Supply Chain Issues and Glyphosate: Building a Weed Control Program Around Herbicide Shortages
March 8, 2022More Info
- [Christy] Hi, this is Christy Sprague. And today, I'd like to talk to you about some of the challenges that we're encountering going into the 2022 growing season. A lot of these challenges are related to herbicide supply. And with that, we're gonna have to be flexible on the types of weed control programs that we have in field crops this next year. So to give you a little bit of background, we're really seeing that we're gonna be on kind of a limited supply of both glyphosate and glufosinate, as well as potentially some other herbicides. With glyphosate, we know that there will be product availability, but we might just be limited on the amount that you can have. We'll talk about some of the ways that we can maybe overcome some of that challenges with some of the limited glyphosate, as well as with glufosinate. We've heard that product supply is very short and we've really started to rely on glufosinate to help control some of our glyphosate-resistant weeds. Some of the other herbicides that we've heard about that look like they're gonna be in short supply is some of the liquid atrazine formulations, as well as potentially some of those premixtures. So it's gonna be important as you build your weed control program to have open communication with your ag retailer to know what herbicides that you're gonna be able to get, as well as looking at some potential alternative, whether it's herbicide active ingredients or different types of programs. And we'll talk about some of the different ones that you might wanna consider or things to consider as you build those weed control programs. Another challenge that we have moving into 2022 is the price increase in many of the products that we use. So just as an example, in particular with some of the products that we have shortages on, we're seeing some of those prices be quite a bit higher. So last year in the spring of 2021, if you went to a local ag retailer, you might have been able to get a generic glyphosate for about $34 for that 2-1/2 gallon jug. If you were to go there in the last month or so, you're gonna see that price be up to about $100. So we're seeing a lot of those herbicide prices increasing by potentially two to three times. So that's one other thing that we're gonna wanna consider as we build our weed control program for this next year. So what I'd like to do today is talk a little bit about how we may overcome some of these different challenges that we're seeing. And first of all, just mention that it's gonna be really important to think about and be flexible with some of the different alternative options and really rely on some of the different resources that are out there to provide those alternatives. And one I would just like to mention is our MSU Weed Control Guide, especially for the newest one that was just released this last December for the 2022 growing season. Each year, our weed control guide we update with new products, also new recommendations based on some of our weed control research from year to year. The Weed Control Guide is Extension Bulletin 0434. If you'd like to purchase a copy, you can get that at the MSU Extension bookstore, which is if you go to shop.msu.edu and go to the bookstore, you will be able to order a copy. They are $15 a piece plus shipping and handling. Additionally, if you're looking at just having that resource online, we have that posted on our website, msuweeds.com. And again, there are a lot of other technical guides, and it's always important to make sure that we look at those herbicide labels and look at exactly some of the different recommendations, but that Weed Control Guide does give you a good start, especially in comparing some of the different products if some of the products that you're looking at aren't available. So as I mentioned before, while there will be glyphosate available, some of it may be limited. And as a grower, you may be just limited on the quantity that you're able to get. So one of the things I always like to think about is if you have limited glyphosate, which crop would you use it in? And we know that kind of three of our main crops that we do use glyphosate in are Roundup Ready sugar beets, Roundup Ready soybeans and Roundup Ready corn. Now, for those of you that are up in the thumb, the Roundup Ready sugar beets is very important. And that might be where you decide you're gonna use your glyphosate allotment that you have. And the main reason for that is we really have no alternative options to control most of the different weed species we have out there. However, if you're not a sugar beet grower and you're mostly a corn and soybean grower, you might also wanna look at soybeans. A lot of times, we see that glyphosate is a main component of many of our soybean weed control programs. However, we do have some new herbicide-resistant soybean traits available that do provide some additional options, particularly for broadleaf weed control. So kind of looking at the kind of scheme of things if I was a sugar beet grower, I'd probably put my glyphosate towards that first, then move to soybeans and then finally at corn. And the main reason for that is because we do have a lot of different herbicides that we can use in corn. We have more options for burn down. We also have more post emergence options and aren't necessarily totally reliant on the use of glyphosate in corn because again of some of the alternatives that we have