Weeds AR Wild Series, S2 Ep7. In this episode, Dr. Tom Barber and Dr. Jason Norsworthy continue the herbicide-resistant weed update discussion with Palmer amaranth, Johnsongrass, marestail (horseweed), and others in corn, cotton, and soybean.
Weeds AR Wild Series, S2 Ep7. In this episode, Dr. Tom Barber and Dr. Jason Norsworthy continue the herbicide-resistant weed update discussion with Palmer amaranth, Johnsongrass, marestail (horseweed), and others in corn, cotton, and soybean.
Weeds AR Wild Series, Season 2 Episode 7.
Title: Herbicide-Resistant Weed Update for Corn, Cotton, and Soybean
Date: March 30, 2022
[Music]: Arkansas Row Crops Radio providing up to date information and timely recommendations on row crop production in Arkansas.
Tom: Welcome to the Weeds AR Wild podcast series as a part of Arkansas Row Crops Radio. This Tom Barber, Extension Weed Scientist with the University of Arkansas System Division of Agriculture. And today, I have with me my co-host, Dr. Jason Norsworthy, Distinguished Professor of Weed Science at the University of Arkansas in Fayetteville. Jason, I think you're pulling double duty, but we're glad to have you back as part of the podcast this week.
Jason: Glad to be here, Tom. Yeah. Last week we talked about some herbicide resistance issues in rice. And I think today we're going to expound upon that in and looking at some other crops.
Tom: Well, I know this probably a good time to have those discussions back to back, because we continue to get calls on what growers can get into their possession as far as herbicides and selection standpoint. So I know that knowing what kind of population of pigweed we have, for example, is important in making those herbicide selections and getting off to a good start for the season. Whether we're talking about well really any crop, but this week we're going to focus on soybean, cotton and corn, I think. So last week you and Dr. Butts talked about the main key resistant issues in rice. And this week we're going to cover some of our other upland crops. So Jason, what do you want to start with the big elephant in the room?
Jason: Yeah, let's start with the big elephant in the room. And I'd say that's Palmer amaranth. And, you know, you've already touched on a key component of resistance management. I'd say even just an effective herbicide program in general, and that is knowing what you have resistance to. Because unfortunately, if a grower doesn't know what's going to work or isn't going to work with Palmer amaranth, Dr. Barber, you know, I mean, once it gets up to about four to five inches in size, two and a half inches per day is something you can see under good, warm, moist conditions. And you can't get back in front of this if you choose the wrong herbicide - the wrong herbicide pre or even the wrong herbicide post can result in failure.
Tom: Absolutely. So, you know, there's a long list that I know you're going to go through and it's probably going to be discouraging to some folks. But, that information is critical in starting off with a good weed control program, especially for pigweed. And if we ever let that stuff get up out of the ground, then it really becomes a nightmare in some of these cases to manage, especially with the weather issues, environmental conditions. A lot of times it's hard for us to get back in the field timely with these post emergence herbicides, to gain control before that Palmer amaranth grows, like you were talking. And so let’s focus in on some key herbicides and key populations. In the state and what they're resistant to. And hopefully we can develop a good program.
