Weed Herbicide Interactions

(Jim) Good morning folks, welcome to That’s My Farm. I’m Jim Shroyer, your host. And we’re in luck because we’re in Manhattan, Kansas, and we’ve got Dr. Doug Shoup with us and he’s going to be talking to us this morning about weed herbicide interactions, herbicide efficacy, weed resistance, and also crop resistance to various herbicides. So, come on back and we’ll start the show. See ya in a minute.Closed Captioning Brought to you by the Kansas Soybean Commission. The Soybean Checkoff, Progress Powered by Kansas Farmers.

(Jim) Good morning folks, welcome to That’s My Farm. I’m Jim Shroyer, your host. We’re in luck cause we’re on the Agronomy Farm at Kansas State University and also we’re in luck because we have Dr. Doug Shoup with us. He is an agronomist from the southeast area. And Doug likes to talk about weeds, weed control, integrated weed management and let’s just do that. Let’s talk about weeds and integrated weed management right now. (Doug) Yea, so that’s my background, and so that’s what I have the most passion about. But so I think the main take away is that when we talk about weed control a lot of times people directly go to herbicides. And that’s not necessarily…. (Jim) Nozzle heads. (Doug) Nozzle heads, right. That’s exactly right. (Jim) Spray and pray. (Doug) I won’t take offense to that I guess. We want to go straight to the chemicals. And it is probably the most popular, one of the most effective ways that we can do a good job of controlling weeds for crops and vegetables and ornamentals too. All sorts of types of crop plants that we want to grow. But it’s not only the chemical side, really, when you take an integrated weed management approach and you don’t rely solely on chemicals,
you can at least, don’t put so much pressure on the chemicals, because what we will develop eventually is resistant weeds. And that’s really what producers are fighting a lot now. (Jim) We’re gonna talk about that at the end. (Doug) Yes. Exactly. But things when we talk about integrated weed control, it’s really tillage. I know we’ve moved so much to no till now, and there are so many benefits about no till from a soil erosion standpoint, but really…(Jim) Soil conservation. (Doug) Yea, and if you don’t use herbicides to control weeds, you open yourself up, you’re very vulnerable to soil erosion and that’s a precious resource we can’t lose. But you know, it’s not only tillage, it’s not only chemical weeds, crop competition and things that we don’t think about. But recently, over the last few years, growers are narrowing their rows on their crops. (Jim) Exactly. (Doug) That is important for yield, but it’s also real important for weed suppression as well. (Jim) Competition. (Doug) That’s right. So, crop competition, crop rotations, we don’t want to get into a habit where we grow one or two crops continuously. If we can mix that up and we can utilize different herbicides, with different modes of action, or different tillage methods, or we’re adding crop competition different times of the year, all of that really plays into… (Jim) Outsmarting the weeds basically. (Doug) That’s exactly right. You
want to have as many different tactics to reduce weed competition seed set as possible, and not only solely rely on just herbicides. And obviously today we’re standing in a herbicide demo. And so we are going to talk about herbicides because it is a really important part of production agriculture. (Jim) And also as I look over your shoulder here, things gone wrong with herbicides as well. So Doug, hang on here. We gotta take a break and you folks at home, now is your time to get a cup of coffee and hurry on back and we’ll be right back after these words from our sponsors.

