Music.
Welcome back to the war against weeds podcast. This is Sarah Lancaster, extension weed management specialist at Kansas State University. I am here today with co host Alyssa Essman, howdy. Alyssa,
howdy Sarah!
and we have an awesome guest with us today. Dr JD Green, we have coerced him into coming out of retirement to talk to us today about a weed that is, I guess you could say, near and dear to him. We're going to talk about Johnsongrass today with Dr green, so hello. JD.
Hello Sarah, hello. Alyssa, thanks for having me on today to talk about one of the plants that's been in the background of what I've done for the last 40 plus years.
We all have a weed that gives us job security. Must have been one of yours, right?
Absolutely, absolutely, from my graduate school days all the way through my professional career.
So that's a great kind of segue into formally, more formally introducing you to the audience. JD, what was that position that you've recently retired from? And kind of how did you get to that point?
So I did recently retire from the University of Kentucky, where I spent 38 years as the extension weed scientist located on the camp main campus there in Lexington. I was very fortunate to be able to start my actually, my my undergraduate degree at the University of Kentucky, and then spent a few years in Oklahoma before I came back to University of Kentucky and started my professional career.
So you have lived in the South, which is where we tend to think about Johnsongrass being more a little bit more problematic. So that makes sense, all right, so let's dig into kind of the topic at hand here. JD, what are some of the identifying features for Johnson grass?
First and foremost, we have realized that Johnson grass is a warm season perennial as a warm season grass, so it's habitat is more associated with the what you might say subtropical to tropical environments where it does, does best and grows best. It is a grass that can get six to eight foot tall. Kind of grows as a bunch grass. Some of the key identification characteristics it has no hairs on the leaf and
or the stem. So no part of the plant that is is hairy, somewhat of a membranous legal or it is membranous, but it can be a little bit jagged towards the tip of that and then it also has a prominent mid rib on which it can can be identified with. There are some things that are similar with other grasses. It is a sorghum species, although it's the perennial perennis sorghum, so other sorghums can be confused with when they're in
the younger growth stages. And then I had a case just a couple years ago where a producer was concerned about his lack of Johnson grass control in corn, and when I went out and looked at the field. The grass was still in some of the seedling stage and the the season, I looked at it and turned turned out it was fall panicum. So there are some other weedy grasses that it can be confused with, as well as volunteer corn.
When corn is in that young, vegetated growth stage, you can, you know at first glance, but what you have to look for with Johnson grass is it's a perennial, so that then, only does it reproduce by seed, which are very long lived in the soil, but also it produces these underground stems called rhizomes. And if the plant has much development at all, if you if you dig it up by the root, you'll find those very prominent rhizomes to help identify it.
Johnson grass will start producing rhizomes when it's like, six or 12 inches tall, like, really quite short for what I or what I would think was short. Oh
yes, within four to five weeks, it can do that. It. It doesn't take long before the initial rhizome from a seedling plant, or it's a plant coming from a rhizome, and fairly quickly, will produce new rhizomes. So
it is easy to confuse it with other plants, especially, you know, I kind of start with that white midrib. Is that kind of key indicator, right? And then gotta go from there sometimes. So right? You talked about Johnson grass being a c4 plant we mentioned kind of mostly being found in the South. What else do we need to know about where to find Johnson grass?
So Johnson grass, apparently has been found throughout most of the continental US. I. Perhaps Maine and some of those north, far northeastern states, it's not there. But when you think about Johnson grass, as you mentioned earlier, we primarily find it in the southeastern quadrant of the US, where it's most prominent, and becomes more much more
problematic in that area of the country. But even Southern Illinois, southern Indiana, and I suspect Alyssa and southern Ohio, it can also be be there in Sarah, maybe you find it in Kansas, in some areas where it can be problematic as well. So when I think about Johnson grass, I kind of think of as a southern weed, but it does extend a little bit more into the northern areas of the other country.
Yeah, we definitely hear about Johnson grass. And honestly, something we're hearing about more in recent years, I was kind of excited. We had this episode on the docket. Actually, my first undergrad research project was examining a Johnson grass population for glyphosate resistance. But as we as we talk about some of these identifying characteristics. JD, I'm curious, do most of the populations that you get calls about or have dealt with, are
they from the seedling stage? I guess my perception is most often it's those rhizomatic populations that are really problematic. Is that your experience? I
think in most cases, the problem has got to the point where the rhizomes are being produced for a year, a few years before people recognize that they have a problem with Johnson grass. So yeah, more often than not, there are rise and zone plants out there in situations I've dealt with over the years. Yes, there'll be some seedlings, but the rhizomes, if you look, you don't have to look too far. You can find the evidence of the rhizomes.
