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Weed species, Board of Ag to consider adding new species to designated list

by Wyoming Livestock Roundup

On April 10, the Wyoming Board of Agriculture will consider adding four new weed species to the State of Wyoming Designated Weed and Pest List, elevating those species and solidifying the importance of cross-county work on the species. 

“At meetings last year, several weed and pest control districts submitted resolutions to add several species. The Wyoming Weed and Pest Council (WWPC) approved the resolutions for ventenata, yellow star-thistle, medusahead and common mullein to the State Designated Weed and Pest List at their annual meeting in November,” says Slade Franklin, Wyoming Weed and Pest coordinator. “They have also voted to remove skeletonleaf bursage from the list.”

During the April 10 meeting, the Wyoming Board of Agriculture will hold a public hearing and then  vote as to whether the four weed species should be added to the state designated list and one should be removed. 

“If anyone has issues with the additions or the removal of skeleton leaf bursage, we encourage them to come and participate in this meeting,” Franklin says.

Top concerns

Since the discovery of medusahead and ventenata in Wyoming in September 2016, weed and pest districts across the state have bolstered all resources available to combat the species’ spread. 

The species have been recognized as an incredible concern for the state’s rangelands, due to their invasive nature.

Franklin says, “Ventenata has already gotten a foothold in a lot of the western states in the last 60 years, so that is pretty concerning.”

Yellow star-thistle

Yellow star-thistle is an additional plant of concern, partially because of its aggressive nature in other western states. 

“Yellow star-thistle is a big issue in California and other western states,” according to Franklin. “It’s in the knapweed family and poisonous to horses, and we’ve seen it show up in a couple of places in Wyoming.”

In the last 10 years, patches of yellow star thistle were seen in Teton and Carbon counties, and there have been more recent findings in Uinta and Washakie counties. 

“Now that we have found yellow star-thistle, we’re seeing it more and more often,” Franklin says.

He adds, “Yellow star-thistle is a good candidate for districts to focus on from the early detection, rapid response (EDRR) perspective.” 

Yellow star-thistle has bright yellow flowers with distinctive spines at the base. It forms pea green rosettes that quickly become silver as the plant matures. The stems of the plant are winged and can be up to two feet long. 


Another proposed addition to the state’s designated weed list is common mullein, which has been present in Wyoming for some time.

“Common mullein often shows up along roads and right of ways in nearly every county in Wyoming,” Franklin explains. “The county districts want to recognize common mullein as a statewide issue so they can  combine efforts and take more of a statewide management approach to addressing the problem.” 

Common mullein is tall, standing two to six feet high, without branches. The leaves of the plant are opposite, and it produces yellowish flowers in June and July. It has low palatability and provides no feed value to livestock.

Skeletonleaf bursage

Skeletonleaf bursage is a native plant in the state of Wyoming, and Franklin says it has been listed on the Wyoming State Designated Weed and Pest List since the 1950s, and has been recognized as a weed in the state as far back as 1896. 

“Skeletonleaf bursage is more of a nuisance plant problem like dandelion,” he says. “It’s mostly identified as a problem for gardens and lawns.”  

Additionally, the plant is very difficult to control, with very few options beyond mechanical control.

“With the limited number of complaints the districts receive for this species and the limited control options available for it, WWPC believes it makes sense to remove this weed from the state list,” Franklin comments. “This would not restrict the individual districts from adding it to their county declared lists as needed.” 

Designated species

The Wyoming State Designated Weed and Pest List highlights those weed and pest species that present a problem across the state of Wyoming and are a priority for Weed and Pest Districts to address.

As of March 2018, 26 weeds and six pests are listed by the state, and most are species Wyoming landowners will recognize.

“We have weeds from Canada thistle and Russian knapweed to Russian olive,” Franklin says. “There are a number of commonly recognized weeds on the list.”

Pests included on the designated list include grasshoppers, prairie dogs, Mormon crickets, Mountain pine beetle and more. 

“A complete list of designated species are available at”

State list

The list provides a useful tool for Wyoming’s weed and pest districts across the state. 

“All 23 weed and pest districts across the state use the state designated list as their priority for control and management,” Franklin explains. “State law says county weed and pest districts shall implement an effective management program for species on the list.”

Districts prioritize management of those species on the designated list and also prioritize landowner projects that involve management of species of the designated list. 

“The list also works as an education tool for us,” he adds. “Those species on our list are elevated and allow us to work with federal agencies and the public effectively.” 

Saige Albert is managing editor of the Wyoming Livestock Roundup. Send comments on this article to

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