Controlling your weeds with Jon Zuk
Jan 16, 2019
Stef W: Welcome to another episode of planning profits with Jessie Wiant and today we have Jon Zuk.
Jesse W: Thanks Stef. So as Stef said we have Jon Zuk here today. As you know, every year we're faced with different decisions that we need to make on a weed-control basis, whether it's mechanical or chemical. Every operation may need a different, more specialized program to control these weeds. I would say in this area our largest concerns are probably giant ragweed and waterhemp. Obviously we've got other weeds that we compete or have to deal with, but probably the two most problematic are giant ragweed and waterhemp. When we look at our chemical options, there's really not an abundance of different products that we can use from an active ingredient level, so definitely management of our herbicide applications and tank mixes are key for success. Like Stef said we have Jon today. Jon, thanks for joining us. Weed control is a decision that growers have to make every year in order to have a successful crop. I want to cover a few things of what it takes to have a clean field at the end of the season. So let's start with the basics, the foundation of weed control. You know, first pass, is it tillage? In some cases it may be. Jon, are we truly doing any good from a weed control standpoint with that early pass of tillage?
Jon Zuk: When I think ofit, and Jessie you talked about the two weeds that we're most concerned about, giant ragweed and waterhemp. Really I think that first pass is probably going to do, and give you a little bit of control on the giant ragweed, but that all depends on what the spring looks like and how deep that tillage pass is. Sometimes it's been documented that those giant ragweed seeds can start germinating, three, four, up to six inches deep in the soil. If we're not going that deep or if maybe we're doing some tillage in those weeds and they're already big, we might not get the kill that we're looking for. So in some cases the tillage pass can work, but most of the time, I mean it's got to be more of a timing issue of when the weeds are going to emerge to when you're going to do your tillage pass. So I'd say that is a pretty sketchy way of trying to control weeds, although it does get a job done on some of them, but the emergence window tends to be a little bit wider than what our tillage pass will allow us for control.
Jesse W: So I would agree with that from a standpoint of, I think it was maybe the spring of 2016. Like you said, we had giant ragweed's emerging from four to five inches down. When we're doing three to four inches, at the most, with that spring tillage pass. Let's jump back into corn here. What's the key to having a clean field in corn? Where do we start with that foundation for corn?
Jon Zuk: Well, I think the main key is, having a pre-emerge herbicide. I always think of a pre-emerge herbicide is like a blanket. So whether you do a tillage or you're not doing tillage, or you're going down and doing that spring burned down, and then following tillage, however you look at it, that pre-emerge or that pre-plant herbicide is going to act as a blanket. A lot of times a one-two punch would be, do a tillage pass, come down and put a blanket application. That blanket, what I mean is the way those types of herbicides work, most of those modes of action are either root or shoot inhibitors and if you have a shoot inhibitor, once that gets to that blanket, it's going to inhibit that shoot for further developing. It's never going to reach the surface to get sunlight. Once those weeds get sunlight, we know that they could start growing and they can sometimes push through our herbicides. The goal with that first initial application in corn and as well as soybean is to make sure that weed never comes out of the ground.
Jesse W: So over the course of the last probably 10 years or even better, we've been pretty spoiled in this area with the use of glyphosate being able to control weeds from a post standpoint. However, I would say, what we're seeing out there today, whether it's tolerance or resistance or just even help the control of weeds in general. I would agree Jon, that pre is definitely the biggest point to start with, even in the corn. Most of the time we think about pre's being a bigger player in the beans because we're more limited in options, but I still believe that when the corn that's the foundation for good weed control the rest of the year. Switching over to beans, you alluded to pre's again there. Some of the issues I've seed a crop response, maybe you could just touch on that a little bit. There's growers that maybe choose not to use a pre because they've had a bad experience with a negative crop response.
