Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) is a selective

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

used for control of broadleaf weeds, especially

thistle Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles can also occur all over the planton the stem and on the flat parts of the leaves. ...

s and

clover Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'leaf'), consisting of about 300 species of flowering plants in the legume or pea family Fabaceae originating in Europe. The genus ...

s. Clopyralid is in the

picolinic acid Picolinic acid is an organic compound with the formula C5H4N(CO2H). It is a derivative of pyridine with a carboxylic acid (COOH) substituent at the 2-position. It is an isomer of nicotinic acid and isonicotinic acid, which have the carboxyl s ...

family of herbicides, which also includes

aminopyralid Aminopyralid is a selective herbicide used for control of broadleaf weeds, especially thistles and clovers. It is in the picolinic acid family of herbicides, which also includes clopyralid, picloram, triclopyr, and several less common herbicides ...

picloram Picloram is a systemic herbicide used for general woody plant control. It also controls a wide range of broad-leaved weeds, but most grasses are resistant.

triclopyr Triclopyr (3,5,6-trichloro-2-pyridinyloxyacetic acid) is an organic compound in the pyridine group that is used as a systemic foliar herbicide and fungicide. Uses Triclopyr is used to control broadleaf weeds while leaving grasses and conifers ...

, and several less common herbicides.Staff, Virginia Tech Cooperative Extension. Revised May 14, 201
Pyridine Herbicide Carryover: Causes and Precautions
Accessed May 27, 2013 For control of creeping thistle, ''

Cirsium arvense ''Cirsium arvense'' is a perennial species of flowering plant in the family Asteraceae, native throughout Europe and western Asia, northern Africa and widely introduced elsewhere.Joint Nature Conservation Committee''Cirsium arvense'' The standa ...

'', a noxious, perennial weed, clopyralid is one of the few effective herbicides available. It is particularly damaging to peas, tomatoes, and sunflowers, and can render potatoes, lettuce, and spinach inedible. It does not affect grasses (family

Poaceae Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...

). Clopyralid is known for its ability to persist in dead plants and

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...

, and has accumulated to phytotoxic levels in finished compost in a few highly publicized cases. This first came to light in Washington, when during 2000 and 2001, residues of clopyralid were detected in commercial compost, and compost made at a municipal site damaged tomatoes and other garden plants planted in it. Word quickly spread to other local and state governments, and in 2002,

DowAgro Dow AgroSciences Limited liability company, LLC was a wholly owned subsidiary of the Dow Chemical Company specializing in not only agricultural chemicals such as pesticides, but also seeds and biotechnology solutions. The company was based in ...

, the manufacturer of clopyralid, voluntarily deregistered it for use on domestic lawns in the US and it is banned in several US states, but it is found in consumer products in Europe such as Scotts Verdone Extra and Vitax Lawn Clear 2. Clopyralid is licensed for lawn use in France and under these names: Bayer Jardin: Désherbant jeune gazon and Scanner Sélectif gazon Vilmorin: désherbant Gazon LONPAR. Brand names of clopyralid in the US market include Stinger, Transline, Reclaim, Curtail, Confront, Clopyr AG, Lontrel, Millennium Ultra, Millenium Ultra Plus and Redeem.

References

{{Herbicides Auxinic herbicides Chloropyridines Carboxylic acids