Australian Weed Seed Control with Michael Walsh

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For questions or comments, contact Michael Walsh via email at m.j.walsh@sydney.edu.au.


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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 Michael Walsh. Michael is an associate professor and Director of Weed Research at the University of Sydney, where he is responsible for leading weed research and development across Australia’s northern grain cropping region. Michael completed his bachelors of science at the University of Western Australia, his masters of science from Latrobe University, and a Ph.D. from the University of Wyoming. For over two decades, he has focused on the development and adoption of harvest weed seed control systems. Hello, Michael.

Michael Walsh: Hi, Drew. How are you?

Drew Lyon: I’m doing well. Herbicide resistance is getting to be quite an issue here in the U.S., but I guess nothing compared to what you’re experiencing there in Australia. I wonder if you can describe the situation with herbicide resistance in Australia for our listeners.

Michael Walsh: Yeah, sure, it’s been quite a dramatic evolution of herbicide resistance pretty much right across the Australian wheat belt. Forty million hectares, now it’s difficult to find populations of annual rye grass, in particular, that are susceptible to herbicides anymore. So, the survey work that we done over the last 10 to 15 years has shown that for annual rye grass, our dominant wheat, on average, we’re seeing 75-80% of populations, randomly collected populations, that are resistant to one or more herbicides.

Drew Lyon: Oh, okay, that sounds fairly similar to our Italian ryegrass here, where we’re seeing a lot of resistance. Not many herbicides that still work anymore. So, you kind of come up with this novel approach to this situation, kind of a non-herbicidal approach. Can you tell us a little bit about what harvest weed seed control is all about?

Michael Walsh: So, harvest weed seed control, as the name suggests, Drew, is all about targeting weed seeds during the harvest operation. So, we learnt — well, farmers actually learnt several years ago that a lot of the weeds in our cropping systems retain their seeds at crop maturity, and that means that during the harvest operation, these weed seeds get collected by the harvester, and farmers were observing that these weed seeds were coming out in primarily in the chaff fraction. So, they would exist the harvester in the chaff fraction, and a consequence of that is that those weed seeds get spread across the field, and it’s almost like a reseeding operation. And farmers were pretty quick to recognize that the impact of that was just more weeds more widely spread the following year. So, they started playing around with systems and techniques that would intercept that process and do something about targeting that weed-seed-bearing chaff fraction, in particular.

Drew Lyon: Okay, so, what kinds of things can you do with that chaff fraction to try to get on top of that situation?

Michael Walsh: So, the first things they started looking at was actually a Canadian innovation called chaff cuts, and in Canada, those cuts were used to collect chaff for feed. Some Australian growers introduced and used them to collect that chaff fraction, primarily just to collect the weed seeds, and then, sometimes they would use it for the stock feed, but typically, they would just burn that material to just make sure that they would destroy those weed seeds contained. So, those first started being used back in the early 1990s. And then, there’s been a progression of systems that have been developed and have evolved since that time, and they all target the chaff fraction predominantly. The next one that came along was something called narrow windrow burning, and the idea was to concentrate material into narrow rows about 50 centimeters wide behind the harvester, with the idea of just setting that material up as a fuel source for a subsequent burning operation. After that, there was the development of a bale-direct system, which followed on from the chaff cut where a grower who had originally introduced the chaff cuts started that he wanted to try and make an economic return from the material that he was destroying. And so, he developed a system where he’s attached a baler that’s driven by the harvester, collects all the chaff and straw material, and then, those bales produced during the harvest operation are subsequently sold off farm, and in the process, the weed seeds are removed, as well. The following system to be developed was the Harrington seed destructor. Again, a grower decided that the burning and the collection of chaff material wasn’t quite as efficient as they wanted it to be. So, he came up with a process to chaff material during the harvest operation to effectively destroy the weed seeds. And then, finally, the latest systems that have evolved are things called chaff lining and chaff tramlining. The idea is you concentrate just the chaff material into a narrow row, either on the wheel tracks in a tramlining system or onto a — in a narrow row just directly behind the harvester. And the process, then is just to leave that material in place. Don’t disturb it, and let what the famers refer to as a multifit occur with the weed seeds are much in a hostile environment, and they don’t tend to germinate and emerge at a very high frequency anyway.

