Title: Weeds AR Wild, Ep. 16: Catching Up and Salvage Weed Control Options (6/16/21)

Arkansas Row Crops Radio providing up to date information and timely recommendations on row crop production in Arkansas.


Jason Norsworthy: Welcome the Weeds AR Wild podcast series as a part of the University of Arkansas Row Crops Radio. My name is Jason Norsworthy and I'm a weed scientist with the University of Arkansas System Division of Agriculture. Today I'm joined by Dr. Tom Barber, extension weed scientist. He's also with the University of Arkansas System Division of Agriculture. Dr. Barber and I today are going to talk a little bit about some of the salvage options we have and some of the issues associated with the extensive rainfall that we've had in portions of the state. And with that we're really going to be experiencing some salvage control that we're going to have to deal with in the coming days. Dr. Barber, this past week. I guess Monday, Tuesday of this week, I was in eastern Arkansas, specifically Tuesday I was in Stuttgart and barely got out of Stuttgart before I think they started shutting things down. It's been a long time since I've seen flooding like what we experienced in portions of central and southern Arkansas this past week and with that I was seeing levees that were busted and fields under water and unfortunately we're going to lose a lot of crop in the coming days. 

Tom Barber: Yeah it's really a bad situation. I think there's been water over roads this past week that we haven't ever seen water cover roads and so we've got some rice that's two feet under water. We've got some rice and beans and corn that are under water. I saw some water up to the top of the corn plants this past week, so it's a bad situation. And it ranges. It's bad where it's bad, it's luckily a kind of narrow corridor where it is that bad. South of I-40 down to McGehee for sure, but north of there they got a lot of rain too and when we start considering two inches is not a lot of rain you now we've had something significant. And regardless of whether it's under water or just based on the rainfall we've gotten and lack of spray days, I think everybody has at least missed one herbicide application at best. And some are missing a crop now, they're going to have to start over, so it's really all across the board. 

Jason: It's, as I look out there, we've got some rice, some of this early rice that we've taken to flood. And we've taken that to flood but we're going to have a lot of levees that are going to break and as a result of that it's going to take some time to get back in there and get those levees repaired and eventually get that ground back flooded again. We had some fields that we were approaching flooding and with all this water here now, we couldn't get our nitrogen out, we couldn't get our pre flood herbicides applications out and for that reason we're going to come back and we're going to have some pretty large weeds that we're going to be expected to control now. Especially in rice as well as some other crops. One thing is that we're going to have to deal with is these residuals that were out there, if you had residuals out there prior to getting all this water on the field, it's very likely that a lot of that residual is gone. When you take a look at the residual herbicide, it's all about moisture and activation. Some moisture is good from the standpoint it gets you in that top 1 inch to 2 inches to get that herbicide activated, that's where the weed seed is germinating and that's where you're going to get uptake of the herbicide, but when we start having soil move within a field or we start having these driving rains with extended periods of flooding conditions, we're going to push that herbicide down and in some of these soils you're definitely going to push it down well beneath the top few inches where a lot of our weed seed is germinating. That is going to be a major concern when we begin to move forward and for that reason, if you're going to have an extended period of time that you're not going to be able to get a flood back on that field, we're really going to have to look at putting a residual herbicide out there to get us back to a flooded condition. And like I said, some of these fields were flooded and again they're going to go without a flood now for several days in terms of repair and trying to get the levees back established before they go back to floods. So what are your thoughts on that?

Tom: You're absolutely right. In the long range forecast everybody's wanting some dry weather, but we talk about residuals we still need rainfall for activation and I know growers are going to bring the flood back as soon as possible. There's likely going to be a window where we have some emergence if it hasn't happened already in some of these fields. And you know unfortunately a lot of these fields may have to be treated as two separate fields in one just because of the way the water washed out levees on one side vs the other. I mean it's just going to, and then soybeans, the bottom end vs the top end. I mean we may have two crops in one field now which is really hard to manage. But I think, yes, it's going to be, it's just going to cost us a lot more money than we wanted it to from a weed control standpoint. 

