Clopyralid
Encyclopedia
Clopyralid is a selective herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

 used for control of broadleaf weeds, especially thistle
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 often occur all over the plant – on surfaces such as those of the stem and flat parts of leaves. These are an adaptation that protects the...

s and clover
Clover
Clover , or trefoil, is a genus of about 300 species of plants in the leguminous pea family Fabaceae. The genus has a cosmopolitan distribution; the highest diversity is found in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes...

s.

Clopyralid is in the pyridine
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...

 family of herbicides, which also includes picloram
Picloram
Picloram is a systemic herbicide used for general woody plant control, sold under the trade names Tordon and Grazon. It also controls a wide range of broad-leaved weeds, but most grasses are resistant...

, triclopyr
Triclopyr
Triclopyr is a systemic, foliar herbicide in the pyridine group. It is used to control broadleaf weeds while leaving grasses and conifers unaffected....

, and several less common herbicides. For control of Creeping Thistle, Cirsium arvense
Cirsium arvense
Cirsium arvense is a species of Cirsium, native throughout Europe and northern Asia, and widely introduced elsewhere. The standard English name in its native area is Creeping Thistle.-Alternate names:...

, a noxious, perennial weed, clopyralid is one of the few effective herbicides available. It is particularly active on members of the Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...

 and the Fabaceae
Fabaceae
The Fabaceae or Leguminosae, commonly known as the legume, pea, or bean family, is a large and economically important family of flowering plants. The group is the third largest land plant family, behind only the Orchidaceae and Asteraceae, with 730 genera and over 19,400 species...

. It does not affect members of the Poaceae
Poaceae
The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...

 (grasses).

Clopyralid is notorious for its ability to persist in dead plants and compost
Compost
Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...

, 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.

Clopyralid is licensed for lawn use in France and under the following 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.

External links

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