available. So as I mentioned before, some of the new herbicide-resistant traits give us some additional options. And particularly, if we look at the different types of soybeans that we grow, we basically have seven different traits. Six of these are herbicide resistant. Most of these have glyphosate resistance, which would be the Group 9, or glufosinate resistance, which are the Group 10. Now, as I mentioned before with limited glyphosate and glufosinate, where would we wanna kind of, some of the additional options that we have would be helpful in planting some of these different or newer herbicide-resistant soybean traits. So for example with Enlist E3, in addition to be able to use either Roundup or Liberty, you would also be able to use the 2,4-D choline formulations Enlist One or Enlist Duo which would be the premixture with glyphosate. And again, this just gives us some additional options, particularly with that 2,4-D to control some of the different broadleaf weeds that we have in our soybean crop. Other traits that we have available are the Roundup Ready 2 Xtend or XtendFlex Soybeans. In both of these traits, we're able to apply dicamba. So whether that's as part of the burn down program to help control early season weeds and maybe give us a little bit of residual control is we can also use dicamba post emergence in these soybean traits. The key thing about that is to make sure that with dicamba use, there are a lot of other considerations that you need to consider to make sure we don't get any off target movement. And we do have a nice fact sheet in the soybean section of the Weed Control Guide, looking at what are some of the restrictions and just kind of remarks on the best use practices for using dicamba in these different soybean traits. So keeping that in mind, what I thought I would do is just kinda outline some of the different strategies for weed control and just get you thinking about some of the things you wanna consider as you're building your weed control program, or if you're looking for an alternative partway down the season if you're not able to get some of the herbicides that you need, that you typically use. Well, first of all, I always like to think of if you're gonna have good weed control, it's gonna be really important to know the weeds that are in your field. And for example, in Michigan, I would say we have about six different weeds that are pretty common in most of our fields. A lot of the grass species are things like giant foxtail. We might have some other grasses like barnyard grass or large crabgrass, but I would say most of the foxtail species are pretty common. Common lambsquarters is one we usually see in a lot of our fields. We have several different pigweed species. We have a lot of the native pigweed species like palmer amaranth or red root pigweed. And additionally, we're really starting to see some of those glyphosate-resistant weeds or multiple resistant weeds like waterhemp and palmer amaranth showing up in different parts of the state. Common lambsquarters, or excuse me, common ragweed, also giant ragweed, our common ragweed is extremely common across the state. We see giant ragweed more in the Southern couple tiers. Eastern black nightshade can also be a problem. And then over the last couple years, we've done some surveys and probably the weed that's been the most challenge has been horseweed or mare's tail. And that's really been a huge issue across several crops, but particularly in soybeans. And then in certain years, velvetleaf does crop up in both corn and soybeans as a major problem. In addition to these common weeds, some of these weed species have populations that have become resistant, and in particular, just wanna point out, there is a long list of some of these different glyphosate-resistant weeds, ALS-resistant weeds, weeds that are resistant to atrazine, and also more recently, some of the PPO resistance. There is a website. If you go to the MSU Diagnostic Lab, you can look at where some of these different weeds are. And just remember that some of these are more widespread and some of these are more localized. In particular when we think of glyphosate resistance, the mare's tail or horseweed, palmer amaranth, or waterhemp probably are most common across the state. As far as ALS resistant, many of our common ragweed populations, as well as waterhemp and palmer amaranth are also ALS resistant. And then as I mentioned before, the PPO resistance would be things like resistance to Cobra and Flexstar in soybeans. And we're starting to see a little bit of those populations pop up, whether it's common ragweed or some of the newer pigweed species like waterhemp and palmer amaranth. In addition, some of the tougher to control weeds have also become multiple resistant. So for example, particularly when we're looking at things like waterhemp and horseweed, glyphosate and ALS resistance in both of those populations are pretty common across the state. So again, it's just really important to know what weeds you're trying to manage, and that's gonna help you come up with some of those alternative programs. The other thing I wanted to mention is it's really important to start clean. We don't want those crops coming out of the field to be competing with some of the different weed species. So with some of the product shortages, what are some of the things we can consider? Well, one of them might be is if you're kind of an occasional no tiller, maybe spring tillage this year wouldn't be such a bad idea. It just really