Weeds AR Wild Series, S2 Ep18. Dr. Tom Barber and guest Larry Steckel discuss mid-season weed control issues and new potential herbicide uses.
Weeds AR Wild Series, S2 Ep18. Dr. Tom Barber and guest Larry Steckel discuss mid-season weed control issues and new potential herbicide uses.
Weeds AR Wild Series, Season 2 Episode 18.
Title: Mid-season Weed Control Options and Issues
Date: June 24, 2022
[Music]: Arkansas Row Crops Radio providing up to date information and timely recommendations on row crop production in Arkansas.
Dr. Tom Barber: Hello and welcome to the Weeds AR Wild podcast series as a part of Arkansas Row Crops Radio. This is Tom Barber, Extension Weed Scientist with the University of Arkansas System Division of Agriculture. Today, I'm very fortunate to have Dr. Larry Steckel with me as my guest. And as many of you know, Larry is an Extension Weed Scientist with the University of Tennessee and is my counterpart across the river of whom I bounce many questions and ideas off of. So, Larry, thanks for being here and welcome back to the Weeds AR Wild podcast.
Dr. Larry Steckel: Oh, yeah, Tom, glad to be here. Good morning.
Tom: So earlier you were telling me you’re just right across the river from Osceola. Right? You’re over there close.
Larry: Yeah. Oh, yeah. Within a mile of it, yeah. So we've got a site here where we're doing research on. It's resistance level of the pigweed is off the chart for auxins.
Tom: So is that where we’re getting all ours from? Is that what you’re telling me? We’re getting all of ours from right there where you’re at? [laughter]
Larry: It’s a very definite a possibility. [laughter] But I think the wind blows west to east, doesn't it? So maybe it’ll blow it the other way.
Tom: Oh, OK. I'll know nothing about that.
Larry: [laughter]
Tom: Well, Larry, I got the opportunity to come over and be a part of your weed tour last week, and I appreciate you, number one inviting me to be a part of it, but I thought you had some really good looking plots, man. You want to kind of – and just for our listeners, if you don't know, this is something that Dr. Steckel does every year. They have what they call the weed tour over at his main site, in Jackson, Tennessee, there on the experiment station. And so, it was a really great tour, a really great crowd. I was surprised, Larry. It was like a hundred degrees, and it didn't seem to bother anybody. We had three different groups rolling through there and had a lot of good stuff to look at. You want to give us kind of an update or just kind of an overview of what we talked about?
Larry: Oh, sure, Tom. Yeah, you laid it out pretty well. It's a tradition. It's been going on for decades and we had about 160 or so there, which I thought was great, considered the heat and all. And I'm sure glad you got to come over and participate and give your insight from what you're seeing on your side of the river. That helped a lot. Had a lot of good comments from the presentations you gave. Yeah, we kind of do a walking tour and I'm sure glad to have help from Tom coming across the river to help tour, because it can't be just all me. My God, that'd be awful.
[laughter]
Larry: So that kind of split it up with some folks and had a lot of good, had a lot of pretty showy. Some of them are showier this week. I always debate on which we have it, whether it's this week or the week prior. We went with the week prior, but have a lot of good things to show. Things that were working, things that weren't. You know, you got to see some of the pigweed on the station is dicamba resistant. It's what I consider a moderate level. It's in that 2 to maybe 3x range, 4x, you know, decide on that. Now it's closer to 8 and we've got another site or two spread around the state that are higher. But it's interesting to see what works, what doesn't work. Unfortunately dicamba and 2-4, D don't work, but Liberty does. And right now, Liberty is really going out everywhere. But anyway, that was some of the plots we showed. A lot of the fertilizer applications – a lot of the work we're doing on that. I know you're doing some too on Zidua.
Tom: Yeah, we're trying to get ours out this week and that is definitely something I want to touch base on because that's kind of an old way of applying herbicides that we're kind of bringing back around. And it's something that I think's pretty unique, because we have a lot of growers that – I won't say that they won't pull a lay-by rig through the field, but they really don't want to pull a lay-by rig through the field. And so, I think they'll do anything they've got to do to control weeds. But this is an interesting take on using some herbicide like Zidua, that contains pyroxasulfone that has high activity on our pigweed populations. So go ahead. I didn’t mean to interrupt you. Go ahead.
Larry: No, exactly that.
Tom: And kind of give us an overview of kind of how y'all are doing that.