Drew Lyon: So, a number of approaches to controlling these weeds. I know I became interested in what you’re doing shortly after arriving in Washington, back in 2012. I read a couple of your papers, and I remember contacting you, and we’ve had a couple projects together, where I’ve tried to do some of this work here in Washington, and very shortly, I’m going to be coming over to spend some time with you and get a first-hand experience. I wonder if you could tell my listeners research we’ll be doing when I’m over there, and what you hope to be able to teach me while I’m there, I guess.

Michael Walsh: Ah, well, we’ve got big plans for you, Drew. We’ve got a lot of harvest work organized, both through New South Wales and even in Western Australia. I guess a focus of it is looking at the implications for harvest weed seed control, as the farming systems change. There’s quite a movement at the moment with the adoption of stripper harvester fronts. Now these have a quite different mechanism of action compared to the traditional draper or real fronts, which has implications in terms of the amount of weed seeds that are collected during harvest. So, harvest weed seed control systems rely completely on the collection of weeds seeds during harvest. So, if these new stripper fronts don’t collect weed seeds, then that makes the use of harvest weed seed control systems a little redundant. So, we’ve got some preliminary studies we conducted last year, and we found that there is quite high levels of collection of annual rye grass. Under certain conditions, the stripper fronts do actually collect the seed heads. They pluck the seed heads like they pluck the wheat heads. So that was really encouraging. I should add the reason for the adoption of stripper fronts in Australian cropping systems is just the need to have standing stubble rather than chopped-and-spread stubble. We’ve learnt that standing stubble is much more friendly to the — or much more conducive to soil moisture conservation. The soil surface temperatures are cooler over summer, which means we have less evaporative losses, which subsequently means that we have more stored moisture for the following crop. And so, that’s, as you are probably aware, being dry for production in Australia is just the ability to conserve low and variable rainfall as it falls is key to successful cropping. So, in terms of what we’re going to be doing this summer, we’re going to be looking at other weed species. Wild radish will be a focus, brassica weed. It’s got pods that we think stripper fronts may not actually collect those pods. We know that the stripper fronts are not particularly effective on canola. There’s lots of seed loss, and we suspect that may be the case for wild radish, which is our second-most problematic weed in Australian cropping. And we’ll test other species, as well, such as brown grass, barley grass, and wild oats, as well.

Drew Lyon: I think it will be interesting to see how the system works across a variety of systems, because here in Washington, we have quite a variety. We have the very dry wheat-fallow area, and then when you get to the Palouse it’s actually some of the most productive wheat country in the world, with very high residue levels, very high wheat production, and seeing whether we can get the system to work across that wide variation will be very interesting, and how you test that will be very interesting to me. Because I’ve been told, and I think I agree with this that herbicides are probably not the solution to herbicide resistance. It’s going to take creative thinking like you’ve shown in Australia if we’re going to get on top of this very complicated problem.

Michael Walsh: Yeah, that’s exactly right. Herbicides are not the solution, but they are part of the answer. And we do need to do things around herbicides to support them and have this weed seed control. We love to refer to it as being the last opportunity to impose a weed control during the growing season. It’s just that last chance before the weed seeds go into the seed bin. So, yeah, we do need to do something at the end of the year, and the harvest has created that opportunity. And yeah, part of what we’re doing now is to make sure that we do retain that opportunity, as the harvesting or cropping systems continue to progress and evolve.

Drew Lyon: Yeah, so I guess it’s an opportunity we’ve missed in the past, and hopefully, we can add it to our repertoire of tools to use for harvest weed seed control. I’m really looking forward to my trip, and I hope towards the end of the trip, or maybe want to get back, we can visit again a little bit, and you can explain to my listeners what we did, what we learned, and whether I’m any kind of student or not.

Michael Walsh: [ chuckles ] Yeah, and it should be good fun, too, Drew. It’ll not only be an educational experience, it’ll be hot, dusty work, as always at harvest time, but yeah, it’ll be good fun.

Drew Lyon: Very good. Well, Michael, I really appreciate you being my first international guest on the WSU Wheat Beat Podcast, and I hope to have you on again. Thank you very much.

Michael Walsh: No problem. My pleasure, Drew.

[ 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 drew.lyon@wsu.edu. You can find us online at smallgrains.wsu.edu. 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.

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