Making the most out of Postemergence Weed Control (Timing and weed ID)
I'm Ryan Miller, Crops Extension Educator. Earlier this morning, we recorded an episode of the Strategic Farming Field Notes program. Strategic Farming Field Notes is a weekly program addressing current crop production topics. A live webinar is hosted at 8 AM on Wednesdays throughout the cropping season. During the live webinar, participants can join in the discussion and get questions answered.
Ryan Miller:An audio recording of the live program is released following the webinar via podcast platforms. Thanks. And remember to tune in weekly for a discussion on current cropping and crop management topics. We do wanna make mention, we, wanna thank our 2 guests that are on this morning, Debalin Serangi, a weed, scientist at the University of Minnesota, and Joe Eichle, also weed specialist or weed scientist at North Dakota State University. So kinda giving us a spread across the the geography of of the states of North Dakota and Minnesota.
Ryan Miller:So thanks to those guys, for being on today to help, with the discussion. Also wanna thank our sponsors, Minnesota, Corn Research Promotion Council, as well as the Minnesota Soybean Research Promotion Council. Thanks for for them, handling some of the funding for the behind the scenes stuff, that goes on to bring these programs to you. So thanks to them for their sponsorship. I'll make mention of a couple of things.
Ryan Miller:Because of our short format today, there is opportunities, this summer to learn a little bit more about weed management and, see some of the tools that are being out, out there and being evaluated. And we have 2, field day field tour opportunities for you. The first one coming up on June 27th in Rochester, and then the second one will be at Rosemont at Research and Outreach Center on July 9th. So those are some some longer format meetings for you to to get out and see how things are are going and what's working, as well as, pick our specialist and educators' brains as far as some of the things that they're working on. So with that, I think we're gonna throw it over.
Ryan Miller:And, to Joe, let's start with you. Give us a perspective of kind of the west central up into the valley, North Dakota area, what, you guys have been been experiencing with some of the difficulties with crop management and and weed management. And then we'll after your synopsis, we'll move over to Debalin, and he can give us kind of a a Minnesota more central and and southeast perspective.
Joe Ikley:Yeah. So thanks for having me on. So kind of in brief, it's been a tale of 2 springs so far. So going up through about the 1st week of May, we were kind of thinking maybe we're in for a drought because it was a dry winter, and we had a lot of our early seeded crops in. Small grains, the most part went in fine.
Joe Ikley:Most of the corn has has gotten into the ground, and small grains are actually still doing well despite the recent challenges. And then about the 2nd week of May, the spigot turned on, and it's it's been a challenge for many since. So struggle to get some soybeans and later planted crops, dry beans, sunflowers. We're still kind of working on getting those in the ground up in this area. And so what that kinda means is with the small grains, we also have these wet spots we're trying to work around as many of them are approaching jointing or maybe even a little bit more advanced.
Joe Ikley:So weed control season and small grains is kind of progressing, as we expected, and then we're gonna have to kind of go to some plan b's or even plant c's for those later planted crops as as we're now, June 5th already. As far as weed growth is is concerned, it's also just been slow. So for the most part, we just have been cool and cloudy in between these rainfall events. So scouting around, it was it was actually difficult earlier this week to find 3 inch tall kochia in June. So to give you an indicator of how slow things have been going, some of those early season weeds are just slow growing, which is good for the crops we've had.
Joe Ikley:It's buying us some time to get out there and make some timely applications, but I I kinda fear once we get sunny and into the seventies or even eighties, what weeds are up are really gonna take off on us. And it'll just be a challenge of working in these wet fields and and trying to get those applications made. So still kind of early for most things considered being June 5th on the calendar, but that's kind of the the quick synopsis of what we've dealt with so far.
Ryan Miller:Alright. Thanks, Joe. Debalin, do you, wanna shine a light on, what, your experience has been in the, kinda as we head east and south into Minnesota?
Debalin Sarangi:Yeah. So thank you, Ryan. Thanks for having me. So, I believe, we have pretty much similar situation, maybe slightly better what, than what Joe explained. And, I was checking the USDA report for planting progress, that came out last Monday.
