Field Crops Webinar - Weed Management - Christy Sprague and Erin Burns

March 8, 2021

In the session on March 8, MSU Extension weed scientists Christy Sprague and Erin Burns focused on “Weed Control—Effective Options for Tough Weeds at Different Price Points.” Herbicides are the main component of many weed management programs in field crops. To reduce weed control costs, herbicide programs can be changed, although the cost of herbicides is relatively small compared to the economic cost and loss that can be caused by weeds.

This presentation highlighted approaches to designing a cost-effective weed management plan for your farm including sharing results from over 10 years of economic comparisons of weed control programs in corn and soybean. 

Video Transcript

Today myself and Dr. Erin Burns, we're gonna be talking about controlling some tough weeds in both soybeans and corn, and really trying to look at some of the economics of some of the decisions that you might be making when you're making weed control, kinda developing your strategies. And what we know is that weeds are the number one pest in US agricultural fields. And really what we do see is that when we start thinking about the commodities in Michigan, we know that Michigan is a very diverse agricultural state. In fact, we rank second, and we have over 300 different crops with over 9.9 million acres of crop land, and really contribute a lot to Michigan's economy. What I thought we do today is talk about some of our big agricultural crops and how weeds actually affect yield. This is a kind of a slide we put together looking at a lot of our past research trials, actually over 150 of them, looking at the impact if we don't control weeds. So really just emphasizing how important it is to control weeds in a lot of our Michigan field crops. And if you look at these, what you can see is what's the percentage yield losses if we don't control weeds. And you can see particularly with corn and soybean, which we'll spend the majority of our time talking about, is if we don't get effective weed control, we can lose anywhere from 55 to 62% yield from both corn and soybeans respectively. And we can tend to see, for those of you that are sugar beet growers, sugar beets, we tend to have a lot more potential for yield loss if we're not controlling those weeds. Dry beans, just because they're planted a little bit later, they're not dealing with as much weed competition. And then winter wheat usually does a pretty good job of competing with a lot of the weeds, but we do tend to see this get a little bit higher with some of the new grass weed species that we run into in some of our wheat fields. So as we look at this, really this is just to kind of give you an idea of why it's very important to make sure that we get good weed control. And this kind of goes along with the amount that we would potentially lose and then what those economic losses are. And if we really focus on both corn and soybeans, we can see that we can lose over a $700 million if we're not effectively controlling weeds in Michigan's corn and soybeans. So what are some of the considerations that we need to make for weed control and really looking at some of our economic returns? And I kinda just put in kind of a little graphic showing you some of the things that we need to really be thinking about. So obviously yield is important, right? So that's really what we get paid for. When we think about yield, that selling price is very important. And we've seen a lot of ups and downs with that over the last several years. Right now things are looking fairly good but we've seen crop prices pretty low, and that can really affect what our economic returns are. And then just focusing on the weed control aspect. And we all know that a seed cost can go along with this some of our weed control prices, but what I'm talking about here really is just looking at the cost of the herbicides and really the cost of the application. So when we started thinking about weed control, obviously these two things are important also potentially if you're using one particular herbicide resistant trait that might cost a little bit more than another one that should also be included in that calculation. And that really takes us to where our economic returns are. And what I thought I would do is just kind of give you a summary of some of the trials that we've done over, oh gosh, since 2004, looking at some of the economics on a weed control, and I'm gonna talk about some of the soybeans just kind of a summary of the last five years, and I know Erin's going to talk a little bit about what she's seen in corn. So really what we've done since 2004 is we've looked at various weed control programs that have been promoted by the companies and really focused on those in both soybean and corn, and then we've done several non-GMO soybean trials where we looked at similar types of programs. And then I would say most of our trials have been on MSU campus where kind of our dominant weed species are annual grasses and the majority of that is giant foxtail, but we do tend to see a little bit of yellow foxtail and possibly some barnyard grass. Common lambsquarters is usually pretty prevalent. We also see a pigweed species, in many times it's Powell amaranth, which sometimes people get mistaken with red root pigweed, but, and then what we generally see at our soybean trials is we have a lot of ALS-resistant common ragweed, so that can affect how some of those programs actually work. And then in some cases, we do see velvet leaf and wild mustard. And what we tend to do is when we construct these trials each year, what we do is we ask companies for what their programs are that they're gonna be marketing, and over the years we've looked at ones that have just been in Roundup Ready soybeans or LibertyLink soybeans, we've looked at the Xtend soybean system, we've also looked at the Enlist soybeans system like for the, for example, for this last year, and some of the different programs that might be used in any of those types of soybean systems. In general, we look at soybean injury. So we evaluate maybe if we have a lot of injury from some of those pre-emergent herbicides, we also