Weeds AR Wild Series, S4, Ep11: Fall Residuals

Drs. Bob Scott and Jason Norsworthy discuss fall-applied residuals, how they fit in weed control programs and its growing importance as Italian ryegrass issues increase in Arkansas. 

Transcript

[00:00] Intro/Outro

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

[00:12] Bob Scott

Hello and welcome to the 11th edition of the Weeds AR Wild podcast here on Arkansas Row Crops Radio. My name is Bob Scott. I'm an extension weed specialist located at Lonoke, Arkansas, and I am joined today by my research counterpart up in Fayetteville, Doctor Jason Norsworthy, a distinguished professor and Elms Farming Chair, of weed science. Today on the podcast, we will be discussing something that's been sort of in the background of our recommendations for the past few years. It's kind of come more to the front, here lately, for a lot of different reasons. Jason, the idea of fall applied residuals and fall applied herbicides, you know, it really hadn't caught on. But, since coming back to weed science, you know, I left six years ago. There's a real interest in this now, what's what's driving all that? What are you saying?

[01:06] Jason Norsworthy

Well, Bob, I'll tell you. I think what's driving it largely is, is ryegrass. You know, if you go back, I can remember ten, 15 years ago where we did a lot of work looking at fall residuals that was more centered around pigweed and what we saw on the fall residuals as it relates to pigweed was if you put them out October, November, by the time we got to let's say March 15th, April 1st, those herbicides really were breaking. And so what we saw there was we needed to burn down again. We need to put a residual down again. And with that, there just really wasn't a lot of, of use. But, you know, I think ryegrass is a completely, different beast that we're dealing with. It's one that's going to emerge in the fall and emerges in the, in the spring. And, you know, with the resistance that we have today in ryegrass, once it gets ahead of you there's not a lot of options. And the one thing I would also just state here, Bob, is that we've seen is back versus six years or seven years ago you were talking about ryegrass was a problem 6 or 7 years ago, I remember down in Ashley County, down in the corner of the state, it wasn't just a trend.

[02:28] Bob Scott

Over in Mississippi, wasn’t it?

[02:30] Jason Norsworthy

Mississippi. Jason Bond, Jason’s done a lot of work, he’s done some very good work on ryegrass. And, you know, it wasn't a statewide issue. But today ryegrass has moved north and I would say probably 3 or 4 years ago it marched right across I-40. And, I can be in one of the most, northern counties here in the state of Arkansas today and those growers are going to be dealing with ryegrass.

[02:56] Bob Scott

I don't know what this means, but, the, the last 3 or 4 calls I've gotten about this have actually been from growers that are well north of I-40. And I'm thinking the guys south of I-40, they're not calling because they kind of have idea what's going on, but I think it's evidenced by your phone calls where the problem is starting to get on people's radar. You know?

[03:19] Jason Norsworthy

No, you know, that's correct. And you know where you have rice and where you have have corn. You know, if you plant into this, ryegrass has very strong allelopathic properties. If we wait until spring to try to kill this, you know, you've got paraquat. Clethodim is not really an option, partly because we believe we're starting to see some Clethodim resistance. Secondly, because Clethodim has some residual activity that's going to prevent you from directly going back in and planting corn. We're not going to use Clethodim again in corn. So you don't have a lot of options once this weed gets established. And that's why I think we've got to spend more time and effort focusing on in the fall. And, you know, I hate to say that considering where we are today with commodity prices and I understand that it's a it's a challenge from a financial standpoint to control this weed. But if you're planning on farming next year, if you're going to farm that ground and you're going to plant crops on it, you've got to stay in front of ryegrass.

[04:22] Bob Scott

Well, and I know it gets into this year's money versus next year's money. And that that's a real issue, for growers at the bank. But, you know, if you've ever tried to land plane a field that has big ol’ stools of ryegrass in it, or you've had to put out sequential burndown applications in the spring, you're talking about a lot of money. You know, where you don't try to do something in the fall.

