04/27/2008

cortfjf / Associated Press

The Oregon Department of Agriculture will relax some pesticide restrictions through August, hoping to prevent a vole outbreak.

Experts believe the vole population is increasing in the Willamette Valley. In 2005, the hungry rodents cost grain and grass seed growers millions of dollars and triggered declarations of agricultural emergencies.

Voles resemble mice but have thicker bodies, shorter tails and smaller eyes and ears. They eat any part of plants.

So this year the state will permit farmers to apply zinc phosphide to entire fields, not only portions of acreage, said Rose Kachadoorian, a pesticide registration and endangered species specialist with the Oregon Department of Agriculture.

Spot-treating vole habitat simply creates temporary vacancies for the quickly-reproducing rodents to fill, Kachadoorian said.

"Voles go back into areas where there are vole holes."

Tests have shown that the residue in gray voles fed a 2 percent solution of zinc phosphide is not heavy enough to poison raptors - such as red-tailed hawks or falcons - if they feed on a poisoned vole.

Farmers also will be able to put the pesticide between windrows and can apply it after harvest this year. Until next Thursday, however, zinc phosphide must be placed underground in burrows, to prevent poisoning geese.

Terry Plagmann, an Albany-area grass seed farmer, said voles already are mowing down his fields in spots. "In 60 days, we could have a lot more than we'd want to see."

Zinc phosphide seems to be the only poison that works on the little wretches, Plagmann said, but it's a touchy subject.

The pesticide was linked to the recent die-off of 67 Canada geese at Staats Lake near Keizer between April 11 and 16.

Plagmann worried a careless farmer might be to blame, someone applying the pesticide illegally.

"We all need to respect the wildlife out there. ... There's always some guy who messes it up for the rest of us," he said. Kachadoorian said it has not been determined who is responsible for killing the geese, but investigators say they're trying to find out.

Vole populations crashed at the end of 2005 and also in 2006. In 2007 they bounced back, said Jennifer Gervais, a courtesy professor at Oregon State University and biologist at the Oregon Wildlife Institute.

"Populations often are variable through time and tend to go through boom and bust periods," usually in a five-year cycle, she said.

Cold weather this winter has hampered crop growth and might also have kept the rodent population from exploding, Gervais said.

Paul Kovasch, the president of the Benton County Farm Bureau, said he hadn't heard of problems, and that things didn't look as bad as 2005 on his 125 acres where he raises cattle and hay.

"I've got an infestation in one field that's raising havoc, but the others don't seem to have an unusually heavy problem," he said. Frank Bricker, who farms near North Albany, said he hasn't seen a vole problem in his 200 acres of annual ryegrass.

Sandra Powell, whose family owns Garland Nursery, said voles from a nearby field haven't damaged her business, but have created a mess of holes in her front yard.

"You walk out there, and if you had something with a heel on, I think you'd break your leg," she said. "We certainly see them. A big increase."

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Information from: Gazette-Times, http://www.gtconnect.com