(Beyond Pesticides, August 6, 2010) Organic farmers and gardeners across a Washington state county suspect that herbicide-contaminated manure and compost obtained from non-organic farms and dairies are responsible for severe crop loss reported throughout the region, raising questions about the adequacy of the U.S. Environmental Protection Agency’s (EPA) pesticide registration process. Tests of soil and tissue samples of local dairy manure that is used in soil and compost mixtures revealed small amounts of aminopyralid, a potent and persistent herbicide approved for use by EPA in 2005.
Aminopyralid is generally used for weed control in pastures and fields that grow silage crops for dairy cows. When cows eat the grass that has been treated with the chemical, it passes through them unchanged and remains in their manure in concentrations that can still be high enough to damage broadleaf crops if the manure is used to fertilize them. Aminopyralid is produced by Dow AgroSciences, a subsidiary of Dow Chemical Co., and often manufactured under the product name Milestone.
Former coordinator of the Washington State University master gardeners’ program Jill Cotton has noticed the damage in her garden and said reports continue to filter in from other gardens around the county. One Whatcom County grower, Kirk Hayes, who sells his crops to the Bellingham Community Food Co-op and four other co-ops in the region estimates that he lost about $40,000 worth of sales in the past two months because of the problems.
“It’s killed off most of our potato crop, our salad crops,” said Mr. Hayes. “We’ve contaminated about seven and a half acres, it looks like.”
Dow says that “inadvertent residues are at low enough levels that you can eat the produce.” Aminopyralid, however, is not licensed to be used on food crops and carries a label warning farmers using it not to sell manure that might contain residue to gardeners. According to EPA, tolerances (residue limits for pesticides used in the U.S. or by countries exporting to the U.S.) have been established only for the following crop food/feed and animal commodities: grass, forage and hay; wheat for bran, forage, grain, hay and straw; aspirated grain fractions; cattle fat, meat, byproducts and kidney; goat fat, meat, byproducts and kidney; horse fat, meat, byproducts and kidney; milk; sheep fat, meat, byproducts, and kidney.
Aminopyralid’s potential to taint manure and harm other crops is well-known and has been documented in other regions, including a case in the United Kingdom a few years ago. The label precautions for Milestone and other similar products containing the active ingredient aminopyralid state that treated plant residues or manure from animals that have grazed on treated forage (within the previous 3 days) should not be used in compost or mulch to be used on susceptible broadleaf plants. Additionally, those who have already used contaminated manure are advised not to replant on the affected soil for at least a year.
It appears that the contaminated manure and compost may have been sold as â€śnaturalâ€ť fertilizer. However, consumers should not be fooled by claims such as â€śsafeâ€ť or â€śnatural.” Though fertilizer cannot contain the U.S. Department of Agriculture (USDA) organic seal, it can be listed on the Organic Materials Review Instituteâ€™s (OMRI) list of approved substances, and will often contain â€śOMRI approvedâ€ť on its label. If it is not listed, then it does not meet the organic standards. For more information on labeling, visit our National Organic Standards page.
Walter Haugen, one regional growers, stressed that this incident shows how important it is to be a self-contained operation. He relies on compost produced from his own farm’s crop wastes, rather than bringing in manure that might have suspect ingredients. You can often create all the fertilizer you need yourself through simple composting of kitchen and yard scraps. This way, as Mr. Haugen points out, you know exactly what is in your compost, and you don’t have to purchase many “external inputs.”
The problem of contaminated compost keeps coming up because pesticide use patterns result in the contamination of treated land. EPA’s Office of Pesticide Programs allows the widespread fertilzer use of treated plant material (such as composted grass clippings). In the fall of 2009, the California Department of Food and Agriculture (CDFA) conducted tests and determined that three of California’s largest compost producers had product which tested positive for the insecticide bifenthrin. Bifenthrin is a synthetic pyrethroid insecticide used commercially and residentially for the control of pests (i.e. ants, spiders, etc.).
Source: Bellingham Herald