In this podcast, Dr. Larry Steckel answers questions about the newly approved over-the-top dicamba product, Tavium, the looming May 15 cutoff for older dicamba formulations, dicamba volatility research and buffer zones.
Also, we’ve had a few requests to include a transcript with the podcasts. You’ll find the full transcript below.
Ginger Rowsey: Hi there and thanks for listening to Call of the Week. I’m Ginger Rowsey and our guest today is Dr. Larry Steckel. No surprise, we’re talking about dicamba with Dr. Steckel. A very important deadline is quickly approaching and that is after May 15, you can only apply Engenia, XtendiMax, FeXapan and now Tavium. This is a permanent rule and you’re getting a lot of calls about this, people are a little confused about how this is going to work.
Larry Steckel: That’s correct. Getting a number of call about the cut off, and some folks are under the impression we don’t have a cut off this year, and when it comes to the newer generation of dicamba products that’s correct, but for the older dicamba products the Claritys, the Sterling Blues, the Banvels, you can spray those in soybeans and in cotton as a burndown up until midnight on May 14th. After that, from May 15th to October 1, you can only spray the newer formulations out there just as you outlined, Engenia, XtendiMax, FeXapan and Tavium.
Rowsey: And to be clear it doesn’t matter if you’re only spraying it as a burn down, none of the older formulations can be sprayed at all after this May 15th deadline?
Steckel: That’s correct and the thought process is that those older formulations have a tendency to get up move even more so than the newer ones and applying them later into May when things start getting warm you’re really, really looking at the chance of them moving out of the field and getting on a neighbor.
Rowsey: OK, so only a couple more weeks to apply those older formulations of dicamba. As we just mentioned there is a new formulation of dicamba that has been approved for over-the-top use and that’s Tavium. Talk a little bit about this.
Steckel: Sure. Tavium is a new premix. It’s the first premix to be approved over the top of Xtend crops that contains dicamba and in this case Dual Magnum or S metolachlor. So, it’s a premix it’s going to give residual control of grasses and Palmer amaranth and it’s here on the market. The dicamba formulation that’s in it is is the same as XtendiMax, and it’s got the same Vapor Grip technology that XtendiMax has, so it’s essentially XtendiMax with Dual Magnum.
There is one difference to that label from the others that is is something you need to consider. The cutoff to spray it in soybean is V4. The cutoff to spray XtendiMax and Engenia and FeXapan is R1. And typically R1 for Group 4 soybeans is V6. So, the cutoff for Tavium will probably be 10 days to a week earlier than you would have with the XtendiMax and Engenias, but it is something to consider.
Rowsey: As long as we’re on that topic, let’s refresh everyone about cutoff dates, because there’s not an official hard cutoff date on the calendar for Engenia, XtendiMax, FeXapan and Tavium, but there are some commodity specific cut-off times so many days after planting soybeans and cotton.
Steckel: There is some confusion because in states around us there are cut-off dates, there are some hard cut-off dates, like in Arkansas. So, folks are calling up asking is it here when it’s not here, but there are specific commodity cut offs. In soybean it is R1 or 45 days after planting. In cotton it is 60 days after planning. And those are considerably earlier than what we had last year.
Rowsey: Ok, and if you still need to take the training, because everyone who is applying XtendiMax, FeXapan, Engenia or Tavium must have the UT dicamba training, that is online. You can go to ag.tennessee.edu. If you look under the “Quick Links” section there on the bottom right-hand corner of the page you can find the link to that training and also some other dicamba resources.
So, if you need a refresher on anything that you watched or heard in the training in January or February that would be a great place to do it. Or, you just call Dr. Steckel on his cell phone at any hour of the day.
Steckel: (laughing) Please don’t do that.
Rowsey: Last week you and Dr. Tom Mueller had several UT Crops News blog posts about some dicamba research you’ve been doing. If listeners didn’t get to see those posts I encourage you to go back and look at those, some really good information. Quickly summarize for our audience some of the findings in your research.
Steckel: Sure. Several Tennessee soybean growers approached us several years ago, and it was just from their observations in the field that it seemed like at times the dicamba was drifting out going against the direction of the wind when they sprayed it. They thought when they saw that happen was when they had glyphosate mixed in the tank with Engenia or XtendiMax.
They didn’t see it so much if they were just spraying those straight dicamba products alone. So, that’s where I asked Tom Mueller / Knoxville he has a humidome set up there where he can do research and he took XtendiMax and sprayed it on a tray of soil and he compared that to XtendiMax with Roundup sprayed on a tray of soil and he did that outside of the greenhouse away from where he was doing all these tests and then he brought them into the greenhouse, put these plastic covers over these humidomes and he essentially has a little vacuum that pulls air over the soil and he monitored the dicamba coming off that soil for 60 hours after application.
Long story short, with Roundup in the tank with XtendiMax, he picked up anywhere from three to nine times more dicamba leaving that treated surface over 60 hours than he did the treatment that was just straight XtendiMax. It did look from that data that Roundup was promoting some volatility from the soil that he could detect.
What’s driving the research is the label was redone this year by the EPA with an eye on pH and knowing what the pH of your tank mixture was. Anything below 5 is considered acidic enough that would make these dicamba products more volatile. So, one of the things we looked at there was adding Roundup. From his research Roundup was promoting some volatility from these products, but is it driving pH down? And indeed it is.
