There’s a reason why “spurge” rhymes with “scourge.”
The last economic impact analysis of the noxious weed in Manitoba, which came out in 2010, concluded that leafy spurge costs the province $40.2 million every year due to lost grazing capacity, costs of chemical controls on roadsides and indirect costs.
In 2010, there were roughly 1.2 million acres of leafy spurge in Manitoba. But left untreated, affected areas will double in size every 10 years, says Jane Thornton, a pasture and rangeland extension specialist with Manitoba Food, Agriculture and Rural Initiatives (MAFRI) — which means spurge acres are likely already much higher.
“Leafy spurge is continuing to move into areas that it wasn’t before. It’s going north on Highway 10 and up into Dauphin. There just about isn’t a rural municipality in the province that doesn’t have it,” says Thornton.
But there are new possibilities for control.
Thornton is the lead on a new Manitoba Beef and Forage Initiatives (MBFI) project attempting to train cattle to eat leafy spurge. The project is based on a U.S. study led by livestock researcher Kathy Voth, who uses cattle as “weed managers” to control weeds like Canada thistle, spotted knapweed and leafy spurge.
“Based on Voth’s methods, we trained 50 heifers at an MBFI farm to eat leafy spurge on one of the pastures. Whether or not it will be enough to impact the spurge is the question I’ll be following for the next few years,” says Thornton.
A “cattleman’s problem”
Leafy spurge is a “cattleman’s problem,” says Abe Unger, who runs a livestock operation in Haywood, Manitoba. “It’s a noxious weed but it doesn’t survive in grain. To control it you can mow it a couple of times a summer so it doesn’t set seed, but once it’s established it always comes up from the root,” he says.
Roughly 200 acres of Unger’s 1,400 acres of pastureland are severely infested with leafy spurge.
The noxious weed can be toxic to cattle, a fact Unger learned the hard way one year when his herd grazed a leafy spurge-infested area in the spring. “They developed sores in their mouths and abscesses in their stomachs,” he said. “They could hardly eat.”
Twenty years ago, Unger invited MAFRI staff to release beetles on his operation in hopes they’d develop into colonies and control the weed naturally. But the beetles haven’t made a noticeable difference. Nor are there herbicide options available that can be used without impact in areas with high water tables, like Unger’s.
“Leafy spurge is always a concern because once it starts somewhere it keeps getting bigger. It’s a bad thing to have on your property,” he says.
Clayton Robins, executive director of Manitoba 4-H Council and a director at the Canadian Society of Animal Science, says leafy spurge is a very competitive plant with a deep rooting system that can grow “in all kinds of conditions.”
Management, says Robins, necessarily must be integrated — there is no one-size-fits-all strategy for leafy spurge. “Once it’s established it’s a long-term process to manage the health of the plants around it and get it under control,” he says.
“It’s a tough customer but one of the reasons it gets out of hand in the first place is overgrazing,” says Robins. “If a farmer can manage grazing the chances of it getting out of hand are lower. If the system has been compromised it can gain a foothold and it’s tough to get rid of.”
Cattle have historically had a much lower tolerance to leafy spurge than other livestock. Leafy spurge can comprise up to 80 per cent of a goat’s diet and up to 50 per cent of a sheep’s diet, but for cattle that figure is only 10 to 15 per cent.
Sheep and goats have been successfully used as controls. According to Thornton, goats can reduce spurge by 80 per cent over a three-year period. But for many livestock producers, the use of goats or sheep is not an economically viable option.
Thornton says her MBFI project is more of a “demonstration project” than a formal research study. By closely tracking her herd, she hopes to learn more about why some cows seem more sensitive to leafy spurge. “We may find some animals are better at handling that toxin than others. Will they teach their young to eat spurge?” she asks.
If her team can convince cattle that leafy spurge is a reasonable addition to their usual pasture diets, Thornton’s project will yield multiple benefits — control of the weed, for one, as well as increased pasture carrying capacity and diversity.
And it’s already bearing some fruit: Thornton says the herd has already begun eating some leafy spurge, albeit in small amounts, and moving into areas of pasture they would have avoided prior to training. So far, the team’s veterinarian has not noticed health problems in cattle consuming the weed.
As for producers currently struggling with leafy spurge infestation, Thornton can only caution them to stay on top of the problem.
“The problem with noxious weeds is that there really is no good way of treating them. If you have a small patch really keep on top of the fringes. Make sure it doesn’t get any bigger,” she says.