Now You See Them, Now You Don’t (But They Might Still Be There!)

Grazing, especially by goats and/or sheep, is often promoted as a control method for weeds or shrubs.  Depending upon the life strategy of the weeds being targeted, grazing can be effective, but it’s important to set realistic objectives.  As you might expect, many perennial grasses, forbs, and shrubs have evolved strategies for surviving repeated defoliation.  In those cases, grazing may appear to effectively control plants while grazers are present, but the plants bounce back right after grazers are removed.

One of my all-time favorite research projects showcases this exact phenomenon at a site in South Dakota owned by The Nature Conservancy.  Back in the early 1990’s, an estimated 75% of the Conservancy’s Altamont Prairie Preserve was covered by leafy spurge (Euphorbia esula).  In 1994, goats and sheep were installed in separate pastures and spurge was treated by using periodic high-intensity grazing sessions during both early summer and early fall.  Both the goats and sheep were very effective at eating the spurge plants, and after five years, managers conducting walk-through inspections the site felt like excellent long-term control of spurge had been achieved.  Inside small exclosures, spurge was still abundant and vigorous, but outside the exclosures, almost no plants could be seen.  As a result, the goats and sheep were removed and everyone was happy.

One of the goats used at Altamont Prairie and an exclosure showing a dramatic difference between abundant and blooming leafy spurge in ungrazed areas and no apparent spurge in grazed areas. Photos courtesy of TNC’s Minnesota, North Dakota and South Dakota Chapter.

…Until the next season when spurge plants popped right back out of the ground and the pasture looked essentially as it had before the grazing treatment had started.  In dismay, the managers looked for another option and decided upon flea beetles (Apthona spp.), which ended up being a much more successful choice, greatly reducing the footprint of leafy spurge over the next several years.

You’d be excused for thinking the use of sheep and goats was a total waste of effort, but additional data collected at Altamont Prairie adds some interesting nuance.  As it happens, mean Floristic Quality (a kind of qualified plant diversity metric) stayed relatively stable within the grazed area during the five years sheep and goats were present.  During the same time period, mean Floristic Quality decreased significantly in exclosures.  In other words, while grazing didn’t eliminate the spurge problem, it may have stabilized some of its negative impacts for a while.

This, to me, is one of the best attributes of many grazing-for-weed-control efforts.  Even if grazing can’t eradicate many weeds/shrubs from a prairie, it might be a strategy that prevents further spread (eliminating flowers and reducing vigor for belowground reproduction) and/or reduces the weed’s ability to compete with desirable plants.  In a large site where more effective long-term strategies (such as selective herbicide application or biocontrol releases) aren’t feasible across the whole area, using grazing as a suppression tactic in some areas of the site while you kill it in others can make a lot of sense.  In other words, grazing might buy you time to work on a problem that would otherwise seem overwhelming in scope.  (However, it’s also important to remember that grazers will also be eating and suppressing the vigor and reproduction of desirable species with similar growth strategies to the invader you’re targeting.  If you do succeed in reducing populations of invaders, you might also reduce populations of those desirable plants.)

Grazing can sometimes provide effective control of short-lived plants if it prevents flowering and seed production and forces plants to die without reproducing.  Just remember that more seeds are likely waiting in the soil, so it will likely take repeated grazing treatments to reach your goal.  Here in Nebraska, we often use short-term intensive grazing as a tool to knock back the competitive ability of perennial cool-season grasses such as smooth brome (Bromus inermis) or Kentucky bluegrass (Poa pratensis).  We don’t expect the grazing to kill those grass plants (and it doesn’t) but we can allow other plants a chance to flourish for a few years until the invasive grasses regain their vigor.  By repeating the treatment periodically, we can maintain a more diverse plant community.

Periodic early-season cattle intensive grazing helps us temporarily suppress cool-season invasive grasses like smooth brome and reduce its ability to outcompete many native grasses and wildflowers.

Personally, I’ve never used goats or sheep to help with a management challenge.  In contrast with cattle, goats and sheep, feed preferentially on forbs, and I’m usually trying to suppress grasses and encourage forb growth.  However, I do think goats, sheep, and cattle can all play important roles in controlling invasives as long as you don’t expect them to do more than they can.  I worry that landowners and land managers can sometimes end up paying an exorbitant price to someone that brings animals in with the promise of weed control.  It’s important to remember that if you do that, you’re providing food for that contractor’s animals, and that should be factored into whatever price one of you pays the other.  When we use cattle for prairie management, the cattle owner always pays us.  That seems not to be the case with many goat grazing operations.  I’m not saying it’s wrong to pay someone to graze their goats on your land, I’m just saying it’s important to fully process what each party is getting from the transaction.  That includes the forage provided to the animals from your land, the time and expenses incurred by the owner of the animals, and  – importantly – the actual effectiveness of the treatment.