look at weed control throughout the season. Then we look at yield at the end of the season and then put the economics behind it, again, putting into context how much that weed control program is, what the application cost is, and then thinking about that yield and what that crop selling price is and kinda give us what our economic returns are. And then what we try to do is post those results on our webpage, msuweeds.com, so you can always go back and look at some of those things. What I tried to do here is just kinda hit some key points from the last five years of our trials. And the reason I wanted to do this is just to kinda show you the range of the cost of some of these herbicide programs, the range in yields, and then what happens from standpoint of weed control, and then how many of these programs are amongst the highest yielding and the highest returns. So if we look at back at 2016, we looked at 24 different treatments and some of these treatments could be used in any particular soybean traits that would have Roundup Ready or glyphosate resistance. And then we had certain treatments that could be used in LibertyLink soybeans. And one of the key things you can see here is that our herbicide costs range anywhere from 26 up to $58. And again, a lot of that's including your application timing, so some of those ones that were a two-pass program would potentially have anywhere from a seven to $8 more per application compared to something that might be just a one-pass program. So you can see where that range is. From this particular trial, we did see a range in yield anywhere from 52 to 75 bushel per acre. And then what we generally do is look at the weed control at the end of the season, and look and see which ones were most effective. And in this case, we kind of set our kind of our baseline is 90% weed control. So we basically are thinking maybe there might be one or two small weeds out there that are really not contributing to the seed bank. In our 2016 trial, what we saw is that two of those only provide a greater than 90% control. And looking back at the data, what we tend to see is that some of the things where we had, some later season grasses that came in and really were not controlled by the end of the season. And you'll see that this is quite, this year happened to be quite a bit different than what we've seen in more recent years, but it does show you that, okay, maybe not all of these programs are lasting throughout the season, and you can kinda look back and see what those are. But one of the things I do wanna point out is that 17 of those 24 programs actually were amongst our highest yieldings. So really showing that we had good season, early good season weed control that resulted in many of those programs providing our highest yields. And then what we also saw was 18 of those programs also fell into our highest economic returns. And so that's really showing that yield is primarily the driver of what we're seeing as far as being amongst those highest economic returns. So maybe even a $58 program, even though it seems like it's, you know, twice as much as what we might see with the cheaper program, the yield benefit that we were getting them for having that better weed control, getting that higher yield, actually made it towards the highest economic returns. And that's really kind of what we're seeing as we start looking at some of these other key points. So this is 2016. When we look at 2017, we basically looked at very similar types of programs. Some of these are different, maybe some different pre-emergence programs there, maybe some two-pass programs. And what we saw was that our weed control costs, again, you can see where that range is, it's quite a bit, anywhere from $14 off to $64, our yield range was 46 to 59. And what we really saw was half of those programs controlled all the weeds throughout the season greater than 90%, which would be kind of our standard there. Highest yielding, we had 21 of those 26 that were amongst our highest yielding, and then with our highest second economic returns we saw at 24/26. So again, that yield was very important, but on this case, we probably have three programs that maybe didn't fall amongst those highest yielding. And what we did see again, yield was a main driver and only one of the economic returns were not the most the highest yielding. And that really had to do with potentially the cost of maybe one or two of those programs and where that yield fell into that spectrum. And in fact, in this study, our highest cost program was $64, that actually was included in our highest economic return. So again, you know, making sure that we have good weed control to maximize those yields, and even with some of those higher price programs, they're making up for themselves by the yield that they're actually able to contribute. And 2018, we switched over and looked at some Roundup Ready treatments as well as some Roundup Ready 2 Xtend treatments, where we would use dicamba in the system that herbicide cost range ran from 23 to $71, and then the yields were 54 to 69. And we saw about a 21 of those 30 programs that were able to control weeds throughout the entire season. We did see that 22 of those were amongst our highest yielding, and then our highest economic returns, there were 16. And again, yield was still a main driver. We only had one of our highest economic returns not amongst our highest yielding. So again, really showing that, you know, maybe those herbicide program costs aren't necessarily the driver for some of our economic returns. We're gonna talk about two more trials. We had one in 2019 that really focused on our Roundup Ready treatment and our LibertyLink treatments. And you can see we had a huge range for herbicide costs, treatment costs, you know, anywhere from one application of glyphosate at $15 per acre, all the way up to $90 per acre where we're including a lot of different programs. The yield range was 34 to 47 bushels per acre. We had 16 of these that provide a greater than 90% control. 