gives us an alternative to having to find some of the products that we need for a burn down application and is very effective at removing weeds. A couple things just to consider, if you're doing spring tillage and you haven't done it for a while, it's always best to try to till those weeds when they're small and those soil conditions are at the appropriate stage, knowing that especially if we till when the fields are too wet, that causes soil compaction. Also remembering that too large weeds are also harder to control. So if we have a wet spring and those weeds are really starting to get a lot of growth on them, it may be important to see if you can come up with a herbicide or it may take multiple passes to make sure that you're able to effectively remove those weeds from the soil. One of the things that's more of a challenge is when we try to do tillage and we're not effectively ripping those weeds out of the soil and you're just kind of bending them over, which can happen with some of our tillage operations. And then a lot of times, those weeds are harder to control later in the season. And one of the tillage tools where we see a lot of that is with vertical tillage tools or disc. In general, if we're gonna do that, a lot of times we're gonna need some additional type of tillage to make sure that we effectively remove weeds because again those vertical tillage tools really are not that effective of removing the weeds. And it's really important to make sure that we start clean 'cause if we don't, we've already put our crop behind to where we could see some yield loss later in the season. Another thing to consider is that a lot of times, tillage can also be helpful in reducing horseweed populations. And this is just a picture that one of our extension educators took up in (indistinct) and you can see in the back part of that picture where it says no-till, there's a lot of mare's tail plants there and really tillage helps bury some of that seed. And in particular, with some of the different weed species, when they have very tiny seeds, they're not able to germinate once they're buried very well. So for example with mare's tail, very tiny seed that needs to germinate from that soil surface are just slightly buried. If it gets much deeper than a half a centimeter even, a lot of times those seeds are not able to emerge and form plants. So as it's not gonna completely get rid of all of the mare's tail out there, it is definitely gonna reduce it to manageable levels. Another thing to consider if you're gonna be doing a burn down application, thinking about glyphosate again. If we have limited glyphosate, where do we wanna use it? So let's say we wanna use it in our burn down application because we know we have some weeds out there where we need glyphosate. It's gonna be important to also include some other herbicides to enhance that glyphosate control. So for example, if we have mare's tail out there, glyphosate-resistant mare's tail, adding something like Sharpen can be very helpful in controlling or is really needed to help control that horseweed or mare's tail. There are some other herbicides that can do that, but again, the addition of something like Sharpen can also help with burn down of some of our cover crops like cereal rye or annual ryegrass. Now, if we're gonna just rely on using that glyphosate in that burn down application, it's gonna be really important to make sure that we have very good post emergence options available. So for example, in soybeans, we do have some great options for grass control. These are the Group 1 herbicides, things like Select Max, Assure II, or some of the generics Clethodim and Quizalofop will work well. Additionally, as I mentioned before, with some of the different herbicide-resistant soybean traits, particularly the Enlist E3 and the XtendFlex Soybeans, we have more options for broadleaf weed control. So it's gonna be important to know what types of options you have. And again, in corn, there are several different options. Now, if we decide to not use glyphosate in our burn down application, some of the places where that's probably more suitable are in some of the fields where we have less weeds. In some cases, some of those fields may have been treated the previous fall. Again, it's gonna be very important to have a comprehensive weed control program for a post emergence application and some of those newer herbicide-resistant traits as well as corn give us some more of those options. Now, if we decide to omit glyphosate from the burn down application, one of the weed species that's gonna be more of a challenge is some of the different grasses. Now, depending on what your fields are, a lot of times, maybe some of those grasses aren't coming up early in the season. One of the grasses that does cause more of a problem is something like annual ryegrass. So that's gonna be one of those problematic weeds. Now, some of the alternatives that we have for grass control are things like Gramoxone that we can use prior to planting both corn and soybeans. And there are several of the Group 1 herbicides that we could use prior to planting soybeans. The key thing about using some of those Group 1 herbicides, and again as I mentioned before, those are things like Clethodim and Quizalofop, they only work really well once those temperatures are above 60 degrees Fahrenheit. So that's really important to keep in mind. The other thing to keep in mind is if we're gonna mix them with other herbicides, sometimes we can see some antagonism. So if you're