Clopyralid is the common name of a herbicide that kills broad-leaved weeds such as dandelions, clover, and thistle. Clopyralid contamination of yard debris compost emerged as a problem in Washington State in 2000 and 2001. Clopyralid has since been banned as a lawn herbicide, removing the risk of contamination of yard debris compost. Because clopyralid is still registered for use on grass hay and some grain crops, the risk of contamination of some animal manures with clopyralid remains.
Questions and Answers for Gardeners and Farmers in Western Washington, 2005. (♣ PDF-Online)
Clopyralid and compost: formulation and mowing effects on herbicide content of grass clippings. 2004. (♣ Request pdf e-copy)
Bioassay Test for Herbicide Residues in Compost Protocol for Gardeners and Researchers in Washington State (draft), 2003. (♣ PDF-Online)
Clopyralid in turfgrass clippings: formulation and mowing effects on dissipation, 2003. (♣ PDF-Online)
Clopyralid Garden Demonstration Plots, 2002. (♣ PDF-Online)
Large Pot Greenhouse Trial with Clopyralid-Sensitive Garden Plants, 2002. (♣ PDF-Online)
♣ WSDA Rule Restricting Use of Clopyralid in Washington (see WAC16-228-1235, WAC16-228-12351, WAC16-228-12352, 16-228-1237, 16-228-12371 (link to WSDA main website).