So that ties into kind of the thought that I was wondering about. JD, it seems like when I get questions about Johnson grass, it's in a less disturbed setting, like my corn and soybean folks aren't normally the ones calling me with questions about Johnson grass, is that? Is that accurate for your part of the world?
No, I don't think so, per se. I mean it, it was just as problematic back in my early years, when we did a lot more conventional tillage as it is now, when we do less tillage, and we also find it out into forage crops, pasture field or hay fields and perf, non crop land areas that are not disturbed at all. So I think, from my perspective, is probably in all those different environments that it can can survive in
all the above.
All the above? Yes.
So I think now would be good, probably, to talk about, like, how did Johnson grass get here? Because I think that also plays into, like, where we find it, why it's a problem.
yeah, yeah, certainly. So I think there's some interesting history on how johnsongrass ended up in the US, from what I've been able to discern. And there was a publication by Dr Chester McWhorter, who did a review of the introduction and spread of johnsongrass in the US back in the 70s, I think it was, and he did a great job of of trying to
track down specifically how it got introduced into the US. And I take from that, from that work, that it's not real clear specifically when it may have first arrived in the US, but sometime in the 1830s would have been when, when some plants were brought into the US. But the probably more interesting fact is it was about 1840s this colonel, William Johnson, had collected some seed from South Carolina and brought it to his farm over in Alabama to start it as a forage crop, and that's how
the name is. Became notorious with Johnson, named for Colonel William Johnson, who brought it into Alabama and began to propagate it and promote it as a forage crop in that that part of the country and some other interesting tidbits. Is prior to that this, this plant was called a lot of different names, gana grass, Egyptian millet, Arabian millet, are a few of the names
that I came across, as well as bankruptcy grass. And then, of course, there's been a few other names associated with this plant over the years that I don't think we need to mention, just because of its ability to thrive and survive and and all these different environments in which you can find it, and kind of dominate these areas once it gets well established and it's not dealt with in a timely manner and efficient manner. So there's some interesting history, I think, and and how
this plant is thought to arrive in the US. Yeah. As a side note, it's kind of interesting to me that, as I've. Worked in the weed science discipline over the years. You know, some of the plants that we've spent the most energy and most resources and expense to control have been plants that were intentionally introduced. And you go right down the list, and Johnson grass
is on my list. You hear a lot about kudzu and some of those others, but, but Johnson grass is definitely was a plant that it depends on who you were talking to, is whether it was a good, a good introduction, or it's been a despised introduction. And I think most people are on the fence that despise in the plant, but, but there are a few people out there recognize it's that does have some value as a forage. So, yeah, I
wondered if you wanted to talk a little bit about kind of the cautions if somebody does choose to use Johnson grass as a forage, like, why was it introduced as a forage? What are some of the limitations there? Well,
they're very they're very similar to the other sorghum species, the forage sorghums that are being utilized as forage crops it had does have good value. It grows quickly, easy to establish, and it provides adequate nutrition for for animals to graze during the summer months. The major precaution is, if you're grazing, it is if it if you get frost or some other major stress on the plant, you can get a toxic compound in the plant that can be deadly or be problematic
for for animals to graze. So outside of those windows, it's, it's, it's, it's a good, good plant for grazing purposes. You know, you've just got to be, gotta be cautious about how you're grazing and when you're grazing, as far as it showing up in silage and other haylage type plants, my understanding is the comp the toxic compounds, break down pretty quickly once they go through that process. So it's it's not as problematic in those scenarios.
Okay, so we know that it can be a problem. Most folks don't want to graze it. So how do we try to control it?
Well, let me back up a little bit on that control question, because when I first started in the Weed Science arena, back in the late 70s, early 80s, Johnson grass, at least for Kentucky, was, was the one of the most prominent weed
problems we dealt with, both in corn and soybeans. And it, it was sort of the top of the list of drove a lot of weed management programs that that we had in place, if you had corn, trying to grow corn, where you had Johnson grass, we use products like eradican and Sutan, plus that you don't hear about anymore. Those were two thyrocarbamic tape products that had to be incorporated immediately into the soil before planting, because they were volatile compounds, and they
quickly lose them as a gas in soybeans. We had products like treflan Prowl, a few other other the yellow compounds, if you will, we could use, but you know, most of those herbicides target seedling plants. They didn't do as well on rhizomes. Of course, the other thing that was used is tillage, trying to do what you could to break up the the rhizomes and control the plants that were up and growing before you planted some in crop.
