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Tennessee Turfgrass – Julie Holt, Content Director, TheTurfZone.com

The Turf Zone: Welcome to The Turf Zone. This episode begins our series on the USDA-funded ResistPoa Project. In this, our first episode, we’re talking to researcher Jay McCurdy, Associate Professor at Mississippi State University. How are you Jay?
Jay McCurdy: I’m doing well, thanks for having me.

TTZ: Thanks so much for joining us. I want to give a little intro about what we’re doing here and why. You are partnering with The Turf Zone and all of our publications to help share some information on the ResistPoa Project. Since you are tasked with extension and outreach, we’re kicking off the series with you and in the coming days we’ll also hear from other researchers that are part of the project. Start off by telling me why it’s so important that this information gets out to turf managers at this time?
JM: Well, the hope is that we’re doing this in a timely fashion and sharing results so that stakeholders can make informed decisions about how they choose to control annual bluegrass this fall – it’s a fall emerging cool season plant. Within our listening range or readership range, that’s going to be sometime starting in September when practitioners are making applications of pre emergence herbicides and then after that, post emergence herbicides, and then maybe implementing cultural practices now that actually also influence the success or failure of some of those applications so I think that’s why we’re choosing to do that now. Hopefully our listeners and readership will take heed of some of the things we discuss.

TTZ: For the average turfgrass manager out there, what has been their experience with poa annua?
JM: Reports to us as a group of university scientists usually lead to the conclusion that annual bluegrass is probably the most troublesome weed in maintained turf and in general manmade landscapes in the United States. It probably is also one of the most most troublesome weeds in international markets as well. So what leads us into this conversation is, we want to try to change that and that’s going to be a very complicated, integrated approach, including herbicides, but also cultural practices and so on and so forth.

TTZ: What objectives are you specifically pursuing as part of the ResistPoa Project, and what other interests pertaining to annual bluegrass are you studying separately.
JM: So a little bit of background on the project, we proposed this project in 2017, and then again in 2018 and had very positive reviews in the first round, and then the second round got approved. We have about 5.6 million dollars in this project covering probably about, it’s not complete salaries, but it’s paying for some research being done by roughly 50 employees. I think there are 16 university scientists involved, there are at least 15 universities so it’s a major project across the United States. A number of different variables including cool season and warm season types of climates, various different industry segments including golf, lawn care, sod farms, sports fields. So on this project, these university scientists, myself included, have, at last count, nine different major objectives. Within each of those objectives, a good example would be understanding the seed life cycle and germination success of various different populations. Understanding the germination of those populations would be a sub-objective of one major objective looking at the germination and life cycle of the seed. So I’m actually on a couple of different objectives.
My major objective that I’m responsible for is the extension and outreach component of this project. Part of that has been building a website. That website is resistpoa.org it’s got a number of different things that we’re going to talk about today. Also, managing the Twitter account in conjunction with a few other folks, we maintain Twitter as a means of relaying information as fast as we can. Also, we’re all, every single person on this project, except for maybe two, who are social scientists, we’re all involved in the survey of resistant annual bluegrass across the United States. So far, we have surveyed over 1500 populations. A population is usually a unique individual from a different, unique site. So can you imagine 15 universities have covered over 1500 sites. That may be golf courses, home lawns, sod farms. I’m also on that project.
I’m working alongside a young man, a post-doc, who’s actually working as my extension associate, named Dr. Eddie Carlos-DeCastro. So he’s been working on much of the survey approach, so we take those populations and we break them apart and look at resistance to at least five different sites of action, but pre- and post-emergence resistance. Then also, I’m on some projects, for instance, I’m on a project with folks like John Kaminski and Jim Brosnan, Aaron Patton, looking at the effects of growing degree day accumulation between time of flowering and seed-set. So we’re looking to see how long it takes for those seed to become viable and does their rate of germination differ depending on the number of accumulated growing degree days. So far we’ve seen some results. I’m also working on a project with Bryan Unruh and Shawn Askew as well as John Kaminski and we’re looking at the effects of non-chemical control agents, so these are things like vinegar, certain acids, certain salts, applied in order to control poa annua without using typical synthetic herbicides. So those are some of the projects objectives that I’m working on as part of this ResistPoa project.