[04:46] Jason Norsworthy

That's right. And I think where you have for ryegrass, where, you know, you've had a history of ryegrass now, and it may have not been over the entire farm last year, but if you had escapes out there, you're going to have worse of a problem this year than you did, the previous year. What you're going to see and you just hit on it, is the cost to control the year at planting or in front of the the planter is going to cost a lot more than what it's going to cost today to get in front of this. I mean, I don't think there's a lot of cheap options out there, especially considering the conditions. You know, I've had some folks call and ask me, what about Prowl? What about Treflan? You know, some of these cheaper options today. And I mean, what I tell folks is, I mean, the best thing going, is Zidua. You know, Clomazone is another very good, Command is another very good option for us especially if we're going to roll into to rice next year. But there's not a lot of, effective options I would say outside of Zidua and Clomozone. And you know, I think Dual probably has a fit in some areas. But what concerns me right now is the fact that in certain portions of the state, northeast Arkansas has a lot more moisture than southern Arkansas. And as you move farther and farther to the west, you begin to lose moisture. I don't see a rain in the forecast, and it's extremely bothersome to sit there and and know you've got a problem like this. And that pre-emergent herbicide isn't going to provide a lot of value to you. Unfortunately, until you get a rainfall to get it activated.

[06:27] Bob Scott

I agree 100%. And, you know, I want to get your thoughts on this, but, a couple of these guys are in that situation that I talked to and, you know, to me, I said, look, I think you need to put those residuals out when there's rain in the forecast. And that may mean that we have to wait a while. Unfortunately, that we do have moisture in the ground in, you know, in northeast Arkansas. And what we're going to see is that ryegrass emerging. And so, you know, the question then becomes, so what do I do if I've got 2 or 3 leaf ryegrass out there? And we we talked a lot about putting Gramoxone on in there. I had questions about glufosinate, RoundUp. Which, it’s probably resistant.

[07:12] Jason Norsworthy

You know what I'll tell you, Bob, I think we screened back. It's been a couple of years ago now. Well, when you were gone, we screened populations, it was 100 or more populations across the state of Arkansas to glyphosate. And what I recall was it better than 80% of those, were resistant. You'd be hard pressed, I think, today to go out there and truly find a susceptible population. So I agree with you. I think paraquat is your best option if you start getting some size on that, on that ryegrass putting a little bit of metribuzin in with it. Just a couple ounces. A metribuzin will definitely heat up that, heat up the paraquat to help take it down. Take that ryegrass down. But again, metribuzin not doing anything for you from a residual standpoint on that ryegrass.

[08:06] Bob Scott

Right. I agree, you know, another product that comes up in this discussion now, I don't think it has a tremendous amount of ryegrass activity, but Valor, flumioxazin, is pretty inexpensive. And getting back to some of those other weeds that you could take care of that would round out a Zidua treatment and probably make it look that much better. Right?

[08:27] Jason Norsworthy

Oh, absolutely. I think that, you know, considering where flumioxazin today, you know, I mean, Valor is the is the the product that's, we really think of when we think of flumioxazin. But there's a lot of generics out there today, and that's a cheap. I've had a lot of folks tell me that they're using that. I recommend that on a lot of acres especially, you know, where you have pigweed, you have a broad assortment of weeds because that's costin gtoday I mean, I $4 or $5 at most is what that treatment is going to cost you. And so I think you're getting a lot of bang for your buck, when you come back in and you start thinking about next spring and I'm thinking things outside of of ryegrass. Yeah, it may start breaking March 15th, April the 1st, but you're not going to have a lot of vegetation out there that you're having to deal with at that time. And, you know, for that amount of money, I really think it's going to pay to be spraying flumi.