Tillage was used as as well in that regard also. So when I did my my graduate work at the University, taking on my masters, I was looking at trying to extend the length of control we could get out of things like the radicand to suppress the microbial degradation process so that it would last longer in the soil. And yeah, we saw some some positive results, but they
weren't great in that regard. Another technology being used at that time was some of the first selective tools for weed management, and that was the use of glyphosate through rope wick applicators, particularly in soybeans and in down south and cotton production areas, where you would load up a high concentration of glyphosate on these rope wicks and wipe it across the field where the grass, the Johnson grass, was
above the canopy of the crop. But then the 1980s we had the introduction of what you might call the selective post grass herbicides, products that people are familiar with. Well, the first one was post, then fusillade, and then we had select, known as clethodim, that's under sold on different names now, as well as a sure and those were were fairly effective for selected control we could use only in our broadleaf crops,
particularly soybeans and cotton. Again, is where that those products could be used, and they really moved us a. Step forward in controlling some of our grassy weeds, like Johnson grass, as well as other weedy grasses. And then 1990 we had the introduction of accent and beacon. These were two als type herbicides that for the first time to be able to selectively control a weedy grass, such as Johnson grass out of a crop,
which is a grass. And to me, that's probably one of the one of the key milestones in weed management that's occurred during my career, was the introduction of herbicide technology that was that selective to take grasses out of out of grass. And certainly between that technology in the the selective post grass herbicides we had for soybeans, was a leap forward in controlling weeds like Johnson
grass. One of the reasons I said that that that was so significant for the accent being introduced or nickel software on be introduced, is it changed, our tillage patterns. Before then we had we were had to do some type of tillage to plant corn where Johnson grass occurred again, because we
needed to incorporate those herbicides into the soil. But once we had those products on hand, then allowed us to do more continuous no till production, even between crop rotations where we had corn and soybeans, we could, we could then stay into a more continuous no till environment for producing those major crops. Of course. The other major change was the introduction of the rounded ready crop technology, where you had a product like glyphosate, which is highly effective on
grasses such as Johnson grass. And we went to this, this era that lasted for a short period of time. Now that we look back on it, we had these clean fields. I mean, we really cleaned up some weeds. And again, with Johnson grass being so dominant in a state like Kentucky, when you could drive down the road and not see that those kind of weeds out in the field. You know that was, that was real progress on the wheat
weed control front. Now, unfortunately, as we've gotten into more recent time, I'm gradually seeing more and more increase of Johnson grass back in some of our fields, our our crop fields. And I don't Are you y'all seeing the same thing showing up in soybeans that wasn't there even 15 years ago.
Yeah, we're seeing some of that towards the southern portion of the state, for sure.
But I've been kind of watching that over the last, oh, 10 to 15 years or so, especially as to seeing more populations Johnson versus and it's not like fields are over, overrun by by the johnsongrass, but it you have pockets of in the out in
the field. And some of my thoughts as to why we're seeing that is that, I think as we went to tank mixing more of the synthetic oxen herbicides, and we started targeting more things like water hemp and Palmer, other problematic weeds, or herbicide resistant weeds, and we're taking we reduce the activity of our grass herbicides, and particularly glyphosate in that case. So I think that's one reason. The other thing is that the emphasis wasn't necessarily on Johnson
grass control. So we developed our programs. We weren't thinking about Johnson grass has been an issue. So, so we might leave out that post grass herbicide. And some years since we, you know, we wouldn't see much of it. And the other, the other piece to that is the timing, just like with any weed control program, the timing of when we make those applications.
But some of the problems that we've seen were some escapes. Is where we were spraying early and when the plants young and earlier growth development stages, like I've seen with a lot of perennial species, when you spray them early, you don't always get the best control. The weather conditions are not good for good uptake. The plants young, it's spending more energy producing top growth, and not so much to the root system of the
plant. Which brings us to the the other possibility of, what about are we developing herbicide resistant populations in in these fields as well? Just to kind of give a background, though, and of course, the major concern is about resistance to glyphosate. We have yet been able to, we have not been able to document glyphosate resistant johnsongrass In Kentucky, because we could take some of those plants that were sent to us or go back to the field where the problem was and go re spray
them, and we could kill them. So I think that's reason, I say some of these other issues are playing into that as a reason why the control was is been lacking in some lot of these situations we've dealt with. But it wouldn't surprise me, it's out there. It could be out there because there are the first case of glyphosate resistant Johnson grass, I think was in Argentina.