Larry: And so this is one of these deals, you know, where I didn't come up with the idea because the growers and the registrants really come up with it. They started it in Texas a couple of years ago, just trying it. And low and behold, they come to us wanting to look at it. And they had some growers jump in whole hog last year. We had around 40,000 acres of cotton where Zidua was supplied via fertilizer and it all worked really well. You just, you don't get the burn with it like you do with a Dual or Warrant over the top. You'll get a little bit of burn from the fertilizer, you know, the if the foliage is a little wet or something. But it's pretty transient and it's a lot less burn than what I see with an acid analyte going over the top. And pyroxasulfone just to me compared to, you know Dual and Warrant – it doesn’t take much water to get activated. Last year, I didn't really have any rain on our research for like eight, nine days, but we had some really heavy dews, and I think that was enough to get it activated at least to a point to when we actually did get some water, it really worked well. And that was pretty much what I saw walking fields that growers put on. We had some growers go whole hog, do their whole crop with it last year, and were really pleased. And like you say, it's the closest thing we're going to get to a lay-by anymore, it seems like. So ,it sure it sure has a play there. And then we also are looking at Prowl. Of course, I used to do that 20, 30 years ago. Looking at Prowl and even the Brake. Folks peddling Brake were wanting to look at it. So, we looked at it with Brake as well. Brake needs a lot more water to get activated. I'm not as convinced it's going to be a good…
Tom: Hey, Larry, I think I lost you. I don't know if you muted accidentally or what. Oh, there you are.
Larry: You got me.
Tom: Yeah, I got you. Go ahead. OK, you were talking about Prowl.
Larry: I don’t know where it cut off. Oh, Prowl. Yeah, we've got some Prowl research going out. We do have some growers putting Prowl out via fertilize. And then just here at the station, we actually looked at Brake, putting it on be a fertilizer. And you know, Zidua doesn’t need a lot of water to get activated. Prowl needs some, and Brake needs a lot. So, I'm not convinced that Break is going to work real well applied via fertilizer, but there's only one way to find out and that's to do the research.
Tom: That's right. I agree. And what you said, and I’ve said too about the lay-by rigs. It's kind of funny that a lot of the growers in south Arkansas or southeast Arkansas, I saw a lot of lay-by bars being pulled just yesterday. So, we've got a little segment of growers that still do that. And I think it's great. And a lot of times those are the cleanest fields as well at the end of the year.
Larry: Oh, yeah. They are.
Tom: We have some that, you know, have just moved past the lay-by bars and the post-direct hoods and that kind of thing, for whatever reason. But I have seen more cultivators running this year, too. So I don't know if that's just part of the year that we're having and just the situations that we've had this year, that are going into that or what. But it's definitely, it's been a tough year for us from a weed control standpoint overall. And so, any new ideas like coating fertilizer with Zidua, I think is great. And like I said, we're going to try to get some out today and look at that as well. And just take an evaluation on that. So why don't we talk a little more about just, you know, broadly on weed control and we're across the river with y'all. What do you seeing this year? I know we talk a lot about the pigweed that's resistant to the auxins. Anything else big that's going on? I know that's really big. And we can definitely focus on that and what to do. But is there anything else that you've seen this year that's unique?
Larry: Well, the biggest call still is we can't control grass. And especially in the counties that border y’all, it's the worst. I was over around Covington. So, Tipton County, just north of Memphis two days ago, looking at some fields and the junglerice and the goosegrass is just crazy in some of those fields. One of the cotton fields I was in, it looked like a hayfield, all the goosegrass in it. And, again, Dicamba is involved. But you know, when you’re tank mixing Roundup and Dicamba or Roundup/Clethodim/Dicamba – when you get the Dicamba in there it antagonizes the grass activity and it's not enough to like – crabgrass we’re controlling. Spangletops we're controlling. Broadleaf signalgrass we’re controlling. And it's not those species. But two species that have really dialed into that niche has been goosegrass and junglerice. And they’ve got a little bit of glyphosate resistance in the population but they've also, just the overall population has built up tolerance to the point that you get a little antagonism, you're not going to control it.
Tom: I agree and you know, I've got a lot of broadleaf signalgrass in my plots, but I agree. I mean, it's not – we're doing pretty decent on the broadleaf signalgrass. The goosegrass, like you say, and I don't know really how much of our population of goosegrass is glyphosate resistant. We do have some, but I really don't know how widespread that is. And I know you all have some of that right, as well? In the goosegrass populations?
Larry: We do. Depending on location, I've seen as much as 15% of it being glyphosate resistant. Sure have. Yeah.
Tom: So what do you think? I mean, I know some of it can be due to the resistance. Some of it is the antagonism. What role do you think this dry weather and just suppressive heat that we've had over the last two weeks this early in June? I mean, is that playing a role in our poor control in it as well, do you think?
Larry: I think it is. I think it's kind of compounding the antagonism we see with Dicamba. I think it's just adding a little more insult to injury there. And that's why some of these fields are just, oh, just terrible grass right now in them. Now, where the guys have gone out with just straight Roundup/Clethodim, and haven't had any Dicamba on that grass for a couple of weeks. They're doing pretty good. But if they've had Dicamba over that grass within seven days, ten days, or even worse, tank mixed – they're just really swinging and a missing.
