Early Season Weed Control
Well, good morning. Welcome to Strategic Farming Field Notes. Before we get started, just a little bit, we need to talk about in terms of our featured guests and some quick webinar tips. If you have questions and so forth, we have a q and a box on the bottom of the screen where you can type in and enter your questions. We're gonna reserve that chat box area for technical questions.
Dave Nicolai:So if you're not familiar with it, you just hover your mouse down below. When we're done today, at the conclusion of the program, when you log off, there's a quick, three question survey we'd like your input on. This session is being recorded and will be posted to your favorite, streaming service here, later today with that. Just a reminder, these sessions are brought to you by the University of Minnesota Extension with generous support from farm families through the Minnesota Soybean Research and Promotion Council along with the Minnesota Corn Research and Promotion Council. We're happy that you joined us today for the May 14, program on early season weed control for corn and soybeans.
Dave Nicolai:My name is Dave Nicolai. I'm a regional agronomist, in Extension located at Farmington, Minnesota. We welcome our guests today, Doctor. Devlin Sarangi. Devlin is the University of Minnesota Extension weed specialist along with Ryan Miller, he's a regional crops educator out of the Rochester area.
Dave Nicolai:With that, I'd like to just briefly mention a little bit about planting progress we get started in the weeds because it it's different in different parts of the state. The report that came out of the state of Minnesota and the Minnesota Department of Ag indicated that as of this past weekend, corn planting was 75% complete. Actually, it's probably gone up from that quite a bit, hitting that mark about six days sooner than we did last year and and really ahead of the five year average. 30% of the corn crop had emerged, about 5% ahead of the average. Soybeans, at the time of the report were, 52% planted.
Dave Nicolai:They were eight days ahead of the 2024 season and, six days earlier than average. And about 14% of the soybeans emergence, was about a week ahead of the five year average. That was actually the report is completed on on Friday and, and Saturday, but I know there's progress made over the weekend. And talking about planning progress, I'm gonna ask, Ryan Miller to jump in here a little bit. He's in Southeast Minnesota, but we've been talking about, you know, there's a differences in different part of the states.
Dave Nicolai:How are things looking in your, in your area, Ryan, in terms of of progress planting emergence and and weed emergence for that matter too?
Ryan Miller:Well, so I think, Dave, when we look at the southern part of the state and kind of, look at this eastern portion of the state, we were a little bit more delayed in the bulk of the field activity that's happened. We really have been at it for about a week and a half with, with the majority of the corn and soybean, effort. Certainly, earlier in the month, there were some, some opportunities in that April 1516, kinda in that window, for some planting, and and the corn that was planned during that time period is up. There were some soybeans planted then too, and I am hearing some reports, I guess, of some some emergence issues with some of the planting dates kinda later in that early window. So certainly a thing to get out and check for because we can correct some of that now, early enough in the season to, to deal with any of the the stand issues that are that might be occurring with those earlier planted, conditions.
Ryan Miller:That said, some of those, plantings look, excellent, but a lot of that activity has happened the past week, which is different because the western part of the state, when we were started, they may have been, you know, 75% done with their corn. So, you know, a very different kind of scenario. The thing that's kinda in common with with the state, though, is in general, when we look at the southern half, is that, that, really, rainfall has been limited. It's been dry. Last Friday, I talked to one of our our colleagues, Emeritus, Bruce Potter, and and, had a text exchange with him, and he was indicating it was desert dry in Southwest.
Ryan Miller:And so it's very different as you head that direction. East, we still have adequate, soil moisture. We've had quite a bit of things that some of those conditions that delayed us actually provided some of those moisture conditions. So we still have, at least according to last drought report, we're still on kind of, for the most part, okay moisture wise. So, so the big thing that comes up then is, like, we put on a preemergence herbicide.
Ryan Miller:We know that we need water to activate activate those preemergence, herbicides, and so we're in a waiting game. We put them on. There's not been rainfall for the most part. Some limited showers this morning, in the Southeast region at least. I haven't seen any measurements yet as far as how much rainfall.
Ryan Miller:But so we're wondering. You know? There's some questions that come up with pre emerge. You know? And maybe I'll I'll throw some questions over to Devlin to kinda get the the situation going here.
Ryan Miller:So, Devlin, how much water does it take to to activate some of our pre emerge herbicides?
Debalin Sarangi:Oh, that's a good question. And, Dave, thanks for having me today. So Sure. Yeah. I mean, it depends on the herbicide, which herbicide we are talking about.
