From the Field

Attacking Invasive Cheatgrass at Its Root

September 7, 2016

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Dixie Dringham holds up cheatgrass on the left and native grass on the right. Photo © Hannah Letinich

What can stop cheatgrass from spreading? Not much. In the 1940s, Aldo Leopold warned this invasive plant posed a grave threat to western US habitats. Since then, it has spread. And spread. Today, it infests 50 million acres of sagebrush steppe habitat.

That’s not only bad for wildlife like sage grouse, mule deer and pygmy rabbits that rely on intact sagebrush steppe for survival, it’s bad for ranchers who are battling this invasive weed and for anyone living in areas where cheatgrass-fueled fires rage. Areas that once experienced fire an average of once every 30-150 years may experience fires an average of once every 3-5 years once cheatgrass moves in.

Cheatgrass creates a vicious fire cycle. Cheatgrass roots grow when it is still cool outside, earlier in the spring than most native plants in sagebrush habitat, and they continue growing later into the fall. The cheatgrass plant produces an extensive root system that is able to take up more water and nutrients before native plants have even started to grow. Cheatgrass then dries out by late spring or early summer and provides fuel for wildfires that clear established native plants nearby, making room for more cheatgrass to seed. Each year, the process restarts. Native plants, unable to compete and unable to withstand frequent fire, soon give way to cheatgrass monocultures.

“Big sagebrush is killed by fire,” says Chuck Warner of The Nature Conservancy (TNC) in Washington. “The only way to reestablish it is by seed. Then it takes about ten years to mature and be reasonable habitat for sage grouse or pygmy rabbit. Fire intervals of 5-7 years don’t give it much of a chance.”

Traditionally, herbicide has been the primary method of removing cheatgrass and, though some herbicides can be effective against cheatgrass, they only take out the grown plants, leaving seeds in the soil that will grow and need to be sprayed the following year.

In August and September 2007, a lightning strike sparked the 48,000-acre Castle Rock wildfire near Ketchum, Idaho. Cheatgrass helped fuel the fire. Photo © Kari Greer via U.S. Fish and Wildlife Service Headquarters on Flickr
In August and September 2007, a lightning strike sparked the 48,000-acre Castle Rock wildfire near Ketchum, Idaho. Cheatgrass helped fuel the fire. Photo © Kari Greer via U.S. Fish and Wildlife Service Headquarters on Flickr

“The herbicide doesn’t really get rid of the cheatgrass, whereas the bacteria will,” says Ann Kennedy of the USDA-Agricultural Research Service.

That’s why research by Kennedy, supported by The Nature Conservancy in Washington, is aimed at attacking the root of the problem — using soil microbes that inhibit the growth of the plant’s root system, allowing native plants to compete and diminish the number of cheatgrass seeds in the soil over time without impacting native plants or crops.

The Solution Right Under Our Noses

The world of soil microbes is a hidden realm all around us that gives scientists additional options to study. Advances in this realm are changing everything from our understanding of the human body to the way that we create materials, and they are set to change conservation as well.

“There is a genetic potential in the soil that we have not even begun to explore,” Kennedy explains. “What this research shows is that we can actually go into the soil and find those organisms or isolates that have the traits we want and use that trait selectively.”

Cheatgrass on the land of Dixie Dringham. She volunteered for D7 (the biocontrol) testing on some plots of her land. Photo © Hannah Letinich
Cheatgrass on the land of Dixie Dringham. She volunteered for D7 (the biocontrol) testing on some plots of her land. Photo © Hannah Letinich

She has been researching microbes for more than 30 years and one day, when she saw a stunted wheat plant in a field, she decided to find out what was going on in the soil nearby. She and her colleagues isolated 25,000 microscopic organisms native to the soil of Washington State and tested their effects on crops and non-native plants, eventually isolating a promising bacterium known as D7 for further testing as a biocontrol.

Testing Microbes in the Field

Working in various locations in Washington and Oregon, including the Nature Conservancy’s Moses Coulee preserve, Kennedy field tested D7 to see how it would perform in varied microclimates and what were the best conditions to apply the bacteria. When it comes to application, timing is everything.

“We have this cold loving organism that we have to be careful that we don’t put it on when the predators from the microbial community would eat it up,” says Kennedy. “It’s like the food web even at the microbial level. There are some paramecium and protozoa that would just as soon eat the microbial community as look at it.”