19 were amongst our highest yielding, 18 were amongst our highest economic returns. So again, that yield was really a driver. And one thing that we even did see is that a program that we had that costs $81 was still amongst our highest economic returns. And really what that shows is again, those yields are very important, so making sure we have good weed control. We also did an Xtend trial in 2019, and you can see where our range and herbicide costs are. Also our yield, we saw that all of our treatments provided greater than 99% control. 21 of those were amongst the highest yielding, and this should say out of 22, I'm sorry. And then our highest economic returns, we had 19/22. We had two of our highest yields that were not amongst the highest economic return. So these are just a few things to highlight, but again, yield really was that driver. And then this last year we saw a huge range of cost. Again, yield 46 to 60, we had 16 out of 19 of our treatments provided greater than 90% control. Our highest yielding, they were all amongst the highest yielding, highest economic returns also. So you know, with the variability in the field, we're seeing that when we run the statistics on this, that we are seeing that again, yield is a huge driver, and we've really seen that over the last five years. So when we started thinking about what we need to focus on to get our greatest economic returns in soybeans is... - Can I interrupt you with a question Christie? - Sure. - Was the seed technology costs included in those program costs? - That's a great question. So in these ones, we did not include the seed technology costs because we've seen that those have vary quite a bit. And for example, with a Roundup Ready program, you could use it in about four or five different traded soybeans. So we're just looking at the herbicide and again, the application cost. In the last few years we've figured in $8 per each trip across the field. Thanks Jim. So when we start focusing on this, the key thing is to make sure that we get good weed control, because we tend to see that when we have our better weed control, we're able to get our highest yields and that really helps us get that highest economic return. And what I thought I would do is talk a little bit more at looking at some of our more problem weeds. So these are really just dealing with these trials, we're dealing with weeds that are kind of more common throughout Michigan fields, not looking at major herbicide resistance issues other than the ALS-resistant common ragweed. So let's take a look at another weed species, but first of all, let's think about how do we maximize our crop yield. So obviously, you know, weed control is important, but we're really trying to reduce that weed competition. And that early season weed competition is where we tend to see a majority of issues. And those weeds can definitely compete with the crops for water, also nutrients, and then really they can compete for light. And those are some of the things that we try to manipulate to maybe help manage some of those weeds, and that's some of the things that we've been working on particularly with row spacings or cover crops to help manipulate that light, so maybe those weeds aren't competing as much with, you know, soybeans. So what we're gonna do is we're gonna look at some different scenarios, and first talk about timing. As I mentioned before, early season weed competition from weeds is probably our biggest challenge. So we're gonna take an example. When you start thinking about weed control, when should weeds first be controlled to prevent soybean yield lost? So we've got a range of different timings of controlling them, and this is without having any sort of pre-emergence down. So we're starting clean, whether it's with a burndown or tillage and planting that crop. And when those weeds start to emerge on that crop, when should those weeds be controlled? So when we look at soybeans, we're gonna look at some data from, you know, several years ago, but really looking at when we start seeing that first timing and where we really start seeing some yield loss. And as we look at this data, one thing that really stands out, you really start to see this jump in lower yield, particularly when weeds start to get be about six inches tall. And we really do see this quite a bit with our narrow row widths. So really what we're really wanna to do for soybeans is make sure that we are controlling those weeds to make sure we don't have early season competition when they're four inches tall. And in general, we tend to say that for a narrow row soybeans. And really what we've come to look at is when we start looking at weeds, they can basically grow anywhere from two to four inches tall, and that usually can happen in one to seven days. So let's look at an average of 3 1/2 days. So if for some reason we get rained out and, you know, aren't able to control it and we have to wait and those weeds get taller, we can see that jump. It occur in about 3 1/2 days. So if we think about what those average losses are basically from this graph, we can see that we can reduce yield or see a reduction in yield from weeds at about three bushel per acre per day and 7 1/2 inch rows, and about 1 1/2 bushel per acre per day in 15 inch rows, if we're not able to get out there early. And what that really does, looking at this last week soybean prices at 13.75, is if we delay our application by two days, we can potentially see a reduction in our economic returns about $86 and 7 1/2 inch rows and $38, just by that two day delay. So when we look at some of our recommendations, we've really wanted to prevent that early season yield loss by trying to control weeds in soybeans, particularly in narrow rows, whether there's 7 1/2 or 15 inch rows, control those before they get four inches tall, and in 30 inch rows, we've got a little bit more time, but again, it really depends on what the weeds are and what herbicides you're using, but we really wanna make sure that we get those weeds controlled by six inches tall, so we're not impacting yields. One way we can also help with this is to use a soil applied or pre-emergent herbicide to reduce that weed competition prior to those post herbicides. So what about early seasonal weeds? So let's say we're in no-till. So when would we wanna control those? So we can think about early season weeds, things