ELBOW, Sask. — Deep within the Willner-Elbow community pasture lies the scourge of cattle ranchers — an abundance of leafy spurge.
Driving through the gullies and dunes of the sandy pasture near Elbow, Sask., volunteers recently made a special trip out to a particular patch. Where there is leafy spurge, there may also be some enemies of this invasive species — leafy spurge flea beetles.
Armed with nets, about 10 volunteers collected adult beetles so they could be moved to another patch.
While the day was overcast and chilly, Krista Ellingson, manager for Nature Conservancy Canada’s Working Landscapes, was happy to see the beetles active and ready for collection. This patch is such a prosperous place for beetles that it is acting as a beetle nursery for Ellingson and Working Landscapes program director, Matthew Braun.
Given the weather, Ellingson said they were taking what they could to ensure the best possible chance for beetles at the release site, but not enough to damage the population at the collection site.
“It’s pretty safe to assume that since it’s all connected there’s spurge beetles all through it, and we’re just focusing our collection on one small part of that… there’s enough spurge there to keep them around for a while and we can keep collecting there without risking the population.”
In its original Eurasian habitats, leafy spurge is just one plant among many, she said, but with no natural predators in North America, it has dominated rough terrains in Canadian pasture land and urban green space.
Putting the plant and beetle together won’t eliminate the plant, but it will keep it under control, said Ellingson.
“Our efforts make a difference. It doesn’t eliminate spurge but it makes it so that it’s part of the plant community, a small component instead of the plant on the landscape.”
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Located in the 23,419-acre Elbow block of the 36,400-acre Willner-Elbow pasture, it took years for the beetles to establish themselves, said Ellingson.
“The past couple years we started to notice a self-sustaining population. So that was really exciting because whatever has changed, whether it’s the genetics of the beetles that we introduced to the site, we finally hit the lottery and got the right ones here.”
Collection day has become a critical event since the beetles were moved to a leafy spurge patch that is encroaching on a critical habitat for smooth goosefoot and western spiderwort, two plant species that are on the threatened species list.
The federal government has deemed the Willner-Elbow pasture and its sand dunes as a critical habitat for both species, said Ellingson, but leafy spurge is threatening their survival.
“Grazing is a part of maintaining the openness in those habitats; getting some hoof action on the sand dunes, grazing in the area helps keep the dunes from becoming completely stabilized. So grazing has been maintaining the habitat but leafy spurge invasion threatens it.”
The noxious weed is easy to spot with its bright clusters of yellow-green flowers, but it is difficult to get rid of. Going deep into the pasture where only cattle, goats and four-wheel drive vehicles can tread, there isn’t access for any type of heavy machinery. As a result, widespread herbicide application is not an option. The plant makes grazing dangerous because it takes over vast amounts of pasture by choking out and overshadowing other more edible plants, while the milky sap is an irritant to cattle.
A pasture’s productivity falls to zero with only 80 percent leafy spurge cover, reported the Saskatchewan government’s Problem Weeds — A Cattlemen’s Guide.
“External contact can result in dermatitis and even blistering in animals and people,” reported the guide. “It has been reported that horses that walk through freshly mowed areas of leafy spurge will develop blisters and lose the hair above their hooves.”
The plant spreads efficiently with seeds and an extensive root system. Adult beetles will feast on the green canopy, but it is the activity of the larvae that is the most effective control, with root damage leaving the plant susceptible to bacteria and disease.
Beetle movement is rare, said Ellingson. Even if two patches are a short distance apart, the beetles won’t make that leap on their own. The collection process is labour intensive, which is why Nature Conservancy made it a public event. Dozens of hours were dedicated to collecting the beetles with the help of volunteers, including a couple who came all the way from Brandon and Ellingson’s 11-year-old daughter, Lena.
Beyond this much-needed assistance, the event brought people from all walks of life out to see valuable management practices and partnerships at the pasture, especially Nature Conservancy Canada’s budding relationship with the pasture’s management company, said Ellingson.
“Our volunteers will come out today and see all the work that they’re (Willner-Elbow Grazing) doing to fight an invasive species and conserve biodiversity. They can see the partnership between conservation groups and agriculture groups and what we can do together. That’s an important thing to share with the wider public.”
Given the spread and isolated habitats of leafy spurge, it is difficult to get exact numbers of acres in Western Canada, said Kathy Larson, research associate at the College of Agriculture and Bioresources at the University of Saskatchewan.
Larson presented on the economic impacts of leafy spurge in the Willner-Elbow pasture during the university’s Soils and Crops Conference in March, and much of the data had to be collected at ground level.
With funding from the Agricultural Development Fund, Larson paid for aerial imaging of the Elbow site in 2019. On a Canada Day weekend, the plant would be at peak flowering, she said.
However, analysis of the digital imagery sorely underestimated the presence of leafy spurge, but when combined with the colour-coded maps collected by shepherds tending the sheep and goats used for targeted grazing, they’ve been able to calculate how much spurge is present at the site, she said.
The current count puts leafy spurge cover at about 63 percent: 14,746 acres of the 23,419-acre Elbow block. Leafy spurge is present at varying levels of severity in every paddock, said Larson.
In her presentation, Larson calculated lost income based on a 418-cow herd at $45,562, or $109 per cow per grazing season. Control methods cost around $5.68 per acre with targeted goat grazing and $100 per acre with beetles at about three cents per insect. Both seem insignificant, said Larson, but that is still lost income caused by the invasive species.
Use of the beetles as a bio-control has been approved by the Canadian Food Inspection Agency. Their niche diet is leafy spurge so no other plants are damaged from the beetle. Nature Conservancy Canada’s leafy spurge monitoring program is funded through the Weston Family Prairie Grasslands Initiative’s Stewardship Investment Program.