[09:23] Bob Scott

I agree 100%. I've definitely see a lot seen lines in the field that where they got a fall application, like valor or some kind of tank mix versus where nothing was applied, and it was a much different management situation. As far as the existing vegetation that was out there. So, you know, if a guy's listening to this, you know what we're saying basically is, you know, there's a lot of land prep going on right now. If a ground is clean, if you're working ground, you know, I would hold off making that application until we have a rain in the forecast. And, you know, if during that time you get finished working ground ryegrass does emerge, then you're and you still want to try to do something in the fall, you probably need to look at putting paraquat, in with that residual again, preferably ahead of rain. Is that a pretty good summary?

[10:16] Jason Norsworthy

I think that is you know, that is a good summary. And, and, you know, I mean, some of these guys are going to, put some tillage out there. Some of these guys aren’t going to put some tillage out there. This, this fall. Most guys I would think just eastern Arkansas in general. Most guys though, are going to try to work ground. They're going to try to get their beds up. And with that again, you will likely have a flush.

[10:39] Bob Scott

So I do want to back up and make sure one distinction and we're a little bit past it now. But I had a note in here that, you know, fall burn down and what we mentioned there at the first for, you know, reducing pigweed seed and morning glory, that's a different animal than what we're talking about with fall residuals. You're doing that right behind the planter or I'm sorry, right behind the combine. To prevent things like pigweed and morning glory from going to seed. That's more what we used to talk about zero tolerance and cleaning up a field post-harvest.

[11:12] Jason Norsworthy

So. Yeah, that's that's completely different. You know, when we think of pigweed especially, I can think of corn, even the beans today, it's amazing. These beans how we've shifted that planting date forward. We harvest these beans beans early. And so if you have another flush of pigweed, what we have seen in our research is that a pigweed that emerges August the 15th is going to produce a seed head, generally within 21 to 28 days after emergence. And those seed are going to be viable, viable within within another seven days. So you're talking 32 to 35 days after the time a pigweed comes up late, you're going to have seed production. You know, a lot of folks may say, well, who cares? I mean, these are small plants. These are plants that are 12in in size. But I've seen a tremendous infestations out in fields. And when you take a small plant like that, we've done some work to show that those plants can be producing 150, 200, seed per plant. And when you've got thousands and hundreds of thousands per acre, your seed bank really goes in the wrong direction. Rather quickly.

[12:20] Bob Scott

Yeah, I agree 100%. Well, Jason, we talked about a lot of stuff, today around this topic. And again, this is, Tom Barber couldn't be with us today. But the reason we did this is he and I are both fielding a bunch of calls, so obviously there's an interest in it out there. You got any other comments? Any new things you're looking at or you want to mention, around this area? Or are we sort of. These are the tools we have and we need to use them.

[12:48] Jason Norsworthy

I think these are the tools that we have. I don't see anything out there on the horizon that's going to, be as effective as what we have there. And I just want to go back in and reiterate it's all about being in front of this. If ryegrass produces seed you're going to have bigger problems in coming years. And we've got to try to you know, you talked zero tolerance. I understand you know, some folks are are more adept at doing that than others. But we've got to try to minimize seed production from this ryegrass waiting to try to kill this stuff. April the 1st, April 15th. A lot of that ryegrass, by mid April, has already produced a seed. It's got a viable seed on it, and it's not going to bring a lot of value to us, it’s going to bring less value, controlling it at that time than it would in the fall.

[13:43] Bob Scott

Yeah. And and again, you know, we've been we've been talking about this for a long time. It's obvious to me that it's become a bigger problem. I can tell you back in the day when we first started looking at these things for zero tolerance, you know, when I got to that part of my talk, a lot of growers and consultants would kind of check out of that meeting and, eyes would roll back in their head and they start playing on their phone or something. But, when you start getting 2 or 3 calls a day about it, you know, it pretty much tells you that that, problem is out there. So, something we definitely would like for guys to pay attention to after they finish whatever they're doing this year with harvest, whether they're doing land prep for leaving it till next year, consider what you can do, to manage that soil seed bank.

