▶ Late Season Weeds and Controlling Weed Escapes

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So Dan’s got a lot for us, and I’m going to turn it over to him. All right. Thanks Laura. We will dive right into this.

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So, late summer weeds. This is likely the result of past challenges, but we also are going to talk a little bit about how long weeds emerge in a typical Wisconsin growing season. But if we’re seeing late summer weeds that are above our soybean canopy or even worst case scenario, above our corn canopy, these are more than likely, due to some challenges that we faced earlier in the growing season.

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On the very left there is a Palmer amaranth plant from Nebraska, where you can see that the top of it was effectively controlled. And now the top is regrowing. So, some of the plant was killed. The other portion was not. It was just too big when it sprayed. So, the I will take action.

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Group, reminds us that really four inch weed seedlings are the size of a pop can is the maximum size that we can really effectively control with most of our herbicides. In fact, a lot of our herbicide labels for soybeans, say, 2 to 4 inches for weed control. So it’s a lot different than if we see a weedy field when you’re driving by it.

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And then we think that it’s time to get out the sprayer. We also have waterhemp challenges with a lot of our herbicides. And you can see that waterhemp plant there in the very middle starting to regrow from maybe a successful application of maybe Cobra there. The top was burned off, but the bottom is regrowing.

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And that’s something that we should be really scouting for because, those plants will produce seed, maybe several thousand seeds, in fact. We also have late emerging weeds in Wisconsin. So, we look at this corn field here on the left side of the screen. That is a nice looking waterhemp plant that emerged after our post emergent application was done to corn.

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And it’s going to go and produce seed. Under the corn canopy, it’s going to be weak, it’s going to be suppressed. But we can still expect that produce several thousand seeds. And then we’re going to combine separate those seeds from the plant spread, and they’re going to be future weeds that again, will produce thousands of weed seeds if we don’t really think about management.

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We also have weeds hanging out under the soybean canopy. And this was actually a photo taken from a field that was sprayed quite successfully. The field was very clean. But when walking that field, there are some plants that just didn’t get quite enough of a dose of the herbicide. For whatever reason, they were a little bit big.

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Maybe at time of application. They’re struggling to be controlled now. Maybe the soybean canopy will actually fully close and eventually kind of suffocate those weeds out. But again, we should be scouting the fields for these. And then finally, the right hand side is just a check plot from the Routt County farm. That’s a train wreck at this point.

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So if we have any fields that look like that, unfortunately, we have to take very aggressive control measures next year. Those may even be lost for this year. But if we do have some places, maybe we ground out early on in southern Wisconsin, or maybe we saw some crops that just didn’t take off due to lack of moisture.

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Even in parts of the state, we might have some areas that look like that. So why? Herbicide applications are tricky. We won’t spend a lot of time on this, but the herbicide label tells us all the information we need to know about implementing a successful herbicide application for that particular product. Where this gets tricky is we’re trying to do multiple things at once.

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We’ve got, maybe some weather conditions, like we’ve got the wind meter out there. We maybe had some days this year that were really tough to spray in. The many too windy days that forced this to spray maybe a lot of acres in a single day. It was a tough spraying year. So that’s why we’re kind of bringing this up.

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Is probably weed escapes are going to be occurring. I think overall, though, Wisconsin farmers and agronomists have done an outstanding job managing weeds this year. There’s a lot of really clean fields as I’ve traveled throughout the state in the last couple of weeks. Herbicide, mixing is really important to get the AMS in before we add the glyphosate or glufosinate, that’s what the measuring picture.

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Measuring, picture is illustrating there. We do see some challenges with getting those mixtures and solution in the right spray nozzle. Application volumes all matter to control those weeds that are pushing our our boundaries for size. We also have a resistance, in Wisconsin, that we have to think about and be mindful of. So there’s some products that just aren’t going to control our weeds.

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And we have to be planning for that. This slide is courtesy of, the WiscWeeds lab and Doctor Rodrigo Werle’s work, but Doctor Dave Stoltenberg, Doctor Mark Renz, many, many people at the University over the last several decades have been involved in this work. A lot of different resistance cases. Again, the slides are recorded. For the sake of time,

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I’m just going to highlight what Doctor Rodrigo Werle told us on May 28th of this year at the Badger Crop Connect. And that’s that we have three confirmed seven way resistant populations of water in the state: Group 2, Group 4, Group 5, Group 9, Group 14, Group 15, Group 27. Those are taking out some of our bigger tools for waterhemp in particular:

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Our 2,4-D and our Metolachlor, Mesotrione products. Those are some tools that we’re really heavily relying on. And then he has Group 10 is a question mark is maybe something that they’re investigating as well there. These are all kind of our core tools for waterhemp management. So if we’ve had some of these failures, certainly reach out to Doctor Rodrigo Werle, to see maybe some screening options, but also think about what we can do better next year.