Jason: Well, when we start looking at resistance in Palmer amaranth today, we have confirmed to this point, eight different herbicide modes of action, or sites of action, to which we have resistance to. And I'll just take these numerically and proceed through them. The group 2 herbicides, the ALS herbicides. 1994 really that's where that began in terms of the first confirmation of resistance in Palmer amaranth here within Arkansas. So those have been the Scepters, the Pursuits. So really, we don't use those much today. And actually, the last time that I did a statewide survey, which has been a couple of years ago now, I believe it was better than 99% of the pigweed populations that I tested were resistant to the ALS chemistry. So, I would love to actually find a susceptible standard these days that I could compare back to, and you're not going to find one or you'd be hard pressed to find one out there today. The group 3 herbicides, things like Treflan, we probably don't use a lot of Treflan, but Prowl. Prowl is a good cheap DNA herbicide that we can use. We've got resistance to it. I'm going to skip on and actually move by a couple of these and then I will come back to them. Glyphosate, the same as what we see with the ALS herbicides. We've got widespread resistance out there. Better than 99% of our pigweed populations will be resistant to glyphosate. If you go to the mid-nineties, you know, Dr. Barber, you working over there at Marion. I did some work there in Crawfordsville, where we worked extensively on understanding the PPO resistance that was out there. And what we have seen is PPO resistance has really spread. It just amazes me at how quickly that spread across the state of Arkansas. And with that you know, the likelihood of having success with the PPO chemistry has diminished greatly. Going back to our research, we do see some activity pre-mergence even over resistant population, whereas it will be just a complete failure post emergence. Also, we've started to see some resistance to the group 15 herbicides, things like the Metolachlor type products, Acetochlor, Metolachlor, the Duals, the Warrants. We've got some resistance out there. We've got some resistance to the HPPD chemistry, now, granted, that's not going to be a soybean issue. That's going to be more of a corn issue, but that's what we have in Palmer amaranth. And, really the one that we started seeing a couple of years ago. And we have three confirmed populations in the state today that is the glufosinate resistance. But when we take a look at these glufosinate resistant populations, I had a Ph.D. student, Lawson Priest, that did his Ph.D. around dicamba and works some on glufosinate. And a key component, or key finding that he had in his research, was that he also found 2,4-D resistance in one of these glufosinate resistant pigweed populations. And, you know that’s very scary to see that you've got gluphosinate resistance in 2,4-D resistance stacked within a population. In just a couple of weeks ago, I was looking at some of my pigweed populations in the greenhouse and we've got two more populations in the greenhouse where the Enlist technology had failed last year. And based on what I'm seeing the greenhouse, I think we've got two more populations of 2,4-D resistant pigweed, and this very, very unfortunate, the rate at which we're losing technologies.
Tom: Absolutely. I mean, it's like you say, you know, the ALS chemistry hasn't worked in a long time. Glyphosate hasn’t worked. It's hard to believe for me, but, really what was that 2006, 2007 - it was pretty widespread? So, it's been a long time since it's worked. PPOs are very widespread now, and I know we're talking about the Metolachlors and the glufosinate and 2,4-D resistance on a limited scale. But, we know what's coming down the road. I mean it's, it's pretty obvious. It's not going to take it very long to get widespread across the state, most likely, once we get it.
Jason: Well, I agree with you. I think if you go back and you look at the ALS chemistry, you look at the glyphosate, you look at the PPO and how quickly that that blew up. I think the one thing that we can do to try to minimize that is, we get in a habit, and I don't fault growers for this, but I think we get in the habit of finding something that works and we continue doing that until it doesn't work. And with that, this a weed that can produce in excess of a million seed per plant. And those populations quickly, quickly spread when you when you have resistance. But as you mentioned there, all we've got today is three populations that we've confirmed this glyphosate resistant. We're doing some survey work across the state. We still continue that on a yearly basis and we haven't seen, to this point, substantial spread. And as I said, the 2,4-D resistance, it appears now we've got three populations in the state that 2,4-D is going to fail on.
Tom: Well, and I think it is concerning though and growers and consultants and anybody that's walking a field should take note of whether or not we're getting decent control of these Palmer pigweed populations after applications. Sure, maybe they're too big when we make the application and that's the reason the herbicide fails. But for sure we don't want those populations going to seed in the field, if at all possible. And I know specifically where two of those glufosinate resistant populations came from in Arkansas and Mississippi County. And I've kind of followed those fields since we've identified that. And you know, for the most part, the growers have done a good job keeping it under control. It wasn't a 2010 again where we walk out and there's multiple fields that just all have to be disked up, I guess is my point. I mean, they for the most part, they took it serious and did a pretty good job preventing those from going to seed and have really focused on a broad scale resistance management plan to keep those fields at a manageable level from a Palmer pigweed standpoint. And I think that's really important as we move forward. Number one, as we went through this big list of what Palmer is resistant to, number one, not one particular chemistry is going to be the answer. It's going to take multiple chemistries to manage this weed regardless of the crop we're talking about. And that's multiple modes of action up front meaning we've got to use the right ones pre-emerge. You know, we mentioned a lot of chemistry. We didn't mention photosynthetic inhibitors specifically to this point. And so in my opinion, that's got to be a key player in the management of Palmer amaranth regardless, you know, in corn, soybeans or cotton. I think we've got to have that chemistry in there.
Jason: Now, I agree with you and not only the PS II inhibitors, but if you think back to cotton, I mean, you've got Brake.
Tom: Right.
