Washington State Bans Compost Herbicide

Kathleen M. White

To prevent contaminating compost further, the Washington State Department of Agriculture (WSDA), Olympia, initiated an emergency ruling in mid-March banning the application of clopyralid, a herbicide that has been shown to damage certain vegetation. The herbicide already has contaminated several lawns and turf in the state that use the compost.

The emergency ruling, which will become permanent after 120 days, makes products containing clopyralid “state restricted use” pesticides that can be bought and sold only by licensed applicators and dealers.

“A new growing season is upon us, and it was imperative that we get something in the works before this spring,” says Cliff Weed, compliance program manager for WSDA's pesticide management division.

Clopyralid, which is manufactured by Indianapolis-based Dow AgroSciences, is a long-lasting herbicide contained in several herbicidal products that typically are used to kill weeds. Although not harmful to human health, soils enriched with clopyralid-tainted compost in Washington have been shown to damage certain flowers and vegetables. Clopyralid also does not break down easily in compost.

“Clopyralid actually is a good herbicide because it's not toxic to humans, fish life and so on,” says Dean Fowler, senior engineer for the Spokane's Regional Solid Waste System. “The problem is that it has a long shelf life — if you put it on your grass and it's soaked up in the leaves of a tree, they'll spread it,” he adds.

The city of Spokane currently has approximately 40,000 cubic yards of clopyralid-tainted compost, some of which is being stored at a closed regional landfill awaiting a non-agricultural use, Fowler says.

Spokane officials first became aware of clopyralid in their municipal compost in spring 2000, says Jessie Lang, recycling coordinator for the city's Regional Solid Waste System. Simultaneously, Pullman-based Washington State University's composting program also tested positive.

Responding to these findings, last summer, Dow voluntarily agreed to not sell clopyralid products to residents in eastern Washington, which, statistically, uses the highest levels of the herbicide than any other state area. “A voluntary agreement was put in place, but some dealers and applicators didn't get the word, so clopyralid still was used,” Lang says.

Meantime, WSDA tested nine commercial composting facilities throughout the state for the herbicide and found that all of the facilities had contaminated compost or contaminated feedstock, Weed says. The scope of the problem prompted the state to form an advisory committee involving the agricultural community, government regulators and composters, who consequently helped shape the current clopyralid ban.

However, the economic fallout from clopyralid contamination already has been realized. “It's had a major impact on composting here. In earlier years, everything our [composting facility] could produce was pre-sold at a good price,” Lang says. “Now, our compost remains unsold and at a lower price.”

Economically, Spokane's composting operation won't turn around quickly, Lang adds. “We don't expect things to change for a little while as there are a lot of unknowns,” she says. “The only thing we know for certain is that clopyralid isn't gone yet.”