Herbicide ruining compost; chemical detected in vegetable gardens
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Traces of Clopyralid, manufactured by Dow AgroSciences and deadly to potatoes, peppers, tomatoes and beans, have been found in compost made from recycled grass, straw and manure in Washington, California, Pennsylvania and New Zealand.
The herbicide, most commonly used to kill backyard dandelions and field thistles, is not toxic to humans or other mammals. But it causes garden vegetables to wither and die.
Sample tests have found Clopyralid residues at rates from 50 to 1,500 parts per billion, five to 300 times more than the amount needed to kill sensitive plants. The chemical first was detected in soil around dying plants in Spokane in 1999 and in Pullman a year later.
Cliff Weed, compliance program manager at the state Agriculture Department, said the chemical has also been measured at Cedar Grove Composting in Maple Valley, the chief composting facility for Seattle and King County.
Dozens of products contain Clopyralid. Dow products that use it include Lontrel, Transline, Stinger, Reclaim and Confront, Hornet, Scorpion and Redeem. Pesticides made by other companies but using Clopyralid bought from Dow include Millennium, Momentum, Chaser Ultra, Battleship, Strike Three and TruPower.
Widely used on lawns and wheat crops, the chemical has found its way into compost through grass clippings, stable sweepings and manure. Compost companies and recycling officials say that if the contamination persists, it could bankrupt the industry.
"If it continues to grow and penetrate the market, it could undermine people's confidence in compost and hurt recycling," said Timothy Croll, community-services director for Seattle Public Utilities, which recycles 48 tons of grass and branches each year through Cedar Grove.
To deal with the problem, the state expects to issue new rules on Clopyralid's use on grass, cereal grains and grass hay in time for spring planting. An advisory committee of compost professionals, users and Seattle officials first met on the issue last month.
While Weed doesn't expect a ban on the chemical for grains or hay — just restrictions to keep contaminated plants out of compost heaps — a prohibition on Clopyralid for lawns and golf courses is possible.
"It could range from a prohibition to something in between," Weed said. "We want to fast-track this thing before the problem becomes greater."
Across the country, compost companies accept about 28 million tons of yard trimmings each year.
Labels ignored, Dow says
Dow officials say the company did not study the chemical's behavior in compost when it originally sought permission to market it in 1987. In 1994, the company began putting warnings on the labels of Clopyralid products saying consumers should not compost materials treated with the herbicide, a company spokesman said.
The problems arose because Dow's label warnings were ignored, Dow spokesman Garry Hamlin said.
But since one company usually applies herbicides to lawns and another cuts and recycles the grass, Croll said changing labels doesn't go far enough.
"Their argument totally misses the point," he said. "Dow has been slow to act."
The garden-waste-recycling industry arose after a 1988 federal clampdown on landfill standards forced states to substantially reduce the amount of waste sent to landfills.
The launch of Clopyralid preceded the composting movement. Formulations involving it first were registered in 1987 to control broadleaf weeds such as dandelions and thistles. It then was approved for use on barley, oats, wheat, sugar beets, Christmas trees, corn, mint and asparagus, as well as for rangeland, pasture, highway aprons and lawns.
Clopyralid kills and stunts target plants by imitating hormones called auxins and causing abnormal growth.
Washington was one of the first markets. As the fourth-largest wheat-producing state in the United States, its farmers have been using the chemical since 1987. Gretchen Borck, director of issues for the Washington Association of Wheat Growers, defends Clopyralid as an essential tool for control of Canadian thistle in a crop worth $458 million a year.
Potent, not toxic to people, pets
"If we didn't have the Clopyralid, we'd have to use less effective herbicides, and that would increase the poundage of herbicide introduced into the environment," she said.
The chemical also is popular with commercial lawn-care companies. Dan Warehime, vice president of Senske Lawn and Tree Care in Kennewick, said his company started using Confront about 11 years ago on home lawns and in schools, parks and commercial properties.
"We like the product because it's very safe to use around homes and residences," he said. "It has a very low toxicity to my employees and to children and pets."
Its staying power — the chemical can remain potent up to 18 months after spraying — spares him repeat applications, Warehime said. But while this sturdiness is a boon for wheat farmers and lawn care companies, it has also made Clopyralid a persistent pollutant.
In 1999, Spokane officials learned from a nursery using city compost that vegetables cultivated in their compost had been dying. In June 2000, the problem was encountered again, this time by tenants of a community garden in Pullman who used compost produced from recycled straw livestock bedding and manure on the campus of Washington State University.
"The potato plants tried to grow but turned in on themselves. They were just mangled and mutilated," gardener Susan Lutzenhiser said.
Investigators, including the university's soil scientist David Bezdicek, discovered residues of both Clopyralid and a sister chemical, Picloram.
Spokane officials pressed Dow to remove Clopyralid lawn products from their market, which the company says it did. But the chemical kept entering the system, Dow suspects through reformulations produced by other companies.
At WSU, compost manager Dan Caldwell said that despite efforts to keep it out, the Clopyralid levels continue to increase in his compost unit.
"We have contamination through everything," he said. "We're really in a quandary about how we're ever going to get clean again."
Seattle Times staff reporter John Zebrowski contributed to this report.