So, that was something we looked at with the soybean growers in the state. We asked them to send water to us that they mix from and they did a good job of that. We had more than 12 samples from wells that were actually used for mixing. I think one of things that came to life from that research is we have water pH that is all over the board across the state. I had no idea how variable they were. They run from 8.4 to 8.5 down to below 5—4.7 to 4.6 you know right out of the tap.
So, those are things you need to consider when you’re mixing. If you have some well water that’s low pH like that, you definitely need to consider bumping the pH up because you could see some volatility as a result from straight water.
Rowsey: In this study you did evaluate some of the pH modifiers. How did they do as far as the stabilizing the pH?
Steckel: Of those first three BASF showed us we went in and looked at those and they indeed did as advertised. They raise the pH of the Engenia and Roundup tank mix up from 4.6 up to about 5.5. So, it did raise the pH. All three of them did. They also did it for XtendiMax. So, very positive on that aspect that it does raise the pH. It should improve dicamba staying put as a result.
As in all research, it seems like you get more questions every time you do it. So, the questions we have now coming in are, “Okay, we add pH modifiers that raise the pH, that’s great, but what about Roundup? Is it still going to work?” There’s a reason why Roundup drives the pH down—it works better at a low PH. So, if you artificially raise the pH, are you going to lose the weed control from Roundup? And that’s an open question we don’t know. That’s something that does need to be looked into.
Rowsey: Another aspect of the study that was somewhat surprising was the effect of pH levels when AMS is added to Engenia and XtendiMax as compared to glyphosate.
Steckel: That was a real point of emphasis in the dicamba training, not to put AMS in the tank or any acidifying agent because it drives the pH down and will make them more volatile. Well, when we started seeing that Roundup PowerMax was driving the pH down 1 to 2 pH units, and that’s a lot, we started scratching our heads, “Well, how much is AMS lowering it?”
And lo and behold it’s like half a point, so it’s driving those pH levels down much less compared to Roundup PowerMax. Now, there could be some other aspects of ammonium sulfate besides pH that are enhancing volatility, but it just kind of goes to show, at least from this research, that Roundup PowerMax in the tank mix could be a culprit in why we’re seeing some of the drift in the fields these last 3 years.
Rowsey: You’re definitely not saying add AMS to the tank mix.
Steckel: Oh, certainly not. Anything that promotes volatility or it leaving the field we are definitely against. I think AMS doesn’t need to be in the tank and really our recommendation from this research is we don’t encourage Roundup being in the tank, either. This data shows that it’s lowering the pH and from that we are seeing more volatility now being captured from the research Dr. Mueller has done. So, both AMS and Roundup we are discouraging.
So you ask, “If I don’t put Roundup in the tank, what do I do?” One of the things you can do is add one of the graminicides, like Clethodim. It doesn’t affect the pH. And really what’s Roundup going in the tank for? Grass control, right? In a lot of fields now in West Tennessee Roundup is not controlling a lot of the grass species, whether it’s goosegrass or jungle rice or Johnson grass, and we’re having to put Clethodim in anyway.
Especially when you’re around sensitive vegetation, sensitive crops, sensitive areas, I think it would really be helpful to leave Roundup out of the tank and use one of the graminicides instead, like Clethodim.
Rowsey: Alright, some really good info to know. Any other questions you’ve been getting this week?
Steckel: Just a whole plethora of people are nervous going into the spraying season. They always are, but with the issues we’ve had I’ve had folks calling up wanting me to come out look at their fields and do a play-by-play on how to spray it. You know it’s going to be a call, it’s going to be on the weather it’s going to be on the crop, it’s going to be on whatever vegetation is around those fields…that’s going to determine the call.
Probably still the most confusing aspect of this whole thing is buffers. I keep hearing people say, “Well, I have somebody’s strawberries nearby, I have to leave 220’ downwind or 110’ downwind. No. If it’s blowing towards sensitive crops you don’t spray at all. Buffers don’t come into play at all. Buffers come into play around sensitive potential species, so basically tree lines or bodies of water. That’s where you have to use your 110’ downwind buffer.
If it’s somebody’s Liberty Link soybeans or the neighbor’s garden and the wind’s blowing towards it, you can’t spray. Buffers don’t come into play at all. We keep emphasizing that, but still it’s hard to grasp and I understand that. So, just keep that in mind if you’ve got sensitive crops downwind don’t even think about a buffer, just don’t spray.
Rowsey: Larry has a great video kind of walking you through the buffer zone requirements. It’s also at ag.tennessee.edu, that’s the UT Institute of Agriculture homepage. If you look at the bottom right-hand corner of the screen in the Quick Links section, you’ll see Dicamba Training Information. Click on that.
Lots of good things there including that video, also the State of Tennessee guidelines for applying dicamba, a link to the dicamba training, so good information there if you need any refreshers. Also, if you’re not listening to this podcast through UTCrops.com, I do encourage you to go back and look at Larry’s blog post series from last week. You can find those posts there at UTCrops.com in the news blog.
Larry, thanks for being with us. I know you are extremely busy this time of year so thanks for taking some time to talk with us. And thank you all out there for listening. I’m Ginger Rowsey and we’ll talk next week.