Jason: We haven’t seen anything about that in terms of resistance. So I think it's the key is keep it guessing. Also make sure that you have multiple effective herbicides on that on that ground. You know, again, one of the major takeaways that I can remember going back to the PPO resistance work that the two of us was doing is, if you're dealing with Palmer amaranth - and it's Palmer amaranth, that's resistant to five, six, seven different modes of action. The key takeaway was start with a sound residual, preferably two modes of action on the ground. If you can get three, that's even better. Those treatments always were head and shoulders above those having a single out AI there for control.
Tom: Absolutely. And I think that is key. I mean, not relying on – because when you think about it, when we first saw the PPO resistance, what were we doing? We were Valor pre in beans following it with Flexstar post. I mean, that was a standard program across a lot of Arkansas acres. And as we've seen and as history tells us, that just doesn't work for pigweed. We've got to keep it guessing, like you say. So, having that multiple residual, multiple mode of action, residual program up front and the more the better is critical.
Jason: The other thing is I know, again, I'm a big believer in herbicides. I think herbicides are foundation to what we do, but we've got to also try to integrate some other strategies in here. Whether that be looking at twin rows, drill rows, something to enhance canopy formation. You know, and every once in a while, tillage is a four letter word to some folks, but a little tillage every once in a while it goes a long ways from a standpoint of helping control this weed. You know, the two of us have done some work in in cotton, and I'm not opposed to dragging a moldboard plow out every three, four or five years and burying that seed. If you’ve got a high, high population of Palmer amaranth, you are in a scenario in which you have a very high risk for resistance. You've got to get that population back down. And what we've seen is tillage helps get that population back down to something that we can actually manage.
Tom: Absolutely. And I think you hit on a key point there, and that's not just using chemical methods for control. Got to incorporate some of these cultural methods down the road, in the future it’s going to have to be done. We can either do it proactively or we will be forced to do it likely at some point, is kind of the way I feel about it. And I hope one day this year, for one of these episodes, we need to focus on the seed destructor we've been working on. And I think that's a good tool, especially in soybeans, to help us integrate some of those cultural or mechanical processes to reduce some of these populations.
Jason: Absolutely. No, I agree with you totally. And I think the key that’d I just tell you, this is herbicide resistant weed management 101, is there's two components to it. I tell this to all the classes I teach. It's soil seedbank management. And number two is diversity in tactics. The more we can keep the weed guessing, the better off that we're going to be in terms of managing pigweed, barnyard grass. You name your herbicide resistant weight of choice, and you're going to be more effective in managing it if you have a diverse weed control program targeting the seedbank.
Tom: Absolutely. All right. Well, anything more on Palmer amaranth before we move on.
Jason: I think that should cover us for Palmer amaranth. So, do you want to move to now?
Tom: Well, I know y'all have recently done quite a bit of work on Johnsongrass, and I got a lot of calls on Johnsongrass last year. So, tell us what you've learned on the on your Johnsongrass screenings.
Jason: Yeah, so I have a student that’s actually spent his master's project, it’s been centered around some of these new technologies in grain sorghum. And when you think of grain sorghum and even to some extent corn, you think of Johnsongrass. And, you know, we've actually gone in and taken - we've got 63 accessions across Arkansas. These Johnsongrass accessions where we've collected seed, we’ve gone in green house we've evaluated these to Roundup. What we found is six of the 63 appear to be resistant to Roundup. Two of the 63 appear to be resistant to Fusilade. Someone might say, “Well why are you? You said grain sorghum. What are you thinking about Fusilade?” We're actually, my program is looking at developing a Fusilade resistant grain sorghum line. We're working with Texas A&M so we wanted to know how much resistance we have out there to Fusilade. Two of the 63, again, were resistant. Pioneer is developing a technology called Inzen grain sorghum. Dr. Barber, you've worked with it extensively. I've worked with it extensively. And that herbicide is going to be Zest, which is comparable to Accent in corn. And what we found is eight of the 63 accessions that we've screened have been resistant. And then lastly, you have the igrowth technology that Advanta is looking at bringing into grain sorghum, and it's going to allow for the use of Imiflex. For those of you don't know what Imiflex is, you may have heard of Beyond in Rice or what Raptor used to be in soybeans. So that's Imiflex herbicide, Imazamox. And what we have found is that six of the 63 Johnsongrass populations we've tested have been resistant. Now when we take a look at these, I wish I could tell you this wasn't the case, but a lot of the resistance when I think of Metolachlor resistance in pigweed a few moments ago – the glufosinate resistance, the 2,4-D resistance. It appears to be, I'm going to say the Mississippi County, Crittenden County - that northeast Arkansas corridor. That’s really where we're seeing the majority of these Johnsongrass samples also pop up. I've heard from some growers over there, that, again, “I’ve sprayed glyphosate, I’ve sprayed glyphosate. I can't kill this Johnsongrass in my cotton, in my soybean with it.” And you're not going to. You're not going to kill it based on what we're seeing here. We actually, if you go back to I guess it was Crittenden county, probably I'm going to say eight years ago - did an extensive amount of research over there in West Memphis. And we had a population that was glyphosate resistant. It was also ACCase resistant, all the FOPs were not effective on it. I'll tell you, Clethodim suppressed it, at best. Sethoxydim which would be Post. Clethodim, would be Select. Those type of herbicides gave some suppression. I wouldn't call it full level field control with those ACCase herbicides.
