BUFFALO - For years, rancher Ryan Fieldgrove could only watch as leafy spurge spread across his land unchecked, forcing thousands of grazing acres out of production and costing his family a fortune.

For years, he tried anything to rid his family's 10,000-acre ranch of the tenacious, aggressive weed, but nothing worked.

Until the goats.

Fieldgrove had researched using goats to eat leafy spurge, a fast-growing weed with a deep root system that had virtually covered the North Tipperary Ranch in northeastern Johnson County.

The Red Angus cattle he raised shunned the weed, and even sheep wouldn't eat it. Fieldgrove's family had spent $1 million over several years battling leafy spurge without success, and he was desperate to try the goats. But his parents resisted the idea.

"My parents retired nine years ago, so nine years ago, we got goats," he said Monday during the Governor's Natural Resource Tour, an annual two-day field trip organized by the Wyoming Department of Agriculture.

"We started with just 10 goats, and we used electric fencing to fence off about 10 acres. I guessed it would take about 30 days for them to make it through all of that. In three days, it was gone," Fieldgrove said.

In 2001, Fieldgrove bought 500 South African Boer goats, and worked with the Johnson County Weed and Pest District, Natural Resources Conservation Service and Lake DeSmet Conservation District to bring the goats to his ranch and develop a program to turn them into a secret weapon against leafy spurge.

He found a retired Basque herder from Buffalo to watch over the goats, trying to keep them in the thickest sections of leafy spurge. But Fieldgrove happily found that the animals preferred the weed to almost anything else on the ranch.

There were a few bumps along the way, but in the last seven years, the goats helped rid all 10,000 acres of almost all traces of leafy spurge, he said.

But they didn't do it alone, said Phil Gonzales, district conservationist for the NRCS in Buffalo.

Gonzales said a combination of chemical spraying and using a beneficial insect helped leverage the goats' efforts as part of an integrated pest management plan.

The flea beetle, a tiny, jumping species in the leaf beetle family that has been used as a beneficial biological control agent against leafy spurge, eats the plant and lays its eggs in it. The larvae hatch in the roots and feed there, helping kill the plant.

Fieldgrove said he had tried flea beetles long ago, but they did not spread quickly from one plant to the next, taking years to have any noticeable effect.

Gonzales said the goats proved to be the perfect "dispersal agent" for the flea beetles, picking them up and dropping them off on dozens of plants every day.

"We used chemicals to stop the plant, and used the goats to eat the plants and move the flea beetles," Gonzales said.

Fieldgrove said herding the goats is a challenge, as the animals cover up to three miles a day and are much more active than sheep.

"We controlled the weeds, but only after we controlled the goats," he said, adding that, "after seven years, we ran out of weeds."

Fieldgrove said his next step will be to study whether the goats, if left on their own, will cover a large enough area to keep the leafy spurge at bay. He equipped the lead nanny with a tracking collar to study where the goats go if they are not herded.

"It looks like they have dispersed pretty good throughout the area," he said.

Fieldgrove said he also wants to research why the goats are so fond of leafy spurge, rejecting almost every other plant, including grass, in favor of the weed.

He theorizes that there may be a chemical compound in leafy spurge that is addictive, or at least irresistibly attractive, to the goats, as catnip is to cats.

No matter what, even the neighbors are happy with the goats, Fieldgrove said.

"They like the neighbors' spurge better than what's left on my land now," he said.