Kennedy’s team found that mid-October is the start of the best time to apply the bacteria, however, conditions must be right — air temperatures can be no higher than 50o F and rain needs to be coming soon in the forecast.

A patch of land on Dixie Dringham's property where the D7 biocontrol has taken effect, allowing native grasses to grow back. Prior to treatment this was all cheatgrass. Photo © Hannah Letinich
A patch of land on Dixie Dringham’s property where the D7 biocontrol has taken effect, allowing native grasses to grow back. Prior to treatment this was all cheatgrass. Photo © Hannah Letinich

The bacteria need rain to drive them into the soil where it can establish; if there aren’t sufficient rains in October and November to drive the bacteria into the soil, freezing weather makes it difficult to apply the bacteria, but Kennedy has found a surprising solution to problems with frozen equipment.

“Once you get to December, the spray nozzles tend to freeze and they can crack and you’ll be out in the field and all the material goes right through that spray nozzle that is cracked so you can’t get it on. Or, if you’re going to apply by airplane, you can’t get the airplane to fly because the weather is so poor,” Kennedy explains. “I use those hand warmers that you can crack. We give those to people and you can actually warm up your nozzles on the spray rig with that.”

D7 and some other promising microbial candidates that Kennedy is working with inhibited not only cheatgrass growth, but also the growth of another invasive, medusahead — without having a negative impact on native plants, wildlife, or crops.

“A big concern was that animals would eat it,” says Warner, “but we found that this biocontrol, when sprayed on surface of ground or plants is gone after 48 hours except for the parts that get into the soil. It’s very safe for wildlife.”

Pygmy rabbits can be difficult to spot in sagebrush habitat. Photo: Matt Miller/TNC
Pygmy rabbits, depend on sagebrush habitat. Their diet is made up almost exclusively sagebrush. Photo: Matt Miller/TNC

And it’s cost effective. Application of the bacteria costs an estimated $8-10 per acre and once you’ve applied it successfully, you don’t need to apply it again. The bacteria establish for the next few years, restricting the growth of cheatgrass and allowing the desired plants to take over. Application of herbicides to kill off cheatgrass costs an estimated $15 per acre every year, indefinitely.

“By year three we’re seeing a 50% reduction in the cheatgrass in almost every plot that we put the bacteria in,” Kennedy notes, “except for where the bacteria didn’t survive.”

What’s the Catch?

D7 doesn’t directly kill cheatgrass. It inhibits the growth of cheatgrass roots at a critical time in the plant’s development, giving native plants a chance to compete. This isn’t a bad thing per se, but it does require a change in expectations as compared to a traditional herbicide.

“A lot of times, when people put out an herbicide, in a week they can see the dying plant and then with the weed suppressive bacteria it really takes several years,” Kennedy observes. “The grandchildren [of the microbes] have to grow and they’re the ones that inhibit the weed. In the first year we see a little bit of inhibition, but not like if you were to spray an herbicide, it takes many years for the bacteria to work into the soil and get ahold of the roots and inhibit them.”

A graph showing the success of the biocontrol (= weed-suppresive bacteria) by year after treatment. You can see that the results take time. Graph used with permission courtesy of Ann Kennedy
A graph showing the success of the biocontrol (= weed-suppresive bacteria) by year after treatment. You can see that the results take time. Graph used with permission courtesy of Ann Kennedy

Furthermore, Kennedy’s field tests discovered that, where cheatgrass has been established as a monoculture for a long time, the void left by the removal of cheatgrass is often filled by broadleaf weeds. This is because there is no seed bank of native plants in the soil, but the broadleaf seeds remain. Extra work may be required to reestablish the seed bank of native plants, for instance by using a traditional herbicide on the broadleaves and planting native seeds.

“If you can add a desirable plant whether wheat or natives into the system and have it grow well,” says Kennedy, “the bacteria has a much better chance of reducing the cheatgrass.”

However, it’s also important that these introduced microbes not last in the soil indefinitely. Although they are native to part of Washington, if they remained, they might cause unforeseen problems.

For instance, a bacterium known as 110 was introduced to soybeans in the 1950s to help plants fix nitrogen. It is now known that there are bacteria that could do the job better, but the 110 bacterium has been so successful in outcompeting other bacteria that it remains in the soil to fix nitrogen for soybeans all over the world to this day.

