Weeds AR Wild Episode 9 J. Norsworthy Welcome to the Weeds AR Wild podcast series as part of the Arkansas Row Crops Radio. My name is Jason Norsworthy & I’m a weed scientist with the University of Arkansas System Division of Agriculture. Today I want to talk to you about some of the factors that contribute to rice injury from the herbicide Loyant and some things that we could potentially do to try to minimize the risk of that injury occurring. Additionally, today we are going to talk about yellow nutsedge and ways to control yellow nutsedge in our various crops. We’ve been getting a lot of phone calls over the last week or two in terms of nutsedge, and with that I thought it would be important to kind of touch on some of the herbicide options that we have within the various crops. So to begin today let’s talk a little about Loyant and the research that we’ve conducted over the last several years to really understand what are the factors that are causing the increased risks of injury that we see with Loyant on rice. One of the factors that really comes to the top and is most prominent in terms of injury is really cultivar selection. I realize most of you’ve made a decision in terms of what cultivars you’re going to put in the field and today a lot of our rice is planted within the state. But what we’ve noticed is that hybrid rice has a higher tendency to experience injury from Loyant than most of our inbred rice. The exception being is when we take a look at our medium grain inbreds we do have a tendency to see injury with Loyant applications on those types of rice. In terms of our inbred long grain, the only variety that I’ve seen any injury on is really Diamond, and Diamond at times can be as sensitive as the medium grain or the hybrid rice to Loyant herbicide. Another factor that we saw over the last year, maybe even two years now in our research, is that if we use quinclorac either preemergence or early postemergence and we follow that with a Loyant application, we are going to have a substantial risk in auxin injury showing up on that rice. So one consideration is that maybe you think about removing quinclorac if you’re going to use Loyant, maybe you remove the Facet or the Quinstar from your herbicide programs or if you’re really set on using Facet or Quinstar in your weed control programs, which they are excellent herbicides and provide a lot of value to our growers, if you’re going to do that you’re probably going to consider taking the Loyant out of your later applications, or at least you’re going to have to realize that you’ve increased your risk of injury. We’ve also noticed over the last few years is that when we make sequential applications of Loyant, we really have a major increase in the risk of injury occurring. Much more so than what we see with single applications. We’ve also seen that where we have flooded rice or standard rice production systems in Arkansas, we’re going to have greater risk for injury in a flooded culture than what we will in furrow-irrigated culture. Very seldom do I see injury to rice from Loyant in a furrow-irrigated system, and I think that probably has to do with the fact that we’re just able to get some oxygen to the roots or to those plants and as a result of that the rice is able to better metabolize or handle the herbicide. When we do see injury in a furrow-irrigated system, more often than not, it’s near the end of the field where we have a tendency to hold water. Some other factors that can lead to an increased risk for injury to rice from Loyant would be air temperature. And what we’ve noticed in grow chamber research as well as field research is that if the temperature increases there’s greater risk for that rice experiencing injury from Loyant. And if you’re going to be applying Loyant and you’re going to expect above average temperatures during application or maybe even for five to seven days following an application, there definitely will be greater risk of you seeing that auxin-type symptomology or injury on the rice. We’ve done some work to also look at foliar applications. Foliar, when I say foliar, foliar spray applications vs that of impregnated applications and actually Corteva this past month or a couple of months ago, have been able to obtain a 2 EE label for the use of impregnated Loyant within Arkansas. The use of impregnated Loyant, it may not completely eliminate the risk for injury occurring but there definitely has been less injury on rice whether it be hybrid rice, medium grain rice, or some of the other sensitive types of rice. We see less injury with impregnated than what we see with a foliar spray of the herbicide. Some other factors that can lead to maybe a slight impact in terms of injury is application rate. Sixteen ounces of Loyant is really the rate if we’re after barnyardgrass. If you go any lower than that you’re not going to have an opportunity to control barnyardgrass, but the majority of the Loyant we are using in the state today goes out somewhere around eight ounces because the growers that are applying that are after pigweed, coffeebean, annual sedges such as rice flatsedge and maybe even some aquatics. In general, you’re going to have less risk for injury with that eight ounce rate than what you will at that sixteen ounce rate. I’ve also noticed that the flood date or the soil moisture status at the time of application can have some impact on injury. Where we have wet conditions, high soil moisture at application, there’s going to be greater risk for injury from Loyant than where you have a little bit lower soil moisture conditions. Generally, if we’re somewhere around probably eighty percent of field capacity, maybe even a little bit lower than that, there appears to be less risk than under, again, saturated conditions or maybe even field capacity when we apply that Loyant application. The last factor that we’ve seen to have some impact is light intensity. What we’ve noticed in our research is prolonged cloudy conditions are going to increase the risk of Loyant injury. It’s really the cumulative effects that can occur from these various factors that I just mentioned. For instance, if I plant hybrid rice and I treat it with quinclorac and I follow that with a foliar spray of Loyant and during that application or following that application of Loyant I have high soil moisture content with above average temperatures, the chances of me seeing injury are extremely high in a situation like that. Again, if we want to