Planning for Prosperity: Paraquat and diquat implications and summer weed control tips with Professor Chris Preston

crop in early in the season. So it's just thinking, I think about the whole system and saying instead of trying to make knock down herbicides work all the time, what if we replaced knock down herbicides with something that's different?

kind of fell into agriculture by accident. But one of the things that I discovered when I started working on herbicide resistant weeds, which back then was more of an academic pursuit than what it is now, was that actually farmers were really interested in finding out ways to farm better, and they were really interested in the sort of research that I was doing that seemed to be perhaps going to give them some insights on how to do that. One of the things about working on weeds is that

things change all the time. Well, there's going to be trying to think creatively about how are we going to tackle these new problems that are coming. And there's already some well and truly on the horizon, I'm sure we're going to talk about on this podcast, but the whole Apvma paraquat review is getting me to rethink, look, what are we going to do, particularly around the double Knock?

getting handed. So industry has made quite a number of submissions to the Apvma about various aspects of their review, and so we might get a few more use patterns back. We might get some higher rates, but I'm moderately convinced that we won't go back to the rates that we have, and we won't go back to all the use patterns we have. I'm looking forward and going, okay, if we're going to have reduced rates and reduced use patterns, what can we do that's going to fill the spaces that

the review is going to lead us in? Some of our challenging situations. And so one of those is the double knock. We've used the double knock very widely to help us manage glyphosate resistant weeds. And if we don't have the right to paraquat we've been using, are there other things that we can do? For example, with the reduced rate of paraquat we've got or adding other practices to that. So that might be other herbicides or maybe other things that we can do that will help us

get over that problem. I'm finding the thinking and the challenge about the double knock in summer as being harder, because there's really fewer options available for us in that space. But nonetheless, I think that we will look at some of those and look to see what the opportunities are. There is a level of urgency about this because the decision will be made probably sometime next year, and then labels will change after that. But it's not something that

we have to get done for this coming season. We'll still be able to use paraquat as the current labels for the time being.

cropping without paraquat. So what we are essentially looking at there is how can we make glufosinate work in that space, and what is the sort of set of practices we might have to get something that'll be effective enough for that knockdown space. So we were looking at Glufosinate plus group 14 herbicide. So these are your spike herbicides things like sharpen and so on. And we were looking at

dry seeding as potential options in that space. So instead of having a glufosinate mixture followed up by paraquat we might have to have a double knock. That's glufosinate mixture followed up by glyphosate. The opportunities for products like Amatol in that space. So there's a herbicide called gorilla, which is a mix of paraquat plus amatol that might have an opportunity in some of that space. But I think

it's a thing that we have to explore. We have to explore what are the things that we can do. And then when we work out which ones seem to be effective, then we should look at how is that actually going to work for a farmer.

attractive option. The sort of new bits of chemistry that are out there, or new bits of non chemistry, I should say, that are out there that you might be hearing about things like we've heard about microwaves, for example, and lasers and electrocution of weeds. Most of those, I think are going to be too slow for that particular purpose. Where we have tried to change things up is to really have a bit of a focus on can we

get all this done with dry sowing? And so we're not actually using knock down herbicides, and we're going to use instead a combination of our pre-emergent herbicides plus crop competition. So really that focused more around dry sowing in particular with wheat compared to say some of the other crops.

Looking at how do we take advantage of that competitive ability we get from sowing wheat early and using the right set of pre-emergent herbicides to actually fill that space and take the pressure off those knockdown herbicides that we've had. So this is it's still using chemistry, but it's using chemistry and other practices. So it's not a direct we're going to replace paraquat with this herbicide. We're actually going to replace paraquat with the system.

our pre-emergent herbicide. Yeah, dry sowing was a thing that people only did when they really had no other choice. With the range of products we have available now, and particularly with our ability to have some use some of these herbicides as an early post-emergent herbicide in crop. So things like box gold, uh, sulfur, carp, mattino complete, for example. We've actually now got an opportunity where we can use that set of chemistry to deal with our weed, our

ryegrass issues. And add to that our crop competition from getting our crop in early in the season. So it's just thinking, I think about the whole system and saying instead of trying to make knockdown herbicides work all the time, what if we replaced knock down herbicides with something that's different?