Debalin Sarangi:And Minnesota has, it is on track for corn planting. About 93% corn is planted, so it's kind of close to the average or, past few years. However, soybean is a little behind. It's about 80% planting is done. So, so we still need to catch up with some soybean planting.
Debalin Sarangi:So that's pretty much, everything about planting. And then, I agree with Joe with this cool weather and the rain and the, lack of sunshine. The weeds are kind of slow and same as the crop because we planted some soybeans, middle of May, and we are expecting there would be maybe v 1, v 2, v 3 stage, but, they're still almost at v 1. Still not there yet. So, it's kind of same story for crop as well as the weed.
Debalin Sarangi:It's, I'm getting some questions because some of our farmers, they planted their corn and soybean back in April 20, and it's than a month. And crop did not grow that much. The weeds are still not 4 inch tall, especially I'm talking about water hemp, which came probably around May 15. They are still not the 4 inch tall yet. And with the moisture, they keep hips they keep coming.
Debalin Sarangi:So the question I'm getting that whether I should start my post application right now or should I wait a little bit? So, what I'm suggesting them, like yeah. So if keep an eye on your weeds because maybe they didn't grow so far. But with this, warm weather that is forecasted with without rainfall, they will start growing now because they have plenty of moisture on the ground. So they just need some sunshine and some warm weather.
Debalin Sarangi:Then everyday they will grow 1 inch, height. So keep an eye if you want to wait 1 or 2 more days, that's okay. But maybe the post emergence timing is almost there for Southern Minnesota. And if as there are a lot of moisture on the ground, I'm suggesting them to add some residual herbicide in the tank like warrant or outlook or Dual because I expect the waterhempers keep coming because of the moisture because they loves moisture. They love moisture, so they will keep coming.
Debalin Sarangi:So that's pretty much the story regarding crop and weeds in, mostly southern part of Minnesota.
Ryan Miller:So I'll I'll just add to what, Debalin was saying there with the, areas where folks took a break from planting to do some spraying. Pres have been working phenomenally well. The soil solution, as we might call it, has kinda been rewetted every couple of days. And so they've really seen some pretty good activity with with our pre's. And and so just to make that comment, I guess.
Ryan Miller:And then the the on the flip side, where folks didn't take a break from planning and doing some spraying, They've been out the past couple of weeks, trying to put on some posts in in corn. And Devlin, Joe, you know, the overnight temperatures have been pretty low, even in south Southern Minnesota, I mean, down in the forties. And some of these herbicides are super slow to work. I mean, we typically see some pretty good activity after 24 hours, and you're like, did they even I saw the sprayer there yesterday. It doesn't even look like it's working.
Ryan Miller:Any comments on on what to expect in those situations, or is that just, wait and see how it worked?
Joe Ikley:Yeah. That for me, that kinda goes back to depending on the exact chemistry, I guess. So, you know, with with contact herbicides, you're you're going to know still within a 3 to 4 day window. Get a general gauge on the activity. Plants may not be dead or weeds may not be dead, but you'll get a general sense of overall activity.
Joe Ikley:With any systemic herbicide, it it's gonna be slow, not just because of the cool conditions, but we discussed how slow weeds are growing. So, you know, we need these plants to be actually growing to get the herbicides to the growing points. And so there's still it it's not a fun thing to say or or follow, but it is kind of a wait and see for the systemic herbicides. And if you're used to seeing some good activity out of, let's just say, glyphosate after 5 days, it might be one of those years. It's it's 7 to 10 before you really get a gauge on how well that systemic herbicide is working.
Debalin Sarangi:Yeah. I I agree with Joe, and there are few studies they showed that when you spray 2 4 d, like, systemic herbicide, like 2 4 d, they're really slow in acting, and sometimes you'll not get sufficient control because of the cold conditions. They they did those trials mostly on ragwits, which emerge early at 2:4 days a good option for killing them early in the spring. But if the temperature is low, you'll not get sufficient control. So I totally agree with Joe.
