybe might want to use a higher rate or a different herbicide. Those are all things we’ve been trying to tease out as we’ve gone through our research here in the last couple of years.

Drew Lyon: Maybe we should back up a little bit for those people who might not know what a weed-sensing sprayer or a Weed-It system is. Can you explain the technology and how people are using it?

Dr. Ian Burke: Sure. You know, this is not a — it’s not actually a relatively new technology. I would say it’s been significantly improved since it was first introduced back in the mid-1990s, and there are a lot of competing technologies. You don’t have to — you mentioned one product, the Weed-It, there are others. WeedSeeker systems come to mind. They all work on the same principle, though it’s a reflectance-based system. So all these tools have a light-emitting diode array they emit in near-infrared weeds. Any really plant species reflects a different spectrum of light back to the sensor, then fallow soil or stubble or rocks, and that’s how the system uses that information to make a decision on whether or not to spray or not. So the new systems that we’re using couple that with some pulse-width modulation sprayer technology that has a very high — a very fast nozzle body activation system on it. So you put that together with a sensing system and it can hit a dime-size weed going 15 miles an hour pretty easy. And in our experience, the system’s not flawless. It will miss weeds. There are certain species that don’t reflect as well when they’re small. There are certain weeds that don’t — even when they’re a little bit bigger, that get missed, maybe they hold their leaves a little bit differently, and so there’s a there’s a lot of, like I said, there’s just a lot to learn about how to use them.

Drew Lyon: Growers, there’s a fair number of them operating right now and, I guess, is everybody just kind of winging it and hoping they get it figured out, or what’s happening out there. Do you know?

Dr. Ian Burke: I don’t have a good sense for the operational aspects of it. I think most farmers are really innovative and know how to — particularly if they’ve bought this particular piece of equipment, and I’m hearing a lot about how they experiment with using it, you know, different herbicides in the mixture. You know, glyphosate seems like the go-to herbicide to use in it, so you can maybe use a little bit higher rates. You know, Sharpen is another product that maybe would fit well with this. Paraquat, Bromoxynil, and other herbicides that maybe might not necessarily be using in fallow would maybe fit because they’re a little more affordable in this system. I’m hearing innovation around what nozzles they use in the sprayer systems themselves. There was some confusion, I think initially, these systems are equipped with what I would call an industrial TeeJet line of nozzles that are very specific to the equipment, and so it’s really hard to just go get a nozzle that would maybe have a different gallon per acre rating off the shelf. That’s just not possible because the angle on the nozzle is very narrow. And so I’m hearing innovation around using like a cone nozzle instead of a flat fan, or maybe a slight angling of the nozzle system instead of pointing straight down on the ground. Those are all things that the system can accommodate with some calibration. So there’s been — I think everybody has a little bit of a different flavor of how they’re using it.

Drew Lyon: Yeah. To me, the thing I can’t quite figure out in a lot of cases is what rate is supposed to be used, right? Do you use the broadcast rate, or do you use the spot treatment rate, and how do people make that decision?

Dr. Ian Burke: Unfortunately, the herbicide labels have not kept up with this technology, at least in the United States. If you look up some of the herbicide labels in Australia, there’s an optical sensor sprayer section on certain labels, particularly Roundup type products, glyphosate-containing products, that they would be using valves for the same situation we’re using the system in, and we took a little bit of inspiration from those labels. If you look at those labels carefully, it says if you’re about 30% weed cover and below, then you could probably use a higher rate of glyphosate, and if you’re at about 30% or above, it’s better just to stick with the label use rate. The United States labels are written more for broadcast sprayers, and so we have to follow that label, and the label is very specific about how much we can apply per acre and in what situations you can apply. You have different rates. Certain herbicide labels do contain a spot treatment section and I think that you can interpret this system as a spot treatment, particularly if you were treating a fraction of the acre, like the weed populations are very low, but that’s a difficult thing to counsel growers on how to decide rate. In general, when I’ve talked with chemical companies about this, they’ve been very clear that they should follow the broadcast guidelines if they’re trading a significant proportion of the acre.

Drew Lyon: Okay, and I think I’ve talked to you a bit about this, so I’m thinking as in the earlier fallow season when you tend to have more weeds out there, maybe it’s better just to broadcast and then save the weed-sensing sprayer for later in the season when it tends to be just patchy weeds here and there. Is that still your thinking?

Dr. Ian Burke: I guess I would say my only modification of that recommendation is just to use the Weed-It at every opportunity. Even if you’re only treating 70% of the acre and you’re running a relatively moderate rate of glyphosate, you’re still going to see some savings. And if you spread that over 1,000 acres, it could be a real dollar amount.

Drew Lyon: Okay. And you start putting some zeros on that and that’s adding up, isn’t it?

Dr. Ian Burke: Yup.

Drew Lyon: Okay, well, I think that’s really interesting technology, something that’s catching on and we’re learning a little bit more about. Another one that I think a lot of growers may be interested in, at least pulse growers, is the labeling of pyridate for use in pulses. Can you tell us a little bit about that?