Jason: I agree with you there. I think a lot of folks are going to want to go out and drop the hammer on this and they're going to have some big weeds and they are going to want to try to get the problem corrected rather quickly. I think in a lot of the instances here, unfortunately we're probably looking at multiple applications and again I don't think that really matters whether you're in rice or whether you're in soybean or you're in cotton, because of the weed size that we're going to be dealing with now and whether again we could talk pigweed in soybean and in cotton, we could talk barnyardgrass in rice and you know me and you have had some conversations about johnsongrass and the issues associated with that. And we'll talk some about that today, but one thing is for certain, when you start having these weeds that are a lot larger than any label that we have out there today, it's highly unlikely that we're just going to take one application regardless of what it is and completely address our issues. 

Tom: Yeah that's exactly right. I agree 100% and I talked to a lot of growers and consultants this week and some last week about what are we going to do, let's get a game plan. Everybody wants to try to get it done with one application but I just think a lot of that is going to be money wasted because of antagonism on grass specifically, so my message lately has been let's take care of the worst problem first. If that worse problem is grass, let's take care of that, if the worst problem is a broadleaf then the first application such as pigweed especially because we know at these temperatures we may be growing 2 inches plus a day, so I'd say pigweed if you've got it is the most pressing issue right now. But then come back in ten to fourteen days with another application to take care of the grass. 

Jason: I agree with you. I think when you're taking a look at soybean, definitely I'd be on top of pigweed first, try to get it under control, but it's going to be real, real challenging to take care of the grass problem and the pigweed problem I think in one shot. Let's talk a little bit about rice and you know barnyardgrass is going to be the issue we have there and we'll have a lot of salvage situations here. We got a lot of Clearfield rice still as well as Fullpage rice within the state and kind of my go to in rice has been, at least on big grass right now, is going to be twenty four ounces of RiceStar HT and mix with it five ounces of Preface or five ounces of Postscript. I'm sorry, Preface would be preflood, Postscript is going to be postflood. That would be Postscript and Beyond also in Clearfield rice is kind of where I am and I think that combination at least in our plots has looked relatively probably the most effective that we've seen in terms of the treatments that we've had. Now I understand that not everything out there's going to be Clearfield, not everything's going to be Fullpage. Where you really start running into trouble is then when you start taking again a ACCase herbicide like RiceStar HT, we've got Clincher as being another one. When you start mixing those with some of these broadleaf materials we really run into trouble in rice so I would definitely say, I'd be looking at going HT alone if I'm in conventional, I might, we've had some luck mixing that with things like Facet, putting some oil with that has given us some success at times, but you're probably not going to go out there and clean everything up like I said with a single pass of that in rice. What are your thoughts in terms of rice?

Tom: Absolutely. We've done salvage, just like you we're done several salvage type situations in the past and I like the Ricestar plus Beyond or Postscript. I think that's some good salvage options. A lot of times we use RiceStar / Facet. You know if you've got the springle top out there, especially Amazon sprangletop you're going to get maybe a little bit of antagonism on that sprangletop from the Facet, so it just kind of depends on what all we're looking at. I know barnyardgrass is the big one for sure. Regiment, I like Regiment in this window, but like you and I have talked in the past and like a lot of these growers know there better not be any beans nearby us when we're flying Regiment on the field. So we need to be conscience of that, I think Regiment has a fit in some places during this window, but the down side to all this or the unfortunate part is we're here needing all the products we can spray but I'm hearing Clincher's low, I'm hearing Rebel X is low to non-existent, Bolero's out for a while, so we're limited to what we can use, not only by the crops around us but also by the herbicides that are available. 