Dixie Dringham and her wolfdog Yutah. Dringham would be interested in having the biocontrol applied to all of her land. Photo © Hannah Letinich
Dixie Dringham and her wolfdog Yutah. Dringham would be interested in having the biocontrol applied to all of her land. Photo © Hannah Letinich

“I swore I would never put anything into the soil that would survive a long time,” says Kennedy, “An added bacterium would have to come in and do its thing for 4-5 years and then die off. We’ve selected these bacteria to be benign in the soil, so they don’t fight, they don’t have the antibiotics to fight against somebody who might come and want to eat them.”

Sowing the Seeds of Restoration 

The next step is to spread the use of these “bacterial herbicides.” D7 has already been approved by the EPA and another bacterium is under review. They will eventually be made commercially available for land managers and owners who are looking for a long-term solution to the spread of cheatgrass and medusahead.

With more than 50 million acres of cheatgrass to combat, it is unlikely that the invasive will be eradicated any time soon, but these biocontrols will be important tools for beating back the invasion, protecting and restoring areas of sagebrush steppe, and could be used to create buffer zones to contain wildfires.

Kennedy will publish the data from her cheatgrass control studies with TNC within the year and continues to look at other collections and isolates of bacteria that could work against other invasive plants.

“It’s not just a one-time deal,” Kennedy explains, “we’re actually showing that the concept works quite nicely. We can find other grass weed inhibitory bacteria in the same situation where we found the other ones [i.e. where there is stunted wheat plant].”

Lisa Feldkamp

Lisa loves all things citizen science and enjoys learning about everything that goes on four legs, two wings or fins - she even finds six and eight-legged critters fascinating at a safe distance. She has a PhD in Classical Literature and Languages from the University of Wisconsin - Madison and enjoys reading Greek and Roman literature or talking about mythology in her spare time. More from Lisa

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  1. I live in Redmond Oregon . Cheat grass is z big problem and appears to be growing in between the sage brush and trees. What can i do to eradicate this weed from growing ?

  2. Interesting, interesting article! Would like to have Ms Kennedy do some projects for us in Eastern Oregon!

  3. Thank you Ann Kennedy. I truly hope this works as advertised and creates no possible future problems with who knows what.

  4. Where can property owners obtain the D7 herbicide for private use? We own 34 acres that border the Crooked River National Grasslands and have large swaths of cheatgrass we need to remove. I had planned to use a traditional herbicide, but would rather try the D7.

  5. I think when people think about Science or conservation they’re not thinking of native grasses and weeds and the important part they play in grasslands and prairies, the importance of them as fire blocks and to prevent soil erosion. Good work Lisa, Kennedy, et al. thank you!

  6. I’m not sure I would support the direction of using microbial herbacides to combat invasion of cheatgrass. Today they state it as a promising solution. Yet time and again the so-called “solution” ends up posing as unforeseen s that are every bit as challenging or Bigger and the microbial method is stated to take years and then may only assist, not radicate the cheatgrass.

    Would it not be better to burn the soil and then replant or use a Preen type that abates seed germination?

    Maybe it would be better to instead burn the soil, replant and see if this method seems faster

    1. Hi Alison, Thank you for your comment! As I understand it from talking to Dr. Kennedy and others, fire benefits cheatgrass, since cheatgrass grows back faster than the native species after a fire. It is true that when not carefully planned, some “solutions” have turned out for the worse. I take comfort in knowing that Dr. Kennedy is very careful in her planning and testing to make sure that this microbial control measure will not damage the native ecosystem.

  7. I have several acres of campground in the Reno NV area that had no cheat grass 4 years ago and is now fully infested. Would you be interested in trying D7 in this environment? How can I get access to the D7 since the article suggests it’s not year commercially available?

  8. Thanks for your work in this area. I was wondering if you have explored using microbes to reduce weed seed banks. We have a real problem with oxeye daisy and Queen Ann’s lace and other weeds in the Willamette Valley where it crowds out our natives and some rare plants. We can kill the weeds but with the seed bank being so large it takes many applications of herbicides to begin to reduce the seed bank. Using microbes to reduce the weed seed bank would go a long way to reducing the use of herbicides and the length of time to reestablish our natives. I would look to use native microbes that are generalist seed killers like you used for cheat grass. I am not worried if we kill off the native seed bank in the process because we can always go in and reseed with natives.

