Clopyralid

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Clopyralid^[1]

IUPAC name	3,6-Dichloro-2-pyridinecarboxylic acid
Other names	3,6-Dichloropicolinic acid
Identifiers
Abbreviations	3,6-DCP
CAS number	[1702-17-6]
SMILES	O=C(O)C1=C(Cl)C=CC(Cl)=N1
Properties
Molecular formula	C₆H₃Cl₂NO₂
Molar mass	192.00
Appearance	White crystalline solid
Melting point	150-152 °C
Solubility in water	~1000 ppm
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) is a selective herbicide used for control of broadleaf weeds, especially thistles and clovers. For control of Creeping Thistle, Cirsium arvense, a noxious, perennial weed, clopyralid is the only effective herbicide available.

Clopyralid is in the pyridine family of herbicides, which also includes picloram, triclopyr, and several less common herbicides. It is particularly active on members of the Asteraceae and the Fabaceae. It does not affect members of the Poaceae (grasses).

Clopyralid is notorious for its ability to persist in dead plants and compost, and has accumulated to phytotoxic levels in finished compost in a few highly publicized cases. In Seattle, Washington, clopyralid was widely used for weed control in lawns until prohibited in 1999. There, a city-mandated curbside grass clipping collection and composting program produced compost with measurable levels of clopyralid. Subsequently, DowAgro, the manufacturer of clopyralid, voluntarily deregistered it for lawn uses.

The deregistration was viewed by some as a triumph of grass-roots activism in the face of corporate and governmental lies.^{[citation needed]} Others saw it as an exaggerated, politically correct response to isolated incidents with no basis in science.^{[citation needed]}