Title: Weeds AR Wild, Ep. 20: Drift and New Weed Control Technologies Update (7/21/21)

Hello and welcome to the Weeds AR Wild podcast series as part of Arkansas Row Crops Radio. My name is Tom Barber and I'm an extension weed scientist with the University of Arkansas System Division of Agriculture. I want to thank everyone for tuning in to this episode, this is episode 20. This is the first year for our weekly weed control updates through the podcast format and we've had a lot of positive feedback so far on these updates and on these podcast, so we want to thank everybody for that feedback and we want to encourage you to continue to listen. I know recently we have backed this podcast up to every two weeks instead of every week, just because there's just not quite as much going on from a weed control standpoint at this time in the season. We've either done a good job or we're just making a bunch of revenge sprays that really won't amount to much of anything. So again, we want to thank you for continuing to tune in.

First I want to provide an update on what we're seeing and hearing out there across the state in regards to the dicamba drift issues that have seemed to significantly increase in Arkansas over the last couple of weeks. So two weeks ago my counterpart and extension weed specialist, Dr. Tommy Butts, reported over 200,000 acres that have been injured by dicamba off-target movement.  However over the last two weeks, that number has increased exponentially, unfortunately. We believe at this time there's more than 650,000 acres affected in Arkansas and that again is from dicamba off-target movement. 400,000 of those acres that are injured are coming from five Arkansas counties. Those counties are Arkansas, Prairie, Poinsett, Cross and St. Francis. These estimates are based on personal field visits as well as discussions and surveys with county agents, crop consultants, and soybeans growers in the area. This number could continue to increase because many times especially with the lower rate of off-target movement of dicamba we can see fourteen to twenty-one days before the full systems appear on soybean from that dicamba off-target movement. The UofA Division of Ag official soybean variety tests have also been affected and they've been affected on every research station in eastern Arkansas. And this is the first year that we've had an issue with dicamba at Pine Tree, Stuttgart or Newport locations. In general, this is the first year since the release of the technology and release of the approved dicamba formulations that we've seen this large amount of acres damaged or affected by dicamba in our Arkansas counties west of Crowley's Ridge. And so it's definitely something a lot of these growers haven't seen before. So most common questions that we're getting out there from the field are, of course #1, where did it come from? In some of these situations and fields that we've visited with agents and crop consultants about, they were several miles away from any near dicamba applications. And so when you look at the symptomology, especially in Arkansas county, and these other counties I mentioned earlier that had so many acres affected, Arkansas, Prairie, Poinsett, Cross, St. Francis, when you go and you look at those beans that are not Xtend or do not contain the dicamba trait, for the most part there is an even symptomology across the whole field, from one corner of the field to the other. There's not a gradient that appears to be from high dicamba rates to a low dicamba drift rate, it's just like the same rate over a lot of acres. And in general, my previous experience as a weed scientist and cotton specialist over the years, and I guess I've had almost twenty years of experience doing this, usually any symptomology you see like that is coming generally from secondary movement. We know secondary movement can occur when we make applications into temperature inversions and in the case of dicamba, a product that is highly volatile, secondary movement can come from volatility as well, so that appears to be where the majority of this injury is coming from, secondary movement. Now I'm not saying every single case, obviously we've been to fields where the application was made across the road and you can see that application was the one or at least part of the damage that we were seeing in the none-Xtend field. Alright, so what do we do now? That's the next question, what do we do now? What do I do with my beans that have been affected? And there is nothing that we have found, and actually the University of Missouri just released a new study on this over a three site-year period, nothing can improve your situation as far as something we can spray out of a bottle or spray out of a jug. There's nothing we can apply that is going to turn this symptomology around. When we look at side-by-side plots, there's nothing we can spray that's going to impact our yield as far as recovering from that dicamba drift. However, one thing we've got to do, is we've got to continue to farm the beans and reduce the stress load on those soybeans that are affected. And the best way to do that is to continue to irrigate them if it's dry, remove any other stresses, pest management type stresses that are in the field. We've got to keep these beans growing and reduce the competition with other factors. So, continue to farm the beans, there is nothing that you can buy that's going to completely reverse the situation, just continue to irrigate and manage the soybeans.

Of course everybody wants to know the potential yield loss they have and this is a question that nobody's going to be able to answer. We can provide some information. We have a lot of data now that shows that the biggest chance for getting a yield decrease or having a negative yield affect from dicamba off-target movement is if the soybean field has been hit or affected around the bloom stage, so R1, R2, through R3, those seem to be the most sensitive stages where we can take a significant yield decrease from dicamba off-target movement. And then it goes back to the rate and how many times the field has been affected. If the field has been affected multiple times during these sensitive stages, then we're probably, we're likely looking at a slight yield loss anyway. It might not be a lot, but it might be a little bit and it can range all across the board. We have seen yield loss with one one-thousand 1/1000 of a field rate of dicamba at the R1 growth stage. And so that bloom stage is a critical stage where we can see the largest yield decrease from off-target movement of dicamba. And again we just need to keep managing the beans and hopefully these drift rates are not very high and it's going to be situationally dependent. Every field is going to be different for the most part. 