lower the risk for injury we think about these factors and trying to minimize the risk by maybe going with the eight ounce rate, maybe furrow-irrigated rice, maybe planting an inbred cultivar that is less sensitive to Loyant. Another discussion that I want to have with you today is centered around yellow nutsedge. Like I said we’re getting a lot of calls on yellow nutsedge and the first thing that I think of with yellow nutsedge is a lot of folks start out with a burn down program. That burndown program has a tendency and rightfully so to have glyphosate within it, and I think a misnomer for a lot of individuals is that they think that glyphosate is a broad-spectrum herbicide, and it is going to control all weeds in the field when in reality glyphosate provides very little if any control of yellow nutsedge. I want to go through each of the crops that we have here within the state, the major agronomic crops, and I’m going to start with corn today. When we think of corn, really a good, I would say a cheap option for trying to start out with a good control of yellow nutsedge is centered around the use of paraquat in combination with atrazine and metolaclor. I would not recommend paraquat alone for the control of yellow nutsedge. You’re going to get a lot of top growth kill, those nutlets (tubers) are going to grow back rather quickly, but when we mix paraquat with a photosystem II-inhibiting herbicide like atrazine, the paraquat becomes systemic, it’s able to move throughout the plant and in doing so it’s able to kill, in a lot of instances those tubers and the metolaclor is helping to provide residual control if we use it in the burndown and maybe even use it as a preemergence application at the time of planting. You also have the option of using Permit preemergence or Permit in the burndown but I think Permit has a better fit in-crop where I’m mixing it again with a metolaclor product like Dual or Dual II Magnum and I’m trying to mix Permit and Dual II Magnum together, maybe again with atrazine to try to have some in-crop control of yellow nutsedge. An option that is also there but I would say is much less effective is going to be use of Basagran. If you do need it to come back on top of what we’ve already mentioned, you could use Basagran and the programs here. Really it’s not necessarily corn specific because you could also use these in grain sorghum if you’re dealing with yellow nutsedge within that crop. As we move from corn, let’s talk a little bit about rice. Permit is really my go to in rice. I like Permit at planting if I know I’m going to have some nutsedge or I have some that’s maybe already up. League is another good option at planting. There’s a lot of folks, that I get calls from and they ask me what about Gambit. I am a big fan of Gambit for a little bit broader spectrum weed control than what I get with Permit, but overall my really major weed that I’m trying to control at planting is yellow nutsedge. What we’ve noticed in our work is that Permit is a better product than Gambit for the control of yellow nutsedge. When I get that rice crop up, Propanil plus Basagran or Broadloom, that combination is really effective on the control of yellow nutsedge. If I’ve used League at planting I have the option of coming back with Permit postemergence, but one thing that’s not going to work very effectively is going to be an eight ounce rate of Loyant. As I was mentioning a few moments ago, we have a tendency to want to try to lower that Loyant rate to reduce the risk of injury and while sixteen ounces of Loyant can be effective on yellow nutsedge, eight ounces is just not going to get the job done. Eight ounces is going to do well on annual sedges like rice flatsedge, but not on yellow nutsedge. Moving now to soybean. Similar to what we talked about with corn, paraquat plus a PSII inhibitor. In soybean the go to is going to be metribuzin. I like paraquat plus Boundary which gives me a combination of metribuzin and metolachlor or like paraquat plus Moccasin MTZ. Also, in soybean, if I’m going to plant a STS variety I would have the option of using Permit at planting. If I plant an STS variety I would also have the opportunity to use Permit postemergence, but I couldn’t use Permit at planting and follow it with a postemergence application of Permit. If I wanted to go back in at planting, another effective option is the use of sulfentrazone plus metolachlor. FMC has a product called Authority Elite (sulfentrazone + metolachlor) and it is quite effective in controlling yellow nutsedge from a residual standpoint. Once we’re in-crop, Pursuit would be an option. Pursuit’s kind of an old standard herbicide that we’ve used. We used it a lot in the 80’s and early 90’s and it does provide a good bit of suppression of yellow nutsedge. But if we’re planting an XtendFlex, Enlist, or a LibertyLink soybean, one option that we have is the use of sequential applications of glufosanate in combination with metolaclor. So, you could use something for instance like Interline plus Moccasin or maybe Liberty plus Dual Magnum. That combination if applied sequentially with fourteen days between those applications you should be able to achieve a high level of yellow nutsedge control. The last crop I want to mention is going to be cotton. And again similar to soybean and corn, it’s all about starting with paraquat in combination with a PSII herbicide like Diuron or Cotoran and Caparol. That’s going to provide us a good base to start with and then once we get that cotton up, maybe to the four leaf or five leaf stage of cotton, we’re going to come back in with something like Envoke, which would give us good postemergence activity on yellow nutsedge. But again if you’re planting XtendFlex or Enlist cotton you could apply sequential applications of glufosinate, Interline or Liberty, and you need to mix it with Moccasin or a Dual Magnum type product. Hopefully what I’ve shared with you today has been informative. I hope it helps you in terms of your weed management programs that you are going to put into place this coming growing season and I hope you’re able to get effective control of yellow nutsedge. It really has become a major problem for us this growing season. Next week, hopefully you’ll join us. Dr. Butts will be with us and he’s going to talk about row rice weed control considerations. Again, I’d like to thank all of you for joining us for this episode of the Weeds AR Wild podcast series on the Arkansas Row Crops Radio.