(Jim) Welcome back to That’s My Farm. I’m Jim Shroyer and with us we have Dr. Doug Shoup. He is an agronomist in southeast Kansas and we’re in, like you said a second ago, a herbicide demo. And I think as I’m looking down here, this is a herbicide we probably should not have used right here. (Doug) That’s right. (Jim) So talk to us a little bit about selectivity. (Doug) Yea, sure, well there’s gobs; that’s a scientific term, right? (Jim) Gobs. (Doug) Gobs of herbicides, right, that we can use. Really you’ve got to understand what herbicides you want to use because it can have different detrimental effects on the crop that you’re trying to spray it on, on purpose. But you also need to know what weeds you’re going after too. Because there’s a lot of selectivity amongst all these different herbicides. Most herbicides that we use are selected, right? We want to remove a weed without hurting the crop. (Jim) Not to mention also, carryover. (Doug) That’s right. Huge issue. There’s so many things that go into herbicide use that we have to be aware of. (Jim) OK. (Doug) So, we’re standing in a plot here of a herbicide actually called Callisto, right? (Jim) Right. (Doug) And this row that we’re standing in front of is a row of milo or grain sorghum. And you can see it’s pretty white, right? Well actually we can use Callisto on milo. But we are only allowed to use it as a pre-emergent. So that’s another thing you’ve got to understand is that when it’s soil applied and we’re using it to help fight weeds as a pre-emergent, we can use that, but you use Callisto as a post emergent on milo and you’re gonna see a lot of damage. (Jim) Just like this. (Doug) Yes. Exactly. (Jim) So, it was emerging. It was out of the ground before you put on the herbicide, the Callisto. (Doug) Yes, exactly. (Jim) And it should have been well before it emerged. (Doug) Exactly right. This is an off label application. You’re not supposed to do this, but we do it for demonstration purposes. (Jim) Exactly. (Doug) OK. So, the one thing that you’ll notice about this is it’s white. Right? (Jim) Right. (Doug) Well, Callisto, is a…what it does is it stops the development of certain pigments in plants. And so that’s why we’re reducing, or at least we’re exposing, more of that chlorophyll and that’s how we kill the plants. (Jim) OK. (Doug) Chlorophyll is exposed and it gets reactive and then we’ll see a bunch of browning. You’ll see some browning here on the tips. Those free radicals kill a bunch of cells. (Jim) So, bad enough it can ding it. I mean it can not only ding it, but it could kill it. (Doug) That’s exactly right. Yes. Actually this will probably grow out of it, you know this was only sprayed four or five days ago, but a producer is not gonna want to see this. (Jim) No. (Doug) So understanding at least how to use it properly so we can use this as a pre, with not spraying it on the foliage. But it will cause damage once it’s on the leaves. OK, so the other thing is that we’re starting to fight a weed called Palmer Amaranth. (Jim) Right. (Doug) We put an article out a couple of weeks ago our researcher Mithila Jugulam, she’s a physiologist here at K-State, she’s found that actually these bleacher herbicides work very good on pigweed, but they’re very sensitive too. (Jim) Ahhh, OK. (Doug) So really you gotta understand the time of day. They work better when it’s cooler. This won’t work quite as good when it’s warmer. (Jim) So, in the afternoon, you shouldn’t use it, but apply it in the morning? (Doug) Or at least when it gets really hot. Maybe above 90-95 degrees. (Jim) OK, OK. Stay with us we’ll be right back after these words from our sponsors.

(Jim) Welcome back folks, to That’s My Farm. I’m Jim Shroyer. We still have Doug Shoup with us. Doug is a weed physiologist and Doug, we talked a little bit about herbicide selectivity. What are some other things that can affect its efficacy or its usefulness, effectiveness? (Doug) There’s a lot of external factors that go into how a herbicide performs, you know, whether it injures a sorghum plant like we saw in the last segment or how well it actually kills the plant. One of the things that are big are the soil conditions. And what we find a lot of times is that the higher the pH of your soil, most of the time most of the herbicides are more… things like Atrazine. (Jim) They’re hotter. (Doug) Hotter. Things like Classic these… Finesse, all these sulfonamide type herbicides. (Jim) Right. (Doug) They’re much more effective, which means they kill better, but they also have a tendency to carry over. And so you know, as you get into the western part of the state, pH’s increase. (Jim) Lower rainfall out west as well. (Doug) Right and more vicarious type soils. (Jim) Exactly. (Doug) So pH’s go up. Carryover is a bigger concern. Here in eastern Kansas, it’s not as much of a concern. So, pH is an issue. Soil texture, if that soil is heavier, it won’t be as active as if a soil is a lighter texture like a sand. That herbicide will be more active. So, the soil conditions play into it. Also, the weather conditions play into how well a herbicide works. So, if we have good growing conditions really that’s more reason for that plant to be more susceptible to a post herbicide. (Jim) Actively growing, no stress. (Doug) Yes. Right, if you stress that out, if it’s drought it may form a thick cuticle. We might not get enough absorption. (Jim) Right, OK. (Doug) Now, the last thing that I think’s really important and it’s something because of all this rain we had in May, we’re getting into July now…everybody’s been really fighting the size of the weeds. I mean they’ve just gotten away from us. Been too wet to spray. So, size of the weed is really important as well. OK, so really with annual weeds in crops, really the smaller the weeds the better, because we’re gonna get better control. When we have…there’s two types of herbicides, a systemic herbicide… OK, it’s still important we still want a small weed, but it’s not as important to have a small weed with a systemic as it is with a contact herbicide. Those don’t move in a plant, OK? (Jim) Right. (Doug) So, if you get a really big plant, we don’t have very good coverage to get to all the growing points that we need to do. (Jim) It might burn it, but not kill it. (Doug) Yes, that’s exactly right. And pigweed is a really major problem we have with the bigger they get, we have a lot of resistance to Roundup to pigweeds. Folks are having to use a lot more of these contact, burner type herbicides. (Jim) Right. (Doug) Weed size is really important on that. So, the bigger the weeds get then those burner herbicides they just burn all the leaves off, but there’s still growing points on the main stem and it grows back. (Jim) You’re going like this…about big. But in reality some of…maybe too big is this big. (Doug) Well, that’s exactly right. It depends on again, there’s so many conditions, the type of herbicide, which herbicide it is, and how effective it is at controlling that specific type of weed. (Jim) So, what do we have right here that we’re standing in? (Doug) We’re in what would be a demo for a rescue treatment on glyphosate resistant pigweed. We have a treatment of Flexstar. This is one that’s a PPO inhibitor, Flexstar, Cobra and Blazer, they’re burners that we use to try and help with Roundup. These are ones that are a great example where we need really small weeds, we need really good coverage or we’re not gonna get a very effective kill on that. (Jim) OK. I think right behind you here we have some escapes right here that just didn’t quite… (Doug) That’s exactly right. You know if we do not get good coverage I think this is a great example where we blow that top growing point out, and we can see that we’ve had some regrowth from this. (Jim) Yea you can see the actual buds coming on there. And this plant is off to the races now. (Doug) that’s exactly right. And then the next time we try and spray it, it’s gonna be even harder because there’s more leaf area that needs to be covered and it’s just becoming a real challenge. (Jim) Doug, don’t run off. OK? We’ve got more to talk about. You folks at home, don’t run off either, we’ll be right back after these words from our sponsors.