TTZ: So for our listeners and readers, Jay, what are some practical steps or cultural practices that can be implemented for the average listeners who’s dealing with this challenge?
JM: Well, a lot of the practical approaches have been known and talked about and discussed for a long time and aren’t necessarily a real part of this project, but I can tell you some of the things that work in the southeast in warm season turf. We really want turf practitioners to be doing whatever it takes during the summer growing period to try to favor the desired crop. If that’s bermudagrass on a golf course, or if it’s another warm season grass in a lawn care or park scenario, then we want to be doing whatever favors that grass to make it healthy. The best annual bluegrass or, for any matter, weed control strategy that we have available to us as turfgrass professionals is to maintain thick, lush, dense, competitive turfgrass. So one of the things that I try to discuss with stakeholders, for instance for golf course managers, is that really raising turfgrass cutting heights is a means of favoring the desired grass. So it’s not just a means of favoring that grass, but also, it is in many ways, a way to suppress annual bluegrass because it is a denser, more competitive turf stand. So even on golf course putting greens, we really want to see practitioners raising those mowing heights ever so slightly in the fall so that we’ve got some amount of cushion to prevent the open canopy that annual bluegrass is taking advantage of.
Then also in general when it comes to chemical weed control, we want practitioners to be paying attention to make sure that they’re using multiple sites of action. We use these terms “sites of action” and “modes of action” interchangeably in many instances. But those sites of action are unique enzymatic processes that are interfered with by a herbicide, so it’s very much a lock and key type of mechanism. That lock is the enzyme and the key is that herbicide. That herbicide binding site can change over time if we repetitively apply the same herbicide. In doing so, we’re selecting for, or evolving, a population to be resistant to that particular herbicide. So not to lose track of this idea here, we really want to make sure that we’re using overlapping or we’re using multiple sites of action, multiple chemistries.
So one way that you can look at this and decide which chemistries to use is to look at the herbicide history and the history of failures of whatever you’ve been doing on a certain scenario. You can then look at our ResistPoa herbicide site of action chart, that’s available on the website, ResistPoa.org, and you can go there and look at this really nifty chart to determine which site of action you’ve been using. We want to see practitioners using at least one pre-emergence herbicide in the fall and following that up with at least two different post-emergence herbicides. So for instance, we see a lot of practitioners using indaziflam, or Specticle. We want to see them using that in combination with a post-emergence follow up with at least two different post-emergence herbicides. That might be simazine plus an ALS-inhibitor like Katana or Tribute Total or Revolver or Transit, which is now Negate or whatever it may be. We also would prefer that practitioners use a pre-emergence with a post-emergence and there’s so many different scenarios that dictate different strategies. But there is no substitute for using multiple overlapping modes of action.
So we talk about switching chemistries, well, it’s not just about switching chemistries, it’s about making sure that we’re using different sites of action. And then also I think one of the things that is becoming evident to us is that we’ve got to reduce the amount of seed in the soil seed bank. So there’s a couple of ways to do that. One is by collecting clippings that have seed heads in them. So by removing those seeds, we’re reducing the population for the following year. We also as a group are starting to evaluate the effects of things like fraise mowing, which are indeed removing that top layer of soil, which should be removing a lot of that seed bank.
So those are just some ideas and we’re stumbling upon several other things that we think are really important. I would add that it’s really important to know if you have herbicide resistance, so there are those of us out there that are running labs that can screen for herbicide resistance. Chances are I’ve been to some of the golf courses or sports fields in the state of Mississippi, so practitioners can probably contact their local extension specialist, myself included and just try to have a conversation with us about whether or not they think they have resistance.

TTZ: So obviously controlling annual bluegrass is a common thread for a lot of turfgrass professionals, especially in your state. How does annual bluegrass rank in the list of weeds in your state?
JM: Well in the state it’s difficult to say, we don’t have statewide data, but we do have survey responses from a 2017 study conducted by the Weed Science Society of America. They do this every year, in fact there’s a survey ongoing right now and they ask extension specialists, university researchers, what are the most common and what are the most troublesome weeds in whatever scenario that they’re specialists in. In turf in 2017, annual bluegrass was rated #4 most common. It was not included in most troublesome, I’m sure it made the top ten list, but it is not in the most troublesome. For me, in the southeast, I think it is right there with goosegrass as far as the difficulties that we have controlling it. Specifically, those difficulties are because of herbicide resistance.