So this is about thinking about how do you take advantage of the competition that barley is going to give you. So you only have to have weed control for a few weeks. If you've sown barley at early in the season, it's going to end up covering the ground and getting canopy closure quite quickly because the soil's warm.

knock to work. What are our other alternatives? The problem of using glufosinate in that space is it's got a plant. Back to sowing your crop of two weeks on the label. So if you're going to double knock, you have to put glufosinate in your first knock so you can come

back with glyphosate in your second knock. And instead of the traditional double knock we've had where you would use glyphosate and you could come back the next day with paraquat, we're going to have to require a longer space between the two herbicides, because our glufosinate tends to be a a bleacher. It burns the leaves off plants. And if you've got glyphosate sitting on the outside and you burn the leaf off, you're not going to get as much

glyphosate taken up. So you need to wait that little bit of extra time until any surviving weeds start to regrow. And then you hit them with the glyphosate component. And I think the in thinking about it that way, the kind of unknown question there is that if you're going to put a group 14 herbicide in to help this, which part of that would you put it in? The work we did with Glufosinate suggested that probably Virachkul was

the best Group 14 herbicide to mix with it. That also has a plant back for most crops on the label. And so in that case, you'd probably think of putting the virachkul in with that first knock. So probably in with the glyphosate component. Now there are other things that we could do because we still will have paraquat at a lower rate. So for example, we could decide that instead of putting glyphosate in as that second knock, we could put paraquat plus our group 14 in that second knock.

And in which case we'd probably want to use maybe something like Terrador where we don't have that plant back problem. So there's lots of options. It's a case of what's going to work. Depending upon the weed spectrum you have and what you're trying to do.

But I think the idea of dry seeding, particularly wheat, but, you know, you can dry so some of your other crops with advantage. It's something farmers can probably do. Now if we get a dry start to a season, hopefully they've learnt a bit about what are the bits of chemistry that really suit dry sewing compared to the ones that don't? And certainly I've talked a fair bit over the years about which ones we should be focusing on.

Things like peroxide Sulfone Trifluralin really suit dry sewing. So if you know you've got a big problem and you're going to go dry sewing, you probably need something in crop as well as that pre-emergent herbicide. So I think this is a practice that farmers can go, yeah, we can take on this now if we get a dry start next year and then we don't have to worry about what rate of paraquat we're using because we're not using it.

It doesn't change our decision. Then maybe we might see some changes more quickly, but I'm suspecting that what will happen is that they'll look at it and they'll go, oh yeah, we didn't actually consider that piece of information. We might have to go back and revisit our decision, and if that's the case, then that'll take extra time. So it's one of those kind of hard ones to predict when we're going to see it. I mean, the reason we've been doing this work is to find different

approaches to a looming problem for us anyway. I mean, because we're getting a lot of weeds that have got resistance to glyphosate, we have to do something about that knock down space.

sizes and prices. Okay, so moving on to summer weed control in general, I think, Chris, we have seen particularly in this area, probably over towards Adelaide as well, that summer weed control has just played such a big role this year in whether a crop does any good or whether it's really struggling. You can really see the paddocks that have either been on fallow, of course, or have had that good summer knock compared to those that might

have missed it. What would your advice be to farmers that are there already, probably in harvest, or doing hay, or about to start harvest to control their summer weeds? away. Keeping in mind they are in harvest, they are really busy and then they want to go on holidays.

you going to rotate into pasture? Because that might change your decision about how you approach some of weeds in those paddocks. I think it's fairly straightforward to say these are the paddocks I'm going to put into crop next year. They're the ones where I need to retain as much moisture as possible. That's fallen over that summer period, and they're the ones to focus on summer wheat control going

into pasture. You can take a much less focused approach to summer weed control in those paddocks, and you might really think about only controlling some specific weeds, like heliotrope if they come up in those paddocks. So when we're thinking about summer weed control, a number of the weeds that challenge us over summer have actually already germinated. They were germinating back late August early September and they'll be

in under the crop canopy. So weeds like fleabane, for example, and we will find them, will most likely be in the crops we have that have got much less crop competition. So pulses and where cereals have been uncompetitive for whatever reason. So they've been late sown, for example, or you've sown them on really wide rows Eyes or whatever's caused them to be uncompetitive. So they're going to be the paddocks where the main planning is going to have to be done.

So things that farmers can do is that prior to harvest, they can actually go out and check crops and see, do I have some weeds already growing there? It's fleabane already germinated. Uh, in which case, I know I've got to deal with that paddock as a priority after harvest. If the paddocks are relatively clean, then you are going to have a much lower weed burden. It's going to have much less impact on how much moisture it takes.

And you can afford to have that as a sort of a second or third priority paddock that you're going to deal with. The I think the biggest issue with the problems that we're having around these spring germinating weeds is that the earlier we get on to controlling those weeds, the smaller they are and the easier they are to

control going. I've got to get harvest off. I've spent long days harvesting and I want to go on holidays for four weeks down the beach, and I'm not going to think about anything until I get back, just allows those weeds to get larger and larger and become more and more difficult to control. If there's the ability to in between harvest and heading to the beach to get those high priority paddocks some weed control on them and reduce the weed burden, they're going to be much easier

to manage further into the summer fallow period. So part of it's, I think, about sorting paddocks into which ones absolutely need some weed control, which ones don't have too much in them so they can afford to wait a little bit. And if I do have to control them, it might be a little bit more difficult because they