Debalin Sarangi:Because different pre chemistry, they, they recur different amount of water. But, as a thumb rule, we say half inch to one inch rain is needed within a week of spraying so that the herbicide is activated. And within two weeks, I mean, we say, like, a half inch maybe within a week and then at least one inch to two inch within, two weeks period so that those herbicides gets activated. So, yeah. I mean, I have been in the field yesterday in the Southern Minnesota, and I, looked at some of the fields.
Debalin Sarangi:Those are planted. The corn or beans, they're not up yet, but waterhemp started coming up. And waterhemp is right now cotyledon stage, so they're very tiny, but they're coming up. And, lamb's quarter, this is a very good year for lamb's quarter. They came up little earlier.
Debalin Sarangi:However, due to the moisture stress, they are not growing as much as we expected because due to the early emergence, we thought lambs quarter might be, like, two, three inch, four inch tall now, but they're about inch or inch and a half. So, next week, the forecast is saying it will be a little cooler, so it'll slow down the crop progress as well as the weed, progress. But here is the reminder for the folks. Like, you planted your crops. You put some prees down.
Debalin Sarangi:If the prees does not have any burn down activity, if it is solely soil residual herbicide, and if your waterhemp or lambsquarter is up, it will not kill those weeds. So you need an early post sooner this year because those waterhemp and lambsquarters are up. But if your field you worked on the field and you planted, you put your trees, the weeds are not up yet, maybe you'll be good because at least the Southern Minnesota is expecting rainfall at least tomorrow or, like, this Thursday and Friday. So if we get at least half inch, rain, that will activate your pre's, and that should be, good for your preactivity.
Ryan Miller:So so, Devlin, I guess it you know, I think it's probably safe to say that if we made our our tillage pass, we often neglect to think about that first field cultivation as kind of our initial weed control. And so so if we're closer to when we made that first pass with the the field cultivator, we're probably in better shape than folks that might be a couple weeks out since rainfall or since planting and making those field cultivations. And so I'd I'd really like to echo what you just said is that don't delay. Once the weeds that have emerged get to that two inch stage, start making applications because we don't wanna wait, until they're six or eight inches tall so that we catch more weeds flushing after this rainfall because it's much more difficult to get post to work well on on, you know, six to eight inch tall weeds. You know?
Ryan Miller:So don't delay. I guess that's my big, my big thing that I wanted to reiterate with that. One other thing, Deb, I know we were talking about earlier is this concept. Folks like to talk about this this concept of reach back where, preemergence herbicides applied, and then they aren't initially activated with rainfall. But then we get some rainfall, and they they can, you know, reach back and kill smaller weeds that have have emerged or just emerged.
Ryan Miller:And and maybe we take a couple minutes and address some of that.
Debalin Sarangi:Yeah. Reach back is something like you put a freeze, and then you, didn't get much rainfall or your soil moisture is inadequate. So the freeze are sitting, on the ground, and then you got maybe half inch or, quart three quarter inch rain that the herbicide will mix into the soil, and it will control the weeds. So, yeah, we have seen reach back in the past, with couple of the chemistries, especially those, HPPD inhibitors. And when they're premixed with some other chemistries like, like, those premixes with HPPD and other chemistries.
Debalin Sarangi:We have heard about some of those, reach back activities, but, you know, like, most of the herbicide, I mean, they do little bit reach back. It's not that I mean, if you are close like, you got the rain close to your application of the herbicide, maybe the reach back will be more. But if you have spread your pre's maybe two weeks before and then it was sitting there dry, there's a very low chances of that reach back apart from some of the strong premixes that has HPPD inhibitor along with some other chemistries.
Dave Nicolai:Know what? Ryan, just to clarify, the reach back and or burn down are two different things here. So sometimes people are mistaken in in terms of that. If we talk about a burn down, most of our pres don't really have an activity from a straight burn down situation with that, especially if you're getting to that one to two inch, you know, height and so forth. Other chemistries might have to be involved, typically with that.
Dave Nicolai:If we're thinking early post emergence, Devlin and Ryan, where do products like, glufosinate, which is, you know, liberty trading with those types of things versus, some of the other unless should we be waiting here, with with that in those situations with that? Of course, obviously, don't know what the rain's gonna do here.
Debalin Sarangi:Ryan, do you wanna go first?
Ryan Miller:Well, you know, Dave, I think that we just go back to the statement. You don't delay. When we get two inch tall weeds, we need to start making post emergence herbicide applications because I'm fairly confident, barring herbicide resistance, we can kill two to three inch tall weeds. Right? And and we can we can do that with with, I won't say ease, but it's much easier than than as things get later.