TTZ: Ok, so how have recent results of this study benefitted the industry, and how will the industry benefit in the future?
JM: We’re in the very early stages of reporting our findings. Those findings are benefitting the industry right now, predominantly through conversations like we’re having right now, which are with stakeholders, in many instances one-on-one, but also in front of live audiences. Obviously the pandemic has made that more difficult, but I think this fall and returning in the spring we’re going to have a lot more conversations about what we’ve learned. If anything, I think that this type of research has brought the issue of herbicide resistance to the forefront within a stakeholder group that perhaps had less attention than our row crop colleagues. The commodity boards, commodity agriculture in general has been very well-funded by federal funding and the specialty crops like turfgrass haven’t necessarily had the same amount of attention. So that’s one thing that I think this project is doing. We’re building a repository of information online, a lot of it is in draft format, I’m sitting here on another page on my computer screen looking at draft formats of information we’re publishing in hopefully the next six months about our findings for the herbicide resistance screening. If we have been to a site and we’ve found resistance, we’ve tried to communicate that with the stakeholder and I think that’s worth a lot in the state of Mississippi.

TTZ: So the more resources that we have available, the more consistent we can be with control, so how should we be looking for more results from this and what’s the best way to access them in terms that everybody can actually use?
JM: It’s mind-boggling how difficult it is to coordinate results across 15 different universities. Some of that is just related to logistics, and then a lot of it is related to just not having enough personnel to have a fast workflow. At our university, we’ve screened 160 populations and it’s taken us two years to do it and we’ve still got another two years worth of work to do to confirm a lot of that and figure out why they’re resistant. Knowing it’s resistant doesn’t tell you why it’s resistant.

TTZ: What’s the timeline of the study – is there an end date or do you continue…
JM: This project is funded through October of 2022. So we’ve got a little over two more years left on this project of funding. But I fully anticipate that there will be research results presented for the next five or six years that are directly related to this project.
One of the big benefits of this project is that it’s bringing together a group of scientists that haven’t always worked together. Not because they didn’t want to work together, or couldn’t get along, but those of us in the southeast have always known each other, but we’ve not necessarily known one another’s strengths and weaknesses. So there’s a lot of benefit coming out of this project because we’re forming these cross-border relationships. For instance, I knew Scott McElroy’s capabilities because I worked for him, but now I’m learning about Travis Gannon’s capabilities at North Carolina State, so we’re starting to build these relationships where we can have more interdisciplinary types of studies and so it just really drastically changes our capabilities in the southeast as turfgrass weed scientists.

TTZ: I like that because even in your last (Mississippi Turfgrass) issue, we ran the article about collaboration. So those outside the research field are actually out in the field and using what you guys are learning in collaborating together to share those things, so it’s interesting that it’s coming back in a larger scale with research like this.
JM: I’m sure collaboration is important for everybody. In our industry, in university research or research in general, it has been and will continue to be.

TTZ: Anything else?
JM: So on the ResistPoa website there’s some pretty nifty tools, and actually under the tool banner on top, you can look up the site of action poster, which can be downloaded and printed and you can request that from us by going to the “Contact Us” tab and contacting us and I’ll try to mail you one. But you can also look up slide sets, so if you’re training individuals at your facility or with your company, there are three slide sets currently and there’ll eventually be three or four more. Introducing annual bluegrass, herbicide resistance, herbicide sites of action where we review all of these different things. It’s only about 30 minutes worth of material. There are recommended sites, there’s going to be a decision support tool that helps deciders, or folks that are making decisions to make those in an optimal way. And there’s a function that is “search available literature.”
My colleagues and I, Alec Kowalewski as well as Clint Mattox, both at Oregon State have really worked hard to create this search feature that allows practitioners to search for available literature, and I don’t mean scientific literature necessarily. I mean trade journal articles, as well as extension publications about this topic. So you can sort by turf type such as cool season or warm season. You can sort by control method – maybe you’re interested in biological control or chemical or cultural control. Then you can also sort by state and look for information from your area of operation. So I think that’s a pretty nifty tool and worth checking out as well.

TTZ: Those are great resources, Jay, and I want to reiterate those. You can visit the website at ResistPoa.org and the Twitter handle is @ResistPoa for all of these resources and more as the sites are updated. Thanks for listening to TheTurfZone and stay tuned for the next episode of the ResistPoa Project.
For more information, visit resistpoa.org and follow @ResistPoa on Twitter.