(Jim) Welcome back to That’s My Farm. I’m Jim Shroyer. We have Doug Shoup with us. Dr. Shoup, talk to us a little bit more about herbicides gone wrong. (Doug) Yea. (Jim) So, sometimes we can do some things to our own field that have negative consequences, right? (Jim) You’re doing it right, you think, but you’ve actually done it wrong. (Doug) Exactly. And then the bad part is sometimes we actually get non-target drift or non-target movement, which is a lot of times just either vapor drift, because some of chemicals that we use are a bit volatile. Most popular being 2,4-D. (Jim) Right. (Doug) Banvel, those are fairly volatile. (Jim) And they move with the wind. (Doug) They do sometimes. So you have to be very conscious about what you’re spraying, not only to your own crop, but you’ve gotta watch where the weather conditions are, the wind, and then all my sensitive crops down wind. (Jim) Which may or may not be our own. They may be your neighbor’s. (Doug) That’s right exactly. (Jim) Who used to be on good terms with you. (Doug) That’s right. Now cotton is extremely… is a great example, right? So, we’re in the… cotton drift with 2,4-D is pretty detrimental and we don’t grow a lot of cotton in Kansas, but we do grow some in the south, in the southern part of the state. And that’s part of my territory. So drift is always a concern. (Jim) Right. (Doug) Now 2,4-D drift, what 2,4-D does is plants make their own auxin. That’s just a hormone that plants make. They need it to function. What we do with 2,4-D is that’s a synthetic auxin. (Jim) Right. (Doug) So what auxin does, it helps regulate growth in the plant. Well, if we apply a bunch of extra synthetic auxin on to the plant, we almost make that plant outgrow itself. (Jim) Kinda like steroids. Like I’ve been taking, right? (Doug) That’s right. Maybe this is worse though. Cause this gets a bunch of twisting. You’re not too twisted. (Jim) Obviously. (Doug) So, we do see a lot of symptomatology of wrinkled leaves, twisting, and that’s really the symptomatology of growth regulator drift like 2,4-D. Well on cotton it’s really bad. It’s a crop that’s really sensitive. Grapes would be another. There’s several ornamentals that are…if you’ve ever seen injury from a drift of a growth regulator, it will always hit the growing point. (Jim) Right. Exactly. (Doug) Because this leaf has already grown, right? And so an auxin really is not affecting growth because this leaf already here is almost fully done with growth. Where you’re gonna see the injury is right where the new growing points are coming out. (Jim) As you can see it’s puckered up on this leaf. And this one’s all gnarled and twisted like you were saying. (Doug) That’s right. And 2,4-D is really sensitive on cotton and actually you know this plant might not actually ever get better if the dose is high enough. (Jim) It will stay stunted. (Doug) Yes. Exactly. (Jim) It will never be thrifty, so to speak. (Doug) You may not actually kill this plant, what we think about is a crispy, dead plant. But this will struggle for a long time, until it kind of breaks the herbicide down itself and then it kinda grows out of it. (Jim) And in cotton and the various crops, you don’t want it to be delaying. You don’t want it delayed cause it just never recovers. And this was not directly sprayed, this was drift. (Doug) Right, this was a drift here. (Jim) So, I’m looking at soybeans here. You’ve got soybeans right next to it. But I don’t…this was probably just a little bit further away. (Doug) And more tolerant too. (Jim) And little bit more tolerant than…but you can really see some 2,4-D, Banvel injury on soybeans as well. (Doug) Yep, exactly. (Jim) Well Doug, again my camera man is telling me it’s time to kinda wind down, so hang on. Folks, stay with us, we’ll be right back after these words from our sponsors.