Tom: Right. And you know, and we're seeing that too, over here. Matter of fact, I walked a lot of soybeans the last week and a lot of the problem – I mean, it's like you said with the cotton. With these beans you can hardly row them out due to the grass or it might be volunteer rice or off-type rice that is coming up. So, between barnyardgrass and volunteer rice in a lot of our beans, I mean, that's our main weed.
Larry: Yeah.
Tom: And that's our recommendation as well. For Arkansas we're not supposed to tank mix glyphosate and Dicamba anyway. But for controlling barnyardgrass, volunteer rice, junglerice that you're talking about or goosegrass – I mean, I really think just keeping Roundup and Clethodim as a separate application is the way to go. And we always get a lot of reports of Roundup by itself not working, and then we'll do a bunch of sampling and then we don't find any resistance or reason why we're not getting good activity in the field. But you know one key factor every year is, it seems to be, we get those calls when we get these hot temps spiking up and have dry weather periods. So.
Larry: Yeah, and I don't know what you think. I’m starting to get the calls on maybe adding AMS. And I'm usually not a big promoter of using AMS, because most of my water is not hard enough to get a response from it. But I think when it gets really hot and dry like we're in now, it probably does help some now.
Tom: No, I agree. And I think you never know with a water source, so it's just kind of a failsafe to put it in there just to make sure. I guess it's not anything, other than the checkbook a little bit.
Larry: Yeah. So and I was going to ask you too. This is a whole totally different subject, but it's kind of unique for this year. I haven't had this call yet. Maybe you have, but I'm getting calls on how you control XtendFlex volunteer soybeans and XtendFlex cotton.
Tom: Yeah, I've had that call several times, Larry. And my answer is, I don't know. [laughter]
Larry: [laugher] Yeah, mine too. No clue. None.
Tom: [laughter] And top it off, some of them are STS. So, you know, you can’t even eat them up with Envoke.
Larry: Yeah. I know some of them are trying to maybe stunt them down with Envoke, but I still don't think it's going to kill them.
Tom: No, I don't think so either. It’s going to make them sick but again, that's where a post-direct rig might come in handy.
Larry: Exactly. That's about the best thing I could think of too, is a post-direct rig. And with XtendFlex soybeans, that's all we're going to have here shortly. That's not going to be an uncommon question going forward.
Tom: Well, it's really not. And, this year for us, especially this year, because there's a lot of guys growing cotton. Some of them had never grown cotton in the field – the previous year were beans just because of cotton price is higher. So, yeah, it's a big deal this year. I have gotten several of those calls.
Larry: Yeah. And I'm like you. I have no good answer. [laughter]
Tom: [laughter] Yeah. That's the hardest part. You know, not even having an idea of an answer.
Larry: Exactly. No clue.
Tom: Do you have a post-direct rig? No. Do you have a hood rig? No. Well, pull them up by hand or chop them out. That’s all I can tell you. [laughter]
Larry: That's all I know. Yeah. Yeah. Nobody wants to do it when it's 100, so.
Tom: Yeah, so. Great. You know, and one of the big things, we go back to that antagonism deal, and this was all my little part of your tour or whatever, but seeing that grass that you had in those plots because you got a response to the pigweed by increasing the Dicamba rates. But also exponentially, you got a response in your grass control as well. And the more Dicamba we put out there, or you put out there, it was your plots – the less grass control that you got in those plots. With, I think you all used Select – is what you told me in that case. And I walked some Select plots that I sprayed in combination with Dicamba. Walked on yesterday. And, man, they've only been out for six days I think. But oh man, it wasn't very good at all. It was a lot of green grass in the plot that was about all that was left was green grass.
Larry: Yeah.
Tom: So, anyway.
Larry: And I think that's at least over here, I think that's part of the puzzle on the grass becoming more and more of an issue. And again, it goes back to the pigweed and the auxin resistance. But I mean, we did it with Roundup back in the day when Roundup resistance started. You just start using high rates to try and control and we did it with Roundup. We're doing it with auxins now, trying to control pigweed and it is helping on pigweed but it's having an inverse effect on the grass. It's a reason the grass has become more and more of an issue over here in Tennessee.
Tom: Well, it definitely is and it is in our plots, and I see it as a drive down the road. That and nutsedge. The yellow nutsedge is about to drive me crazy. And that's another one that I, and depending on the situation, don't have a lot of good answers for.
Larry: Yeah, nutsedge had a great year.