like chickweed, maybe henbit, when might we wanna control those? Well, from some of our work what we've seen is that we start to really see a big reduction in yield when we aren't controlling those weeds that tend to be out there when we plant and we wait until potentially the unifoliate stage. So we wanna make sure we're controlling those weeds when those weeds are either prior to planting soybeans or at planting soybeans. If we aren't controlling those weeds, we tend to see about a quarter bushel per acre per day yield loss, and if we were to delay our application from that unifoliate stage to V1, which in many cases happen about 11 days, we would see a reduction of about $38. So again, timing is very important. So let's look at one of our herbicide-resistant weeds, in this case, we're gonna look at mare's tail. So when we look at mare's tail, we've talked about the best ways to control mare's tail but really what I want to focus now on is this burndown plus residual and look at some of the application prices. So when we think about mare's tail or horseweed control and we look at pre-emergence herbicides, there are basically two groups that we can use. We can use the Group 5 herbicides which are Metribuzin or the Group 14 herbicides which would include things like Valor or Authority or Sharpen, and we can get some residual control from Sharpen, and there are some pre-mixes that each one of these herbicides are in. So for example, things like Boundary, we've got that Metribuzin in there that Group 5, Dimetric charge, we would have two of those. We have Valor plus Metribuzin, Authority MTZ, we would have too. And then we've got some other pre-mixes that would contain either one or two of those herbicides for additional control. So let's look at horseweed again and look at those potential yield losses if not controlled. So we've got two passes of glyphosate here and then we have an effective treatment. So if we don't control horseweed or mare's tail, we see that we have a 24 bushel per acre in this particular plot, where if we are effective in controlling it, we see 42 bushel per acre. So let's look at what the cost of some of those effective treatments are. So this is just an example of some work that we've done in Roundup Ready 2 Xtend soybeans. So we're really looking at some of those dicamba applications. So here's kind of our standard treatment, just looking at Roundup as the burndown, and then all of our post treatments are followed up with Roundup. So you can see what that application is. So we got the two application costs for two applications of Roundup. And then we include XtendiMax in our burndown and you can see what the price goes up to. But we've really talked about if we're gonna control mare's tail effectively or horseweed effectively, we need to have a pre-emergence or residual herbicide in there. So we add those in there. In this particular study, we used eight ounces of Metribuzin. Many times we can get on really with six ounces depending on soil type, and then we use 2 1/2 ounces of Valor and in a lot of times we can use two ounces. So that's about $51 when we include that with the Roundup plus the XtendiMax and then following it up with that Roundup application. You can see some of the different pre-mixes that would contain both a group 5 and a group 14. So for example, Dimetric charged or Authority MTZ, we also have Fierce MTZ, you can see what those prices are. Zidua PRO is another pre-mix that is used a lot, really relying on the Sharpen for of course we control. And then again, all of these would have the Roundup plus XtendiMax plus one of these residuals, and then we just looked at Zidua PRO plus Roundup. So taking out the dicamba application, and you can see what those costs are. And then just looking at two applications of Roundup plus XtendiMax, and you can see where our prices range. So anything that we think would have an effective herbicide in their range, anywhere from the cheapest 41 to the most expensive about 69. So let's look and see what happens with yields. So when we look at yields, basically what we've included here is the yield over the Roundup application twice. So pretty much where this is the difference between Roundup by itself or including one of these different programs. And what we saw is that when we had effective horseweed control, we had anywhere from a 14 to 17 bushel per acre increase in yield. So that's very important. And what we saw from this research was we had no differences between treatments. When we look at yields and economic returns, and in this case we used $10 per bushel, we saw that yields range from, or the economic returns ended up being $120 to $154 more if we're using an effective horseweed control program over using just glyphosate alone. So just really showing you what that economic advantage is by including, you know, a pre-emergence herbicide, whether it's say a single active ingredient or a pre-mixture and including something that would have a good burndown, in this case, we looked at XtendiMax. One of the things I will tell you is as far as control, we had excellent control throughout the season with all of these treatments, and we only had about 73% control if we did not have that residual in there. So the XtendiMax alone, yes, the yields and the economic returns were up there, but we still had some weeds in the field. So again, really pointing out the importance of having those residuals in there. The next thing I wanna just kind of mention is that we do have, you know, some of those options out there when we can follow it up with a post because again, mare's tail is resistant mostly to glyphosate and ALS treatments. When we look at our treatments that are gonna be cost-effective, we have different soybean traits we can use, obviously, using Liberty and either the LibertyLink or Liberty GT27 soybeans, we can use Xtend, any of that XtendiMax or Engenia, Tavium, and the xtend soybeans, so we have one effective site of action post. And then we've got the two, either Enlist 3, where we can use either the registered 2, 4-D formulations like Enlist One or Enlist Duo, and glufosinate or Liberty and then Xtend Flex, we now can use Dicamba, either XtendiMax, Engenia