Ryan Miller:So one thing to kinda cover here, and it's, you know, everyone's favorite subject are dicamba, over the top of dicamba tolerant beans. So we know that the registration of the few products we had for that have been vacated, but there's been a further issuance of existing supplies. Do you guys wanna make some comments on that and in the context of our current calendar date and some of, the challenges that might, might be there as far as what we need to think about?
Debalin Sarangi:Yes. So yeah. Go ahead, Joe. Go ahead. Go ahead.
Joe Ikley:I was gonna say I'm I'm north of I ninety four. You you start Debalin.
Debalin Sarangi:So yeah. So if, somebody has a stock that should have been sold by May 13th, on the part of south of I 94 and north of I 94. The selling date was, May 31st, so it should be showed by now. And for post application, the deadline is, still the same, like June 12th for south of 94 and June 30th for north of 94. And the temperature cutoff is still the same, like, 85 degree, whether it is the present temperature or forecasted temperature.
Debalin Sarangi:So 85 degree cutoff. So if it is above 85 degrees Fahrenheit, you should not spread Ikemba. So the all the restrictions are still in place, and, I assume there will be less tech application this year due to those, court ruling, but, we'll see. I mean, probably there are a few farmers who are still planning to spray dicamba. So probably this is the time because if you are south of I94, June 12th is that cut off for you.
Joe Ikley:Yeah. For for north of 94 in Minnesota, then for anyone who might be checking in for North Dakota, June 30th for for those geographies. And I you know, most people who are using that, technology still are probably dealing with some kosher. And so we're still gonna have a a window here to be able to utilize that technology with June 30th coming. As far as growth stage cutoffs, as slow as things are, I don't really anticipate us entering reproductive stages.
Joe Ikley:So, really, the calendar dates and working around the weather is is what we're gonna be looking at, but we still have the month of June for the north of 94 folks.
Ryan Miller:Okay. And just a kind of a note there too. Just a reminder, these are restricted use products, so they require license as well as the additional registrar training. So those things are still there as well as all of those additional record keeping requirements and and restrictions. So, make sure we're following those, but, certainly, that's kinda we're we're kinda crossing that finish line this year.
Ryan Miller:We'll see, over the winter if things change or whatnot, but good to make mention
Debalin Sarangi:of that. And, Ryan, we are talking about XtendiMAX Ngenia, and type Devium. We are not talking about other current products like
Debalin Sarangi:Diflex or Diflex Duo.
Ryan Miller:Correct. Yeah. Good good to mention that. And again, those dicamba products for dicamba tolerant soybeans, you know, and the the corn products are only for corn. So, just, just to just to make mention of that.
Ryan Miller:I encourage anyone that's out there that has questions, you can put those in the box. I do wanna bring up another topic with you guys, and I'm actually gonna post a link here. I talked to Dennis Toddy down in in Iowa a couple of weeks back because I was under the perception that we had really windy conditions this this spring and early summer. And and, I'll put a link in there. Folks are curious about clicking on this, but it is some some wind data that they developed through the National Weather Service and the Climate Hub down there.
Ryan Miller:But we have been. If you look at the maps on here, I looked at it yesterday. There isn't a map up for May yet. But in April, we certainly were were, were trending way windy, much windier than average. And so that's just been an observation.
Ryan Miller:And I don't know. You guys wanna make any mention to the challenges there as well as things to think about when we we start talking about spray drift and and what, folks might be doing to manage around some of these windy conditions?
Joe Ikley:Yeah. So, you know, for me, one of the things I'm thinking about with drift is we're gonna have varying stages of crops in trying to make these applications. So we we we have some folks that are gonna apply burn down on on some soybeans and try and run with the seabed that they have, then you might be next to wheat that's tillering or jointing. And and so, you know, certainly if you're applying some products next to wheat fields or as we're getting into glyphosate applications, whether it's in corn or soybeans, and it's it's, it's gonna show up pretty readily on on small grains. And kind of vice versa, if we're still spraying some late things on small grains and we have sugar beets or some smaller soybeans or probably not any edibles up yet, then it it's gonna be pretty apparent if we have some drift injuries.