don't have too many weeds. It's not a problem. Ones I can put the sheep in to eat the weeds for a while because they're going to go into pasture, and therefore that summer moisture retention is not going to be quite as valuable. What we also get as we saw last year is we can get those really big summer rainfall events and those really big summer rainfall events will do a couple of things. One, if you've got existing weeds in the paddock, they will really allow those

weeds to push on. They're already deep rooted. They're just going to grow into massive, great monsters, but it'll germinate a whole bunch of new weeds. So if you're weed free and you get a rainfall event and it just wets up the surface and dries out again, all those surface germinating weeds won't come up. What might happen is you might get things like melons and so on. That

can be a bit troublesome. They might come up, but you probably end up with a lot lower weed problem than if you get a large rainfall event where the soil remains wet for three, four, five days because that'll germinate those summer weeds as well. Are those some sort

of spring germinating summer weeds? So. Things like fleabane. Often in the South, we don't see a lot of fleabane germinate over summer because we just tend to have these thunderstorms that drop ten 15mm of rain, and then we'll have a couple of 30 degree days, and they dry the surface out where we will see them germinate in those circumstances, often in the crop row where there's a bit of shading and the surface doesn't dry out as fast.

So I think there are places to actually go and look after these summer rainfall events to work out what's really happening. So, you know, driving around the paddock and going, I don't see anything, stop, move some of the straw away and just see that you don't have anything germinating where that moisture has been accumulating.

collects on the roadside edge. We've got vegetation and other material on there, which helps shade the surface so it doesn't dry out as fast. So we're looking at those places where the soil doesn't dry out quickly. But I think the big issue we often have is that we'll after harvest, we'll end up with those big weeds that require a lot of attention. Dealing with those later ones is often a not every year problem, because you don't

always get a big rainfall event over summer. You might get a few millimeters here and a few millimeters somewhere else, and it's really not adding up to a whole lot. So you're often trying to protect that first rainfall event you got in time for harvest. The planning component of it is to really make some decisions about which of your paddocks are a must for early summer weed control to reduce the weed burden so they're easier to manage as the season goes on and you have less losses.

Which ones can you get away with? Being not so rigorous around some of weed control on that gives you a bit of flexibility.

a holiday. So I really like what you're saying about break down your paddocks, prioritize the ones that are really important, perhaps put some sheep on some other ones, and hopefully you've got someone to look after your sheep while you go on holidays. That's the next problem. But we won't go into that. Um, and then would you also suggest

getting a contractor in? Because I'm just thinking, again, all very easy to say, and I know contractors cost money, but it's just so important that farmers get to have a break. It might not be four weeks, it might be one week. But if they feel like they're tied to the farm and they have to get these summer weeds, which are obviously really important and they need to be killed, and it's going to be cheaper, isn't it? If they get them when they're smaller as well.

timely fashion. We see that every year, where we have a lot of summer rain, is that farmers struggle to get across their paddocks to do all their summer weed control. So I think it's understanding what your own limitations are and just thinking about all the practicalities around this and how to do a good job may really make sense that you've got a few paddocks that a contractor needs to do, just to make sure that the whole of the farm you need to get done gets done in

a timely fashion. That's probably what you should be thinking about doing.

But secondly, we're using stored moisture. And that stored moisture can be worth depending on how much is there can be worth, you know, up to a ton of grain. That's the bit. Is that how much do you have to protect is how much you've got to lose where we get those big seasons like some guys had last year, there's some farmers in the Valley who've virtually grown their

crop on on stored moisture this year. If you'd lost all that because you didn't get your summer weed control done, then you've lost a significant amount of this year's revenue. We know in the big picture the average is you get $35 back for every dollar you spend on summer wheat control. Um, but that varies widely from almost nothing to hundreds of dollars.

out of the ute and actually seeing what's underneath. Talking about with those summer rainfall events to get out and check after those rainfall events, knowing that if you just get one rain and then five hot days, it might actually not do anything. Whereas if something's being sheltered or you really need to get in and see if the

ground is still damp to see whether something's germinating. So prioritizing those paddocks, perhaps putting some sheep on, maybe getting a contractor in, and then also you're talking about with the apvma and the diquat and the paraquat to just wait and see, obviously what happens. But knowing that you, you and your science buddies and people at BCG were working on strategies to to help farmers because we know that these things are just going to pop up all

the time. And as you say, we have to look at these strategies anyway because we're seeing resistance. Was there anything else that I capture that okay. No, I think.

What will I do? Will I change any of my decisions and understand how you might change your decisions before that event happens? That if it does happen, you can step into those new decisions. Prioritise how you're going to plan. Because those paddocks that had more competitive crops in this year are probably going to need less attention than those ones that had less competitive crops.