Voles Head for Oregon Vineyards, Orchards

Tiny rodents called voles that have been chewing up the grass seed crop and causing tens of millions of dollars in damage are moving into vineyards and orchards.

EUGENE, Ore. — Tiny rodents called voles that have been chewing up the grass seed crop and causing tens of millions of dollars in damage are moving into vineyards and orchards.

Gray-tailed voles, also known as field mice or meadow mice, are a perennial problem for Oregon farmers, but every few years their population explodes.

To make things worse, an unseasonably wet spring caused major damage to the grass seed crop in a state that is the world's leading producer.

"It seems like a double whammy this year," said Shedd farmer George Pugh. "This is the worst I've seen."

Voles gobbled up some 60 million to 80 million pounds of grass seed this year, about 10 percent of a crop that yielded 783 million pounds last year -- or about $35 million in losses, said David Nelson, executive director of the Oregon Seed Council.


"It's going to be a huge financial hit on a lot of those guys," he said.

Annual ryegrass, a staple of Oregon's grass seed crop, was hit especially hard, suffering a 40 percent crop loss, based on preliminary estimates, said Mark Mellbye, field crops agent for the Oregon State University Extension Service in Linn, Lane and Benton counties.

"This is the worst (outbreak) on record for the south Willamette Valley and caused the worst damage to our seed crops that anyone can remember," Mellbye said.

The U.S. Department of Agriculture last month declared nine Oregon counties agriculture disaster areas because of weather and vole damage. Farmers who suffered crop losses of 30 percent or more are eligible for low-interest emergency loans if they are no longer able to get bank financing.

So far about 75 grass seed farmers have sent notice of crop losses to the USDA's Farm Service Agency, though not all will apply or be eligible for loans, said farm loan manager Patrick Joerger.

This fall, voles are adding variety to their diets by moving into vineyards and orchards up and down the Willamette Valley, said Ross Pennhallegon, horticulture agent for the OSU Extension Service in Lane County.

At least two vineyards have reported 10 percent of their vines have been girdled -- meaning pests had chewed of the bark around the base of the vine. Voles also will go after bulbs, shrubs, berry vines and tree fruits, Pennhallegon said.

"There's a real potential for disaster that people need to be aware of," he said.

The only legal pesticide against voles is zinc phosphide, but it can be spread widely only from May 1 to Sept. 1. After that, farmers must resort to labor intensive efforts to put treated oats or pellets down mouse holes.

Farmers hope for a cold, hard winter and an outbreak of tularemia, a rodent disease that would reduce the vole population to more manageable numbers.

While the vole explosion has been bad news for growers, it has been a bonanza for animals higher up the food chain. Raptors, coyotes, skunks, foxes, snakes, raccoons, herons and cats all feast on the rodents.

"They're the Gummi Bears of the animal world," said Dan Edge, head of the Department of Fisheries and Wildlife at OSU. "They're a nice little packet of protein."

Source: Associated Press