Weeds AR Wild Series, S2 Ep1. On this first episode of the 2022 season, Dr. Tom Barber discusses potential herbicide shortages and options for winter weed control prior to planting.
Weeds AR Wild Series, S2 Ep1. On this first episode of the 2022 season, Dr. Tom Barber discusses potential herbicide shortages and options for winter weed control prior to planting.
Weeds AR Wild Series, Season 2 – Episode 1
Title: Herbicide Shortages and Burndown Options
Date: February 17, 2022
Arkansas Row Crops Radio providing up to date information and timely recommendations on road crop production in Arkansas.
Tom Barber: Hello and welcome to the Weeds are Wild podcast series as a part of Arkansas Row Crops Radio. My name is Tom Barber and I'm an extension weed scientist for the University of Arkansas System Division of Agriculture, and I have the privilege of bringing the very first episode of the Weeds Are Wild podcast to you in 2022. So again, this is a series that we started last year. I think we had 25 to 28 episodes, something like that. You can find all of our previous episodes if you just want to do a Google search for Arkansas Row Crops Radio. You can find them there. Wherever you download your podcast, you can get updates and, and notifications when we submit a new one. Again, this is going to be the first one of 2022. Hopefully, if everything goes well, we're going to submit one a week pretty much from here on through to the end of the growing season. And I think last year we had a lot of good feedback on these and we always welcome your feedback. If you're a listener and you want to hear us cover something, send me your Tommy a text and we can cover a specific topic. You can look us up on the Internet, send us an email, let us know what you want to hear. If we're not covering what you want to hear, we can be sure to get it on the schedule. So for the first podcast, I think I'm going to cover some burndown questions that we've been getting.
You know, it's been real nice, of course, everybody's recovering from the COVID and what we've had to do in terms of meeting and getting together and talking about farming. You know, I just like talking to farmers, talking to consultants, talking about farming. That's what I like to do. And I've missed getting to see everybody and visit with everybody in person. But this year, for the most part, our meetings have all met. We had to move the Crop Management Conference to virtual. But other than that, I've had the opportunity to go to Beltwide. I've been to our Southern Wheat Society meetings, been to a lot of county production meetings. The National Cotton and Rice Conference, which was in Jonesboro, was a pretty big hit. We got to see a lot of people there. So, it feels good to get back in the groove, if you will, and see everybody in person to talk about what I love. And that's row crop production, or farming, and that's what I love to do. So, and killing weeds, that's fun. So again, I'm going to focus a little bit about burndown today.
Started off the morning headed to White County to do a production meeting there and got a call first thing. An individual on the other end of the line said I can't get any Select. I can't get Clethodim to add to my burndown program for ryegrass. What am I going to do? And so I think I'll just start with that because we get a lot of those questions. There is some chemical shortages out there. I think it's, you know, based on several different variables and a lot of those are where you farm, what chemicals are available at the particular dealer that you use commonly for your chemicals, and so it seems to be spotty. This is the first situation I've heard of a Clethodim or Select being short in a specific area. But I'm sure it's not the only one. I'm sure there are many others out there that have the same question. And so when we've gone to our winter production meetings again over the last couple of months talking about what we're going to do if glyphosate is short. or glufosinate, atrazine? We've heard issues, there may be some shortages with atrazine and several other chemicals, like Select, that I just mentioned. And so what we thought would be probably a pretty good plan is, well, if we're only going to have so much of Roundup or glyphosate in the system, then maybe we should look at moving all of that into our cropping window. And so taking it out of our burndown – our winter annual burndown application, and moving it into an end crop application for corn, soybean, cotton or other crops that we might could use it in. And so I think that's kind of where we've landed. So if we take glyphosate out of that burndown window for winter annuals, what are we going to replace it with? And it's such a backbone for a lot of winter weeds, just has good activity across a large variety of winter annuals. It's hard to take out, to be honest, and this is not going to fit everybody. What I'm going to say the next 17 to 20 minutes is not going to probably work for everybody, because everybody's under a different farming scenario or situation. So, you know, we're always a phone call, a text or an email away. If you got specific questions, we'll be happy to answer those. You can contact your county agents, you know, and get the information there. Get you an MP44. We've got a lot of options in there for burndown.
But if we move glyphosate out of the burndown window, to me, it has to be replaced by paraquat. Paraquat, or Gramoxone, is used pretty commonly. Especially we've been using a lot of it at planting to get rid of any pigweeds we might have in the field, if we're planting beans or cotton. But, you know, Paraquat has a broad spectrum of activity. The downside of paraquat is it's a burner. It doesn't translocate much throughout the plant, so coverage becomes increasingly critical. We've got to cover all the growing points of those weeds in order to kill them, and so several things to that. But number one, we need to start early enough before the weeds form such a mat that we can't cover all of them - right? - across the landscape or across the field. So we want to be able to get good coverage. We need to attack all the growing points in order to kill them with Paraquat. Now, several years ago, you know, Dr. Ken Smith and Bob Scott and Jason Noseworthy and Dick Oliver may have had something to do with this as well, but they discovered that if we mix a PSII, a photosynthetic inhibiting herbicide, in with the paraquat, or Gramoxone, it actually significantly increased our control of various weeds. And one great example is when we're trying to remove a failed corn stand - this is a great example. If we just sprayed Gramoxone over those small corn plants, all we would do is burn the leaves down. The growing points below the soil, those small corn plants will come right back. In order to take that corn stand out with Gramoxone, we had to mix a PSII herbicide with it, like three ounces of metribuzin or a pint of atrazine. That allows that paraquat to translocate down to the growing point, which is under the soil line that time of year for corn, and we get a good kill. As long as we get coverage on those small corn plants, we get a good kill to do a replant with.