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So these remain very effective in the state of Wisconsin against state waterhemp. But we have to apply those within usually three days of soybean planting. So we really have to have our plan together. Post emergent rescue applications are really not an issue. With this, are really not an option for this. So again, many different cases where

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The resistance is there. Ranging from giant foxtail all the way to Palmer amaranth. Limited cases in some areas. But you can look all that information up, at the, weed science website, he, put together. So weeds emerging after post emergent timing. These are a couple photos from some research plots that I have this year.

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The photo on the right is hairy galinsoga, so got germinating, about a week ago today. Still underneath a really healthy soybean canopy. I don’t think those weeds are going to do much. They’re not going to be an economic threat, but it’s illustrating the point that the weeds are still emerging. And then the photo on the left was actually sprayed with a really good pre and a post program.

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However, the pre never got activated. We didn’t get rain and then the post program was sprayed before the giant ragweed were up. We were spraying obviously weeds. We were killing some. Otherwise we’d have that, think back to that first giant ragweed photo I showed you, we’d have fewer weeds, but we still have some out there, and those are going to be escapes unless something is done.

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Now, of course, we have a lot of really label restrictions to think about, but, the data shown on the slide from, Doctor Hartzler and Buhler, shows how long velvet leaf and waterhemp can emerge. And they did some work for their tracking emergence all the way through July. And in Wisconsin, we see waterhemp from germinate until almost silage corn harvest.

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So it’s really incredible how late these species can emerge, but velvet leaf I threw up there because that’s one that we really don’t think too much about. It can certainly be a real weed threat to us in Wisconsin. Can emerge all the way through the end of July. Weed escapes are going to produce seed. So, if we have female waterhemp plants, they’re going to be producing seed.

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Our common lambsquarter plants out there are going to be all producing seed. We’re going to have a lot of weed seed. And again, this is resulting in thousands of weed seeds being germinated, possibly the next growing season. So we want to do some scouting this year. A UAV or drone works really good to do this.

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We can go out and get a pretty good idea of where those weed patches are. You can clearly see in this photo we got some volunteer corn that made it through. We’ve got some giant ragweed that’s made it through. We’ve got some lambsquarter we’ve I’m sure have some waterhemp in that photo. So we’ve got a variety of weeds there.

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In that photo, here’s a patch of waterhemp here for sure. In that photo, that we know are going to be problems here if we don’t do something later on in either this growing season, either rolling those out, or, planning for those next year. We want to take note of those really heavy, weedy areas.

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And then we also want to celebrate successes, though. And I think that we don’t do this well enough in weed control work is celebrate what works. And think about how we can tweak it for next year, because of course, we want to be rotating herbicides and mode of action groups. But we do want to celebrate what works and think about using those same practices again, possibly on different acres though.

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Soybeans, we’re going to be able to easily see those really weedy areas, corn where after we get out and walk a little bit more. Giant ragweed, we’ll obviously be able to see from the road. But those really weedy areas will show up too. But there could be a lot of grass pressure, in particular hanging out under the corn canopy.

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And waterhemp hanging out underneath the corn canopy as well. So as we’re working with Wisconsin farmers on weed management practices. In 2021, Josh Kamps received a call about a case in southern Wisconsin where, a field had been essentially overtaken by Palmer amaranth. And, this particular farm had, a really good weed management strategy, but had limited tools in the toolbox.

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So, we put together a plan and threw out an idea of, well, what if what if this gets seeded down to alfalfa? So the following fall of 2021, it was mobile plowed to bury those seeds, six inches deep to start the decomposition process of Palmer amaranth seed. And then alfalfa was seeded in. This ties into what Doctor Renz is going to present here in a little bit.

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Came back in 2023. There was virtually no Palmer amaranth in that field. So just two short seasons of alfalfa had eliminated that weed of concern. Now, of course, there’s a lot of seed there. As you can tell by the photo, the entire field looked like that. Necessarily, the game’s not over for weed management here, but there’s a lot that can be learned from using different crops in a crop rotation.

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I think it’s really interesting that this farmer did this and did a great job. So we have some tough looking fields we can think about that, emerging threat. We’re not going to talk about this by through this in today because, there’s possibly some populations of Johnsongrass out there. This really shows up, around corn silage harvest and throughout the fall.

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If you have any populations and, Mark or I an email, and I’d like to go out and check those out. I’m drawing some, right now as well to see if we can get rhizomes out of it right now. The populations we’ve been looking at are struggling to produce rhizomes, a characteristic of true Johnsongrass.

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To try and distinguish this from other populations that may be in the state, such as, sorghum. So.

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Somehow I think I got muted there. So we’re going to want to think about harvesting these fields now that may have some weed escapes in this photos from a high like soybean field a couple of years ago up in, Scott Reuss’s area of the state in northeast Wisconsin. Chris Clark’s up there. Kevin Jarek up there. But this was a field that, Scott had, some high oleic in.

