Print

Graze weeds gone

04/05/2013 @ 10:42am

Leafy spurge has been the bane of ranchers for over a century. Its impact on the farm community is stunning.

Infestations in the Dakotas, Montana, and Wyoming alone are estimated to cost agricultural producers and taxpayers $144 million a year in production losses, control expenses, and other impacts to the economy. North America-wide, it’s estimated that spurge has impacted 2.7 million acres.

Historically, Montana cattle ranchers like John Lesnick’s late father, Leo, could do little to reduce the economic impact of spurge. When the plant’s tissue is damaged, it emits a milky sap that irritates the skin and makes the plant unpalatable to cattle. Once a site reaches the 50% infestation level, cattle refuse to graze at all, rendering the land worthless.

“I remember when I was a teenager, one draw on the ranch was so thick with spurge we couldn’t ride through it without the horse tripping on the stuff,” says John.

At the time, in the early 1960s, it was estimated that over 250 acres of the Lesnick ranch had spurge infestations of 60% or higher. The average density of leafy spurge in these pastures was about 100 stems per square yard.

Today, Lesnick says it’s rare to see a flowering spurge plant on the ranch. So what caused the dramatic decline in a plant that is viewed by many as unstoppable? In a word – sheep.

Unlikely Ally

In 1964, after seeing how a fellow beef producer, Wilbur Holms, used sheep to rehabilitate ground claimed by spurge, Leo Lesnick invested in a small band to graze his infestations. In a little over a decade, the spurge population had dropped, in even the densest stands, to around 5%.

Today the senior Lesnick’s daughter, Peggy, and her husband, Ken Joki, own and operate the Lesnick family ranch. They maintain around 60 ewes in addition to beef cattle. In June, the sheep are grazed on the pastures with a history of spurge. The cattle follow on the same ground in the fall, after competing grasses have reached maturity.

While Joki has no complaints about his present spurge-control regimen, neither does he have illusions about his sheep eradicating the tenacious weed.

“If we stopped grazing, it would come back,” he says. “Its roots are still in the ground just waiting for the chance to kick up adult plants.”

Joki believes that long-term control of spurge for those who don’t graze sheep regularly lies in establishing insects like the black dot spurge flea beetle and the brown legged spurge flea beetle, two introduced bugs that feed on the plant.

Early Large-Scale Success

One of the first of the large-scale beef operations to use sheep to control spurge was the 43,000-acre N-Bar Angus ranch operated by Tom Elliot.

In the 1980s, almost 10% of the central Montana ranch’s acreage was heavily infested with spurge. All efforts to control the infestation with herbicides proved to be temporary fixes, at best.

While the N-Bar battled its spurge infestations, Pete Fay, livestock researcher at Montana State University, was conducting a unique feeding experiment involving sheep and spurge. For years, spurge had been considered toxic to sheep. Unconvinced that it actually harmed livestock, Fay’s sheep-feeding studies proved three things:

  • Sheep could consume the notorious plant without side effects.
  • They actually preferred it to grasses.
  • They were able to achieve weight gain on it.

The experiment’s unexpected results offered N-Bar’s management team new hope in its ongoing war on spurge. After consulting with Fay, the N-Bar owners asked a local sheep operator to try grazing a band of his animals on one of the ranch’s numerous spurge sites.

By 1990, approximately 3,000 sheep were being pastured on the N-Bar’s spurge-infested acreage. As of 2002, when the ranch changed hands, the N-Bar was grazing about 4,000 ewe/lamb pairs. The number of gallons of herbicide it used for leafy spurge control had dropped from 500 gallons a year in the early 1980s to 10 gallons after 2000.

Knapweed on Radar

If leafy spurge has a rival in the pasture- villain category, it is knapweed.

It is estimated that close to 1 million acres in the western U.S. are now infested with spotted or defuse knapweed. When knapweed establishes itself in a pasture, it can reduce the land’s annual production value from $5-$10 per acre to under $1 per acre.

While knapweed still poses a major problem for beef producers, in some parts of the country where sheep are available for spring grazing, the economic impact of the plant is being reversed.

One large-scale joint field study, involving several groups and agencies including Montana State University (MSU), The Montana Sheep Institute, and the Madison Valley Ranchlands Group, used sheep to graze spotted knapweed for 7 miles along the Madison River in south-central Montana. Researchers monitoring the project reported the sheep grazed 70% of the knapweed and only 30% of the grasses. Seed head production on the grazed knapweed was down between 65% and 70%.

Every summer Riley Wilson of Harrison, Montana, grazes sheep on knapweed and leafy spurge. “I take in 1,200 yearling ewes from other sheep producers, break them up, and do a lot of contract work along the Jefferson and Madison rivers,” he says. “They are very effective at controlling knapweed as long as you’re on them every year.”

Wilson shares Ken Joki’s views that plants like knapweed and spurge will never be eradicated, and that the most effective way of dealing with these invasives is a combination of grazing and biological controls like knapweed weevils.

An 11-year MSU study tracking the progress of a release of Eurasian root weevil on one particularly severe knapweed infestation recorded a 99% decline in knapweed density over that period of time.

Deadly Invasive

In the garden, the delphinium is an innocuous flowering perennial. But on the range, as larkspur, it is one deadly customer. A beef producer leasing a pasture in southern Idaho learned that lesson the hard way. Ignorant of the consequences of grazing larkspur, he released over 200 animals onto the site.

“In four days, he lost 54 head including several bulls,” says James Pfister, USDA research rangeland management specialist and an authority on the toxic plants that kill livestock.

Unfortunately, such a misadventure is not uncommon in the western states, adds Pfister. Larkspur poisoning sporadically kills 5% to 15% of the cattle on North American mountain rangelands.

John Helle runs Helle Livestock, a Dillon, Montana-based beef and sheep operation that has a reputation for using sheep to end larkspur-related stock losses. In addition to controlling the toxic plant on his own acreage, he has worked with other ranchers to mitigate the losses in their herds. One four-year grazing arrangement with Three Forks Grazing Association involved running 1,300 sheep two months ahead of 4,000 beef cows.

“The sheep loved eating the larkspur flowers, and they really got on them,” recalls Helle. “Over the four years, we never lost a cow where we grazed.”