Joe Ikley:So, that's adding on to the challenge of working around the wet field conditions and having these wind speeds, as as you mentioned, being relatively higher. So there there's still usually some good windows on either end of the day. You, of course, don't wanna spray into an inversion, but usually, it's it's been at least here. Even though we're windy, it seems like we get a window until about 10 or 11 AM, then it all hell has been breaking loose as far as high wind speeds. So we do have these windows.
Joe Ikley:They're small, and that's frustrating, but certainly working around them and then and knowing what's downwind, is certainly most important.
Debalin Sarangi:Ryan, I'll just add one more thing. It's not related to this, drape, but it's definitely the windy condition. So in our research plot, we are struggling to find a day and time for spraying any kind of post emergence right now because of the first, it was the rain, and now it is the windy conditions. If you see the forecast for, Southern Minnesota, I think we have only Saturday is the only day where wind speed would be, like, 4 to 5 miles. Other than that, like, 10, 12 miles per day.
Debalin Sarangi:So, so 10, 12 miles per hour speed every day. So that's that's a challenge for, applying some postemergence herbicide. Especially, you have to follow the cut off stages, growth stages for corn and soybean for different herbicides, and you have to find a day. And then if you spray some of the herbicides like Liberty or even like other herbicides, like systemic herbicides even. If you spray in the dawn or dusk time, they have limited activity because of their movement inside the plants.
Debalin Sarangi:So, you it is always better idea to spray on a sunny day kind of close to the middle of the day so that the weeds are growing really fast and, that uptaking the herbicide. And early morning, if you see nowadays, there are a lot of dew cover on the, leaf surface. So it is challenging to find a time for applying the post emergence herbicide. So it's good idea to look at the weather application to see the wind forecast and find a day and time to spray your post emergence herbicide.
Ryan Miller:Debalin, you did bring something up. Maybe we make mention of a couple of the restrictions. We're kinda another kinda window that's closing in some of the products that we use in corn with our our post herbicides, you know, with the temperatures predicted to swing a little bit, warmer as we head into this week and plenty of moisture out there. I know corn will start to grow fast, particularly we get that v34 stage. Things start to move along.
Ryan Miller:Certainly, by v five six, you expect things to to really cook. So what kind of, what kind of things do you think about with the product, cut off restrictions with corn applications?
Debalin Sarangi:Yeah. So in corn, a lot of the products they mention about, maybe v two stage of the corn or maybe, like 12 inch corn. So those are the corn product should be, like, should be applied right now. Because, if it is like 12 inches corn, I'm pretty sure the corn is really close to that 12 inch height or maybe some of for some of the farmers who planted, like, back in April, their corn is more than 12 inch tall. So, so that's a big concern because we are facing the same challenges for our research trial.
Debalin Sarangi:There are few restrictions like atrogene and things that should be applied to, 1 feet tall corn or 12 inches corn, and the corn is growing really fast. Now we are not finding a day due to the rain and wind. That's that's what I try to bring up here. And, yeah, I would love to hear what Joe would like to say because they're probably a little behind. They have a little bit more time, but still, it's a concern for them as well.
Joe Ikley:Yeah. So for for corn growth stage cutoffs, the the big one biggest one for me is atrazine at 12 inches. And and particularly in this geography, a lot of years, we're not gonna have a pre down on many cornfields, pretty popular for that early post timing, v 1, v 2, v 3. And and particularly with our compacted planting window and the wet conditions, there's probably a lot of fields that will need that first application will be a post application. So we we do still have time, but for anyone wanting to use atrazine, 12 inches is is the the big one that stands out for me.
Joe Ikley:The the other thing that's probably worth mentioning, you know, with corn, a lot of these a lot of corn products, you can use pre or post. There's a few exceptions that are pre only. What we've ran into in a few cases already up here is, with our soybean preemergence herbicides, if you use Sulfentrazone or the Spartan Authority products, flumioxazin, which is valor or metribuzin, those ones are pre only. So we we've had a few cases of getting rained out, coming back 7 to 10 days after planting, and some soybeans were just poking through, and we we've had a couple big incidences there. So that that's kind of the other thing to pay attention to.