really focusing on using those as part of your burn down strategy, you may wanna make a separate application so you get the full effectiveness of that. So that's a key thing to keep in mind. Another thing to consider is we can use some lower rates of glyphosate to help control some of those grass weed species. Another thing to think about with some of the different burn down herbicide applications, excuse me, is that many times we wanna make sure that we have two or three herbicides in that mixture that have some substantial burn down activity or fuller activity. Keeping in mind that we wanna make sure, especially when we're using alternatives to glyphosate, that we use the highest label rate of that alternative herbicide for a particular soil type, as well as keeping in mind the weed size, and also remembering that things, sometimes you have to wait from that application until planting. So for example, with 2,4-D ester, we'd have to use, if we use one pint per acre, we would have to wait seven days prior to planting soybeans. And there are some other different herbicide options that we can use either at higher rates as long as we give enough time prior to planting soybeans. And in general, most of that is usually somewhere between 14 and seven days prior to planting. Another thing to consider is that some of our pre-emergence herbicides actually have some foliar activity and we don't necessarily consider them our burn down herbicides, but things like chlorimuron or metribuzin can also add some activity. And for example, with metribuzin, that can also give us some fair control of annual bluegrass. In the Weed Control Guide on Table 2Q, we have a full listing of some of those pre-emergence herbicides and what kind of activity they might have. Additionally, in corn, atrazine does have quite a bit of foliar activity. As I mentioned with some of those newer herbicide-resistant traits, those work well for some of our burn down applications. So example, Enlist D3, we can actually use higher rates of 2,4-D than what can be used prior to planting conventional soybeans. So for example, where we could use a pint of 2,4-D ester seven days prior to planting soybeans any trait, we can use up to a quart of the Enlist One products or Enlist Duo products, or excuse me, Enlist One products prior to planting Enlist D3 soybeans. So you can see those rates there. The one thing that's gonna be important with a lot of these newer traits and some of these newer herbicides is there are some restrictions on some of the tank-mix partners. So it's gonna be important to check out those websites. For example, enlist.com/tankmix. The same thing with the Xtend or XtendFlex and some of the dicamba applications, knowing that either XtendiMax, Engenia, or Tavium, which would also provide us some residual control because of the metolachlor in there, will also give us some good additional burn down activity prior to planting those different soybean traits. Also, the dicamba does provide a little bit of residual control of some of the glyphosate-resistant horseweed we deal with. And again, we've got a whole section in the Weed Control Guide talking about some of the use restrictions around some of those dicamba products. Another thing to consider, so we wanna know our weeds, we wanna start clean, and we also wanna think about using residual activity. In many of our crops, we wanna make sure we have a good pre-emergence based program. And that residual activity really comes from those soil-applied herbicides. And those herbicides are gonna provide a foundation for control of harder to control weeds as well as herbicide-resistant weeds. What those pres do is they reduce the number of weeds that are present at the time of the post emergence application. So we're not relying solely on that post emergence application to control a large number of weed species out there. And also with our pre-programed or soil-applied herbicides, they can be applied after tillage or in the burn down treatment. For example, many of the soil-applied products that we use in soybeans, we usually wanna apply them prior to those soybeans coming up. And with some cases in corn, we have a little bit more flexibility and there's a whole table in the Weed Control Guide that talks about some of the soil-applied products that we can apply post emergence. And here's just an example of how important it is to have a residual out there. So this is some pictures we took several years ago. On the left-hand side, we have 2,4-D plus glyphosate as a burn down application and without residual and you can see all the weeds that emerged after that application. Many of that is lambsquarters, some pigweed species. And then by having a good residual in that burn down, you can see we really reduced the number of plants that come up. So again, that's very important. And in particular, this is extremely important when we look at controlling weeds like common lambsquarters. So for example here, you can see here's a chart. This is a one pass program with glyphosate. This is over several different programs. If we use a pre-emergence program followed by glyphosate, you can see that we're almost at 100% control for over 100 observations of common lambsquarters. And with two passes of glyphosate, we've got an average of about 90% control, but that range is really from about 85 to about 98% control. Those pres really improve the consistency control of several weed species like common lambsquarters. And if we don't have residuals in our program, a lot of