Jesse W: Yeah, so that is definitely a point of existence I think, especially with using the pre's. I think for the most part, if we could follow organic matter trends and we could follow timing of application and then if mother nature cooperates with us, most of the time our crop responses' are going to be pretty negligible when it comes to measuring the yield component of it. Typically I guess my biggest call that I get is a group 14. They'll get splashing up of a group 14 on the soybean stem or hypocotol area or coddled lead. And like I said, most of the time that is a little bit of a crop response. Most of the time it is somewhat negligible, but then you also have the weigh, you potentially maybe have a little bit of a crop response or set back and have excellent weed control because I think the weed control is what's going to haunt late season and that's where we have to get ahead of the game. The reality is, if any of those two weeds that you talked about the giant ragweed or the waterhemp, if they come up and they get away from us, our hands are really tied with the timing of application with a lot of the modes of action that we're looking at. Yeah, we have dicamba soybeans as a tool, but our timing of application in our window is probably not going to be as flexible as what we can want it to be. So starting with a clean field and trying to keep that clean field should be a target and then trying to work through potential crop respond issues if they come, I'd have to say that's just the nature of the game of trying to get a clean field. I mean if you skip, in soybeans especially, if you skip a pre, you could. But the problem is, a lot of times we'll skip pre's and what happens is we're trying to finish planting soybeans, were trying to start spraying corn and then we get about two weeks of rain and pretty soon what happens is, like you said, our weeds get off label and we're spraying a six inch weed that should've been sprayed at three inches. Then we're saying we got resistance and it's like, well maybe you got resistance, but maybe you've got resistance because you've done that for the last five years and you've been spraying a full rate on a weed that's twice as tall for it's label, so that technically it's a half rate. I think that's a big component to maybe why we need to be consistently using pre's. I also think that sometimes we make a mountain out of a mole hill with that crop response. Now, I'm not denying it. I totally think it's there and I've seen it with my own eyes every year in some way, shape or form. But I think it's really hard to put a yield of value on that one. I think there's other things that are haunting us on yield worse than what that's going to have, unless, like I said, we're losing the standard where we're severely damaging the health of that soybean plant.
Jesse W: Right.
Jon Zuk: And then the other thing I might add in there is I always tell them growers, if you're spraying your soybean field and you feel like you're spraying it, and you're like, "oh yeah, I'm spraying it. The weeds are perfect height. You know, it looks like we're going to kill weeds today." You're probably two weeks too late. If you're spraying it and you see weeds in the field and you think that you've got good control, you should be spraying your soybean field and you should be sitting in the sprayer going, "Oh man, it's not even weedy out here. I shouldn't be spraying this yet." If you feel that way, you probably now have hit the right time of when you should be post applying your soybean field, as far as weed control goes. That's the way when I see the best control acres with the least amount of weed, it's the acres that got sprayed, a pre down and they got sprayed early posts and there was no waiting for the weeds to get to the right size because as soon as we do that, I feel like that's where we start to get all the escapes and we just don't get as good of a kill.
Jesse W: I would agree with that. That's the same message that I pass on the growers as well as. If you're trying to sit there and wait until the weeds are quote unquote "the right height", that's when it starts raining and now you're off label. I would rather see the guy out there spraying, where they're like, "why am I out here?", but that's the best time. There's weeds out there that you maybe can't see from the spray cab, but if you would lay down or kneel down on the ground, you can find them and those are the weeds that we want to kill.
Jon Zuk: So one thing that I would want to add there would be, sometimes that crop response tends to be a big issue and maybe they don't grow as quick or maybe they're a little stunted, or sometimes you don't see it at all. But what I would argue is the way that yield is produced on soybeans, is really late season and physiologically soybeans don't necessarily think about yield until we get flowers. So in my mind as an agronomist unless I have flowers on that soybean plant, sometimes as long as I know I have a plant there and it's growing and gathering sunlight and if it's healthy at the time of flowering, I have a hard time attributing that back to a yield component, unless there's extreme stand loss or there's something else going on. But again, you have to weigh the benefits of having clean field versus potentially having a soybean that's stunted. The main thing is, is that soybeans of stunted and just slowly growing or if it's unhealthy and damaged. And I think that's where we have to separate those two and make sure that we're looking at what's actually going on, on the farm.
Jesse W: So that's a good point. I mean, when we looked at form of safe or some of type of a burner product later, maybe before reproductive stage when we're out there spraying, we don't necessarily see a negative yield effect. Even though we're burning those beams down, they look terrible. So I think the point of not really producing for yield until we hit that reproductive stage, that's where I would agree with you Jon that what possible damage that you can have up front isn't going to necessarily hurt your yield. Once you can get over the fact that you may see a few beans that show some sort of a crop response fromthat pre, maybe where there's some overlap or something like that in the field with spray, I think the benefits outweigh the visual aspect at that point. I look at our post options in soybeans today and we're very limited. In corn, we at least have some different options of products that still work on the weed spectrum that we deal with. But in beans, you know, I guess one thing that we promote here at UFC is using a layby product , a residual product, something like that for that late season flushed. What's your thoughts of that?