Joe Ikley:As corn, you can more or less stick with your program until its corn starts getting taller, and then you have to pay attention to products and growth stage cutoffs. Soybeans, if that pre didn't get on and you got rained out, you may have kinda go to a plan b and then switch to a different chemistry.
Ryan Miller:Okay. Maybe the last thing to mention there is the cetachlor products. Pay attention to those because some have the 11 inch cutoff, some have a little bit different, the taller, 24 inch restrictions. So make sure you're just reading those labels and paying attention to where your your corn's at as far as height. Next up, let's let's address 2 of, 2 of our favorite weeds, some of the ones that cause us the most trouble.
Ryan Miller:We wanna talk a little bit about waterhemp, a little bit about kochia. And so maybe we'll, we'll start with waterhemp and, give us some insight controlling waterhemp. What do we need to be thinking about, when we're look at our our different crops out there?
Debalin Sarangi:So, I would start with the waterhemp because I'll, let Joe talk about both waterhemp and Kocia. And I know that Kocia is kind of coming on our way, and we are concerned about it. And we'd love to hear from you, Joe. So for waterhemp, we did, a survey to, 2 years back. And that survey, we did based on 90 population collected 47 counties in Minnesota.
Debalin Sarangi:And that result definitely is not looking promising because we found all sorts of resistance except Liberty resistance so far. So so far, we found populations. Those are, registered to NIST 1, XtendiMax, Atrazine, Flex Roundup, All sorts of resistance. And even we found some populations, those are 6 soy resistant that are surviving all 6 herbicide sites of action that you can think of for post emergence application in corn and soybean except for liberty. So, there is a lot of pressure on liberty and maybe, we'll not have enough time, but, after Joe talk about it, we can talk about the, some best management practices for liberty application.
Debalin Sarangi:And we had a crop news article recently. Maybe Phyllis can, post that link here. So, there's a lot of pressure on Liberty, so we have to preserve that option. And for that, we are talking about now spraying, like, smaller weeds so that you are not stretching out the plant but not killing it. You know?
Debalin Sarangi:And, we are talking about adapting something else. Like, definitely, you should rotate and, tank mix your other sites of action. But, also, we should think about, some other management like maybe tillage, if you're not doing it, if you're not big fan of tillage. I know there are a lot of challenges with tillage. Then maybe what about cover crop, which will give you some kind of cover early in the season, then, kind of suppress the weeds.
Debalin Sarangi:So water hemp, control is going out of our hand, and, I expect in few years, if there is no new herbicides coming up, we may expect that we'll, fail to control waterhemp just like what happened in the south. So, we have to really be mindful when we're selecting our management practices so that we can think about not today or about 10 years after what the situation would be if there is no herbicide sites of action news herbicide sites of action.
Joe Ikley:Joe, do you wanna
Ryan Miller:talk waterhemp or kosher or both? And
Joe Ikley:Yeah. Only thing I think I'll add for waterhemp is I always like to say it's got the word water in it right there in its name. So even though we've been wet, and we've actually been wet enough to we've cut off a couple of flushes at our local research site and growth has been repressed, it'll still be one of the first weeds to really come out of these wet conditions okay and start growing. So keep an eye on the size for what's so effective is is top of mind for me on waterhemp. For kosher, that that's just gonna be certainly, very challenging in our broadleaf crop specifically.
Joe Ikley:Even if I look at small grains or corn, we we still have our group 5 and 6 herbicides are are pretty effective, but we are relying a lot of on those, particularly a lot of reliance on bromoxetine on small grains. So that's concerning long term, but those group 5 or 6, combined with the group 27 herbicide are still largely effective for us, as long as the size is right. So in corn, atrazine in the group 27, small grains, many of our common premixes, and then throw on some floroxapyr. But in in general, for kosher, we want at least 3 effective active ingredients regardless of the crop. There's just more options for us in in small grains and corn.