times especially if we don't have glyphosate for use post emergence, we're probably gonna end up with poor common lambsquarters control. And this is particularly important in soybeans because we really do not have a lot of effective common lambsquarters herbicide options with some of the different resistance profiles that we're seeing in lambsquarters across the state. Additionally, pres are really important, particularly for controlling waterhemp. So you can see here on the left-hand side, an untreated, a post emergence application, and then a pre followed by post. You can see those pres really help. And there's several of those and we've got really good recommendations in the back of the Weed Control Guide. So having that residual or pre-emergence herbicide's gonna be very important. Thinking about a timely post herbicide application is also gonna be important as well as we'll mention something about overlapping residuals, particularly to control things like waterhemp, palmer amaranth, some of those tougher to control weeds. So with our post herbicide options, a couple things we wanna consider. In general, it's best to apply our post products before weeds are four inches tall. If you were thinking in corn, a lot of times we might wanna think about less than two inches tall just to make sure we don't don't see any reductions in yield based on weed competition if you don't have a pre out there. But again, we're really promoting the use of those soil-applied or pre products. And that's extremely important this year when we don't know if we'll have glyphosate as a cleanup or rescue option. And control of our post herbicides or weed control is often reduced as those weed size increase. With our post herbicide applications, remember most of our post herbicides need to have an adjuvant. It's gonna be important to know what those adjuvants are. And we've got those all outlined in the Weed Control Guide and making sure that we have good coverage. So in general, we like to say for post applications, make sure we have a minimum of 15 gallons breaker. And in some cases to get good coverage, you might need more, and nozzle selection's also gonna be very important. So here's one of our tables from the Weed Control Guide looking at post emergence herbicide options in soybeans. So for example, you would come out here, look at what weeds you're trying to control. Here, we've highlighted Eastern black nightshade, common ragweed and waterhemp, and we're looking for good to excellent control across all of those. And you can see that a lot of the Group 14 herbicides are the ones that we look at. So again, these are things like Cobra, Flexstar, and you can see there's a lot of these different ones. Additionally, if you go down, you see the product Prefix and Warrant Ultra, and we have a premix guide that you can look and see what those components are, but both of those would have a foliar product, in those cases a Flexstar, that is tank-mixed with something that would give you some residual control later in the season and we'll talk about those. So for example, if we decided we're gonna choose Flexstar, we have a whole remarks and limitation section for all the different products that we have. And just all of them are set up the same where you look at what the use rate is, what the adjuvant selection is, as well as some of the different remarks and limitations. And just to remind you, especially as we might be looking at some more different premixes or tank-mixes of different post herbicides, in the soybean section, we have a whole section where we can look at different herbicide tank-mixtures and what adjuvant soil we might use. So for example, Flexstar plus Harmony, we see it's a C+ so we'd want to use basically an eighth of a percent of (indistinct) with the nitrogen and that's gonna give us our weed control without causing the most soybean injury. Additionally, a couple things we wanna keep in mind, particularly in soybeans is that grass control can be antagonized with certain grass herbicides and broadleaf tank-mixes. And the way to overcome some of these is really by increasing the grass product rate and usually that's by 33%. So for example, with SelectMax, in general, if we're gonna use nine ounces, if we tank-mix it with something like a Flexstar or Cobra, we would increase that rate to 12 ounces. The other way to do it is to make separate applications. If you're gonna do that, that usually overcomes that antagonism the best. You'd usually wanna apply the grass herbicide first and then come back with that broadleaf herbicide. Or if you do it the other way, you'd need to wait seven days for that application. Another thing to consider is volunteer corn's gonna be an issue this next year due to some of the late harvest and some of the issues that we had with tar spot. So remember, we've got a lot of these Group 1 herbicides like a SelectMax or Assure II that are gonna be very useful for volunteer corn control. Also consider that some of those tank-mixtures, if we're gonna use like a dicamba or 2,4-D, they might also cause some antagonism both on grasses and volunteer corn. And we have a lot of these things outlined in the Weed Control Guide. Particularly if we're gonna be using that very similar to what we see with Flexstar or Cobra, we wanna increase that grass product rate. In particular, if we're looking at tank-mixes with dicamba and Warrant, it's usually best to apply that separately and separated by three days. Another thing that I wanna mention is overlapping herbicides. With