Jason: I agree with you there. I'm hearing the same thing. I think, I mean Rebel X is a relatively cheap option in terms of trying to get Clincher and trying to get grass on the acre. I think it's hard to come by these days, Rebel X is and Clincher is. Is there some out there, yeah it is and RiceStar HT is the same way and what I sit there and tell a grower today is that if you've got water on your field and you know that when you get it off you're going to be in a salvage situation, I wouldn't wait another ten days, fourteen days to try to go out there and try to secure those chemicals because I think a guy that waits another ten to fourteen days is really going to have very few if any options because of the availability of the tools that are out there at this point, so definitely get out there and try get those things secured as soon as possible. You know also we were talking about, from a salvage standpoint, that we're seeing more and more johnsongrass and I know kind of shifting gears here back to soybean and to some extent maybe even cotton, but we've been doing some screening work looking at johnsongrass and it continues to increase throughout portions of the state and we're seeing glyphosate resistance, ALS resistance, and ACCA resistance. I think a lot of guys are learning a hard lesson where they've gone out and they've got some big johnsongrass out there and they've sprayed it with glyphosate and they've sprayed it with Clethodim or Select and all of a sudden they're realizing, well that didn't work and what's option B. Are you hearing anything along those lines?

Tom: Absolutely, in the meeting yesterday at Newport, IPM meeting for Jackson County and there was a lot of concern in there about johnsongrass. Just like you say they're not able to kill it with the things that we've been killing it with. I mean at best we're burning it back, Glufosanate's in the mix and it's coming right back. And even in row rice I've had a lot of questions about johnsongrass in row rice and the fact that Regiment's not working, the Clearfield or Fullpage system is not. Those herbicides are not doing anything to it so that goes back probably to your ALS resistance that you're talking about. 

Jason: Yeah, I mean it's really scary when you take a look at johnsongrass. Glyphosate resistance, ALS resistance and ACCA's resistance in some of these populations and with that I mean we're only, we only have Glufosonate and in an Xtend bean, Glufosonate's not an option and in an Enlist bean it is. I guess we have an Xtend Flex soybean this year so thank goodness that we have that option there, but think it was 2008, 2009 I had a graduate student in here and we did a good bit of work over in Crittenden County looking at a Glyphosate resistance as well as ACCase resistance population of johnsongrass, we've got some resistance there. What we've found in our work was that you can take two applications of Glufosinate and it's going to get you probably 90, 95 % control of some of this  johnsongrass. I'm going to tell you I'm not aware of anything out there today that's going to get you anything better than that if you have this three way resistance of Glyphosate, ALS and ACCase resistance. Now you can get to a hundred with a seedling johnsongrass. We can kill that again with Glufosonate products, like Liberty products, like Interline, but on this rhizome johnsongrass, we're probably looking at multiple applications of Glufosonate. You know Tom, we were talking a little bit about tillage and you know folks don't like to use tillage and we've been afraid in terms of moving things, but we're going to have to look at some strategies other than just spraying some of these resistance populations with herbicides because it's kind of the same situation that we're in with barnyardgrass in rice and pigweed in cotton and soybeans. It's getting to the point where we really don't have a lot of options.

Tom: No and to be honest it kind of snuck up on me this year because I really in the last couple of years haven't had a ton of questions, but whatever reason it is really bad and it's showing its face this year on the johnsongrass. You know we just don't have any great answers right now. I wonder when we think about burndown because actually this year I had a lot of questions about it a burndown window. It was one of the first things out of the ground. Some of this rhizome johnsongrass. I wonder how, just thinking ahead, but how much like Paraquat plus a photosystem two inhibitor if that can translocate enough to do anything. But it's really got us scratching our head right now. 