Ryan Miller:Particularly, when you look at a chemistry like glufosinate, it's critical that we get great coverage, and it's much easier to cover small weeds than it is to cover taller weeds and and to get good kill of of all that tissue. So so I think, yeah, certainly, if you're looking at a product like, like, glufosinate that's dependent upon, contact action, and that would be any of the contact type products. So your your Flexstars, your your Cobras, anything like that, you're gonna wanna burn down or not burn down. I shouldn't use that. You're gonna wanna, spray small weeds.
Ryan Miller:It's just gonna be much more effective. I think I'd echo the same thing with their systemic chemistries that that really we should be targeting those two to three inch tall weeds. That's it's just gonna work much better. You know, there's a little more flexibility there, which is, you know, if you get a rain shower or something, you can't get into the field. Certainly, you get a little bit more flexibility there, but I still think as a general kinda goal, I I like that two to three inch tall, you know, window to start controlling weeds.
Ryan Miller:And, you know, if you start at two inches tall by the time you finish, depending on your acres, you know, hopefully, you're wrapped up by the time things are four inches tall. Let's just say that. So so that's that's kinda where I'm I'm thinking with that, I guess. Devlin, did you have other comments?
Debalin Sarangi:Yeah. That's a very good point, Ryan. So, yeah. Like, glufosinate is a contact herbicide, and we all know that, when the weed size or height is more than four inch, the glufosinate efficacy drastically reduced. So, like, if you spray a three inch tall plant versus five inch tall, you'll see a clear difference when it is it comes for the contact herbicides.
Debalin Sarangi:But the systemic herbicide like, know, like two four d, we also have seen, like, when you spray, like, more than four inch tall waterhemp with two four d, you have low chances of getting total kill with, two four d. I mean, you have to have something with that. So, it's, yeah, for contact herbicide, it is very important to pay attention to the weed height. But for the systemic, some of the chemistries, they also don't like to work well when it is when the weed height is more than four, five inches tall. So even if you are tank mixing your Liberty with two four d for your soybean, but still pay attention to the weed height.
Debalin Sarangi:Maybe, yes, Liberty with two four d, they have a really good activity to kill those weeds, but still, like, if you are spraying on a one feet or 80 inch tall plant, good luck with that. Maybe you may not get % kill with even tank mixing two forty with, Liberty. So pay attention to the weed height, whether you are spraying two forty or Liberty.
Dave Nicolai:Let let's talk a little bit about the dry weather conditions for both both of you. Now we've been extremely dry and a lot of these growers may may have already applied pre emergence, but we've had no really incorporating rainfall in there. Given the fact that the soils are so warm, are we going to have a skip here where we're going to have weed emergence from deeper down, larger seeded weeds and so forth come up through these pre's already coming up or just peaking through here before we really get that herbicide in the soil solution. And I'm talking about a little bit of mistiming, not on the fault of the grower, but just on in terms of when that and rainfall in there. So I guess my point is just because you have a preemergence doesn't mean you can walk away from it, but you can still get weed emergence that is already coming through with these warmer conditions.
Dave Nicolai:Any comments about that thing you've observed either this year or in the past?
Debalin Sarangi:Yes. So Dave, I'll start. So, what I what I'm seeing right now is the due to the warm soil, the weeds like to germinate really quickly. Like, waterhemp, probably it is one week ahead of the germination because it came later last week and early this week. And but the interesting thing is they germinated, they're sitting there because there there are not much soil moisture.
Debalin Sarangi:But once it will get that rain this week, if we get, like, half inch rain at least, the weeds will grow crazy. I mean, next week, again, it will be cooled down, so the weeds growth will be slow. But until the weekend, with all the soil moisture, they'll grow really quickly. So, that's what I'm seeing, especially in the Southern Minnesota. Due to the warm weather, the weed tries like, they tends to germinate really quickly.
Debalin Sarangi:They're sitting there. They're waiting for that rain. Once the rain will be here, within two, three days, they'll grow maybe one inch or one and a half inch, and then they'll wait for, the good weather. So I think, if you have planted and put a pre and if you started seeing those, waterhemp started coming up right now, maybe, you you you expect to spray your early post emergence May or early June because I don't think those waterhemp will wait after the Memorial Day weekend. Yeah.
Ryan Miller:And, Dave, I just to to add a couple things, I guess. With with the moisture being, at least in the Southeast currently, our our we're not bone dry. So, I mean, the upper inch or whatnot is is pretty much bone dry. But as we get down into the soil profile, pass that inch more to the seed depth, where we'd be seeing our crop, we've got adequate moisture at least to this point in most places, I would say. And, and what we'll see is some of the weeds that are gonna be emerging here as we approach, at least in up to June.
