Dow Agrosciences, the agricultural arm of chemical company giant, Dow Chemical, plans to seek permission from federal regulators to sharply curtail the use of its powerful herbicide, aminopyralid, in Washington and a number of other states. This follows reports that the weedkiller has been making its way into compost, causing widespread crop damage on commercial farms and home gardens in Whatcom County and elsewhere in western Washington and around the U.S.
A Dow Agro spokesman told Crosscut in December that the company will this month ask the U.S. Environmental Protection Agency, which regulates the herbicide, to approve a label change, limiting its use on hay, grasses, and other forage crops. Aminopyralid, which Dow introduced under several commercial herbicide names in 2006, is harmless to humans but can make its way from hay and wheat straw into compost, killing tomatoes, raspberries, beans and other crops when it is present in amounts as low as two or three parts per billion. The herbicide remains potent years after it is initially sprayed. Agricultural officials in the United Kingdom banned its use in 2008 after widespread reports of crop damage.
Dow was allowed to put the weedkiller back on the market in the U.K. last year after agreeing to limit its use on forage crops. But in 2010's growing season, the herbicide began turning up on small farms and gardens in western Washington that use manure-based compost instead of chemical fertilizers. In Whatcom County, one farm reported losing $250,000 in vegetables and Whatcom County extension agent Colleen Burrows told Crosscut her office had received between 50 and 100 calls about the herbicide, including many from backyard gardeners.
Washington State Department of Agriculture investigators have also found aminopyralid on small farms in Kitsap County, including one operated by the author of this article. In its statement, Dow said it had received “fairly isolated accounts” of aminopyralid contamination of compost from other states as well.
In 2001, WSDA banned the use on lawns of clopyralid, an earlier version of the Dow Agro herbicide. The ban came after the herbicide began showing up in retail compost used by gardeners and posed a threat to commercial composters. However, WSDA did not extend the ban to forage crops after extensive lobbying by big hay and wheat growers, according to reports at the time.
Clopyralid, which is not as powerful as its chemical cousin aminopyralid, is mainly used now on rangeland and other rights of way.
In an internal memo circulated in December, Timothy Miller, a Washington State University weed scientist at the Northwestern Research and Extension Center in Mount Vernon, said the source of the Whatcom County compost contamination came from aminopyralid sprayed on forage crops that were fed to dairy cows in the county. Manure from the dairies was distributed to small farms and gardens that composted it and spread the compost on their crops.
Indianapolis-based Dow Agro said it will seek EPA approval in January to limit the use of aminopyralid to hay and other forage that remained on the farm where it was sprayed. “Under our proposal, it would be illegal for anyone in Washington State (no exceptions) to move hay that has been treated with aminopyralid off-farm,” Dow said.
Dow said under its proposed label change "every label on every container of every newly made aminopyralid product sold in the U.S. would state that the product could not be used on hay to be moved off-farm unless authorized under supplemental labeling."
The proposed limitation would also apply to the herbicide’s use in California, Oregon, and states in the Midwest and Northeast, Dow said. In some other states, the company said, it would issue a supplemental label that would allow hay and other forage sprayed with the herbicide to be moved off farm.
Montana currently is the only state where federal regulations allow aminopyralid to be sprayed on wheat, because of farming practices in which the straw left after harvesting is used for dryland erosion control. That use would continue, under proposed label changes for aminopyralid, Dow said. WSDA officials and some farmers told Crosscut that while aminopyralid is not sanctioned for use on wheat in Washington it is widely used by wheat farmers and others on the east side of the state to control noxious weeds.
Such use would continue to be illegal under the proposed label change, Dow said.