Agency limits use of herbicide

Tainted compost threatens gardens, flower beds

JOHN DODGE, THE OLYMPIAN

Originally published Saturday, March 2, 2002

OLYMPIA -- The state Department of Agriculture on Friday banned the use of the herbicide clopyralid on lawns and turf in a bid to avert a statewide crisis in yard-waste composting programs.

The persistent weedkiller is contaminating compost purchased by gardeners anxious to boost the growing power of their vegetables and flowers.

Vegetables and flowers at risk from tainted compost include peas, beans, potatoes, tomatoes, peppers, daisies, petunias and sunflowers, recent studies show.

Tests of compost at the Thurston County Waste and Recovery Center in January found clopyralid at concentrations ranging from 34 parts per billion to 49 ppb, county Solid Waste Manager Scott Schimelfenig said.

The chemical can be damaging at a few parts per billion. It is persistent in compost for as long as two years.

It isn't highly toxic to humans, pets, livestock or wildlife, scientists say.

County officials are recommending the compost produced at the Hawks Prairie project not be used on gardens, Schimelfenig said.

It can be used safely for trees, perennial shrubs and houseplants, he said.

Weed killer

Stunted plant growth from contaminated compost was first identified in Spokane County in 1999.

The impact of the problem grew after research at Washington State University and recent tests of yard-waste composting centers throughout Western Washington.

Clopyralid commonly has been used by lawn care professionals to kill broadleaf weeds such as dandelions and thistle, said Neal Wolbert, owner of Wolbert's Inc., an Olympia area landscape healthcare company.

"It will take a while to find a replacement," he said.

"This ban is meant to keep clippings from grass that has been treated with clopyralid from being sent to municipal and commercial facilities," said Cliff Weed, the pesticide compliance program manager for the state Department of Agriculture.

Clopyralid has been detected in straw used for animal bedding and in the manure of animals, typically horses, that have eaten treated grass hay, Weed said.

"Manure from any animal that grazes in a treated pasture is a potential source," said Keith Underwood, project manager for the Thurston County Master Gardeners program.

Alfalfa manure safe

The presence of clopyralid in compost from South Sound livestock shouldn't be too big an issue, said Brian Thompson, a resource technician with the Thurston Conservation District.

Most farms use wood shavings -- not straw -- for bedding, and dairy farms often use alfalfa to feed their herds, Thompson said.

Alfalfa is not treated with clopyralid. It's a member of the legume family, which includes peas and beans, that is damaged by the chemical.

Nevertheless, uncertainty over the condition of livestock manure means the popular manure giveaway program the conservation district and master gardeners offer the public each spring and summer at Dirtworks Demonstration Garden at Olympia's Yauger Park is unlikely this year, Underwood said.

The ban on clopyralid doesn't extend to agricultural uses -- at least not yet, Weed said.

"This is just the first step," he said of the lawn-care ban announced Friday. "We're not saying agriculture isn't a contributor. But we want to measure the effectiveness of these rules first."

Only seven of the 30 allowed uses appear to pose a threat to the state's growing composting industry, he said.

The state Department of Ecology estimates that about 450,000 tons of organic material is composted statewide each year, or about 20 percent of all recycled materials.

The Thurston County compost center takes in about 7 tons of yard waste annually, producing 3.5 tons of compost, Schimelfenig said.

"We've come a long way in the last eight to 10 years," he said. "We don't want to damage that industry."

John Dodge covers the environment and energy for The Olympian. He can be reached at 360-754-5444 or by e-mail at jdodge@olympia.gannett.com.

On the Web:

- Clopyralid methyl

What you can do

Here are options for gardeners concerned about clopyralid in compost:

- Ask your compost supplier if it can guarantee its product is free of clopyralid.

- If you've already purchased and applied compost, try some test planting indoors in pots before the outdoor growing season. Peas are a good test crop because they sprout quickly and are susceptible to clopyralid damage.

- Grow only nonsusceptible vegetables.

- Grow the susceptible legume crops in areas of the garden with the least amount of compost.

For more information, check out this Web site: www.css.wsu.edu/compost/compost.htm.

The Olympian Copyright 2002

back to Home index