(Jim) Welcome back to That’s My Farm. We have Dr. Doug Shoup with us and we’re talking about weeds and weed herbicides and effectiveness and weed resistance is a big issue but also developing crops, or developing lines or varieties or hybrids that are resistant to the herbicides is a big deal. (Doug) Yea and actually you think about it, that can play back into this whole weed management strategy. (Jim) Right. (Doug) And so, the development of new herbicides has really stalled because there hasn’t been as much market share for it. And so, the next strategy would be, well if we don’t find a brand new chemical to help us with weed control, well we can develop crops that were once susceptible to it. (Jim) Right. (Doug) We can develop those to be tolerant and then we can use a new mode of action on that particular crop. (Jim) Well, a good example would be you know soybeans and 2,4-D and Banvel have not got along for generations. (Doug) Ha, ha. That’s exactly right. (Jim) But now… (Doug) Starting maybe next year, is that when we can start using 2,4-D and Banvel on a genetically modified, right? It’s a safe way to make these beans tolerant to 2,4-D and Banvel. Very safe herbicides in their own right. And so you know, that’s really the way I’ve seen the weed control industry move towards is development of these crops that tolerate it. They’re not all GMO’s right? So we have weeds that tolerate any herbicides. Imidazole is a known herbicide, OK? (Jim) Right. (Doug) That’s not a GMO. And we have the same chemistry for sunflowers. Those are not GMO. We have it on sorghum. Hopefully coming out in a year or two. So, they’re not all GMO’s but GMO is a great technology for us to develop tolerance to those herbicides. (Jim) So what do we got here? (Doug) Right and so I would say the most common one that we have is Roundup Ready, right? But Roundup’s had its problems because we used it so much and we have resistance. Right here, is what we have is an alternative to the Roundup Ready system, which is what we call the Liberty Link system. (Jim) Right. (Doug) And so they developed resistance to another herbicide called Liberty, it’s glufosinate, not glyphosate. And so what we can see is they cause a browning symptomatology on the sorghum. And ordinarily we see a nice little corn plant in front there that is dead. This is what normal corn would look like sprayed with Liberty. It’s got a burning and that plant will probably die. But these plants back here are green. They were obviously sprayed, they’re big, they tolerated it. That’s a great example of corn. We have Liberty Link corn. We have the same example over here in soybeans. We have a nice healthy soybean right here. (Jim) OK. (Doug) Versus a lot of crispy soybeans there. (Jim) So, this is what normal soybeans would look like sprayed with Liberty, they’d be nailed. But you’ve got a variety here that’s tolerant. (Doug) Excellent tolerance. Great safety. It’s a great…different tool that we can use to control glyphosate resistant weeds. The biggest market for Liberty I almost think is in the cotton market because they fought resistance so bad and they’re really relying on Liberty. (Jim) OK. Doug, I appreciate you… (Doug) You bet. (Jim)…taking time to talk to us today. (Doug) No problem. (Jim) You did a good job. Folks, glad you were with us today and don’t forget next Friday we’ll be back with another show of That’s My Farm. See you then.

Closed Captioning Brought to you by the Kansas Soybean Commission. The Soybean Checkoff, Progress Powered by Kansas Farmers.

No Comments Yet.

Leave a reply

You must be logged in to post a comment.