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Weed & Pest

In mid-June Mark Daluge, Wyoming Weed and Pest Landowner Program Coordinator, found an infestation of Austrian fieldcress in Teton County – the first detection of the species in the county and third in the state. Austrian fieldcress has also been found in Sublette and Park counties.

“While we can’t be completely confident how Austrian fieldcress became introduced, we speculate that it was likely brought either in material used to construct a berm or potentially contaminated equipment,” said Wyoming Weed and Pest in a news release. “It appears to be spreading both by seed and aggressive lateral root creep.”

Spreading invasive

Since locating the primary infestation, Wyoming Weed and Pest has reported one other satellite infestation along a county road that sees relatively high traffic.

In Sublette County, Austrian fieldcress was located in 2008 in a hay field near Pinedale by a Weed and Pest employee.

“Similar to Sublette County, Park County found Austrian fieldcress in a field that had a center pivot system,” Wyoming Weed and Pest Coordinator Slade Franklin says. “Sublette County’s case was found in an irrigation ditch.”

Finding fieldcress

Austrian fieldcress is likely to be found in areas where there is water at least six months out of the year. Sublette County reported that the plant grew “out of the water” from the irrigation ditch it was found in.

“Austrian fieldcress is a very competitive and persistent perennial that typically grows in wet soil,” says Wyoming Weed and Pest.

The invasive primarily spreads through its creeping root system, though it can also be introduced by seed and detached root fragments.

“If fieldcress is present, it will likely be more than just one or two plants,” Franklin comments. “It will more likely be a big patch of yellow flowers before people start to notice it.”

When looking at the plant, flowers form in loose clusters at the tip of branches. Each flower has four small, yellow petals.

Alternate leaves are distributed down the stem, and the plant can grow up to three feet tall.

“There are a lot of yellow flowered plants in Wyoming, so if people see something they aren’t used to, take a sample to the Weed and Pest so we can identify it.”

Austrian fieldcress will outcompete native grasses and other vegetation.


“With the university, Sublette County worked to determine treatments,” Franklin comments. “It is a very hard plant to treat, and there are experiments with various herbicides that are ongoing.”

Franklin also notes that Sublette County has seen success in treating Austrian fieldcress through application of Plateau, an herbicide with the active ingredient imazapic.

“It is also a perennial, so we can’t just mow it off to deal with the problem,” he adds.

“We need to be vigilant in looking for Austrian fieldcress,” Franklin comments. “We have a lot to figure out on treating this plant, but we are working hard to find good treatments.”

Preventing spread

Because invasive species threaten natives across the range, Wyoming Weed and Pest recommends taking several steps to help prevent their spread.

First, drain, clean and dry all gear and boats to avoid transferring plant seeds or residue between locations. Also, burn local or certified firewood and use weed-free hay.

Staying on trails when outdoors can also reduce the chance that plant materials may be transferred.

After visiting an area, make sure to remove mud and seeds from boots, gear and equipment, including vehicles.

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Sheridan – With the goal of influencing open conversations, the Wyoming Weed and Pest Council (WWPC) facilitated three roundtable discussions during their 73rd annual meeting, held in Sheridan from Nov. 14-16. One of their big questions hinged around the objectives and purpose of weed and pest districts and the WWPC.

“It’s important that everyone shares their opinion, so we can hear from everybody,” said WWPC Executive Director Slade Franklin.

“Defining the overall objectives and purpose of WWPC is a big question,” said Aaron Foster of Fremont County Weed and Pest during a roundtable panel on the question.

Statutory obligations

Foster referenced Wyoming Statute, saying “We are meant to pursue an effective program to control weeds and pests.”

While the definitions of “effective” and “control” are left out of statute, Foster believes both are covered using an integrated pest management approach.

He also marked education, public outreach, an early detection rapid response approach, a focused commitment on containment to limit expansion of weeds and a focus on asset improvement.

Education was identified as a particularly important part of WWPC’s role, according to several attendees in the meeting.

However, there are challenges associated with the ability to educate landowners, including lack of attendance at meetings and training events.

“I question whether our purpose is clearly defined in WWPC,” Foster said. “There are a lot of good things going on, but I believe, with the transition we have seen in WWPC in the last couple years, it wouldn’t hurt to re-align ourselves.”