Yeah, and then states like Mississippi and I think Arkansas and maybe Louisiana, those southern count of states, and I'm maybe even Tennessee, West Tennessee, have reported that
they have some resistant Johnson grass. But again, we have not been able to document that in Kentucky, with the with the sampling that that we've done, the cases we've looked at, what we have documented, however, is probably the first case of resistance in Johnson grass that we observed was with fusillade back whenever it first was put on the market, and then it was primarily used for two or three, you know, several years in a row on in soybeans, where we had some resistance that that showed
up. It was a very small population. And then with some changes in other technology, that's that sort of went away in itself, then, then when accent started to be used in the 1990s about 10 years later, I got a call to go look at a field in the southern part of the state, for lack of control, with accent. And I did some field work, and then some greenhouse work. And not on that field, but another field as well. In this particular case, this was a grower that started using he was
a he produced silage corn and wheat. He was kind of a corn wheat rotation dairy producer, and he had been using accent year after year after year. And not only was it that population resisted by accident, but also some of the other ALS
chemistries as well. Then from there, the most recent cases I've gotten involved with was only about four or five years ago, back in 2221 22 we have some areas in the state that are producing non GMO corn for the bourbon industry, and so they're trying to stay away from using glyphosate as a, as a, as a herbicide in those those programs as a post treatment. So they've gone back to use an accent and some of these other
herbicides. Well this particular case, we did field trials. We did confirm we had some accident resistance in that field, but also looked at select as well as assurers. And in this particular field, there is evidence that not only do we have the population resistant accident, but also the group one herbicides, the the thoughts, but not the DEM. So it was as did not control it very well, but, but clethodim Or select was still, still effective. So there's some interesting
dynamics that's going on there. Both when I was investigating that case, the next year, we went out to collect some seeds, or molecular biologists could start doing some work on that, and we went to a field of corn that, to me, looked exactly like what I was dealing with back in the early 1980s I mean, just fields covered. You know, fields just dominate by Johnson grass,
and you're hard pressed to find the corn. So it's disheartening in some ways, that we've come so far, but yet, there's evidence that we may be regressing back to dealing with the with the problem. We'd like Johnson grass in
the case where you have non GMO corn. So glyphosate is not an option, and you've got resistance to the two kind of main tools. What was your recommendation there? JD, going quote for that armor going forward.
Well, this particular farm is a pretty good sized farm operation. They farmed several 1000 acres, so they've got the problem also spreading it around through their equipment and so forth as they as they go farm to farm, I think the answer is they've got to change up the system. They they will not be
able to continue that approach long term. They can probably keep it at bay by, by using the crop rotations of having soybeans in these corn fields, you know, ever just like it's kind of way we were back in before, before we even had accent, you know, we were using, we can, you know, stay in soybeans for two or three years and then come back to corn and try to knock down the population, and then then come
back and plant your non GMO corn in those fields. So, so I don't have a strong answer to that at this point, other than you just going to have to shift up and just admit that there are fields you're going to have to plant some traded crops that allows you to use the full tool, range of tools we've got to work with. As you all know, I don't think I'll see much new chemistry that's going to tackle that problem for us immediately anyway, so I'm going to figure it outeventually.
To my knowledge, also have not confirmed glyphosate resistance, but I know we get reports of control issues, and I know you mentioned the synthetic auxins. And I also want. Wonder if you know how much we're relying on glufosinate. Post, do you think that's reducing control with glyphosate in some instances too?
That's a good point, yes, where we're trying to use glufosinate instead of glyphosate, the glufosinate is just, which is basically liberty is not as effective on Johnson grass and other grasses as as glyphosate would be. So, yeah. So we get those failures with, you know, you burn it back, it looks like you've got some initial activity, and then within weeks, it's gone. So or it comes back, is what I'm meant to
So going forward, what do you think the answers might be, if we think about the tools that we have and maybe some of the tools that could be coming, what do you see as the future for Johnson grass management?