Tom: Right. And I'm like you. Like I said, we're getting calls year after year. They seem to be increasing a little bit on Johnsongrass. And thankfully it's not spreading as bad as the pigweeds spreads, for example. I remember first coming back over across the river into Arkansas in ‘07. I believe y'all found the first populations of Johnsongrass at some point, not far from there.
Jason: That’s correct.
Tom: Like in Crittenden County, wasn’t it?
Jason: It was Crittenden. West Memphis.
Tom: West Memphis, yeah. So yeah, thankfully it's not spreading as fast, but there are likely populations that are becoming resistant a little more widespread than we've seen in the past. But Johnsongrass is just one of those, it's hard to kill in general sometimes, especially the rhizome Johnsongrass, when it’s coming up from rhizomes.
Jason: It is. And you know, where you have ACCase resistance, glyphosate resistance, ALS resistantance. I mean, you just don't have a lot of post emergence options there. Brent Johnson, who again it has been probably seven, eight years ago – Brent worked on his masters under me. What he found was the best option was multiple applications of glufosinate or Liberty. On those you're looking at probably about ten days between the applications, and I'm going to tell you that I mean is that the level of control that you're going to get with the glyphosate sensitive population? No it's not. We could get about 90% control of rhizome Johnsongrass with multiple applications of glufosinate, but those applications really need to be timely, and it's just difficult to kill rhizome Johnsongrass.
Tom: Well, I know. And it may be up in the field now. I know last year when we started putting some of our plots in, Johnsongrass was already up. And so just kind of depends on the environment or the environmental conditions at time of planting or when you plant. But it could be one of the first things up in the field. So, and I know something like Gramoxone is not going to work that great on it either. Really, it’s just going to burn it back and that's about it. So, I guess our just our recommendation is just to keep monitoring in the field. And, if we're not killing it with Roundup [laughter], then obviously we're going to have to have a different game plan. And, you know, we've got corn hybrids that are tolerant to glufosinate or Liberty. And maybe that's what we should move to. But if we've got grain sorghum, I don't know what we're going to do. Still. [laughter]
Jason: Yeah. I mean, it's a scary situation here when you take a look at grain sorghum. Thank goodness, like I said, I mean, from an ACCase standpoint as we're starting to move in that direction. I didn't mention, but you've got the Double Team technology which is quizalofop-resistant grain sorghum. But I would expect that quizalofop numbers to look very similar to what we're seeing on Fusilade. I wouldn't expect a lot of difference. Sometimes we can get some subtle differences in there, but overall, I would think quizalofop would be a pretty effective herbicide for us. If we go down and start planting Double Team technology, the Double Team technology, I believe, became commercially available this year. I don't think you're going to probably see any of that in Arkansas. There's probably going to be a Texas/Kansas at least coming out of the gate, from a grain sorghum standpoint. But maybe we do have some options on the horizon as it relates to Johnsongrass control in grain sorghum.
Tom: Alright. Well, unless you have something else on Johnsongrass, let's kind of move on down the list. I have written down here on topics for today. What about the ragweed species? Now, I know several years ago we confirmed giant ragweed and common ragweed resistant to glyphosate in the state. You know, I don't get any calls much at all really on either one of these, Jason. I mean, every now and then I'll get a picture of giant ragweed, “what's this creeping out from a ditch?” But for the most part, I just don't see them as big issues for us, at least not as big as they are in the Midwest.