Dr. Ian Burke: Yeah, this is a herbicide that was introduced under I think was a Section 18 in the early 2000s, so there are a few people who still remember how to use it. The product hasn’t changed. It went through a couple of different companies, and now Belgium — out of Belgium is going to be marketing it in the United States. There’s been some mint growers that have had an opportunity to use it in the last couple of years, but this will be our first opportunity to use it in chickpea. There’s quite a rate range on the label. I think you can go from 12 to 24 ounces of Tough, and I think growers are going to have to carefully consider cost and what they want to get out of the treatment. You know, we’ve had really good success at 12 ounces for control of just common lamb’s quarter, but if you’re up against some other weeds, particularly mayweed chamomile where we’ve seen some activity, you might want to consider a higher rate. But again, that’s going to have to be balanced against cost. The other big question I have, you know, we’ve done a lot of small plot work where we mixed it with clethodim formulations, the old 2EC formulations in particular, and we haven’t really seen a lot of crop injury as a result of that mixture. But we do know that that potentially could cause some crop injury, and so if growers are considering tank mixing, they might want to maybe be careful with the surfactant mixture they’re using with that. But otherwise, we’ve had really good success, excellent crop safety in our chickpea with pyridate and it really helps out with common lamb’s quarters. That’s really what it does best.

Drew Lyon: Okay, and you mentioned chickpea. Is it going to be labeled in any other of the pulse crops?

Dr. Ian Burke: I anticipate maybe a pea label in the next couple of years. I know they’re interested in expanding that label. Joan Campbell at the University of Idaho has also been exploring its use in lentils, although that might be a little more finicky. But yes, we’re interested in seeing this post-emergence broadleaf herbicide expand into some of our other pulses.

Drew Lyon: That’s really been what’s missing in all of our pulse crops, is a good post-emergence broadleaf product, and this may not be the end all/be all, but it does — it is a good tool to add to our chest of tools.

Dr. Ian Burke: You know, I can’t overemphasize that enough. It is not a system unto itself. You’re still going to have to use pre-emergent herbicides. You’re still going to have to go out and control your grasses post-emergence. It’s something that can help you get through that weird season like we’re having apparently this year where it’s going to be dry, the pre’s might not work as well, and lamb’s quarters seem to come along in these sorts of years and it might be really helpful.

Drew Lyon: Yeah, good point. Another area I think you’re working in, and I’ve done a little work in, is the harvest weed seed control. Can you tell us a little bit about what you’re doing there?

Dr. Ian Burke: Yeah, and this is definitely something that you’ve been a leader in. This is more of an opportunity for me to get into it with a graduate student who expressed some interest in Italian ryegrass research and this seemed like a good opportunity for us to kind of collaborate on it, and there’s a lot of different ways you can manage weed seed at harvest, and the Australians have been leaders in this regard. We’ve been slow to adopt this sort of technology, mainly because we haven’t had the herbicide resistance issues that they’ve had, although I think that’s changing. And so we’re trying to think of ways to adopt some of their innovation into our own systems and I don’t think it’s going to look the same. I think a lot of farmers we’re working with are going to have to lean in and innovate along with us to identify opportunities for us. So there’s chaff lining. There’s the seed terminator technology which involves a hammer mill mounted up underneath the combine or in a trailer. There’s direct bale systems that also serve the same purpose. There’s windrow burning, which we observed on occasion here and there, here in the Palouse. So there’s a lot of different variations of technology we could do. Chaff lining in particular seems to be very popular in areas of Australia that I visited and it’s I think popular because farmers can essentially make a chaff lining system that mounts on their combine relatively inexpensively. You know, a few thousand dollars worth of investment and you can use that sort of tool. Where the Aussies do it, they also couple that with control traffic or tramlining and that’s a little bit harder to swallow here on the Palouse. I’m not sure what that’s going to look like. Most farmers go, “Well, I just don’t think that’s going to work.” So when you tramline, you got to have sized equipment. So if you have a 30-foot header, you got to have a 30-foot planner or 60-foot planner, and you got to have a 60-foot sprayer or 120-foot sprayer, and you want to really make sure you’re driving over that chaff line as often as possible to really make that area as inhospitable to the ryegrass as possible through compaction, and that’s harder to do on our very unusually shaped fields and with all our contours, but I think if the technology works, then we’ll figure it out. The seed terminator works a little bit differently. It just grinds the chaff coming out of the combine and dust along with the weed seed. You don’t necessarily have to do control traffic to do that, but it’s a lot more expensive, and I think that that’s going to be sort of a value proposition. And it’s expensive not just to mount on a combine, it’s an industrial hammer mill. It costs diesel to run, and that diesel is measured in dollars per acre, and so there’s a lot of numbers we’ve got to crunch to figure out if that’s worth it for us.