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And high oleic soybeans are, roundup ready, but not necessarily anything else at this point in time. This year and moving forward, there’s a lot of Enlist traits available there. So that brings in some really great tools, for our wheat control program. But, in this particular case, we need to go and combine those soybeans.

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And that’s going to take extra time. It’s going to take extra money this year. But we also want to really think about limiting those seeds from spreading, because those are going to be some really small seeds. And unfortunately those seeds are retained on the plant. So research done while I was in grad school here at UW, showed us that Palmer amaranth and waterhemp retain about 99% of their seed until they’re mechanically separated from the plant.

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That means if we have a waterhemp plant out there in the fall, like several those photos have shown, we’re going to have seeds on that plant until we combine those soybeans, or corn. This is also true for red root pigweed. We see about 85% of the seeds, retained. Make sense there in the amaranth species, but common ragweed, about 78%, common lambsquarter, about 55%.

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Common cocklebur, 39%. Giant foxtail about 50%. Large crabgrass about 40%. What’s not up there is giant ragweed. And giant ragweed will drop the seeds, before we combine in most cases. But there’ll be a small percentage retained. Those we see in the grain tank some years. So, fall weed management’s pretty critical for some species, but it is species specific.

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If we can do much about it, if we continue to let these seeds spread of course, they’re just going to take over our crops. Robbing those crops of yield. But where that competition really comes in, oftentimes in the spring, we’re limited for water. They’re going to be taking up crop nutrients. They’re going to be stealing our light in the case of giant ragweed and corn.

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But that yield loss is really illustrative. That’s my hand from, a plot that was in grad school about 2015. Full of giant ragweed. So that area of the field yielded just maybe 10 or 15 bushels per acre. This is in Rock County, where we should see you know, 250 bushel an acre corn. So huge, huge yield losses are resulting in this, all from challenges that we really can’t do anything about once fall comes.

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So now what? What do we need to think about? So, we’ll reflect here with the baby badgers. We really have to come up with a plan for this fall. We have to prevent weed escapes and resistant challenges. So we have to know and understand the weeds. Like I said, fall weed seed management.

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There might not be anything we can do about it. The weed seeds might already be out there. We really can’t manage those because they’ve dropped to the soil. And they’re going to be there next year. So that’s where we make a plan. But know the life cycle of the weeds, knowing that you should be scouting for them, knowing they’re going to be germinating.

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We have to diversify our weed management approach and focus on reducing weed seed bank and seed production. That’s got to be a really big emphasis. And all this. No seed, no weed. We want to start clean and stay clean. So whether this is a burndown or a cover crop, whether this is some tillage, in all of our cropping systems, there are ways that we can start clean.

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I think if we’re not exploring using cover crops in our soybean crop rotations, we’re really missing out on a big tool. But we really should think about that. We have to be purchasing weed free crop seed and forges. This is really important on the forage side. Not maybe bringing in, feed components that may contain, some of our trouble weed seeds.

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We see this in hay from, say, Nebraska cotton seed from the south. There are really good sources for these products. So, no negativity towards those, but we just have to be careful. Bringing anything into our farm. But in fact, buying cover crop seed from our neighbor can even bring in weed species that we might not be familiar with.

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So we just have to be careful there. We want to scout. We really should be scouting before it’s warm enough to do anything in the field. Go out and walk the field, check for winter annuals and perennial weeds, say, in mid April. See what’s going on out there. Scout at planting at our burn down paths, but then go back out and evaluate those practices.

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Take notes of why did this burn down paths that worked really well? Or maybe it didn’t work so well. Look back at your spray records. Maybe it’s a little cold. Really dive into your own data and see what you can do better. Using some of this free information that we have available and then finally scout throughout the growing season for weeds in particular, after our post emergent passes have been done.

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Check on those fields that we maybe had a cover crop in and see what the differences are compared to the some of those fields we might be tilling. We have to use the most effective and multiple effective tools against the most troublesome weeds, like waterhemp to be effective. We want to apply the herbicides at the labeled rates.

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But probably more importantly is the weed size. And we see a lot of this in Wisconsin because our spray days are tough. Weeds get a little bit bigger than what we want. Use cultural practices like, waterhemp, use mechanical and biological practices, as applicable. And then manage the field borders. And manage weed seeds. So for the sake of time, we’ll continue on here.

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The combines do a great job. Spreading weed seeds and I first got interested with this in, I think about 2017. Kevin Jarek pulled me into some work. I had already been thinking about some things that combined weed seed management, but there’s a lot of opportunities here for for slowing down the spread of weeds with a combine.

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And it’s a very simple approach. We won’t spend a ton of time on this today, but you can see the common lambsquarter seed there on the stripper plate of the combine, hanging out when you combine in your fields this fall, check out those areas. But weed seeds will even grow in a combine. So these are some photos that we’ve captured, over the last almost ten years.