Ryan Miller:We'll see some giant ragweed become an issue. We're gonna see personally, I've seen a lot of velvet leaf this year. In, like, double the same. They've they've germinated, but they're they're just cotyledons right now. They aren't growing real great because there's not an excessive amount of moisture for them to really get racing along, so to speak.
Ryan Miller:But those are some of the weeds we're seeing. Somehow, you know, lamb's quarter is just it's like it's magic. It's a it'll germinate whenever, and, it's it's coming out of dry soil, and it seems to be quite prolific this year. And so that's that's kinda where that's at. Now I've got a couple of questions that I was thinking about yesterday.
Ryan Miller:Was riding with a custom applicator. We were doing a little bit of work, and and just watching the dust come off of the crushed rock road and blow, you know, a good 800,000 foot into the field. Certainly, on some of these busier roads, we get a lot of traffic and we get a little breeze. We're getting a lot of dust into the field. The application equipment's stirring up a lot of dust, and that leaves us some questions about, you know, are there things to think about with dust in some of our post emergence herbicide applications?
Ryan Miller:And so I Devlin, you wanna mention anything there?
Debalin Sarangi:Yeah. So I'm familiar with some of the studies when they did those studies, especially with the Roundup efficacy on the roadside plants. As in the roadside plants, especially not even in The US, some other, like, foreign countries, they see a lot of dust on those plants, lot of anyway, so they spread Roundup, and they saw that the efficacy was reduced because of the dust cover. So, personally, I I have not done any studies so I can talk about any data, but I came across some of the studies in the past regarding the dust covered weeds when you spray with some of the herbicide, which tend to show lower efficacy.
Dave Nicolai:You know, one of the things that might happen, kind of a comment that came in here with our list of our coworkers is if, for whatever reason, if if, if they've delayed a a pre application, maybe hoping that it looks like rain, is there an opportunity to put a pre with a post together and layering here some at some point in time, before it gets too late if that hasn't been done already for whatever reason? Any any comments about, about that if there is a delay of of, going with some kind of a tank mix?
Ryan Miller:Well, you know, Dave, a lot of our corn products, have a residual component with them. And so we look at any of our bigger multimode of action products that are are used quite widely. You know, a lot of those folks, they might be splitting them, you know, half the rate up front is a pre as post. If they skipped on the pre because they were concerned with not having activating rainfall, there's certainly some adjustments you can make and and probably stay the course with your product choices. As far as what you're gonna use, you're gonna have to add probably a little bit of glyphosate if you've got glyphosate tolerant corn or maybe glufosinate, in some situations, particularly if you're starting to see waterhemp emerge in your corn.
Ryan Miller:If you've got the option of using Liberty, that might be a might be a go to for you if you if you had a history of glyphosate tolerance, or resistance in your in your waterhemp populations. I will mention, like, when we go over to the soybean world, we were talking about reach back earlier. Really, those products don't offer opportunity for that kind of reach back concept. And, and so so if we skip the pre with, with our soybeans and we're seeing there with nothing down, I think, I think I'd certainly, add a residual with my first post emergence application. Right?
Ryan Miller:Still think it would have been wise to use a pre to start with, but if you didn't do it because you're seeing the dry conditions, certainly, certainly gonna add that residual in when I hit my first post.
Dave Nicolai:I don't know when we'll be back again as a group, but you wanna just mention any quick guidelines on not just, lamb's quarters, and pigweed and and waterhemp, but also giant ragweed in terms of weed height, in terms of when it really are the sweet spots for for, let's say, phenoxy like an Enlist versus a Liberty. Anything about, you know, when you should be in there or before a certain stage kind of as we as we kinda close out this section?
Debalin Sarangi:So, Dave, the thumb rule is using any kind of post emergence herbicide before the weeds reach to three to four inch high. That's the thumb rule for any herbicide. And if you want a reference point, like, soda can is, four and a half inch tall. So the weed height should be less than a soda can. So, and, Ryan, you were talking about the reach back versus, like, layering residual.
Debalin Sarangi:My colleague from Purdue University, he usually says a term like, reach back is like more like buying a lottery ticket. You know? So you never know whether you'll get it or not. So I think you better use some layering residual approach, especially for the waterhemp because you have some excellent corn product that already premixed with some of the residual herbicide. Also, you can tank mix some of the, group 15 herbicides, with your post emergence in both corn and beans because they allow you to spray on the top of the crops a little later.
Debalin Sarangi:So, if you can tank mix those, group 15 herbicides, you may extend your residual control for waterhemp a little longer. I mean, depending on the season, but I'm I expect there will be some rain sometime in late May or June that will activate those residual product.