Well, we we have some good tools that are still working for the most part. We just need to use them in the right way, in the right timing, and not rely just on the one tool in the box to to get the job done. So I think we just gotta, gotta be conscientious of of being diversified in our weed management program. And I think that's the main message that we're trying to get across as weed scientists, that it's, it's
gotta be a variety of tools. And I won't mention another scenario where I've gotten a lot of Johnson grass questions in the past 15 plus years, is Johnson grass in grass hay fields? You know, we're back to not having a herbicide tool that works in that situation. And most of our grass here in Kentucky is cool season grasses, things like orchard grass and tall fescue and so forth. There are no herbicides that we can apply to
a grass hay field that's going to be fed to cattle. Now, the non crop folks have some tools that they can use, but they're not approved for use in pastures, and probably because of the chance of risk of injury to the desirable species is one,
one reason for that. Now, cool season grasses, like Bermuda grass, they do have a couple of products that that can help them on Johnson grass down south in those environments, but I bring that up in hay fields from the standpoint it's been one more frustrating scenarios for me to come up with answers for, because I don't have any good answers. But the things I talk about is you've got to do something different. Your hay
production system is propagating Johnson grass. Now, once you get a get a pocket started, how many times do you roll through that field to cut it, to rake it, tether it, and then front probably run the baler through the field. You're just moving stuff around, particularly those later season cuttings that we have with Johnson grass is in its full reproductive stages of growth. So my main message is you've got to do something different, and that may mean taking that field out of
production for a few years. If it's a field that could grow grain crops, use that as your as your your tool. Now we have some producers. That's not an option for them, very logically. And the other is, I can go ahead and produce hay for the first cutting, but let's turn it into pasture field, because where you continuously graze pastures, Johnson grass is basically, you know, animals are continuously grazing. In fact, I hear a lot of people tell me, cattle prefer to graze Johnson grass over the
other grasses that are out there. But again, going back to our earlier conversation, you've got to be you gotta manage that. We get late in the season and and it comes time where we're going to start transitioning to the fall of the year and frost happening. We need to get those animals off of there so, you know, the exposure standpoint. But, but to me, as an example,
the grass hay scenario was, is, is, it's there are. There's no good answers for other than that basic principle for weed management overall, we have to do different things so you can't rely on one tactic time after time and expect to be successful.
Think that is a great summary of weed control, but it's kind of nice to take that kind of big art from kind of the beginning of your career to today. JD, and just thinking about how things kind of what's old is new again, right? Kind of back where we started and so absolutely. So. Alyssa, did you have anything that we maybe missed talking about today? Nope.
The only other thing that came. To mine was brought up right at the end, you know, the grazing and and, or mowing, or, you know, those kind of non chemical control options that he touched on there. I think it's another tool,
yeah, I mean, it's, it can be a tough space. It's interesting for me to hear you talk about Frost being the major concern, because we get concerned about Frost, but we also worry a lot about drought stress,
right? I guess yes, because that
triggers all of those, those stress responses
that, yeah, they can be at the same concern under under drought stress as well. Yes.
So, all right, did you have any closing thoughts, JD, anything that I should have asked you, but didn't you know, not
necessarily, but I mean, this has been a good opportunity for me to come opportunity for me to kind of reflect back on my my career working with, when with one particular weed. That's not that I've spent my whole time working on Johnson grass problems, but it's was one of the key weeds I worked with, specifically when I first started my career, and then as I've wrapped up and dealt with this last case of potentially multiple, multiple resistance and it, and what is,
you know, you ask a key question there. So what do we do when we run into that? And, and I'm going to actually just just jog my memory, is when I was doing the my initial work with accent documenting the accent resistant population back in oh, about 2000 or so. We finished up that project. The county agent I was working with this one Roundup Ready corn was just being introduced for use, and he and I were just having a nice little discussion and saying, Well, you know, the roundup pretty corners
probably gonna solve this, this individual's problem. But he was very insightful. He says, so how long would that last? Getting at the fact that, you know, ultimately, we may have
resistance there as well. And as we've discussed here today, you know, we don't have it documented yet in Kentucky, but there are states around us in which they are already starting to find some resistance that that they can confirm, and as much as which beginning to show up these populations, I think it could be a matter of time before we want to have a document again. Documented case for for our state, and perhaps other
states like yourselves in Kansas or Ohio, where, wherever. So I hope not soon, but keeps us, keeps us in our careers,
job security, and you know, nothing like a weed to keep a person humble.
Absolutely, absolutely.
So hey, thank you JD, for taking time to kind of polish off all the some of the points of your career and for talking with us today. We appreciate it. We also appreciate folks listening today, and we hope you'll join us again next time. Thanks for listening to the war against weeds podcast. We appreciate support from the north central Integrated Pest Management Center and the collaboration with the Crop
Protection Network. At crop protection network.org, you can find this podcast, other podcasts, and a variety of other pest management resources.