    1. Thank you for the question Greg! Ann Kennedy has retired, but there are plans to continue her work at ARS, if the tests continue to go well, I expect to see more experiments using microbes to control a wide variety of plants. I have a story coming soon about researchers in Oregon who are working on improving sagebrush restoration success using a variety of seeding technologies – including seed coatings that can include beneficial microbes. Here is an earlier paper on their work (mostly behind a paywall, but the abstract is free) that you might be interested in:

  9. Thank you to the writer, researchers, Ann Kennedy and Dixie Dringham for tackling this cheatgrass problem and spreading the word. I am so grateful that you are aware of and working on this. As I travel around this beautiful country it amazes me to know about the ongoing efforts to keep it natural and wonderful and true, wherever possible.

  10. Hi Lisa. Great article on Cheatgrass. I’m writing a report on the invasion of Cheatgrass in the Mammoth Lakes area. Research indicates that cheatgrass burns 10 times hotter than any native species. Is there any research that indicates that a temperature that hot would have a direct affect on the D7 bacteria? All the Best! George

  11. Is there an update on the use of bacterial herbicides for getting rid of cheat grass?

    1. Hi Debra, Ann Kennedy retired. ARS is continuing the research, but hasn’t yet published any new results. Thank you for your interest!

  12. We recently bought 6 acres outside of Cody WY and have 6 acres of cheatgrass! Do you know if it would work in a dryer climate if put down as prescribed in the article?

    1. Hi Tina, I recommend contacting ARS (Agricultural Research Service) to find out if they have tested in a drier environment and to find out what products contain the biocontrol agent. Thank you!

  13. Thanks for the information! I only have 10 acres but I think I have a lot of cheatgrass that I would love to get rid of. How do I get the D7 and how do I apply it?

  14. I had a good response to planting vetch(Hand broadcast)in medusa head rye.The medusa is gone now and tall wheat grass has come in very thick with some scattered vetch.the site was south exposure and dry,whiteish clay soil. this property is in north central oregon

  15. I had a thick patch of medusa head and I broadcast vetch into the stand and is has out competed the medusa head and now tall wheat grass dominates.

  16. I have read your report, and find it interesting and quite possible to be a solution for a nasty problem. Since the research is being conducted in Washington, I am inquisitive if the problem can be attacked farther south (such as Colorado) where season temperatures and climate conditions can be very different any time of year. As you know this is a problem all over the west. Also is there a program (or one underway ) for financial help from the department of agriculture? Many of us have limited funds to tackle a campaign such as this.

  17. Thank you for such great information! I have been trying to figure out how to rid my Colorado property of cheatgrass. Your research will help me a lot.

  18. Hello from Sisters, Oregon. I have a small art gallery in beautiful downtown Sisters, in the heart of the Hood Avenue Art District. As with all, we have been closed for two months. The alleyway between my gallery and the adjoining building is suddenly filled with cheat grass, nearly two feet tall. And, it’s spreading to grow in between the concrete panels of the sidewalk in front of my gallery. We are rural, but this weed patch is in the middle of town. How can I possibly deal with this? I do not own the property, and the space in question belongs not to my landlord, but to a different landlord. And, it does not affect the adjoining building, since their frontage is around the corner. I cannot pull this by hand due to allergies. Please help! Please advise.

  19. Where can the D 7 be purchased? I have used panoramic which works, but am reluctant to continue with it.

  20. My neighbor has established cheet grass that is spreading to my property. I need help to combat this problem! I have a creek that runs through my property I’m concerned the cheet could spread throughout this valley. Can you tell me where to purchase D7
    Any help will be appreciated. Bj Colwell

  21. Could you offer some sources for native seeds please? We are just beginning to do some eradicating of cheatgrass on our small acreage in the Okanagan of BC.

  22. Could you offer some sources for native seeds please? We are just beginning to do some eradicating of cheatgrass on our small acreage in the Okanagan of BC. Also wondering best practices for disposal of noxious weeds and grasses?

    Much thanks.

  23. How can I volunteer to help eradicate cheatgrass? Is there a formal organization?
    I live in Phoenix and have a car and unlimited time, year-round.
    Please let me know.
    Randolph Williams

  24. Is D7 commercially available yet and if so, where? Cheatgrass has just begun spreading on my property in the Sierra foothills in California.

  25. We live in an area in Colorado at 8300′. Between Salida and Buena Vista. I dont think it is Sagebrush Habitat, but rather high prairie. We definitely have a cheaters problem. Everyone mows or cuts down otherwise. But, after reading this I see that is a futile task. Is the D7 available. I am in touch with CSU Extension about. Just put a call into them. Interested in this. Thankyou. Carole Blake. 720-244-3378.

  26. So interesting.

    Is this product available now, summer of 2022?