The next question I get a lot is does this off-target movement of dicamba hurt rice during the rice sensitive growth stages? And we have also done some work on this. My counterpart, Dr. Jason Norsworthy and one of his students published some of this work in the B.R. Wells publication that you can find online on our website. Basically what it says is that it takes a higher rate to affect rice. A significantly higher rate. So the rate that it takes to affect rice would most likely kill the soybeans in a lot of instances. And so, because the soybeans, in most of these cases are not dead or the terminals have not turned to the ground in a lot of cases, we don't believe that the rates that are affecting these beans are enough to affect rice at this time. We have some of that data and you can look it up on our website, just search for the B.R. Wells publication. So, I think that's all I'm going to talk about regarding the dicamba situation. Again, it is a fluid situation in that we have passed the cut-off date of June 30th for applications and so we should start to see maybe not numbers decreasing is the right way to put it, but I don't know how many more acres affected we're going to see past the cut-off date. And so hopefully everybody stopped spraying it at the cut-off date and we limit the injury to what we have at this time. 

The other things I want to talk about in the podcast today are just some updates on some research that we're doing. The first thing I want to talk about is the seed destructor. And as many of you know we started working with an integrated Harrington seed destructor system. About four years ago we put it in an older Class 7 John Deere combine. It took a lot of engineering to get the system to mount to the combine and work and then when we tried to use it in the fall to harvest soybean, there was just too much green material in that lower chaff fraction for one mill to handle. It was a single mill system in the back and so the mill continued to clog up with any green material. Now after a killing frost we were able to harvest fine with that one mill system but we know that most of our beans are harvested in Arkansas or in the mid-south prior to a killing frost. So we knew we needed to try a different system. Fortunately last year we were able to work with a company out of Canada and acquire a different seed destructor and this one's called the Rede-Kop Seed Destructor and so we also updated our combine to a larger S-680, so a Class 8 combine. A little newer model than what we had and this RedeKop dual mill seed destructor is made to hook up to those S-series combines. It attached easily with not near as much modification as it took with our other, the Herrington seed destructor. It is a dual-mill system. To me it fits a little cleaner up against the combine so that lower chaff fraction and the upper chaff fraction separate better and we don't get a lot of the stems and larger plant material down in that lower chaff fraction entering the mill and causing clogs. So it's a cleaner system. To me  it appears the air flow is a lot better through those RedeKop mills and we were actually able at the end of last year, the end of the fall, to harvest some soybeans with it containing significant green material and it worked great and then just recently a few weeks ago, two or three weeks ago now we harvested wheat with that system and we let a lot of weeds go in the wheat just to see how good we could do. To be honest, I was very pessimistic at the beginning when we started but it worked excellent is the only way I can put it. It worked flawlessly cutting the wheat. And so we collected some of the material coming out of the ejection ports of the seed destructor and we planted some of that material in the green house and we're going to see what kind of weeds we get out of that and if there are any that survived the destructor mills. There was a lot of green material that moved through those mills, through that RediKop system and we never plugged up not once. So we're very, very optimistic in our ability to use it in soybeans and we've also got some rice that we're going to put it in this year. So I'm very optimistic and I think that's going to be an important tool moving forward in our fight against resistant Palmer pigweed and a lot of other weeds that will hold their seeds until harvest.

Another thing I wanted to update you on was Rogue herbicide in rice. We were able to get a section 18. Jason submitted for a section 18 this year and we've got it out on a few fields. So I followed up with consultants that I know that have used it and growers that have used it and places I know that have put it out and really I think overall it was a very positive experience with Rogue. Rogue herbicide has to be applied in water and we have to maintain the flood to get good activity and anybody that was able to do that, make contact with water and maintain the flood easily, I think were very happy with the Rogue. And again this herbicide is very good on aquatics. It has really cleaned up some fields where we struggled to kill sedge this year, ALS resistant rice flatsedge or annual sedge and so I've got a lot of positive reports on sedge control where we got it in the water and were able to maintain the flood as well as control of sprangletop and even larger sprangletop  populations in some fields and so again I think it's a positive update for Rogue. I think it does have a fit in Arkansas. Again, it's going to fit the acres though that we can easily flood and maintain a flood of the best because we lose the water we lose the activity from that herbicide. Again, it gives us another option and I think again it's going to have a good fit on some acres in Arkansas. 

The other herbicide update I was going to provide at this time is on Brake. I submitted a section 18 for Brake herbicide in peanuts. I know a lot of peanut growers got to look at it this year and for the most part all of the comments I've heard back from them are very positive. I know in our weed control plots, two to three ounces of Valor plus twelve to sixteen ounces of Brake has looked very good. And again, as a standard, it looks very good. Or against the standard I should say. I've also looked at Outlook plus Brake as a pre-emerge and again I think we got a lot more injury this year from Valor that really shows up if you've got some side-by-side plots that you didn't use Valor, but from a Brake injury standpoint I got zero calls concerned about the Brake injury number one and in our plots we just didn't see it this year. Unless we got up to well above the label rate and so again I think it's a positive year for Brake. We also applied it to a lot of cotton acres this year and if there was ever a year to use Brake for the most part it's this year with all the frequent rainfall we got in the springtime continued to reactivate that herbicide and provide the protection that we need. So I think moving forward, Brake can play as big role for us in peanuts as it's starting to play in cotton. 

And so that's really all I had to talk about today. Again we're keeping these podcasts to every two weeks. It will be two more weeks before the next one is released but we want to thank everybody for tuning in and being supportive of us doing this podcast and we thank you for your comments. Join us next I guess in two weeks, I wanted to say next week, but it's two weeks as Dr. Jason Norsworthy will be handling the podcast and probably talking about the current issues at that time as well as maybe going over a few key results from trials we had this year. Maybe we can talk him into giving us some updates from that. 

So thank you for joining us for this episode of the Weeds AR Wild podcast series on Arkansas Row Crops Radio.


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.