To ensure WWPC doesn’t cheat their objectives, Foster said a renewed focus should be taken to ensure positive work is able to continue collaboratively in the state.

Landscape scale

“The question is always, what are we doing?” Park County Weed and Pest’s Josh Shorb said. “Right now, we have a list of 26 plants and six designated pests. Is that what we should be working on? Is that what we strictly should be working on? Are we only working on them because they’re on a list?”

He noted that operating with an approach of “kill this, save that” is akin to putting on blinders by ignoring other potential problems.

“Should we view ourselves as large, landscape level invasive species managers?” he asked, noting that WWPC may be better poised to take a larger role.

“We need to work from a landscape perspective,” added Bob Finley of FCWP. “We’re preventing the spread of weeds, controlling what’s there, mitigating and more. Everything we do is a part of prevention and control.”

“We have to look at ourselves as overall land managers or else we end up being just reactive,” he said. “We’re about much more than just spraying weeds.”

Project focus

While invasive species is a focus of many weed and pest districts, Foster emphasized, “We have to also expend some of our resources on range improvement projects.”

“Should we be focusing on that? Or should invasive species be our primary focus?” he asked. “This is something we need to decide.”

Audience members suggested developing strategies or priorities on a state-wide level to allow districts to work toward a common goal or focus, since the action in one district affects neighboring counties and states.

Rod Litzel of Buffalo noted WWPC should also be cognizant to avoid narrowing a focus too much.

“We are invasive species managers, but we are also resource managers,” Litzel said. “We have to pay attention and not lose sight of one species that may take over.”

Managers in the state are also concerned about budgets.

“We have to focus our priorities to be able to leverage our resources,” said Uinta County Weed and Pest’s Chris Aimone.

Working for stakeholders

“The other thing that is important for districts to think about when we consider our purpose is to make sure we are actually considering all the stakeholders in our districts,” Foster said.

Hale Redding of Weston County Weed and Pest noted that WWPC is one of the few government entities that has a largely positive rapport with landowners.

“We’re here to help people with their problems, and we strive to do that every day,” he said. “The majority of our work is on private ground. Our local taxpayers fund us, so I try to focus on helping them take care of their problems and educating them on how to minimize the impacts of weeds and pests.”

While many think of agriculture as the primary stakeholder for WWPC, Foster noted that recreationists, small acreage landowners and business people are important.

“Many people use lands that we do work on, and they deserve a seat at the table, too,” he said.

Working together

“The purpose of WWPC is for collaboration and a voice for all districts on weed and pest activities,” Foster said, noting several objectives in WWPC’s by-laws include information exchange, information sharing, cooperation and promotion of uniformity and coordination of activities, among others. “We could work on promoting uniformity and coordination of activities. There might be room for improvement there.”

“As a council, I think our strategic plan needs to involve working on a story for the state – not just for us, but for the people we are working for,” Franklin said.

He also noted a narrative should also be developed to work across state boundaries, and WWPC should be working to tell a unified story.

“The more we try to manage invasive species, the more we realize what we don’t know,” commented Brian Connelly of Natrona County Weed and Pest. “It’s a constantly changing landscape, and it’s going to be different next year and the year after. Our focus changes from year to year, so the important thing and beauty of our weed and pest law is we do have the freedom to make on-the-ground decisions for our micro-conditions.”

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

The recent story on Wyoming Public Radio by Willow Belden, “As agencies control invasive species to protect diversity, some worry about side effects,” poses an interesting question on whether impacts caused by invasive species have a net negative impact on invaded systems. 

The question – “Are invasive species really as bad as they are often perceived?” – seems to be gaining some traction these days while, at the same time, more organizations are participating in efforts to reduce invasive species distribution and abundance. The question digs deeper than the direct management of an undesirable species and begs a response different than one solely answered from biology or ecology. 

This discussion could quickly go many different directions – from esoteric rabbit trails about why diversity and native species are important to pragmatic challenges like water management, forage availability or toxicity to livestock.  Here, I will explore the impacts of invasive plant species instead of all types of invasive species to keep the discussion more focused.