our post emergence herbicide applications, many times we can add something in to give us some residual control for later season waterhemp and grass emergence. Those herbicides are generally the Group 15 herbicides. These can be used both in corn and soybeans, things like Dual, Outlook, Warrant, Zidua. There's a lot of generics. There's some other product names out there. Just remember these herbicides are not gonna control emerged weeds, and they would need to be tank-mixed with something that would be effective for control. So with some of the late season rains this last year, we had some later grass escapes or later waterhemp escapees. Having that overlapping residual there would be very important. Another thing to consider is to scout for followup post applications if needed. Many times, if we're using those overlapping residuals, we're gonna have good weed control throughout the season, or if we have a timely post emergence after our preapplication. One other thing to consider is that with many of the residuals that we use, there can be some carryover to certain crops. So keep those in mind. In the Weed Control Guide, we have Table 12 and that's our herbicide crop restrictions table. So for example, in corn, if we look at Acuron, we come across and we wanna plant alfalfa, we would need to wait 18 months. So those are just some things to keep in mind. As I mentioned before, glyphosate is one of those ones where we might have a limited supply. One of the questions is, how low of a glyphosate rate can you use? Because a lot of times, we're gonna be putting glyphosate with other products so we're not gonna be relying on it by itself. And many times, we have very susceptible, many annual grasses and some annual broadleaves are very susceptible with glyphosate. So one of the key things I wanna point out is over the last five years, we've really increased the rate of glyphosate that we're using probably because it's been a lot less expensive, we've been able to get more of it, so we've really increased that amount and it gives us a little bit more flexibility on weed size. But as we're looking at trying to control weeds this next season, Roundup PowerMax, that formulation's gonna switch to Roundup PowerMax 3. And we remember about five years ago with Roundup PowerMax, kind of our 1X or general use rate was 22 ounces. With PowerMax 3, that would be 20 ounces. That's that three-quarter pound acid equivalent. And that's where we wanna focus on weeds that are less than six inches tall. You can see if you've got some weeds that are bigger, you might need to increase that rate, but just a couple things to keep in mind. Another thing I do wanna mention is in the back of the Weed Guide on Table 10, we do list all the different glyphosate formulations. And it's really important to look at those pounds acid equivalent and see what the different glyphosate rates are for some of those different formulations because some of those are very different. Additionally, if we're just trying to control grasses in some of those in mixes, sometimes we can go to some lower rates because usually they're very susceptible. And remember with glyphosate, the addition of ammonium sulfate is really important, also with glufosinate. The only exception would be if you're doing tank-mixes with dicamba, which you cannot use AMS. Another couple things to keep in mind is it's important to take steps to maximize herbicide activity. Again, AMS is a key thing, making sure that we're using some of the different adjuvants that are important for some of the post herbicides and remembering that it's always important to optimize those spray parameters. If we're wanting to make sure we have optimum coverage, the droplet size from the nozzles, making sure we have the right volume, the right spray speeds are all gonna be very important. One other thing to keep in mind is there are some different premixes that contain glyphosate. You can see those in corn, also in soybeans. And we do have those premix tables that you can look at and see where some of those are being used. So for example, in soybeans here, Flexstar GT and Sequence both have glyphosate in them as premixes. However, it looks like those may also be limited on supply this year. And finally, it's really important to always follow the label. And just as a reminder, just a few take home messages. As we move to 2022, it's gonna be important to have a comprehensive weed management plan and also keeping in mind that we do have herbicide-resistant weeds that are showing up. Also, look for some alternatives. Keep in mind that there are several sources of information. And then the key things, using your pre-emergence herbicide, using one of those soil-applied herbicides are gonna go a long way to reduce the pressure on our post herbicide applications. Our post herbicide considerations to think about, weed size, tank-mixtures, what adjuvant is used, and then potentially using overlapping residual herbicides. And it's gonna be really important to scout prior to and after post herbicide applications. So again, I think we can have a really successful 2022, but some of the things just to keep in mind, open communication with your retailer on what products you can have. And then again, having those resources available to look for some alternatives. So here's our weeds website listed above, as well as the field crops guide. Just remember that those resources are available to you to help make sure you have the best weed control recommendations going into 2022.