Tom: But anyway. Well, anything else? Any other key points we have left out that you think's important? You know, we're not at bloom yet. You know, I think for the most part from a cotton standpoint, even for a lot of our beans, we're at least two weeks behind on a lot of this crop and we're approaching the midpoint of the season. We know a lot of fields, we've either done it or not, but now we've focused our attention on irrigation. Is there any key points as we're starting to run this water? You think we need to let our listeners know as we get into the mid-season here?
Larry: Well, yeah, I think just, if you’re starting to run water – at least over here we do a lot of overhead. I know you all don't. But, cutting them on and especially all these double crop beans we’ve got in now. Getting the PREs activated, it also helps get the beans out of the ground when it’s so hot. But you know, I think it's worth running that pivot around the field.
Tom: Oh yeah. And that's something back to the fertilizer encaps… you know, the herbicide on the fertilizer. I don't know how well the row water is going to work versus the overhead irrigation on that type of application. But we have a lot more row watered acres than we do pivot irrigation acres, I guess. So.
Larry: OK, yeah, we have very little row water over here. It's pretty much all pivot. So that really kind of helps with that.
Tom: Right.
Larry: Putting it on better, you know, via fertilizer.
Tom: But either way, even if it's just giving us some control in the middles, that's kind of our recommendation too. You know, before you start all this water, let's get a residual herbicide out because it's been dry so long. We put some nitrogen out, at least in the case of cotton. We've put the nitrogen out in beans. Either way, it's been dry. We flush the water to it. Weeds are fixing to come in these middles. And I think getting some residual herbicide out, whether it's Zidua or, depending on what crop we’re in. Zidua or anthem, or Dual or Warrant. I mean, it's going to be important for us to get some residual out ahead of this water because we got a lot of season left and we're not even close to covering the middles with most of our crop right now.
Larry: Yeah. So, no. We're not even – like you we’re two weeks behind, too. Now, with all this heat, we're starting to catch up. And we're two weeks behind by calendar. But the thrips were just terrible and just could never keep them off this cotton. And, I think that's held them back too. Between the thrips and the winter we had through Memorial Day. It's really got us behind where we usually are at this time of year.
Tom: Well, that's absolutely right. And I talked to several consultants yesterday. Said the cotton we actually got planted in April is our best cotton. Usually it's hottest. Usually it’s the May cotton that's the best got. But they like, you know, the kind we planted in April. It was up. It was growing before that cool snap. Everybody that planted in that cool snap or just after I mean, it it's been a struggle and we're like you. The thrips have just beat it up, eat it to death, and then the winds have thrashed it around.
Larry: Yeah.
Tom: We're finally getting good looking leaves on our cotton plants, basically is where we're at now. You could actually tell it’s cotton now growing.
Larry: [laughter] Yeah. Yeah, it looks like cotton for the first time.
Tom: Yeah, right.
Larry: Same here.
Tom: Yeah. I think we're right there turning a corner, but we're easily two weeks behind, if not a little more on that.
Larry: Yeah.
Tom: So it's probably going to take a little more residual herbicide to get us through the season, and...
Larry: That's a fact. Yeah.
Tom: But anyway, well, I want to thank everybody for tuning in to this episode of The Weeds AR Wild podcast. And again, special thanks to my special guest, Dr. Larry Steckel, for joining us live. Larry, it's always a pleasure to visit with you and have you as a guest on our podcast. Appreciate you taking the time this morning.
Larry: Oh, sure, Tom. Thanks for having me. And thanks again for coming over last week.
Tom: Oh, yeah, I had a blast. And you know, for our listeners, we always welcome your feedback or any ideas you have for guests on the podcast to discuss management decisions. Again, Larry and I both work for the extension service for, so we're here to answer your questions, if you if you have them. But just get in touch with your local county agent. Larry, anything you want to say before we sign off here?
Larry: Oh, no, I think we're good. This is the Milan No-Till Day year. The last Thursday in in the month, the month of July will be over at Mud Island. So that's our next big field day here.
Tom: All right. So the Milan No-Till. It's a big production, too. I've been there as well. It's pretty big, right? It's a big to do for everybody, the family, everything, right?
Larry: Oh gosh, yeah. It’s a pretty big production. It's yeah, it sure is. It's an event.
Tom: And when did you say that was?
Larry: It's the last Thursday in July every year. And I forget what date that is off hand.
Tom: Oh that’s fine.
Larry: It's the last Thursday in July.
Tom: Last Thursday in July. OK, well, yeah, everybody should make a note to try to make it over to that if you haven't been there. That's a that's a good one as well. So, thanks to Larry. And thanks for everybody for joining us for this week's episode of The Weeds AR Wild podcast series on Arkansas Row Crops Radio.
[Music]: Arkansas Row Crops Radio is a production of the University of Arkansas System Division of Agriculture. For more information, please contact your local county extension agent or visit uaex.uada.edu.