To accurately determine how invasive plants affect natural systems requires documenting the impacts, both negative and positive, and determining the net result of exotic species invasion and dominance on a particular system. Impacts can occur at multiple levels: ecosystem, community, population — even genetic characteristics of a system may be affected by invasion.  The difficulty often arises when attempting to quantify the cumulative impacts of a single specie, or suite of species, once exponential growth and dominance has occurred across highly variable ecosystems over large spatial scales. 

An international research group led by Montserrat Vilà, an ecologist from Spain, analyzed almost 200 journal articles representing over 1,000 field studies investigating ecological impacts of invasive plant species (Vila, et al. 2011). One of the group’s primary questions was whether clear patterns exist regarding impacts of invasive plants across the globe. They found that some impacts of invasive plants vary widely across locations, depending on species and types of impact they investigated. 

However, 11 of 24 impact “types” showed quite consistent results across the studies. Invasive plants consistently reduced fitness, or reproductive capacity, of resident plants and decreased species abundance and diversity. Overall plant production was consistently higher when invasive plants were present. 

Animal abundance was generally reduced in areas with invasive plants when compared to non-invaded locations. 

Invasive plants also enhanced soil microbial activity, increased available nitrogen and decreased soil pH. Nitrogen-fixing invasive plants, such as Russian olive, had a more dramatic impact on soil nitrogen than non-nitrogen-fixing species. The authors conclude that, although impact magnitude and direction varied, invasive plants exert strong effects on recipient communities and ecosystems. 

Some of these impacts are relatively easily observed – especially if vegetation monitoring data are routinely collected. Decreased species diversity or decreased amount of forage accompanied by an increase in a specific invasive plant could be quantified with a vegetation monitoring program, but other impacts, such as altered nitrogen dynamics or microbial populations in the soil, are not as easily observed. 

The potential broad-reaching implications of these less-noticeable changes are probably not well understood by managers and scientists alike, but that does not mean they are less significant. 

Recent research in Idaho and Wyoming indicates that Russian olive presence alters nutrient, particularly nitrogen, cycling in streams where it has invaded, potentially leading to cascading impacts on multiple species (Mineau et al. 2011). Other examples of how invasive species alter nutrient cycling abound in the literature. 

Such effects alter how the system works and may, in some cases, reduce the site’s suitability for desirable plant species and facilitate further invasion of other invasive plants. This “invasional meltdown” as described by Simberloff and Von Holle (1999) leads to an increased effect of various invasive plants on a location – the combined effects of the multiple invaders is more severe than if a sole invasive species occurred. 

Drastic changes to site characteristics, such as reduced species diversity or altered soil chemistry, can persist even after the invader is successfully removed from a site. Such “legacy” effects may require efforts beyond removal of the unwanted plants including restoration practices designed to mitigate the persistent changes induced by the invaders (Corbin and D’Antonio 2012).

More research is needed to understand the best combinations of restoration practices on sites dominated by invasive plants over the long-term. Setting clear goals for the long-term use of a site may assist in developing a restoration plan that may not closely approximate the pristine pre-invasion condition, but that may still meet the goals of the individual landowner. Reestablishment of desirable plant species that improve habitat conditions over the invasive-dominated state, but not quite what was there before invasion may be an acceptable alternative in some cases. 

The question of whether invasive plants are generally a “bad” thing requires attaching values to the impacts that they cause. An ecological impact in itself is neither good nor bad until an individual or society determines how they will be affected by such a change in the current environment. 

Those of us directly involved in weed science and management have likely internalized the negative impacts of invasive species from years spent in efforts to reduce their populations and, thereby, reduce associated impacts. I think the invasive plant management community emphasizes the need for control so strongly that the overall approach can easily be misinterpreted. 

Complete eradication of all invasive plants from Wyoming is widely recognized as an unattainable goal. Because of this, the need to prioritize efforts on species and locations that offer high potential benefits is needed and encouraged, although opportunistic projects also occur in some cases. 

Do invasive plants impact natural systems, altering their characteristics to the detriment of native plants diversity, wildlife habitat and agricultural production? Multiple examples in the literature support consistent, often long-term, impacts. Are they all bad? For now, I will leave a more thorough discussion of how individuals and society value ecosystem goods and services and their potential loss due to plant invasion for someone with a better understanding of the human psyche than me.