Jason: Yeah, it's like you say, that's a burndown situation, and unfortunately that's not going to going to help. It's no short term help. I don't know, I think we're going to have to probably begin to look at doing some things like some tillage and see what impact that that's going to have in combination with these herbicide options we have as well as cover crops and you know we're doing some work right now and you know you're part of that too in terms of this harvest weed seed control and johnsongrass, being able to knock out seed production will help us tremendously. One thing is rhizomes, rhizome is a major issue but when you talk johnsongrass has spread across field it's really all about seed movement for the most part. In terms of having very rapid movement of that resistant bio-type across there, so I know we're going to focus a good bit in trying to understand what utility that we have with some of these seed destructors and on species like johnsongrass in the coming years, so that's kind of where we are there. But back to kind of all this, all this water, there's going to be some guys, you've seen it, that the soybeans, they're going to lose soybeans. There's probably some, I hope there's not a lot of rice that's lost, but there's probably going to be some rice that maybe even is lost. What's your thoughts when it comes back into planting back into this? I mean we don't have a lot of crop, soybeans is really from a cropping standpoint, this late in the year is our only option, what are your thoughts in terms of planting back into some of these rice herbicides? I've heard some guys are in some bad shape in corn. I don't think we're going to walk away from a corn crop, but some guys are looking at whether they're going to keep the crop, walk away from it, if they do walk away from it, can they potentially come back and plant beans?

Tom: That's questions we're getting on a daily basis and it's just situational dependent. A lot of cases we'll be able to come back with beans but you know like you say from a herbicide standpoint we need to make sure we get the right level of tolerance in there. If we need to have an STS bean or a bolt bean for whatever reason, make sure we do that. Some of our corn herbicide, some of these HPPD's, technically we're not really suppose to be planting back to those before six months I think on most of them. So they may give us trouble now. If we can find some of the Alite 27 soybean lines, we might could go that way, but for the most part it's a situational basis. I think behind rice if we needed to, which I'm with you, I think rice is fairing the best out of all of this. I doubt we'll have to re-plant a lot of rice fields, but we might, I don't know. But soybean fields, cotton fields definitely will have to be re-planted and if we've got Brake under that cotton acre or peanut acre if it's on peanuts by chance. I mean there's really nothing else we can come back with. You have done a lot of that work with replant behind Brake. I know Zach that works for me now, did a lot of that work. I just think especially Brake being an aquatic herbicide as well, I just feel like the chances of being able to plant back behind that are not very good. I don't know, what do you think about that?

Jason: I agree with you. You know we looked at Brake at one time in terms of trying to get a label in soybean and I know you've done work to get a section 18 on peanut in with Brake and you know it was kind of hit and miss in terms of sensitivity on soybean. Soybean is not the most sensitive species I would say out there in response to Brake, but it definitely with all this water, one thing is for certain, that's a herbicide that loves water from an activation standpoint, where some of these we sit here and say well you're probably going to have a lot less activity of the herbicide because you've had so much water. That may be one that you get more activity out of it than what you were expecting, but along those same lines, me and you actually had a conversation about this yesterday, we're in a situation where we're re-planting beans and some of my plot work, talking about some of the work me and you have together and we've got residuals out, we've had residuals out now for a month and we've lost a crop and we're going to have to go back in there and we're going to have to plant. One thing is for certain, we can't go back in there and plant back into that field and make the assumption that we've still got some residuals there that's going to provide us any benefit at all. We're really going to have again start back at square one and that is starting with a good sound residual. One thing is with the moisture where it is, when the water comes off this field or in these areas that have had a, maybe they didn't have a lot of flooding, but pigweed is at the peak point right now. Here we are, early to mid June, and it is coming on like crazy in these fields from an emergence standpoint and like you said it is growing two inches a day. To go out there without a residual in front of this I think is really suicide, it's putting a lot of pressure on these post-emergence herbicides and we've got enough resistance in this state. We don't need resistance to additional chemistries post-emergence and I really hope that we're able to get some residuals out. And with that folks sit there and tell me well that's an expensive crop and I understand that it's an expensive crop. I think we're very fortunate right now to have commodity prices where they are, but I don't see how we can really go back out there and not have a good residual out.