Jon Zuk: I love the benefits of using a layby, for those that don't know, the definition is typically referred to as a product that goes down as a blanket application in-season, so it's more of a residual application, a layby application that comes after emergence We really only have one mode of action in soybeans that we can do laybys with, and that's the group 15. And so in that group 15, one thing that allows us to do is get another mode of action in the mix. Sometimes we are using a group 15 at the pre emerge as well, but a lot of times what I'll see is that group 15, in some cases, is relatively quick to break down. So if we can use it as a pre and stop the emergence from happening and then come back as an early post with another blanket application or layby in that group 15, we've now enhanced that overall residual power to hopefully lengthen us through the growing season. We talked about giant ragweed, most of them emerged before June and emergence is done. So if you can kill giant ragweed before June comes along, most of the time you can give yourself an a-ok that you're not going to have a complete disaster with the giant ragweed. But then the other weed that we're after with his layby, I think is going to be the waterhemp and waterhemp don't really start emerging until the end of June, or maybe at earliest the middle of June, and they really don't start getting flushes until mid to late July. So I see waterhemp almost emerged for two months throughout the season and that's where having that residual power later in the season is going to help us keep those fields as clean as we possibly can.
Jesse W: So as long as we're talking about waterhemp, obviously, like you said, that's a tough hard to control the weed. There's been a documented resistance or definitely a field tolerance, is there a way to test for that? And I guess if there is, what's the best way to do that?
Jon Zuk: So it's pretty difficult to test, but there are some ways we can. Now you can't do this with every weed, but with waterhemp you can collect samples and you can test for group 14 and group 9 resistance. There are a few instances where we can look at like group 27, maybe some group 2, but it's really difficult, because depending upon the resistance mechanism, just because one says it isn't resistance, here might be another mutation that's going on that does still make a resistance that the test doesn't test for. So what we really see with the glyphosate resistance, is there's a lot of mutations that allow that plants, especially a giant ragweed or waterhemp, to mutate itself and be resistant to the group 9 herbicides and sometimes you can't test for them all. But if I would say that you are suspecting resistance, it never hurts to send a sample and really it's $50, you collect a sample and you can send it to multiple different laboratories. I always use the University of Illinois, but there are several different laboratories that you can send it off to and within a couple of weeks you'll get an indicator of whether or not you have group 14 or group 9 resistance.
Jesse W: Over the last 3 years, here in this area we've quite a few samples into the University of Illinois specifically to test for PPO and glyphosate resistant waterhemp and most of them have come back as resistant to glyphosate, but we've had a couple that have actually come back resistant to both. So, with our options being very limited in soybeans specifically post, when we look at something like this, that's where these layby products, these residual products really seem to make a difference for us. Like you alluded to, a little bit of ago, the Dicamba use in soybeans, which is great, but that's not always the tool that's available based on the surrounding fields, etcetera. Like you said Jon, having that pre down, following it was a post, mixing up your modes of action, and using a residual product are all good things. Say a growers doing all that and you still can't seem to get on top of your weeds. What's the next step? You just plant corn and try to control them in the corn.
Jon Zuk: I go back to, if a grower's doing all that and you still can't get ahead of the weeds, number one, I'd say go barking up the tree of resistance and then look at modes of action that you're putting on as a post. How many of those weeds are you spraying when they're emerged? Because if you are spraying an emerged weed, the likelihood of resistance and poor control in-season is pretty good, especially with waterhemp because like I said, they emerged from that two month time frame. A lot of times we're not doing enough water, potentially we're not conditioning the water the way we should. All those sorts of factors really add up when we're talking about weeds that grow really quick and they harden off compared to the weather. The biggest thing that I would do is if you're doing all those things and you feel like you're spending a boatload of money and chemistry on soybeans and you're still not getting controlled. I go back to your core program and what I would venture to say is, sometimes the weed control issues that we have in soybeans actually start in corn. And because of that late emergence of waterhemp, what I've seen in the last several years is we got these corn hybrids that dry down pretty quick, we let them stand in the field, the sunlight starts to penetrate that soil, and we get these waterhemp that are emerging and they're putting on a seed head that two, three, four inches big in some cases which could have up to 100-150,000 seeds and that's what's giving you a fresh seed bank coming into your bean year, I think on a lot of these tough to control fields. So I always back up and start back in the corn and make sure that weed control is perfect in the corn, because we do have the modes of action and the ways in corn to control those weeds that will really help with more consistent weed control in the soybeans.
Jesse W: Well Jon, I appreciate your time. Just to kind of sum it up, whether it's corn or beans, I think the biggest keys are to have that pre down, have that foundation to start that field of clean. Then, mixing up your modes of action, using multiple tank mix partners and then the last thing, to me, is making sure your rates are right. Not trying to skimp on rates because of the price of the product and price that you're getting paid for the ending commodity. Making sure that the weeds are on label, whether that's the two inch weed or three inch weed and not spraying a so called two inch weed that's actually 9 or 10 inches. So again, Jon, I appreciate the time and the information and look forward to another spring.
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