[14:30] Jason Norsworthy

I'll just say one other thing here. You know, as I think about as you know, we've already mentioned pigweed. We talk about pigweed a lot in beans and in corn and in cotton. And when I think of rice, I think of barnyard grass. And if I look at the state of Arkansas as a whole, I would tell you today that I think ryegrass is probably right behind those those two weeds in terms of problems that we encountered, difficulty in terms of management. So, you know, I hate to see it there, but I really think it's on the increase and we've got to try to get in front of it.

[15:06] Bob Scott

I do too. And, you know, I sometimes I hate to mention this because I don't want to make it sound too easy, but I've been working on ryegrass my whole career. I mean, I started out on my master's program at Oklahoma State. It was a problem in wheat, you know, and so it's one that I'm very familiar with. And, you know, one of the things about ryegrass, it's not long lived in the soil and doesn't have the, you know, pigweed that our data shows can last a very long time in the soil. But but most of your ryegrass will germinate the following year that it’s produced or the following fall that it’s produced and then some throughout the winter with only smaller amounts hanging around the seed bank. So this is a weed and you may disagree or not, but this is a weed that I think we can manage in these fields. We can possibly get it under control if we do the proper, sanitize the field margins and don't let anything go to seed, you can have an impact in just one year on the populations of these weeds. At least that's what I've seen in wheat.

[16:07] Jason Norsworthy

I would. I would agree with you from the standpoint of ryegrass, I think ryegrass does have a very short live soil seed bank, you know, and would also come back and tell you I don't consider pigweed being a long lived, weed in the soil seed bank. I think that's why zero tolerance has value there. I mean, we, there's a wealth of data that we have, we have generated that shows if you're out there and you're practicing zero tolerance for three, four years, there's not much seed bank left on on pigweed. So that's why I come back and just tell you, those growers out there that have some of these late emerging pig weeds out there, you might want to consider getting in front of them and trying to make sure that you're preventing seed production. Up here we had our first, frost probably freeze night before last. I'm going to venture to say you guys are probably several weeks…

[17:05] Bob Scott

We’ve had two light frosts.

[17:08] Jason Norsworthy

Two light frosts? But have you had enough to kill pigweed?

[17:16] Bob Scott

Probably not.

[17:18] Jason Norsworthy

That's what I would venture to say. I would venture to say that you probably, definitely South Arkansas, I would venture to say has not.

[17:25] Bob Scott

I should mention we're recording this on October 18th, so people know what time frame we're talking about. All right. Well, Jason, any other thoughts or anything you want to mention?

[17:39] Jason Norsworthy

No. I'm good.

[17:41] Bob Scott

Okay. Well, I will add, always contact your county agent for more information. They've got access to resources. We've got several fact sheets out there, that you can peruse through, as well as recommendations in our MP44. All that can be found at www.uada.edu

[18:04] Jason Norsworthy

So I do have one other thing that I want to mention, Bob, is before we close and when you said October the 18th, it did jog my memory and that is that, I've gotten a wealth of barnyard grass samples and weedy rice samples. And at this point, I just want to remind if any of our listeners actually collected weedy rice or barnyard grass samples this year. They've got to get those in to me by, November the 1st. That's the drop dead date. I will start screening shortly after that. And so if a sample comes in here end of November, 1st of December. Unfortunately, I'm not going to be able to, to screen those. So please get those to your county agent or if you have gotten them to your county agent, you may just want to follow up, make sure that your county agent has gotten those to me.

[18:51] Bob Scott

Yeah. And I will as well, take those here at Lonoke and, and make sure that they, that they get to Jason. So we appreciate everybody listening. We appreciate your support. We appreciate the support of the various promotion boards, that help fund all this research. I think we've talked about just about every crop today, so I won't I won't name them all, but, certainly we couldn't do our program, without all that. And with that, I'll just say thanks for listening to our 11th episode of the year,2024 to the Weeds AR Wild podcast here on Arkansas Road Crops Radio.

[19:29] Intro/Outro

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.