Dave Nicolai:Okay. Excuse me. We're getting towards the end of our our time. Both for Ryan and Devlin. Any last statements you'd like to make?
Ryan Miller:Well, not to neglect our small grains crops. We don't have very many acres in Southern Minnesota, but in Southeast with some of the planting of oats, barley, that sort of thing, this spring, we are kind of hitting that window of, you know, kind of that five leaf stage, and the weeds are going to be about the two inch tall stage, not quite. And so this week and the next week is gonna be post emergence herbicide time for those crops too. Just, get out there and look. I was out yesterday, there are some lambs quarters and velvet leaves coming in in those crops.
Ryan Miller:And so something to think about. The last thing I wanna mention is, there are some folks that have been doing pre plant incorporated herbicides, with their with their soybeans, doing a little cultivation afterwards to kinda help incorporate those. And, Devlin, I don't know if you have a quick comment on how does that play a role when we're in a year where we're seeing limited rainfall. Do those sorts of activities help or hurt? Yeah.
Ryan Miller:I'm getting
Debalin Sarangi:I'm getting, yeah, I'm getting some cautions last few weeks. I mean, we know those DNA product, those dinitroaniline product, those tends to work good when you incorporate in the soil. But some of the herbicide they strictly mentioned do not incorporate because you'll injure your crop because the crops will start emerging from whatever the depth you planted, and then, you'll see a lot of, injuries. So, please follow the label. If they mention do not incorporate, I would say, do not incorporate those, herbicides, to avoid some of the, injury.
Debalin Sarangi:But, yeah, sometimes those, in dry conditions, the incorporation may help, But sometimes there is a disadvantage of incorporation because you may incorporate little, like, deeper and then you'll miss the top layer where the weeds will emerge. So there are some pros and cons, and we can chat about that maybe in the future, like, which chemistries would be good, which may not. So I think, Dave, there are some cautions. Maybe I can try to answer.
Dave Nicolai:Sure. There was one one that came in from a little bit about on how how fast does waterhemp typically grow, especially given this warm conditions and situations with that. I mean, they may be some of the things you know know at Rochester, Ryan, it might be, you know, to call it, they can rapidly grow. Correct?
Debalin Sarangi:Yeah. So, Dave, in the middle of the season when your growing degree days is really high, like June, July time, waterhemp tries to grow, like, inch per day. But right now, they're not growing as fast as you think. But but, you know, with this moisture that you'll get maybe tomorrow and then if there is couple days of, like, like, hot weather, water may grow quickly. But still, it will not be one inch per day.
Debalin Sarangi:But still, like, maybe within a week, you'll see they'll like, from the cotyledon, they will grow one and a half inch tall. So, yeah, look out for those waterhemp and scout your field pretty regularly. You know?
Ryan Miller:There there so, guys, there's one last question I see in here about carryover in the dry conditions, lack of snowfall. And so we're kinda setting ourselves up for potential to see some of these carryover injuries. And I'll just make a couple of comments quick. My experience in the past, there are some potential issues with if we're using a lot of Clopyralid in our system, if we've had dry and we're really pushing the envelope as far as how much we've been using, there could be the potential to see some some injury with soybeans. I think also with the HPPDs, we don't get adequate rainfall between time of application and and when we're planting again, we can see injury.
Ryan Miller:We can see even some of those symptoms sometimes show up in corn, where we've used the you know, if we're going corn on corn and we're using HPPDs again, we're kinda layering it in there, and it it seems to, sometimes show up, with injury with these dry conditions. Typically, we get enough rainfall and degradation that we don't see those things, but certainly could be seeing some of those issues.
Dave Nicolai:Okay. Great. Thank you very much. I think we're up against our, allotted time and certainly, I encourage folks to look at University of Minnesota crop news. I anticipate more articles coming out here shortly about that and dry conditions and weed control with that.
Dave Nicolai:So we wanna thank folks for attending this University of Minnesota Extension field notes program today. We really wanna thank our sponsors, the Minnesota Soybean Research and Promotion Council, along with the Minnesota Corn Research and Promotion Council. Just a reminder, when you log off today, there's a quick three question survey that we'd like you to fill out. It gives us a little bit of a heads up and some guidance for future programs. Also, we'll be back again next week at this time, next Wednesday, which I believe is May 21, to discuss our planning progress, with a couple of our state specialists, and, we'll have an opportunity to, to do that again.
Dave Nicolai:It'll be at the same time at at 08:00. We really wanna thank Ryan Miller and Devlin Swerengi for being our guests today. Appreciate their time, with us and situations. So thanks again for attending, and, we'll look forward to visiting with you next week. Have a good day.