or Tavium and then also glufosinate, so those are new. So that would give us two effective sites of action for post applications. So just to kinda give you a heads up we have these fact sheets out there and that really just focuses on mare's tail control, and we also have one that's available on waterhemp control. And again, with even the increased prices in some of these programs, the yield benefits you get by controlling those weeds are gonna be very important. So with that, I'm gonna go ahead and turn the presentation over to Aaron, unless there's a few questions that I might be able to answer. - Yeah. There are a couple of Christie. What are your thoughts about the need to include a residual with the post application? - That's a really good question. I was gonna cover that, but again I tend to talk a little bit too long, but with waterhemp, I would say the residuals with the post-program particularly with waterhemp that's one of the ones where we do potentially see a benefit. In a lot of times where we would see that would be in soybeans that are planted earlier in the season. If we get later planted soybeans, a lot of times our post application might be hitting towards the end of that waterhemp emergence cycle but if we're early, that residual post-emergence really helps. - So I'm gonna switch gears and talk about weed control and corn for a little bit, but largely the same principles that Christie just went over in soybean and then hopefully we'll have some time at the end to kind of loop around with some of your questions also. So how do we do reduce the impact of weeds in corn? And the first are using those sound agronomic practices that Christie outlined. So weeds compete with crops or water, nutrients and light. So if we can help minimize that by ensuring that we're having good agronomic practices, that will help the corn become much more competitive. So it starts with variety selection and planting timing for your particular location, and then using good fertilizer and nutrient management strategies to make sure those corn plants are growing at a competitive rate, especially early on in the season, and then crop rotation. We're quite a diverse state in cropping systems here in Michigan, and that really helps us drive down weed pressures too by having some of these diverse rotations overall. So if we think about having all those agronomic practices in line then, then our second key to weed control which Christie also went over is timing. And timing plays a large role in rest of the topics that I'm gonna be talking about. - So this a similar question as to soybeans, but this is in corn. So you can think of when should weeds be controlled to prevent yield loss in corn, two inches tall, four inches tall, six inches, nine, 12? You can think about when you might think they need to be controlled and when realistically you might get around to controlling some of these weeds also. And how we arrived at our number for weed control timing and corn was based off of a study that was conducted in the Midwest. Over 34 different sites, so a pretty great sample over those states. And what they did is they went and applied a post-emergence herbicide at two inches tall weeds, four inches, six inches, nine inches and 12 inches, and then they kept it weed free for the rest of the season. So this is just looking at that implication of that very early season weed control on yield. And what they found is that if you could control weeds at two inches tall, that's that green bar on your screen, made 100% percent of yield was obtained. So there was very little to no yield loss when we can control weeds at two inches tall. But if we waited till four inches tall, we see a slight yield reduction, so a 97% of yield was obtained, six inches, 94, nine inches, 91, and then if we go all the way down to 12 inches or waiting to spray pretty tall weeds, we only have about 78% of yield compared to the weed-free conditions that we'd have. So taking this number, we'd look at two inches being the the most or the highest height you'd wanna be applying those herbicides to have zero impact on yield. And then very little impact if we spray four inches weeds. But similar to what Christie outlined in soybean, so weeds can grow pretty quickly, two to four inches in one to seven days. So if we just look at 3 1/2 day interval, our average yield loss using this data is about 0.9 bushels per acre per day in corn. So if we think about what can impact our timing and why we might be delayed in applying some of these herbicides to corn, and those are largely environmental parameters. Such things like wind, rain, anything that can keep us out of the field spraying. And then I also probably should have put up just your time. In the spring, there is a lot going on on farms, and you might get ahead of yourself planting and, you know, crops might come up and weeds might come up and we might not spray them at the time that we originally had targeted. So also time just plays a large role in our spring weed control operations. So if we think about it, if we just delay our application by two days, the average yield loss could be $6 and 84 cents per acre. So you can kind of scale this out if you waited a week and what that kind of yield loss might be. And that's just so that these early season weeds are very competitive with the corn crop. So for thinking about timing and we're trying to control small weeds, when we're looking at herbicide programs, we're gonna look at application timing within those and how we can optimize that and we play around with that to look at economic returns. First program we're gonna go over, two-pass programs, these are pre-followed by post-herbicide applications and ways that we can protect corn yield from weeds. And these programs are looking at the impact of that pre-emergence herbicide on end of season yield. So this is on your screen, if weeds are controlled at six inches, 12 inches and 18 inches without a pre-emergence product. So this is just going in clean but then applying a post emergence product when they were at those various heights. And we see anywhere from a seven bushel per acre yield loss for six inch weeds, 31 bushel per acre if we