Jason: Well, I would agree with you on that. You know, I confirmed these. I don't know how long it's been now, you know. Time flies. It’s probably been close to 15 years ago I was working with common ragweed and giant ragweed. 12 to 15 years ago when we confirmed this. Most of these, I think there's probably a few possible populations. Most of these have been in that Newport, Jackson County area over there. But I just don't get a lot of calls on ragweed. And, when I do see ragweed, it's a ditch weed for the most part. You may see where some individuals have some tillage and they pull a little bit of it into the edge of the field. But I don't see the same infestations. The guys up in the Midwest, they just want to talk about fields being inundated with giant ragweed. I just don't see that here.
Tom: Right. I don't either. I think you're right. I think it's more of a ditch weed, thankfully. That's one less problem we have now. In the future, who knows? I mean, we hear about weeds making a comeback. And I know one that Tommy, or Doctor Butts, has talked about getting a lot of calls on his common cocklebur. And I'll be honest with you, I get a lot of pictures, actually, from year to year from consultants or growers. Haven't seen one in a long time or may be too young to remember common cocklebur. But I mean, when I was a kid, that was our biggest problem in the soybean crop, was common cocklebur. And so, you know, I think it might be making somewhat of a comeback. But, you know, when we look back at the weather conditions, all the rain that we've had. For the most part, when I see cocklebur it’s along a river, along a stream, in the ditch. But I know it can creep out. It can be some issues in the fields. And I know for sure many, many years ago it was a big-time issue. And back then we had a lot of ALS resistance to the Scepters, or Scepter similar-type herbicides. So, are you hearing anything on common cocklebur, Jason?
Jason: You know, I get more and more calls. I'd say over the last two or three years I've had more calls on common cocklebur than probably I had the ten years prior to that, maybe even 15 years prior to that. I have, as I walk fields, as I’ve been in fields, I see more common cocklebur out there. I'm not going to say that it would be one weed that I'd put in our top ten list of important weeds here in the state of Arkansas, but I am seeing more and more of it, and I think it's probably a result of the pigweed issues that we're having. And what I mean by that is, as we've had more and more of this pigweed just continues to explode and we’ve dealt with it. Some growers are, as I mentioned here a few moments ago, they're having to go back and put more and more tillage in these systems. And as you put more and more tillage in these systems, you bury common cocklebur and might even bring it up. And there's actually some pretty neat research that back when we were grad students, I don’t know if you remember before that, it was Doctor Bararpour, who's now at Mississippi State. He did his Ph.D. project on looking at common cocklebur and the effects of tillage. And what he saw was if you went to a no-till system where you really reduce the amount of tillage that you have in that system, you can virtually eliminate a common cocklebur. That bur really needs to be buried about an inch or more in order to have good germination of it. And I think as we brought more and more tillage back into these systems, we've really stimulated the germination and emergence of common cocklebur.
Tom: Well, it needs to be buried and it needs to be scarified too. You've got to crack that hard bur, because you know, from time to time we'll go sample some in the field. Grower may suspect glyphosate resistance in that population. And we’ll put it in a concrete mixer with a bunch of rocks and try to beat it to death, and we'll put it on an acid drip or something just to scarify the seed coat so it will germinate. So, it's hard to get germinated, especially in the greenhouse. But through all what little work I say we've done, we haven't found anything resistant to glyphosate yet, at least on our end.
Jason: No, we haven't either. And like I said, I get more calls, more intrigue around common cocklebur, but in terms of folks sending in a sample and asking to screen for glyphosate resistance or resistance to any herbicide, I haven't had any samples come through my program in the last several years.
Tom: And we really haven't seen any in our plots. You know, I assume most of this is still resistant to ALS chemistry. You know, I scratch my head wondering, well, where did it come from, if it came from a river or if it came down the river and out into the field? Are they all ALS resistant or not still? And I don't know. I guess probably most of them likely are, but I guess there's a chance we could have got out of some of that. What do you think about that?
Jason: No. I mean, I think that. You know, when I spray these populations and just populations of weeds in general, it's not a homogeneous population, where everything out there is bulletproof or does not respond to the to the herbicide. If you go out there and let's just say you kill 50% of them. I mean, I think you know this, common cocklebur considering how it is actually the most competitive weed. It’s more competitive than the pigweed. On a plant per plant basis most competitive weed that we have. You go out there and you kill 50% of the common cocklebur you have in the field, and you probably still aren't going to run a combine through the field at the end of the day. So, it really doesn't matter whether it's partially sensibly or partially resistant, and it's all about can we fully remove those from the field?