And so it's the same process - thought process, when we talk about burning down these winter annuals. We want to mix a photosynthetic II inhibitor, three ounces of metribuzin - that's three ounces of the 75DF dry metribuzin, in with Gramoxone - a quart of Gramoxone, let's say, is a pretty good program. And it will - as long as we get good coverage, it will control 80 to 90% of our weed populations out in any given field in Arkansas. There are a few that will slip through that. Weed size, again, has a lot to do with that. Coverage has a lot to do with it as well, but it slows down the paraquat allowing it to translocate to get a better kill.
So, let's talk about some ways that might break through that program. Marestail, or horse weed, is the first that comes to my mind on the top of that list. Unless it's very small in the rosette stage, we're probably going to miss Marestail with a paraquat plus metribuzin (if we're going to beans or corn), or plus atrazine (if we're going to corn), or plus diuron, (if we're going to cotton). We'll probably miss that horse weed if it's got any size to it. So, what we need to do, is add our six to eight ounces of dicamba, that we normally add to Roundup, or add an 1oz/A Elevore. Those are my first two options. You could also add 2,4-D if you wanted to – if we've got some other problem weeds that 2,4D is a little better on out there in the field. So, we can still add the things we normally add, to get Marestail and other trouble broadleaf weeds to get a decent control. And, in all of our burndown plots, the main one that slips through that Gramoxone plus PSII inhibitor is going to be the Marestail, or horse weed. That's the main one. Ryegrass is another one that can evade Gramoxone application, because it is a grass. But as long as we attack it early enough, before it moves into the reproductive stage, we do a good job with good coverage of Gramoxone plus that PSII inhibitor.
So, let's talk about the in the PSII’s and what crops work for which ones. I mentioned it a little bit already, but if you're going to plant soybean or corn, we could do the three ounces of dry metribuzin equivalent. If we're going to corn, we could do a pint of atrazine with a quart of Gramoxone, let's say. The problem with that one is, I'd rather save that atrazine for in-season of the corn crop. I'd rather not use atrazine in our burndown if we don't have to. Let's not think atrazine, let's be on that metribuzin. Again, that's good for soybean or corn. If we're going to cotton upon a pint of diuron is probably going to be the best thing to add to your paraquat. Rice is the one we really don't have one for. And so, you know, propanil is a photosynthetic inhibitor type herbicide. I really haven't had much experience mixing propanil with Gramoxone to see if we get that same effect, but you know, it might be an option. Or we might just have to buckle up and make two applications of Gramoxone in front of rice. Another thing we might could do in front of rice, if we're far enough out, is mix Valor in with paraquat or Gramoxone application. Now Valor is not going to help us translocate as much as those PSII inhibitors will, but it does give us some extra burn, a little extra control of certain weeds, and again, will give us some residual control - as long as we're about 30 days out. And so that's something else we could consider. But at the end of the day, with the Gramoxone based system, if we're taking glyphosate out and using Gramoxone - coverage is going to be key. Getting one of those PSII inhibitors in the tank, with the Gramoxone, or the paraquat formulation, is going to be key to improve our control.
Okay. I want to talk a little more about ryegrass. So with our ryegrass populations, I've got a Ph.D. student working on that. Lou Adams is his name. I think I talked a little bit about him last year going around sampling various ryegrass populations. The results of his work so far indicate that out of 20 samples from southeast Arkansas (this is the bottom three or four counties in southeast Arkansas) seven of those have come back showing some signs of Clethodim resistance. So, if your Clethodim, if you've been disappointed with Select or Clethodim on your ryegrass population in the past, may very well be because that population is resistant. The other issue we're seeing with Clethodim or Select, is when we add 2,4D or dicamba with it. We get a significant amount of antagonism, and the larger that ryegrass plant is, the more likely that antagonism is going to affect the control of it. And so through various trials that we've put out in the last couple of years, I mean, we lose as much as 50% control. For example, if we take glyphosate out of the system, and just add select back in with our 2,4D or dicamba, we've seen a 50% reduction in control of ryegrass that is susceptible to Select, or Clethodim. So again, if you’ve had troubles in the past controlling ryegrass with Select, it may be because of antagonism or maybe because you've got a little resistance in that population. And so the first thing I would do is probably take those auxins out of my tank mix off select. And so, some things that we've seen that don't cause any issues really glyphosate, even though 98% of all of our progress in the state is probably glyphosate resistant, having that glyphosate in there doesn't really reduce the activity from the Select. So it will pick up some of the other problem weeds that we have while select will work on the grass. Sharpen, which is a common PPO we may use and burn down in front of corn or rice and so that one seems to be okay mixed with select and not affecting the ability that Select to control ryegrass. There's a new PPO called Reviton. I'll talk a little more about the minute. Also doesn't seem to be causing us any ill effects in terms of antagonism. So, take the auxins out. If we've got a ryegrass problem, we need to get control of that raw grass, take the auxins out of our first application, mix and then maybe come back in our second application with those or again, include a PPO instead of those to help us with other broadleaf weeds that are out in the field at the time of application.