Tom: Well and then the same, at the same time, what goes along with those questions of you know, how much residual, which one to put out. We've got some beans in a lot of these fields that are going to live. I talked to an individual this morning that had about forty thousand left scattered across the field that are V3, V4 and want to just drop in there and plant on top of all that, which is not anybody's situation they want to be in, but our recommendation has always been to kill that existing crop and kind of start clean and you know if you've got pigweeds out there, depending on the technology, obviously if it's XtendFlex or if it's Enlist on a soybean then you can't go in there and kill it with Glufosonate, but if it's just straight Xtend you could. But what I usually recommend is Gramoxone plus a PS2 or Gramoxone plus Verdict, five ounces of Verdict. So it would be Gramoxone/Boundary, Gramoxone/Metribuzin or whatever just as long as our variety that we plant is tolerant to it to help us get the pigweed out, remove the stand and give us another shot. But I would tell everybody in that same breath to just be real careful about what's around you because we've been walking Gramoxone plus PS2 drift quite a bit this year because of the wind speeds and everything.

Jason: I agree with you on that. Yeah, we both been comparing notes on some of that and you're right Gramoxone and PS2 herbicides. We put those PS2's in there really to heat up that Gramoxone and get translocation of that herbicide, but also when that thing drifts all of a sudden you get a lot more activity from that Gramoxone as it drifts onto rice, corn or whatever the crop may be. You know as you said, I think a lot of the bean crop in the state's probably got a Metribuzin containing compound under it and one thing again just thinking about and I keep saying this every time I talk about Metrubuzin is, if you're going to come back in and you're going to have to plant, you're going to plant a different variety, just make sure that you've got a variety that has Metribuzin tolerance and yes I would still be a big fan of putting Metribuzin plus a group 15 in soybean. There's a lot of different options you got out there, like you said, Zidua. Based on our work again, it's Metribuzin plus another herbicide on some of this resistant pigweed if you're going to have success. Don't look there and say well you know what I'm going to skimp and I'm going to pull Metribuzin out of this. Metribuzin is needed to help burn down what you've got out there as well as make the other residual herbicides work if you're going to have success. 

Tom: I think it's even more important in this kind of planting window than it is, I mean I think it's important period and that's always our recommendation. We're in the middle of pigweed growing season right now. And there's going to be a barrel of pigweed that's going to come up following all this rain and if you've got flood in from a ditch there's no telling what's coming in the field on the soil that's coming in or that was moved in. So anyway it's just a good, I have to have this conversation or basically starting back at ground zero if you're re-planting field. 

Jason: Yeah it's unfortunate and I feel for everyone that is having to go through that, but that's definitely the case. I appreciate what you touched on there and this is another thing that folks are just going to have to remember is that you're probably going to have some weeds that you've never seen before in your field. I mean the thing about these weed seed is that they all float and we've got ground that's flooded now that hasn't been flooded probably in the last hundred years and with that everybody's, well one persons weed problem is now everyone's weed problem as all this water comes off, so you may even see some new species or you go out there and say I've been able to kill this weed with this herbicide, but you may be shocked when you see that the next flush of weeds you're not able to kill because of some of these new weed seed that have brought in. 

Tom: Yeah that's right, I just say you know as things come up, call us, text us and we'll work through it with you best we can. 

Jason: Well hey Dr. Barber, again I appreciate you joining my podcast today and I really appreciate your thoughts and again as I said this is a difficult situation for growers across the state. I've never seen anything like this and I'm confident that we're going to work through this and we're going to get through this. You're taking phones calls every day. I get phone calls too. We'll do our best to help growers come up with a solution to these issues that they have and so with that, again thanks for being here today and next week Dr. Barber, it's  my understanding that you do have next weeks podcast.

Tom: I'm on tap again.

Jason: Yeah, you're on tap again, so you want to tell everyone what you're going to focus on next week. 

Tom: Yeah I don't even know what the list says. I think by now we're playing by ear.

Jason: One thing is for certain we weren't planning on talking about the flooding situation.

Tom: That's right. Everything changes. We may be talking about trying to activate residual herbicides in the absence of rainfall here. 

Jason: That may be true. 

Tom: The forecast, I think the next eight to ten days is not actually looking favorable for rain, but hopefully we'll get all this water off the field and get our residuals out and get them activated.

Jason: Again thanks for joining us today. I hope you found this episode of the Weeds AR Wild podcast series on the on the Arkansas Row Crops Radio to be informative. Look forward to seeing you next time.


End notes: 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.