As long as you have clear objectives and a good understanding of the plant(s) you’re targeting, grazing may be a great tool for invasive species control.  Just remember one of the biggest lessons from the South Dakota spurge experiment: just because you can’t see the invasive plant anymore doesn’t mean it’s gone!

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About Chris Helzer

Chris Helzer is the Director of Science for The Nature Conservancy in Nebraska. His main role is to evaluate and capture lessons from the Conservancy’s land management and restoration work and then share those lessons with other landowners – both private and public. In addition, Chris works to raise awareness about the importance of prairies and their conservation through his writing, photography, and presentations to various groups. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press. He lives in Aurora, Nebraska with his wife Kim and their children.
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25 Responses to Now You See Them, Now You Don’t (But They Might Still Be There!)

  1. Todd says:

    Great article!! Could I share this on the Nebraska Weed Control Association facebook page?

  2. Whoops! In your photos with goat and spurge, you have a confusing caption that refers to flowering spurge (which could be read to mean E. corollata, a native) when you meant leafy spurge (E. esula) plants in flower.

    Just thought I’d pass that along — perhaps you can amend it to clarify. As a fellow prairie ecologist, I enjoy your blog and look forward to your new posts each week!

  3. Hi Chris,

    I was involved with one goat project where hand crews went in and cut and treated all the invasive woodies after the goats denuded everything. The human crew did their job much faster and easier following the goats, but I do not know if there was any cost savings compared to the expense of just hand crews and no goats. On another project goats were brought in to a public park. People flocked in to see the cute goats. Signs were in place outside the goat paddock to explain the restoration process. I doubt the goats had any lasting effect on the landscape, but perhaps some folks learned about ecological restoration through the novelty of the goats?

    David

    • Jeannette Hall says:

      Hi David,

      I would say it depends on the plant species. I know plant removal in the southern states and west cost is definately easier following goats and the man hours are greatly reduced. I have been given much thanks from crews in BC fighting himalyan blackberry. An invasive plant that was too costly to remove by hand given how treterious the task, that is until the goats cleaned them up first for them.

      • Cailey Chase says:

        Yes! The invasive plant control we did last year with target grazing goats on spotted knapweed I found that cleaning up any left over seed heads or plants by hand pulling was way easier. Goats, hand pulling and bio-control can work synchronous with each other. Target grazing goats has so many positives! Goats draw people to the land; herbicides repel people because people are getting sick of the chemicals.

  4. Patrick says:

    I’ve seen goats being used in oak savannah restorations mostly to control woodies and brambles. It would be interesting to compare the effectiveness of goats on the different biological targets. Never heard they’ve been used to control spurge, so I learned that today!

  5. Jeannette Hall says:

    I am very aware of what this writer is trying to convey as this is what I do. I agree, realistic objectives do need to be set, they are close to unicorns but not quite as magical. 😊

    The TNC study he is referencing is from 1994 when research and use of goats was just starting out. It is now standard practice to use goats followed by beetle (root eating) on leafy spurge and the combination are still the most effective method. He also mentions he’s never used goats or sheep, so I wonder why he is writing an out of date article on it? Lol just my thoughts.

    Might I suggest to this writer he research the associated costs to target browsers before he starts slamming them or comparing them to cattle grazzing. For starters, all of my goats work for free and if you want to start having us pay for eating your weeds than you can kiss good bye any weed management and expect that the site be fenced. Infact, its more cost effective for me to stay on my own farm, feed my animals and work another job than to come manage weeds or lease your site. Sites with goats for targey browsing rarely just fence them in for a summer. They have to be managed 24/7 and the herder is making sure grazing isnt so intensive it hurts the native species, so factor in a lot of man hours. You also have to factor in transportation and increased medical from the stress of being transported more than twice a year unlike cattle. Then remember, they are often visiting sites that dont have fencing or are public parks and so require potable panel corrals, electric fencing, bedding and portable shelter and water. Then you have the cost of the dogs, herding and LGD. Both cost over $10,000 each when all is said and done, we run 4-6. We also but 8-10 hours a day on our horses so uou can imagine how many horses we run through compared to cow horses.

    I think you’d be hard pressed to find a rich target browser. We arent doing this for money and we certianly aren’t ripping anyone off. We do this becuase it’s eco-friendly and an alternative to damaging, soil depleating, toxic chemicals and helps sequester carbon.

    Prehaps this writer should also recommend that people factor in the carbon the goats are adding to the soil that would otherwise be lost by weeds and the chemicals and the nutrients that arent being washed away from pH changes resulting from herbicides. Again, its something I dont charge for, just a bonus for my clients.

