Farms’ problems with a herbicide may be back
Seattle Tilth's urban demonstration garden at the Good Shepherd Center in Wallingford Credit: Leslie Seaton
As state agriculture officials scramble to pin down the source of a mysterious crop die-off that has cost farmers in Whatcom County hundreds of thousands of dollars so far this year, a Washington State University researcher who traced a similar crop kill a decade ago said he had worried that the problem would re-emerge.
The researcher found the earlier problem stemmed from a powerful and long-lasting herbicide that made its way into compost, and he said he had feared the state’s failure to ban spraying the herbicide on hay and wheat might lead to a new round of trouble.
The herbicide, Clopyralid, and its newer and more powerful chemical cousin, Aminopyralid, are used by hay and grain farmers, primarily on the eastern side of Washington, to keep down thistles and other broadleaf weeds. Washington State Agriculture Department (WSDA) investigators recently found both herbicides in compost on several Whatcom County farms where the latest crop kills have occurred.
Garry Hamlin, a spokesman for Dow Agrosciences, the Dow Chemical Co. subsidiary that makes Clopyralid and Aminopyralid, told Crosscut the company is aware of its herbicides are showing up in Whatcom County.
“We’ve been working with local regulators to get to the bottom of this,” Hamlin said. “There’s been a breakdown in the stewardship of our products and we need to find out how that happened and shut it down.”
While the latest Whatcom County problem has mainly been confined to organic farms, compost made from animal manure is widely used on organic and non-organic farms and gardens all over. Tracking a long-lasting herbicide through a chain of hands — from hay farmers, to truckers, dairies, and horse farms — before it finally ends up as compost on a vegetable or fruit farm could pose a daunting problem for regulatory officials.
Both Clopyralid and Aminopyralid are classified as safe for human exposure by the U.S. Environmental Protection Agency. WSDA allows the herbicides to be sprayed on wheat and other grains.
“In the testing (of Clopyralid and Aminopyralid) WSDA has conducted to date in this investigation, residue levels we are finding are far below what is allowed to come into the marketplace,” WSDA spokesman Jason Kelly said in a statement to Crosscut. “The issue here is inadvertent damage to plants, not impact on human health.”
Clayton Burrows, a Whatcom farmer who operates Alm Hill Gardens, a 70-acre organic farm in Everson, Washington, said he asked WSDA for help in June after the farm lost $250,000 in produce this spring. Alm Hill usually harvests some 3,000 pounds of tomatoes each year from each of its several greenhouses, Burrows told Crosscut. This year, the farm’s July tomato crop, he said, was just 20 pounds, although the season has just started and there will certainly be much more to pick, with some areas of the farm unaffected by the problem.
Burrows said he was surprised when WSDA investigators found Clopyralid and Aminopyralid in compost the farm was spreading on its beans, tomatoes, peas, raspberries and other crops. “We’re an organic farm and we don’t use herbicides,” he said.
Since then, Burrows said, he has heard from a half-dozen other farms and a number of home gardeners in Whatcom County who are having similar problems. Whatcom grower Kirk Hayes told the Bellingham Herald last week that he lost $40,000 in organic potatoes and salad crops in two months after he spread tainted compost on seven-and-a-half acres of his farm.
Dow voluntarily pulled Aminopyralid off the market in Britain in 2008 after farmers there reported the failures of crops exposed to compost that had been made from silage sprayed with liquid manure that contained the herbicide. Dow reintroduced Aminopyralid in the UK this year, Hamlin said.
Clopyralid has also shown up in manure in California. Kjell Kallman, general manager of Grab & Grow, a Santa Rosa, Calif., commercial composter, said his company now tests every load of manure if receives from local ranchers because of herbicide concerns. “Occasionally, we find traces of Clopyralid,” Kallman said. The company rejects any manure containing the herbicide, he said.
Craig Cogger, a WSU soil scientist who worked on a similar crop failure in 2001, said the damage then came from Clopyralid that had been sprayed on hay and lawns to kill weeds. He traced the grass clippings and hay manure and then to farms that composted it.
Clopyralid is particularly attractive as an herbicide, Cogger said, because it doesn’t decompose quickly, passes through animal digestive systems without decomposing, and can kill weeds more than a year later. He said the herbicide killed tomatoes, potatoes, beans, peas and other crops at concentrations of 2-3 parts per billion, more than 14 months after it had been sprayed.
WSDA banned Clopyralid as a lawn herbicide in 2002, but hay and grain farmers were permitted to keep spraying it on their crops. In 2007, Dow Agrosciences introduced Aminopyralid, which the Indianapolis company says is up to four times as powerful as Clopyralid. The new version was not supposed to be used on crops intended for composting, Dow officials said.
However, Cogger said he worried that the herbicides last so long they would be difficult to trace. Moreover, unlike most herbicides, Clopyralid and Aminopyralid gain potency when they are composted because they break down more slowly than other organic material in the compost, Cogger said.
“We did greenhouse and field studies and a year after it was composted Clopyralid did moderate to severe damage on crops,” Cogger said. “You could almost see the pea pods twisting up. Cherry tomatoes ended up looking more like bullets than tomatoes.”
While Dow and state agriculture officials say they warned hay farmers of potential downstream problems with Clopyralid, Cogger said he worried the herbicide would be difficult to control after it was sprayed. Since Dow introduced the more-powerful herbicide Aminopyralid, Cogger said, “We’ve been waiting for the other shoe to drop.” At least a half dozen commercial composters in Illinois, Missouri, Washington and other states have filed lawsuits against Dow Agrosciences, alleging that Clopyralid’s staying power is a product defect and Dow should have known it would ultimately make its way into compost and kill crops.
“People use lots of herbicides on their lawns but this stuff lasts for years and it’s toxic at very low levels,” said Jerry Bartlett, chief environmental and sustainability officer for Cedar Grove Composting in Maple Valley, one of the companies suing Dow.
“The only thing you can do about this stuff,” Bartlett said, “is wait it out.”
Dow declined to comment on the lawsuit.
While federal and state regulators have cleared Clopyralid for human exposure, the herbicide has had a somewhat varied history with regulators. EPA allowed it to be sold in 1987 but Dow’s own laboratory tests on rabbits raised concerns in the federal agency in 1991. An internal EPA memo in that year says the lab work showed “substantial” toxicity to rabbit fetuses and birth defects in rabbits exposed to the herbicide.
“Developmental toxicity in the form of skeletal abnormalities was evident at all dose levels tested,” the 1991 EPA memo said.
Six years later, the federal agency reversed itself on the herbicide’s toxicity, saying in a 1997 statement that the earlier rabbit studies, when combined with other data, “suggest minimal concern for developmental or reproductive toxicity.”
In another finding on Clopyralid in 2001, the EPA said, “There is a reasonable certainty that no harm will result to infants and children from aggregate exposure to Clopyralid residues.”
Hamlin, the Dow Agrosciences spokesman, told Crosscut the dose levels of Clopyralid in the original 1991 rabbit studies were much higher than the amounts of the herbicide found in soil and produce testing on the Whatcom County farms.
“EPA requires animal studies used for regulatory purposes to be conducted at high enough levels to cause significant toxicity or the studies themselves will not be accepted,” he said. Clopyralid dose levels in the original rabbit tests were either too high to be significant, or at lower levels the birth defects seen in the rabbits “were chance outcomes consistent with normal variability in the strain of animal used in the study.”
An EPA spokesman did not return a request for additional information about the rabbit tests.
This article has been changed since it was first published to correct the amount of tomato production at Alm Hill Gardens.