Tom: Well, and I wonder, too, are we seeing it because of the PREs we're using on pigweed. I mean, if we shifted PREs to the point to where if we do have some cocklebur showing up, that they have as much activity. You know, if we just do something like Metribuzin and Metolachlor or Metribuzin and Zidua. I mean, how much activity does that actually have, at the rates we're using? And it's kind of like morning glories. You know, we get a lot of calls on morning glories now because they're slipping through some of our pigweed PREs, and that kind of thing. So anyway.
Jason: I think you're right on that. You know, Metribuzin is not going to be a home run on common cocklebur. You know, if you take a look at Metolachlor, it's not doing anything to it. So, with that, I think we probably are allowing some of this common cocklebur to come up in and get going . And with that, also, if you don't have some residual down, as that soybean canopy begins to develop if you just don't get good coverage on that common cocklebur, you’re going to have trouble killing it. I'm not going to sit here and tell you that glyphosate is going to be a home run on large cocklebur or cocklebur that's underneath the soybean canopy that we can't get good coverage on. So, there's a lot of factors, I think, that are contributing to this.
Tom: No, I agree 100%. 100%. So, thinking about another weed that I know that we're dealing with right now. And I know I've touched on it in some burndown podcasts earlier and maybe even a blog, but glyphosate resistant marestail or horseweed, you know, I don't know how much we've screened lately. Personally, I haven't screened any of this lately at all. But most of it, as far as I know, is still resistant to glyphosate. So, glyphosate is not going to be a key component to a program for control of marestail or horseweed. Any updates on that one that you've heard?
Jason: Well, I haven’t screened any either. But based on what I've seen in the field, we still every year, we'll put out one or two horseweed trials and everything I've seen to this point, if you've got horseweed, it's going to be glyphosate resistant. You know, that's a weed, also I think that's been very environmental specific in terms of emergence and the issues that we've dealt with. You know, if I go back to, I’m going to probably say 2005 to 2006. 2006 is when I came back to the University of Arkansas with the Division of Ag and, horseweed was everywhere. I mean, you just couldn't find it. I mean, you could go to a field and not find it, at least northeast Arkansas. And then it began to spread and it pretty much spread across most of the Delta. But we've gone several years there where we just didn't have a lot of horseweed. And, you know, it'll blow up only a year and you’ve got it. So, I think really it's just key to being out there scouting those fields, understanding what you have. And if you do have horseweed, it's a lot easier to control it small before it starts bolting. When it starts bolting is really a challenge. I would make the assumption today that everything you've got out there is glyphosate resistant. I still think our go-to is going to be dicamba. I like dicamba with a Valor underneath it to give me a little bit of residual. There are some horseweed populations we've seen out there that can emerge pretty late over into the spring. So, I like to see that Valor, just to make sure I'm pushing into that crop - making sure that I'm clean. What are your thoughts?
Tom: I agree. 100%. And I think, one thing with the auxin-based systems that we have in soybean and cotton now, especially with the Xtend or XtendFlex systems, you know, I think some growers think, “well, I'll just wait until I plant and I'll take that horseweed out,” but you know, really we're encouraging these growers and consultants to not wait. Go ahead and get the horseweed out before we drop the planter in there, because I've seen it. I know you've seen it. If you take a look at where a horseweed is growing, you plant into that next to cotton, next to beans, that plant's going to have an area of influence that's going to negatively affect our crop through allelopathy or just competition. I mean, there's going to be a negative effect and we can lose some yield that way. So I think it's important, even though, yes, we have dicamba as an option in the Xtend and XtendFlex crops - that we focus on killing this horseweed or marestail when it's small and not waiting until we drop a planter into the field.
Jason: And you know for me, that's a minimum of four weeks prior to planting. I want to make sure that I'm planting into good, clean, clean soil. Like you said, I don't have any residue there - at least horseweed residue. Because I do agree with you. I don't have the data to sit there and tell you that there's allelopathy associated with it. But when I take a look at planting into residues of horseweed, I have difficulty getting a stand of cotton. I just have difficulty there, and I'll tell you beans isn’t too far behind it.