    Speaking of things you arent seeing, would we all like to dicusss the hidden liabilities and environmental consequenses from excessive chemical spraying? Prehaps, this writter could help his readers calculate those costs in his next article?

    • Patrick says:

      Thanks for posting. Since I have been thinking about using goats on my property, could you give me some idea of the typical cost per acre I should expect from a goat lease operation?

      • Jeannette Hall says:

        Hey Patrick,

        Chris has no-idea and hasn’t actually used goats. I recommend you contact local target browsers in your area for quotes. It’s usually site-dependent.

        I personally try to work with each landowners budget and more often than not just cover my expensise and dont make any profit. The sites I do actually pay myself are usually municipalities. Some local governments also give grants for alternative weed magagement but they are few and far between.

        • Bob says:

          Jeanette – Can you please provide an example or two of a client site description, client goals, and outcome? Could you also provide a rough estimate of how much it cost your client to maintain the specified site with your animals?

      • Patrick says:

        This operation provided quite a bit of useful information, but not up-front pricing. http://www.goatsonthego.com/faq/

        A related story from the Iowa Farm Bureau indicated the cost to be roughly $1000/acre, but could be more or less depending on distance, vegetation, and other factors.
        https://www.iowafarmbureau.com/Article/Goats-on-the-go

  6. Jeannette Hall says:

    Chris,

    In re-reading your horrible article, I would like to point out some PAINFUL ERRORS you made.

    When done properly (not fenced in) the goats don’t eat desirable plants.

    Selective herbicide application and bio-control releases AREN’T “effective long term solutions” DUH- you have to re-apply and re-apply and re-apply herbicides some sites as long as 60 years and with bio-control releases, populations collaps once a large part of the weed population dewindles and then the weeds all pop back up! Dont you know how these things work?

    • Chris Helzer says:

      Jeannette, I’m sorry you found this blog post objectionable. I stand by my statements, and now you’ve had an opportunity to make the points you wanted to make. Nothing I wrote was intended to push people away from the idea of using goats, sheep, or cattle. The post was about the importance of understanding the life history of invasive plants and designing strategies to fit. I mentioned that I haven’t ever used goats or sheep, but I also said the reason for that is only that I haven’t had a specific instance in which those grazers made sense. I also didn’t “slam” goat grazers when I talked about cost. All I said is that they should be sure they understand all the associated costs as they evaluate the price of the treatment. I wish you much success in your work.

      • Jeannette Hall says:

        Chris,

        Thank you for your prompt response. I feel your cautionary statement “Just remember…your feeding the contractors animals”(paraphrased) followed by “When we use cattle for weed management the cattle owner pays us”. (Paraphrased) Along with your clear message that you dont feel grazing is that effective. Mostly marked by your comment that it “could by you some time while your spray half of the site.” (Paraphrased), is a slam to the target browsing industry.

        In the way in which you wrote that cattle owners pay you following your comments on weed control mehods, you are suggessting whether intentional or not, that target browsers, particularly goat owners pay for feed.

        Insinuating or making that suggestion or comparison is absolutly absurd.

  7. Chris Muldoon says:

    Jeannette, there’s lots of good information in your post, but may I suggest you could have been more diplomatic. You might not be aware that Chris has been a tremendous source of valuable information for a lot of us for a long time. The fact that he works for TNC and is passionate about what he does, that he’s been doing it for a long time, that he keeps a good discussion going with a great many other people that — like you and he — are experienced and well-informed, AND as is obvious from his posts (if you’ve been following them) that he’s not only a scientist, but is a curious life-long learner type who willingly shares his knowledge, indicates that he’s no light-weight in his field. For you to comment in your list of criticisms “Don’t you know how these things work?” is a real insult.
    May I suggest that an apology is in order?

    • Cailey Chase says:

      Hello Chris Muldoon, my name is Cailey Chase and I am part of the growing target grazing industry in Canada. Jeannette doesn’t need to apologize for anything. Her words were clear. The environment needs immediate change from unhealthy human habits; chemicals being one of those. Get to know Jeannette for yourself and experience the work with the goats for yourself and you will see she’s right. There’s no more time for wordiness and no tolerance for lack of research, the envonment is at a tipping point and she’s trying to convey that to people.

  8. James McGee says:

    To be fair to the goats, I have often seen plants I thought were completely dead after an application of herbicide rise again the next growing season. Maybe the lesson of the study is what people doing invasive control already know well. It typically takes more than one season to control tough weeds.

    However, I don’t think goats or sheep could help in Chicago Area preserves because one of our biggest and most persistent problems is an over population of deer.
    Goats are used at O’Hare International Airport to control woody species on slopes that are too steep to be mowed. However, the purpose is not conservation and they are able to pay quite well for this service.