More information can be found in the following sources, which were referenced in this article.

Corbin. J.D. and C.M. D’Antonio. 2012. Gone but not forgotten? Invasive plants’ legacies on community and ecosystem properties. Invasive Plant Science and Management 5:117-524.

Mineau, M.M., C.V. Baxter and A.M. Marcarelli. 2011. A non-native riparian tree (Eleagnus angustifolia) changes nutrient dynamics in streams. Ecosystems 14: 353-365.

Simberloff, D. and B. Von Holle. 1999. Positive interactions of nonindigenous species: Invasional meltdown? Biological Invasions 1:21-32.

Vila. M. et al. 2011. Ecological impacts of invasive alien plants: a meta-analysis of their effects on species, communities and ecosystems. Ecology Letters 14: 702-708.

Brian A. Mealor is an assistant professor and Weed Extension Specialist at the University of Wyoming and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it.. More information about ongoing weed science research at the University of Wyoming can be found at

Many ranchers and rangeland managers are trying to find ways to halt prolific spread of cheatgrass, medusahead, leafy spurge, yellow star thistle and other invasive weeds and reduce or eliminate them in areas that are already dominated by them.

Jeremey Varley, Idaho Department of Agriculture Manager for noxious weeds, says the first step in any control program is knowing which weed is taking over pastures, fields or rangelands. 

“We also need to determine if the weed problem is beyond the threshold where other control measures might be better,” Varley says. “For instance, if it’s a small patch it might be easiest to just pull those plants. Or, maybe we can spray for three years in a row and it might be gone.”

  He adds, “We need to look at all options, and sometimes a combination of strategies might be best.” 


For instance, Varley recommends producers try mowing or grazing and biocontrol with insects. 

Intensive grazing with animals that eat a particular weed might provide an option for producers to control invasive species. Sheep and goats are often used for that purpose. Producers just need to make sure the weed is not poisonous to the animals that would be eating it. 

Some times of year, producers can graze invasive plants – especially when they are still young and palatable – and set them back. 

“With leafy spurge, many people have utilized goat grazing,” Varley comments. “Biocontrol agents have more effectiveness after grazing. The plants have new growth following grazing, and the new growth is more susceptible to the biocontrol agents.” 


“A producer might choose biologic control if weeds are widespread and beyond the point where they can economically cover the area with conventional control method,” Varley comments. “In that situation, biologic control may be the best tool. Just make sure to use the correct biologic control agent for the target weed.”

“For instance, the root weevil for spotted knapweed doesn’t do well in riparian zones or shaded, cool areas,” Varley notes. “These weevils prefer hot, dry conditions. If we release them next to a stream or where there are a lot of trees, where they don’t want to be, they won’t establish very well.”

For producers who need help in determining the best strategy for using biologic control, talk to a professional. Most states have a biocontrol specialist, federal contact or county weed superintendents.


Biocontrol research is ongoing, to find the best way to control certain invasive weeds. These agents are species-specific and affected by climate and habitat conditions. 

“An organization called the Center for Agriculture and Bioscience International (CABI) from Switzerland is doing a lot of research on biocontrol agents and always looking for species that will work on certain weeds,” Varley says. “They go to the native land of a plant we consider a noxious weed here to find the native range of that plant and its natural predators.”

CABI then determines the life cycle of the predator agent and makes sure it only feeds on that particular plant and can’t complete its life cycle on any other plant, says Varley. Then we know we can safely release these agents in a noxious weed patch in this country, and they won’t damage any other plants.

Various people fund this research. 


“For instance, a group concerned with rush skeleton weed is looking for a new biocontrol,” Varley says, noting that after CABI finds a potential biocontrol agent, they send it to the U.S. for more testing. “After all the studies are done, we can be sure that a certain biocontrol agent can be approved for release.” 

Each agent must go through this process to be approved for use in the U.S. It takes several years and a lot of money to bring biocontrol agents to this country, Varley comments. In some cases, these agents work well, but in other situations, they may not be as effective as hoped. 

“We keep studying these agents and following up to make sure they are working how we want them to. In many cases they do, by reducing seed count or plant vigor in the target weed,” says Varley.


