Vermont composting facility reports four samples of off-the-shelf Purina horse feed it had tested for clopyralid indicate the presence of the herbicide at levels between 142 ppb and 465 ppb (.142-.465 ppm).
Williston, Vermont… The Chittenden Solid Waste District (CSWD) suspended sale of compost at its Green Mountain Compost facility in late June following crop damage linked to herbicide contamination. CSWD now reports that four samples of off-the-shelf Purina horse feed it had tested for clopyralid indicate the presence of the herbicide at levels between 142 ppb and 465 ppb (.142-.465 ppm). Susceptible plants such as peas, beans and tomatoes have shown adverse affects at exposure levels as low as .03 ppm, between 4.73 and 15.5 times lower than the levels detected in the horse feed. Initial suspicions of tainted feedstock had pointed to manure brought in from area horse farms.
“When we got the results back from the first set of individual horse farms, we sent letters to both the hauler and to the horse farms saying that we no longer could accept their horse manure,” says Tom Moreau, CSWD general manager. “It just so happens that two of the first five horse farm owners knew me and gave me a call. It was apparent that Purina feeds was a common element between the two farms, so we instructed staff to go to the same feed store and purchase some.”
CSWD staff, wearing Latex gloves, took samples of the feeds and placed them into Zip-lock bags. The samples were sent to Anatek Labs in Moscow, Idaho, one of the few facilities in the U.S. capable of testing for clopyralid and picloram (another persistent broadleaf herbicide detected in the Green Mountain Compost) – at levels below 10 ppb, according to Moreau. “Obviously, someone should follow up with more sampling and testing — it would be good to get a second lab to confirm.”
Both clopyralid and picloram were discovered in residential lawn clippings dropped off at area composting centers. “EPA promotes municipal composting … but both grass samples we tested showed detectable amounts of clopyralid,” says Moreau. “These samples came to us in trucks within the past few weeks and after the stories had been in the press.” Label restrictions do not even allow for residential use of picloram, which requires a professional pesticide applicator’s license for other specific uses. “We are still taking samples, as is the State of Vermont, to determine where the picloram is coming from,” says Moreau, who notes that one thing is for certain — the existing labeling system restricting use of hay or digested materials to disposal, or to use only on the land of original application, is not working. “EPA has to find a better way to allow the agrochemicals to be used, in perhaps a more limited way, but still protect the downstream users,” he says.
Update, August 10, 2012
Recently, a Vermont composting facility reported that off-the-shelf Purina horse feed had tested for the herbicide clopyralid at levels between 142 ppb and 465 ppb (.142-.465 ppm). We have not independently verified the accuracy of these tests.
Land O’Lakes Purina Feed [LOLPF] has not confirmed the presence of any harmful pesticide [sic] residues in our horse feed, and our customers have not reported any related problems or complaints concerning their horses.
The indicated levels of residues reported fall well within the tolerance levels set by the Environmental Protection Agency for residues on various types of grains/commodities that are used in the animal feed formulations.
Even though these residues at these levels are not harmful to the health of horses, the existence of various chemicals in manure may cause the manure to interact with compost in a way that could be harmful to plants. Consumers having difficulty related to their composting issues should contact their local horticultural expert.
Holly Flemister, LOLPF