    Professor Nyberg of UIC advocated injuring weeds to accelerate the evolution of diseases. I don’t know if the evolution part works because that would require more time than I have to experiment. However, after repeatedly cutting resprouts I can report that new growth was heavily colonized by various aphids and white flies after the first or second cutting. I think these parasites are attracted to the new growth I had made available just like Chris’ cattle returning to their grazing lawns. This might similarly be the reason the flea beetles would be more effective after grazing.

    Chris often discusses the importance of pollinators having flowers blooming throughout the growing season. I must wonder why he does not discuss the importance of native cool season species (sedges) to grazers and for competing against cool season invasive grasses.

  9. Jeannette Hall says:

    Chris,

    It just puzzles me that a man would write about something he has no experience with and use data 23 years out of date. Why would a man plant the seed of doubt without using actual current, relevant referance material? Why insinuat a fear or oroblem that isnt actually there. I can help but notice your over use of the words “sometimes”, “maybe” and cautionary “just remembers”. This bares a stricking resemblance to the works of paid lobbiest fear tactics.

    Chris, have you been paid by a chemical company, a marketing firm, publicit, or law firm employed by a chemical company?

    In the modern era of fake news Chris, I would hoped you do more research.

    • Chris Helzer says:

      Ok Jeannette, you’ve had your say, and you’re clearly passionate about the issue of goat grazing. I re-read the entire post and am still comfortable with everything I said, but I did clarify (via a small edit) one statement where I talked about the costs of goat grazing to be completely sure no one would misinterpret what I meant – that the landowner is contributing forage for goats, the goat owner has expenses and time invested, and that it’s important to weigh both of those factors, as well as the likely result of the treatment, as the price paid (in either direction) is determined. I don’t see how that is unfair to anyone. No, I don’t work for a chemical company, and I don’t have an agenda other than to provide thought-provoking information to people trying to figure out how to deal with important land management challenges. You seem to dislike my use of the words “sometimes”, “maybe”, and “just remember” and consider those as negative or insinuating terms. In contrast, I see those as words used by someone who is not trying to prescribe any particular strategy or technique to his readers. That is consistent with the long history of this particular blog, and is the reason many people read it. Finally – You’ll notice that I’ve allowed all of your comments so far, so as to provide you with a platform for your rebuttals. That won’t continue if you persist with your current tone. I welcome discussion, especially when it broadens the scope and potential understanding of a topic, but I also get to moderate that discussion, and will do what I need to keep it civil and constructive. Again, I wish you success in your work.

      • Jeannette Hall says:

        Thank you Chris,

        I invite you and yours up here to Canada to come see some of the incredible work our goats have done.

        I will happily pay for a few night in a hotel room if you’d like to see first hand how we manage and how effective the goats are.

        Prehaps it will help spread aome light on the value of our work.

        Much love.

        • Cailey Chase says:

          Chris Helzer: I double dog dare you to take Jeannette up on her invitation! It would be an experience of a lifetime, and you would meet some great people and see that the invasive plant industry is about to enter an era where true Integrated Pest Management is making a comeback! (I’ll even chip in for the room)!

  10. Keith Long says:

    You may be aware that researchers from Kansas State University are using sheep to help control sericea lespedeza at the Bressner unit near Yates Center, KS. The sheep are not put out on the pastures until after the cattle have been shipped, usually in early August, and then they are removed at the end of the growing season. This targets the S.L. just before and during the flowering stage. Results have been good at keeping the S.L. from producing seed, but as you said in your blog, there is a tremendous seed bank, so a few years of grazing is probably not enough. There have been some other benefits too, like eating the ironweed that cattle won’t, so overall it is an encouraging project.

    Thanks for this blog.

  11. Gary Gerth says:

    Chris, thank you for this blog topic.I am personally familiar with the Altamont Prairie and also have some experience with grazing animal, sheep, goats, and even cattle, in Utah and Montana, in organized weed control efforts. Grazing herbivory has taken off as an alternative to other forms of weed control and has attracted much attention and rightfully so. Most real problematic weed species have many competitive advantages and it takes a combination of practices over long target frames to effect lasting control. Many of us, landowners, scientists others have been impressed by early results from various control efforts but management persistence over the long haul is what it takes to get in control of the situation. One major point I got from Chris is that we can’t regard sheep/goats as a quick onetime fix. No matter what combination of diversified management practices are used, this is a most important point. There is no silver bullet and landowners need to realize they will need a combination of practices over the long haul. Sheep and goats often will certainly fit into the scheme of integrated management if you are lucky enough to get them under defined strategies. In the case of very persistent leafy spurge stands they best be used in combination with other practices, else we will get the results of Altamont Prairie.

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