waited to 12 inch weeds and then 28 if we get up to 18 inches. But we can look at the implication of a pre-emergence product, so if we got a pre-emergence herbicide down and then waited and then still waited till those, the subsequent flush of weeds were six inches tall, 12 inches tall or 18 inches tall, you can see there's very little impact on end of season yield. So overall, those pre-residual herbicides are a great insurance policy when we're looking at season-long weed control. So if you can get those PREs down timely early on in the season, you just have a lot more time than to do a lot of other tasks that you have to do your farm and also preserve yield and then be able to apply the post emergence herbicide programs a little bit later in the season. So some advantages of our two-pass programs is that it lengthens the application window for POST herbicide application as we just looked at based on that study, looking at the timing, and this means that it buffers that environmental variability. So we've had some pretty high cool wet springs in the past few years, which if you're able to get that pre-emergence herbicide down, it's gonna help buffer that timing that you may not be able to get it, especially if we just went with an early POST herbicide application, and then it would have to wait a few days and you can see that yield drop pretty quickly. And then we'll touch on some implications on later emerging weeds in a few sides. So ultimately these two-pass and the PRE component of that program helps minimize early season weed competition that could reduce yield overall. There are a number of PRE herbicides that you can use in corn and we wanna target products that can control weeds greater than 80%, and that you'd wanna use a combination of both broadleaf and grass herbicides targeting the weed spectrum on your field, and the rate will be dependent on how complex of a weed problem you have, what's the seed bank, how dense is that and then do you have some more aggressive, large-suited, broadleaf weeds that you'd wanna make sure that you use full herbicide rates? And instead of going over a number of programs that you could use, I just wanted to highlight the snapshot of the weed control guide, and this is looking at soil applied herbicides and corns. When you're going in the guide, you'd wanna look at the bold Gs or Es, those are products that provide greater than 80% control of the various target weed species and then that herbicide name. So when you're designing a program, you can use this guide as a way to start dialing in on what pre-emergence products you would want to apply. And then now, for POST herbicide application in these two-pass programs, once again, we wanna target smaller weeds and then also smaller corn 'cause that weeds will be smaller at that time, and then looking at residual herbicide application along with the post-emergence past to prevent yield loss from later emerging weeds and also new weeds that are gonna go into the seed bank that you'll have to control later. So the second grouping of herbicide programs I'd like to talk about are these early POST program, so these are POST herbicide applications that also contain a residual herbicide. And these are programs that are also effective at reducing the impact of weeds in corn, but there they're essentially to how effective they are, is that timing component. So if you are doing an early POST herbicide application, you have to get those weeds when they're less than two inches tall, which can be fairly difficult, or there's a number of studies that have identified the critical period of weed control. So looking at how many days after planting that is, which is roughly about 18 days or the corn stage would be about V1-V2. So we're out scouting, we'd look for less than two inch weeds and then V1 and V2 corn would be our trigger that we'd want to apply that early POST application. And keep in mind once again, our average yield loss is about 0.9 bushels per acre per day, so for pushing this on those early post applications, you can start doing the math of what kind of yield loss you might be looking at. For early post programs, we wanna make sure they have multiple effective herbicide sites of action. This is both to control the broad spectrum of weeds that you have in your field, but also to delay the evolution of herbicide resistance. And then once again, those delays can have large impacts fairly quickly on end of season yield. This is another snapshot from the weed control guide looking at residual herbicides that you can put on with that early POST application. So we have the herbicide name and then the maximum corn stage. So when you're looking at applying some of these products, you'd wanna look at both what weeds they can control, but then where your corn is in phonology and how tall or how many collars that is, 'cause that's often the upper spectrum of many of these herbicides and what herbicides you can end up using. So there's a large number of effective options within corn that are available to use and to layer in with that post herbicide application. So we've talked a lot about, you know, putting in a residual program, both to control weeds and also to control later emerging weeds. So Christie touched on weeds can emerge throughout the entire seasons. We have a large number of weeds in Michigan that have the ability to emerge later on, not just in the spring. So this is looking at corn year loss due to waterhemp competition. And what they did was they allowed waterhemp to either emerge with the corn, so VE, or they kept it weed free and then allowed waterhemp to emerge at V4 throughout the rest of the season V6 and V8. So we often think sometimes that these later emerging weeds have maybe small impacts on yield, which in they did this over a number of years. And the blue bars are percent yield loss under years where there's ample precipitation. So we see little impacts about 10% if water has emerged along with the corn, and then down about 1% would be, but if the corn was drought stress, we had a much larger invocation of waterhemp competition, but we also wanna keep in mind can some of these later emerging weeds produce weed seeds? Especially in