Joe Ikley:Soybeans and and other broadleaf crops is becoming more challenging. So basically, our starting point now for kochia is we do have glyphosate resistance. You're you'll you'll kill some plants, but most populations have glyphosate resistance. We do have increasing pockets of of dicamba resistance. And we've talked a lot the last year or 2 about group 14 resistance in.
Joe Ikley:And so that's important because that's mainly for the burn down products that we use in no till, things like Sharpen or or Aim. The difenal ether herbicides that we can use in in soybean, and and even fomesafen or reflux that we can use in dry beans or or blaze that we can use in sugar beets. We're still seeing activity out of those products on these group 14, resistant kosher populations. The issue is once kosher is over 2 inches tall, then you you're not gonna get great control. So we still do have some options, but it's once Kosher gets over 2 inches tall, it's it's gonna be difficult to get complete control.
Joe Ikley:So I'd I'd really kinda stay on top of scouting for Kosha. Know we have some of those options left. And then as Debalin indicated, really, our our last big horsepower we've got left is glufosinate. And I long term, I'm nervous about the pressure we're gonna be putting on that molecule on on kosha, but it's still largely effective on on populations for us.
Ryan Miller:Okay. We are getting close to the end here. We did have one question that came in, and it has to pertain to late season emergency or maybe revenge type sprains to, manage seed banks. If we get in that scenario, What are your guys' thoughts on that where we've got really late, kind of rescue type treatments?
Debalin Sarangi:Well You're going first. Yeah. Go ahead.
Joe Ikley:Yep. So in general, I'm not a fan of the revenge treatments or or the rescue treatments. And and and the reason being I I know we wanna try and minimize seed production and and things like that, but, a lot of times what we would do is we'll kill off the most susceptible weeds to that particular herbicide. And the ones that survive, are they resistant? Maybe, maybe not, but they're certainly more tolerant than the ones that we killed.
Joe Ikley:So so kind of long term, I I think it's problematic for shifting either to tolerance or resistance for some of these herbicides. If it's a late season and we've got small weeds and we can kill them, then, yeah, sure. But the the tall weeds that may not completely die and will still set seed always make me nervous from a longevity standpoint.
Debalin Sarangi:Yeah. So I I I agree with Joe about that. Yeah. Go ahead, Ryan.
Ryan Miller:Oh, I was just gonna ask if you had anything to add before we wrap it up.
Debalin Sarangi:Yeah. So, we, couple years back, we did a trial on, rescue treatment, what we can apply in endless soybean, and we're mostly focusing on enlist 1 and roundup versus Liberty as a rescue treatment. And what we found is if you have one shot of post before that rescue treatment, both of the treatments worked fine and worked great for yield and weed control. But if you see the variability, the liberty has more variability if you use it as a rescue treatment versus enlist 1 and roundup. So it all depends on the, susceptibility of the weeds.
Debalin Sarangi:If it is sensitive to list 1 and Liberty both, maybe I would prefer list 1 and Roundup versus only Liberty, but I know some people are using analyst and roundup together. We didn't test that in that study, but I know that is also working fine for them. But, again, like, you know, Liberty works great on the smaller reads. If it is a smaller weed, as Joe mentioned, like, make your decision based on the weed scenario. If it is a smaller weed, maybe Liberty will be an option.
Debalin Sarangi:You have that option, for spring. But if it is bigger weeds, slightly bigger weeds, or already injured weeds from your previous post, I would probably prefer at least 1 and Roundup instead of Liberty.
Ryan Miller:Oh, excellent. Well, hopefully, we don't end up in those rescue, sort of situations making those kind of decisions, and and we get our plans put in place, and and we have some some good weed management out there, and can avoid some of those. But with that, I wanna thank, the 2 guests today. Thank everyone for kind of tuning in and, and listening and participating in the webinar today, as well as thank our sponsors, the Minnesota Corn Research Promotion Promotion Council as well as the Minnesota Soybean Research and Promotion Council.