However, Varley says producers may not see immediate results from releasing a population of insects because it takes between three and five years before the insect populations become establish. 

“It’s not like herbicide where we spray the weeds and go out the next day and find them dead. With some biocontrol agents, it may be five to 10 years to get good control of those weeds,” he says.

Monitoring the site with photos can show the reduction of a target species, over time. 

“These agents are living organisms, and it does take time for them to multiply and have a beneficial effect. They have to get their numbers up, but then they will do a good job – if they are in the right place, targeting the right species,” he explains.

Every region is unique in climate, and there are weeds in some parts of the U.S. that we don’t see in other areas. 

“Ranchers in southern parts of the country have to deal with weeds we will never see in Idaho,” Varley explains. “There are biocontrol agents available, however, for most noxious or invasive weeds and some that we haven’t discovered yet.” 

“Anyone facing a noxious weed problem, losing production or seeing a drop in land value because of invasive weeds should look at all tools available,” Varley says. “Biocontrol agents may provide the best benefits because they provide a long-term solution.”

  Heather Smith Thomas is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to This email address is being protected from spambots. You need JavaScript enabled to view it..

I have received many requests for information this year about the grass that was turning purple early in the summer, but that was not cheatgrass. Bulbous bluegrass (Poa bulbosa L.), like cheatgrass, is an introduced grass that matures early in the year. Unlike cheatgrass, it is a short-lived perennial species that produces a bulb from which roots extend each year. 

The species is very interesting from a biological standpoint because it is reportedly the only grass to produce a true bulb. It is also known for its unique inflorescence that produces bulblets rather than seeds – essentially giving rise to small live plants where we would normally see seeds. The bulblets, which are small copies of the parent plant, make the plant easy to identify once they are produced.

Bulbous bluegrass was reportedly introduced to the United States in two separate events. It was accidently introduced as a contaminant in alfalfa and clover seed, although this introduction scenario is often speculated for many invasive species. 

It was also introduced intentionally by the USDA Office of Foreign Plant Introduction in the early 1900s to be evaluated as a forage species. The evaluations determined that bulbous bluegrass had no promise as a forage source, so the program was abandoned at that time. Further work to develop suitable cultivars for turf and forage purposes occurred in the 1950s, but the efforts were not continued. 

Bulbous bluegrass matures very early in the season, and palatability decreases rapidly resulting in a narrow window of grazing for the species. This short window and low biomass production make the species undesirable as a grazing resource. Bulbous bluegrass also competes with more desirable grasses for early spring moisture, so high bulbous bluegrass densities may reduce the productivity of other grasses.

The first Wyoming specimen of bulbous bluegrass in the Rocky Mountain Herbarium was collected near Gillette in 1938, so it has been present in the state for quite some time. The species has been collected in most Wyoming counties since that time.

It is nota new species in the state, but it is not an invasive plant that has received much focus in the past. It is generally adapted to areas of Wyoming that receive greater than 12 inches of precipitation annually, but it does occur in drier areas as well. Because of these moisture requirements, it is commonly seen at relatively higher elevations within the state.

Bulbous bluegrass grows well in areas that have been subject to soil disturbance like roadsides, field edges, energy development sites, etc., but it will also spread into pastures and rangelands. It may also be problematic in hay fields, but the establishment of a healthy stand of alfalfa should reduce bulbous bluegrass infestations in those sites. 

Intensive grazing in the early spring for multiple years has been reported to reduce bulbous bluegrass populations – this control method should be planned carefully to minimize potential damage to desirable grasses. 

Unfortunately, there are not many herbicides specifically labeled for bulbous bluegrass control in range and pasture settings. Removing a perennial grass weed from a site where perennial grasses are also the desirable plants, such as a rangeland or pasture, can be difficult using herbicides because of potential non-target damage. For more information on chemical control of bulbous bluegrass, visit

2013 has been an excellent year for bulbous bluegrass in much of Wyoming, so it was highly visible and noticeable as it began to mature. There has not been much information collected about this species in the state and more research is needed to develop clear recommendations for management of this potentially increasing invasive plant. 

Brian A. Mealor is an assistant professor and Weed Extension Specialist at the University of Wyoming and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it.. More information about ongoing weed science research at the University of Wyoming can be found at