Now, again, the one that's going to break through a lot of those is going to be our Marestail, or horse weed. And so if we have a problem with both, I would probably be back to my Gramoxone plus PSII, and throw in six to eight ounces of dicamba or an ounce of Elevore, to take care of the Marestail horse weed, and the rest of the weeds in the field. And I've got several callbacks on that mix on either one of those, especially from South Arkansas where we put more burndown out, and most have told me it's working really good. So, I think it's going to be a viable, viable option if we need it. Again, if you think you have plenty of a glyphosate to use and burndown and use during your cropping season, by all means, I'm not trying to talk you out of using it at burndown. This is just one of those deals. It's one of those years where it's going to be weird and supplies are going to be limited in certain areas. And so we've just got to live and roll with the punches on that.
All right. So that kind of covers are burned down for the most part. I do want to talk about this other PPO called Reviton a little bit. And again, it is very similar to Sharpen, and I think I mentioned that earlier. It is a PPO group 14. The big difference between it and Sharpen is it has very little residual activity. And so, our plant back to soybean and cotton is 14 days. Corn and wheat is zero days. And in our rate structure is ranging from one to three ounces based on our label. In my work and ounce and a half to two ounces is kind of where we need to be depending on what we have in the field. It works better when we have a MSO type surfactant with it, regardless of the mix that we're putting it in. Again, with Roundup, it looks good. With Roundup and 2,4D, it looks good. Just our standard burndown where we might substitute a first shot for a Reviton or something like that. Again, we haven't seen much issues antagonism wise with Select or Clethodim. And so anyway, it just gives us another option. I did find out earlier this week it doesn't have an aerial label. We are working on a 24 C right now to get an aerial label for Reviton. So again, it looks like another good option that we're going to have in a burndown window.
Okay. I guess the last thing I want to talk about is just the importance this year because of all the talk about chemical shortages. I mean, just yesterday I had all these text with pictures from a released statement from Bayer saying that “due to a force majeure,” something out of our control, basically, I had to Google it to figure out what that meant. I'll be honest, I had no idea, but due to something out of their control, the Glyphosate supply chain was going to be shorter than they thought. And so did talk to several of my industry representatives with Bayer on that. And the thought, I think, is, you know, when we talk about a global standpoint, may be short, for us in the US, it seems to be like it might not be quite as big of a deal, at least for the amount of glyphosate that Bayer is going to supply to the market for us in the US. So hopefully that's not as big of the deal as folks were making it out to be yesterday, at least in texts to me and in calls, and that kind of thing. So, you know, products are short if they're not short they're going to be maybe double what they cost last year, in some cases. And in those situations, to me, I would just feel a lot better if I knew I had the residuals that I needed in my shop or on order to help get me through that first six to eight weeks of the growing season, regardless of the crop I'm talking about.
I think this year residuals are going to be key because we don't know what kind of shortage we're going to have or where it's going to be. And if we can get the products that we need for pigweed and we know those products are basically glufosinate, your approved dicamba, formulations or you're Enlist formulation, you know, depending on what crop and system we have for cotton and soybean. On the corn side, if atrazine is short, you know, we don't talk about this a lot, but we have a lot of pigweed populations in the state that are resistant to post-emergence applications of our HPPD herbicides. And without atrazine in that mix, those herbicide programs are not going to look near as good. And so, you know, get some atrazine if you can get it. That's one of those residuals on talking about, you know and it may take looking at the premixes ,such as Bicep, in order to get the atrazine that you need for the year. So anyway, just some things to ponder while we move into the start of this next season. If, if I can answer any questions or if I've confused you on what we've talked about today on the podcast please give me a shout, text, or call email.
Again, I did just recently release a blog about some of these burndown topics that were we're talking about today. If you just want to Google Arkansas Row Crops Blog, you can find that and it will give you the link to some of our popular publications such as the MP44 the MP519, and just some other key things, you know, has some other key publications there that are in quick links that you can look at, if you want to. So, with that, I want to thank you for joining us on this week's episode of The Weeds Are Wild Podcast series on Arkansas Row Crops Radio. I think it's going to be a great year. I wish everybody a happy 2022, and be looking for more episodes to come on a more weekly basis.
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.