Drew Lyon: I think that the chaff lining might be a good entry point into harvest weed seed control to see whether it works for you and your system, and then if it does, you might consider some of those more expensive approaches, but there are, as you said, a number of different ways to do it. So you mentioned harvest weed seed control and Italian ryegrass. You have a student wanting to do some work. What’s happening with Italian ryegrass? It seems like it’s the bane of just about every farmer here in the higher rainfall zone.

Dr. Ian Burke: It’s really, I think, for the last couple years been obvious to everyone, particularly here in the southern Palouse, but in other areas as well, that we’re changing the rotations because of it, and it’s by pure serendipity that we happen to have a rotation that makes sense where we’re rotating to RoundupReady canola, particularly spring canola, and so we’re substituting that spring canola in place of a pulse, sometimes in place of even the spring wheat rotation. I’ve observed a few farmers even double-cropping spring canola to try and clean up their italian ryegrass populations, and that’s really a symptom of our problem. You know, our typical tools that we’ve used for decades now in our winter wheat rotations are really not very effective anymore. These days I like to say that if you’re not using a pre-emergent herbicide, like Zidua or Anthem Flex, for managing italian ryegrass and winter wheat, you’re likely not going to be harvesting that winter wheat in certain areas. So that’s been also an incredible change for us over the last, I would say, six years. So these are all tells that ow our system is not as sustainable as we thought, and this is a particular weed that can really fundamentally change how we farm.

Drew Lyon: Yeah, I’m a little concerned that while it’s nice to have a tool like RoundupReady canola, but if that’s all — if we’re just going to start putting a lot of selection pressure on this italian ryegrass for glyphosate resistance, we know it can develop — it’s in the orchards where they’ve relied on glyphosate heavily, that will just find a biotype resistant to that and then what do we do? So it’s a weed that really poses a lot of concerns for a lot of growers.

Dr. Ian Burke: One of the most interesting discoveries that came out of your program, Dr. Mark Thorne had an opportunity to monitor ryegrass populations after a direct bale system pass, and so he was able to do a study where he was looking at a lot of residue and not a lot of residue, standing stubble sort of situation, but it was very short, and he was able to document that the Zidua treatments after a direct bale pass were far more effective than in areas where there was stubble that was laying on the ground. And so I think for those farmers who are pulling heavy harrows around and really trying to make that stubble layer uniform, and that’s actually a detraction from the activity of some of our pre-emergent herbicides. So I think there’s a lot of additional work we need to do to understand how to use these tools effectively and make them fit into our programs and our conservation systems.

Drew Lyon: So while italian ryegrass is the bane of farmers here in the high rainfall zone, you go to the drier regions and it’s downy brome, seem to be having similar sorts of issues with downy brome. Can you talk a little bit about what you’ve been seeing and doing in that realm?

Dr. Ian Burke: Yeah, downy brome, we’ve essentially exhausted all our tools for downy brome in certain areas of eastern Washington. You’ve heard me say that before. It’s, in my mind, far more impactful on a far greater number of acres than even italian ryegrass. It really scares me. So we’ve been trying to think about how to take a different approach and maybe understand why downy brome is avoiding some of our inputs so effectively. The Latin for “downy brome” is “Bromus tectorum,” and “tectorum” translates to roughly “of thatched rooves.” So where downy brome originated in Asia Minor as a species, it was quite common for it to infest the thatched rooves of houses, and that kind of gives you some insight to what that plant can do. It can exist in these residue layers that we leave sitting on the surface, and even if you use a pre-emergent herbicide, it’s not going to root into that soil. It really doesn’t have to, and it can still make some seed. It’s an extraordinary plant. So we’ve started to really try and understand how flowering time and climate interact to try and figure out if we can get a little bit better sense for more opportunistic times for management, try and understand seed dormancy mechanisms. We know that there are a few at work in that particular species. I’m not going to tell you that we’ve made a lot of headway. I guess the most important take-home, you know, we think of russian thistles being pretty mobile, and what we’re beginning to realize is that our implements are dragging weed seed around, the downy brome seed around to different fields, and it’s having sort of the same effect. The more you enrich that seed bank by moving the seed around for downy brome, the more adaptable it is. So if we really want to select against it in our farming systems, we’ve really got to start being more proactive about cleaning gears that move from field to field, and so we’re beginning to really try and think evolutionarily about this weed, long-term about this weed. I think that’s what it’s going to take to solve that problem.

Drew Lyon: All right, Ian, I could talk to you all day about different weed options out there and what’s happening in the weed science world, but we’ll leave it there for now and hope to have you back on not too far down the road to talk about some more things.

Dr. Ian Burke: Thanks for the opportunity. Good to visit, Drew.

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Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcasting app. If you have questions or topics, you’d like to hear on future episodes please email me at drew.lyon — that’s lyon@wsu.edu –(drew.lyon@wsu.edu). You can find us online at smallgrains.wsu.edu and on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human and Natural Resource Sciences at Washington State University. I’m Drew Lyon, we’ll see you next time.

The views, thoughts, and opinions expressed by guests of this podcast are their own and does not imply Washington State University’s endorsement.