corn we have a lot of great cost effective herbicide options for some of our more aggressive species that we have a hard time controlling in soybean, so if we can control those pretty effectively in corn, that's gonna help weed control on our soybean side and overall weed control across our rotation. So what they found was that plants that emerged starting with the corn can produce 3,000 seeds or 16,000 seeds per plant. This was reduced to 5,000 and 13,000 at V4, V6, 92 and 1,200, and then it V8, zero to 11. So pretty low weed production when we are that late into the season. But it just goes to show that some of those later season weeds can produce new seeds that goes into the seed bank, and now you have to control those for years to continue. So looking at the overall impact of some of these later season weeds is important. This is the same idea, but for velvet leaf, so allowing velvet leaf to emerge at V1, V3, V5 or V7, and overall we see that impact of the later emerging weeds having a reduced impact on overall yield loss. Once again, plants that would emerge at V1 produced over 2000 seeds, VE, or V3 sorry, a little over 1000 seeds, V5, 300 and V7, 800 seeds. So these are other things to keep in mind or designing, especially these early POST programs with residuals as part of that post-emergence past, there's the idea of trying to control some of these later emerging weeds so that you can reduce overall seed bank inputs and then more effective weed control across your rotation. And then briefly like to touch on the corn commercial comparisons trials. So like soybeans seeds have been conducted for a large number of years and I've only looked at this graph the last five years just for simplicity and these are box plots. So how to look at a box plot is that horizontal black line that I'm circling on your screen right here, this is the median. So that's the middle number that of the dataset. So this would be the middle economic return from these programs over five years. And I've just grouped the herbicide programs based on timing. So the green bar are PRE only programs, gray would be early POST programs and blue are two-pass programs. And the median for our PRE only programs, that middle economic return was $540 per acre, early post programs, those were $650 per acre, and then our two-pass program were $720 per acre. So you can see as we have some of these programs that have multiple passes with effective herbicides and residuals, which we often think as being a little bit more costly. So that total program, the median is much higher, so that you're starting off at a higher rate of economic return compared to some of the other programs. So overall the median for our two-pass program was $180 more than PRE and $70 more than early POST, and then the median for the early POST programs is a $110 more than our PRE. So overall we've seen a very similar to soybeans, we can have some programs that might feel a little bit more dollars for cost per acre, but our over all economic return is much greater, and this is consistent over a large number of years and diverse environments that we've had on campus over those years. So overall considerations when we're designing a cost-effective program is scouting your field. You need to know what weeds are in your field and ensuring that you're designing that herbicide program, so you control all your weeds and using residual herbicides for some of those harder to control weeds. Weed size, one large weeds are difficult to control. So we often see breaks when we're trying to control large weeds, we might then need to go put on another application and also you've already had that early season weed control impact that yield. Sprayer calibration is something to keep in mind also, so you're not over or under applying herbicides as these can have costs both ways, and then using full herbicide labeled rates. So for using lower than recommended rates, this can lead to increase selection for herbicide resistant weed issues and also poor weed control. And then finally, just to touch on those commercial comparisons as a general conclusion on those, often the cheapest weed control programs did not always result in the highest economic returns, and many times we did see those expensive programs did result in higher yields and greater economic returns both in corn and soybean. And then we can put this into the chat later, but our website that I share with Christie has all of the commercial comparisons trials over the years. So you can look at where your current herbicide program fits in and what some of the options that we evaluated over time were. And then finally just to note, we do have our 2021 Weed Control Guide out. You can just Google 2021 MSU Weed Control Guide and you could get the link to that or visit the MSU Extension Bookstore and get a copy if you don't have one yet. And then once again, these are the URLs for our websites, msuweeds.com or cnar.msu.edu/weeds, both of them will get you the same spot. These have all the facts sheets, commercial comparisons and lots of great other research that the MSU weed science team does throughout the year. So with that, I think I can exit out and we can see if there's any general questions that have come up. - Thank you very much, Erin. Christie's been doing a great job responding to questions typed into the Q&A as they've come in, so everybody on the meeting can click on that Q&A icon and read through the questions that have come in. Some of them are, have to do with equipment and technology, but there's some very good questions and Christie has answered them quite thoroughly, typing her answers in there. We asked our presenters this year to focus on economics on their subjects, and Dr. Sprague and Dr. Burns certainly did and we appreciate that very much. It's just kind of just what we were looking for, appreciate that so much. We do have time for a few more questions. John has asked ammonium sulfate primarily addresses hardness, but not pH, is that correct? - Is this in regards to a previously answered or question that... - It's kind of a string of questions about penetrating a weed with a thicker cuticle, maybe Christie could respond, she's been