Tom: I agree. I've seen it time and time again. 100%. There is something going on, something going on there. So, the key to all of this, if you listen to theme across this whole podcast is timeliness, being timely and reducing competition early with these weeds. And there's one more. I'm going to take just a little bit of time, and I know y'all talked about it last week, but I think it's become a fairly big issue in our soybean and cotton crops, especially, and that’s yellow nutsedge. I get a lot of calls on yellow nutsedge. Again, I mentioned Johnsongrass being out there. Yellow nutsedge may be the first thing up in the field that you actually plant into thinking it's a grass that you'll take out easily with Roundup or something like that. But yellow nutsedge is becoming a problem on some of our sandier soils with cotton and beans.
Jason: I agree with you. And, it's a weed that has increased over the last five to ten years, I've seen more and more yellow nutsedge out there. You just touched on what I think is the misnomer for a lot of folks is, “well, at the end of the day, I'm going to spray this field twice with Roundup and it's going to kill everything out there. I understand I've got some issues with pigweed, but everything else out there is going to be controlled with two applications of glyphosate.” If you want to select for yellow nutsedge in the field you spray it twice with glyphosate, and it's not going to be a very effective option.
Tom: It's really not, and it just goes back to me, and I know y'all talked about some sporadic ALS-resistance to yellow nutsedge, but really in upland crops, having a robust pre-emerge program or program out when we're clean - go out there with a robust pre-emerge program. You know, for yellow nutsedge, to me that probably has a little bit of ALS chemistry in it.
Jason: Oh, absolutely.
Tom: And for morning glories as well. You can add a little ALS chemistry in there to help with the yellow nutsedge, the morning glories, maybe even sicklepod. Sicklepod is becoming an issue. So really it just goes back to knowing the field history and what problem weeds, or what weeds are causing us the most problems - in addition to pigweed. [laughter]
Jason: Well you know, I've got some cotton plots, some long term studies, and over the last couple of years I've actually had to go back in and start using some Envoke in there, just to just to try to beat back these nutsedge populations. That's a herbicide that you when you start thinking of ALS chemistry, a lot of folks don't think of cotton and ALS chemistry. We kind of put that behind this because of the pigweed issues. But Envoke is a very good sedge material, where it'll help you at least get some height differential between that cotton early on in that sedge.
Tom: Yeah, absolutely. And Staple is worn as well. And Staple we can put in cotton, we can put it out PRE to give us a little help. And you know, the more you add, the more expensive these programs become. But, as you've mentioned before, it's just easier in my opinion. We're going to either pay that money upfront or later on down the season. We may actually have to pay more later in the season to get rid of it if we don't do it right on the front end. So making sure we have the right premixes going out and planting or prior to planting, to me, is important in managing our overall weed control budget later in the season, especially dealing with resistant Palmer amaranth and these other resistance issues we're talking about today.
Jason: Well, I think another key component there is that if you let these populations explode and get ahead of you, yeah, they're having some impact in terms of yield, quality, at least in cotton. But the other component you need to think about is the amount of seed that’s being produced. And even yellow nutsedge, the tuber, the proliferation of the seedbank. And what's going to happen is you've got a population you may be able to semi-manage this year. Next year, you're going to have to have multiple applications of diverse chemistry to try to get back in front of that problem because you've allowed the soil seedbank to build up.
Tom: Absolutely. And it's just going to get worse from there. You know, it's kind of like a snowball [laughter], just gets bigger every year. The issue that we're dealing with. Well, I appreciate you joining me as my co-host today and discussing some of these weeds, these problem weeds and these resistant issues. You've got any words of wisdom as we move into this next season? I know that planters are getting greased up and ready to go. Some may be planting, whether they should or not right now [laughter] in front of the rain they've got forecasted and other things. So anyway.
Jason: I appreciate you having me on today. And again, I'd just like to leave everyone with start clean and let's try to stay clean. I always tell folks it's a lot easier to kill them before they come out of the ground. I don't care what the weed is, it's a lot easier to kill it with residual herbicides, than relying on POST emergence herbicides. When they come up, it's a challenge.
Tom: Well, it’s easier and it's going to be a lot cheaper or more economical, I think, this year. You know, with glyphosate pushing 60 plus dollars a gallon and glufosinate being high. These prices are unheard of that I'm hearing people are paying for herbicides, so it's going to make that residual program that much more important from a budgetary standpoint too. Well, alright. Again, I appreciate Dr. Jason Norsworthy joining me today. And as always, we welcome your feedback to the podcast. So if there's a topic you'd like to hear any of us cover, please drop us an email, let us know, give us a call or a text. We wish everyone a safe and successful start to the 2022 season. And thank you for joining us for this 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.