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A weed growing in a combine, northeast Wisconsin, some, amaranth, this species growing in the feeder house of the columbine. This combine here was in central Wisconsin and had some waterhemp seed in it. And then this is Palmer amaranth from that same farm that Josh Kamps had, that he worked with these folks on helping reduce their weed seed bank.

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Palmer Amaranth growing on the corn head. So wherever there’s a little bit of moisture, in some weed seeds, we’re seeing these things take off. If we’re going to be thinking about cleaner combine, we’re not doing a entire front to back, top to bottom clean out like we’re switching from a GMO to a non-GMO crop.

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That’s not what we’re recommending here. In fact, the Farm Journal article on this had, almost 800 comments. Pretty negative comments talking about how, there’s no way we could really do this, in 30 minutes, and there’s not any good way to clean a combine in 30 minutes. However, there’s a good way to clean and combine for weed seeds in 30 minutes.

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And that’s using either a leaf blower, probably a cordless one, or an air compressor, if you really have, you know, maybe multiple machines you’re trying to clean out quickly. We’re going to blow off the feeder house, dump the rock trap and blow off the header, the grain platform. That’s really all we need to do. That’s where all the weed seeds are hiding out based on our research.

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We don’t need to go into the rotor. We don’t need to clean out every bit of biomass out of the combine. The photo, there’s just illustrating the air compressor. We don’t need to clean the back of the combine out. It’s just not necessary. But safety is very important. It’s really dusty, very noisy. The combine is very dangerous to have the head up.

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We have to follow all, instructions and read all the safety instructions with combining cleaning equipment and follow those to be safe. We’re doing this. But also personal protective equipment is really important. So a respirator, goggles, ear protection, that type of thing. But again, read the manuals for this equipment. Plan for next year.

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So this is where we’re going to somewhat wrap up. We can use university available data. All the Midwestern states have different data sets, for different weed species. So maybe Wisconsin, you’re looking at the screen here now saying, well, my broadleaf weed isn’t listed there, and maybe Illinois or Iowa has it in their data set. These data sets are out there online, widely available.

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I know Doctor Werle widely promotes the new data when it comes out. There’s a lot of different options. Put together a program that works for your farm. Got to check, obviously, the economics of this, the use rates, the application windows. There’s a lot that goes into this. But if you have, say, really bad foxtail this year and you see that when you’re running all the foxtail through the combine, going to into A3646, use, the newest reports to pick out some herbicides that have really good effective control.

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The data shown on the screen is a rating system. It’s 1 to 10. Basically, you want to look for a product that’s seven or higher, to provide decent control of your weeds. Nine is going to be preferred. But again, we can start to make some combinations of things as well.

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Think about a new approach. Think small though. Start small. There’s a lot of options for a diversification of weed control program. This photo is, from where I live. The farm decided to try some cover crops, so they chop some corn silage. They planted oats and rye together. And beautiful stand of cover crops in the fall and then planted into the next spring.

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Really nice cover crop for weed suppression. Think about new herbicide options. There’s new tools coming to the marketplace all the time, but use university data to look and see how those are performing, how they fit on your farm. Think about row spacing adjustments. Maybe it’s time to upgrade the planter, anyways, maybe we can go to 15 inch rows.

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I know there’s pros and cons to this, but, we can think about, all the different things we have to consider. I know makes this a complex decision. Crop rotation is important. Bringing in a small grain, if possible. Bringing in a cover crop. Start small, learn from neighbors, producer led watershed groups, agronomists, then us at the university.

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We’ve got a lot to share. And be happy to chat more with you as well about different approaches for weed management. Dedicate time though to fall weed seed management. So the photo on the left is from Nebraska again, that’s Palmer amaranth growing in a hay bale that maybe sold to you of one day. That, of course, was, the photo was about five years old now, so we don’t have to worry about those weed seeds anymore.

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But, we see a lot of feed on the interstates. A lot of bedding on the interstates. Know where that’s coming from. Know if there’s any weed seeds coming to your farm. If there are, plan for them. You can easily defeat these if we have a plan for them. And then the other photos there from southwest Wisconsin, it’s waterhemp growing on a hay rack.

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So think about how much waterhemp seed after Doctor Mark Renz presents on alfalfa and waterhemp management. Think how much seed must be in that field to actually have weed seed settle out of a bale and land and grow in a hay rack. We’ve got some videos. The team will share a link to this, but Rodrigo and I just did a new combined cleaning video this last fall, where we walk through that 30 minute procedure on how to clean a combine.

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Pass that along to anyone who might be interested. And then finally, like to wrap up with the badgers again. Thanks everybody. And feel free to throw questions in the chat and I’ll work through those as Doctor Renz presents.