good. - [Christie] Sure. Yes, it does really focus on hardiness. Some of the issues with changing pH can also affect the effectiveness of some of those herbicides. And for example when you add glyphosate, it actually drops the pH itself. So we haven't really looked at a lot of pH modifiers. A lot of times what we're trying to do is actually get that pH up a little bit, because we do tend to see a huge drop when we include some of the different herbicides. - There is one in there from Bruce. Many times the PRE weed control only controls some of the weeds and grasses, and not all. What do you suggest? Seems like a waste of money. - I guess that, you can go Christie. - [Christie] Oh, I was just gonna say that the thing with pre-emergence herbicides is what they're doing is reducing the potential for early season competition. So you have a good portion of those weeds that are controlled, and not all PREs are necessarily gonna last throughout the season, but what it does is it reduces that early season competition. If you were able to make two timely post-emergence herbicide applications, for example, in soybeans, you could get very, you know, you can get very effective control, but the timing of those are very critical, you'd wanna make sure that you got the first set of weeds controlled by the time they were four inches tall, and then you would, if in soybeans, for example, and then you would have to come back and control ones that would come up later. A lot of times in soybeans, a one-shot program that doesn't work, whether it's pre-emergence or post-emergence. So that's generally, we're gonna to have to do two, and what that PRE does is it really gives you some insurance upfront because you don't know what's gonna happen with that POST application. Erin, I don't know if there's anything else you wanna add? - Yeah, just, I mean, getting at like, you know, reducing the density of weeds that come up, you know, later and then just giving more time to make an application of POST herbicides, you know, when they're still small as opposed to having those come up the same time as the crop. So... - [Christie] I think I can answer that question that Kyle has posed, is there another options other than balance of PRE in soybean or sugar beets are being, are in the rotation? Kyle depending on what weed species, Valor's kind of the only one that would give you any sort of horseweed or mare's till residual, but let's say you're dealing with something like waterhemp, any of the group 15 herbicides, like a Warrant or a Duo or an Outlook or Zidua, all could be used prior to planting sugar beets. So a lot of it has to depend on what your weed control spectrum is. So that would be, if you're trying to, let's say you had to control something like a mare's tail, you might wanna make sure you hit it pretty hard with a good burndown that wouldn't have, if you couldn't use residual like a Valor or a Metribuzin, but also make sure that you're really timely with a post-emergence herbicide, with potentially some of those newer soybean traits. Here's another question. Is there more weeds in 30 inch row soybeans than narrow beans? In general, we tend to see more emergence of weeds where there's more light. So we do tend to see, you know, we've been doing some stuff looking at cover crops and narrowing row widths to suppress, let's say a horseweed or mare's tail emergence and growth, and we do send a see that being reduced in using either 7 1/2 or 15 inch rows. - [Narrator] So I will pose a question that was in the Q&A box and Christie banked on a really thorough answer, but I'll open it up to both of you and then folks can add on other side questions to that. Dealing with cover crop research, it's kind of not an apples to apples comparison, but could you compare both the efficacy of weed control with using cover crops? And then also if you have any insights into even economic comparison, what might be cost-effectiveness of using cover crops for weed suppression? - [Christie] So I can try to answer that. We've been doing some work over the last three years looking at kind of planting green, so probably terminating either cereal, rye or winter wheat about a week after we plant a soybean. And we have seen some early season suppression and really what we've been focusing on is horseweed or mare's tail. And we've seen that what that cover crop can do is reduce the size at about four weeks or five weeks when you would typically apply a post-emergency herbicide, and in some cases we might see lower numbers. So there are some benefits. So it would be kind of like acting like a pre-emergence herbicide. Now, we've also done some work where we have applied a pre-emergent herbicide with that cover crop and terminated either just before planting or at planting before the soybeans emerge and have seen some really good luck with that also. The key thing with the cover crops is they most of the time are not gonna provide enough control throughout the season to surpass or, you know, basically completely replace herbicides. So you're really looking at it as kind of a twofold practice. So it's, you know, using the cover crop as well as using some herbicides to control some of those weeds. - Another question's come in, in soybeans, what's your best recommendation to control lambsquarter in non-GMO beans? - [Christie] So that's a really good question. We do tend to see that a lot of our soil pre-emergent herbicides can provide some good control of lambsquarters. So what I would recommend is looking at our weed control efficacy chart, and you can see which ones provide good control of lambsquarters, and then kind of focus on what other weeds you have in there. So we have a good listing of what the herbicides are and which ones provide a good or excellent control, but with lambsquarters, we definitely do need to provide, or control it on the pre-emergent side 'cause there's very few options if really not any because of some of the ALS-resistant lambsquarters that we have poor controlling it, post-emergence. - Thank you, Christie. And I wanna to thank our presenters very much for your time and expertise tonight. Great to have you on the program.

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