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Triclopyr (3,5,6-Trichloro-2-pyridinyloxyacetic acid) is an organic compound in the pyridine group that is used as a systemic foliar herbicide[2] and fungicide.[3]

Skeletal formula of triclopyr
Space-filling model of the triclopyr molecule
IUPAC name
[(3,5,6-Trichloro-2-pyridinyl)oxy]acetic acid
Other names
Trident (Agriphar)
3D model (JSmol)
ECHA InfoCard 100.054.161
Molar mass 256.46
Appearance Fluffy solid
Melting point 148 to 150 °C (298 to 302 °F; 421 to 423 K)
440 mg/L
Solubility in acetone 989 g/kg
Acidity (pKa) 2.68
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references



Triclopyr is used to control broadleaf weeds while leaving grasses and conifers unaffected[2] or to control rust diseases on crops.[3]

Triclopyr is effective on woody plants and is used for brush control in rights of way and defoliation of wooded areas. In the USA it is sold under the trade names Garlon and Remedy, and in the UK as SBK Brushwood Killer.

It is also used for broadleaf weeds, particularly Creeping Charlie (Glechoma hederacea). It is sold under the trade names Turflon, Weed-B-Gon (purple label), and Brush-B-Gon ("Poison Ivy Killer") for these purposes. It is a major ingredient in Confront, which was withdrawn from most uses due to concerns about compost contamination from the other major ingredient, clopyralid.

Triclopyr is formulated both as an ester and as an amine salt. The usual tradeoffs regarding effectiveness, drift, and toxicity to humans apply to these two formulations.[further explanation needed] It is chemically very similar to the herbicide which it generally replaces, 2,4,5-T, which was phased out in the U.S. in the 1970s amid toxicity concerns.

Environmental issuesEdit

Triclopyr breaks down in soil with a half-life of between 30 and 90 days. One of the byproducts of breakdown, trichloropyridinol, remains in the soil for up to a year. A study in Massachusetts reported a correlation between exposure to trichloropyridinol and lower testosterone levels in men[4]. Triclopyr degrades rapidly in water. It remains active in decaying vegetation for about 3 months.

The compound is slightly toxic to ducks (LD50 = 1698 mg/kg) and quail (LD50 = 3000 mg/kg).[5] It has been found non-toxic to bees and very slightly toxic to fish (Rainbow trout LC50 (96 hrs.) = 117 ppm).[6]


  1. ^ Merck Index, 11th Edition, 9572.
  2. ^ a b Appleby, Arnold P.; Müller, Franz; Carpy, Serge (2001). "Weed Control". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a28_165.
  3. ^ a b Shanmugasundaram, S.; Yeh, C.C.; Hartman, G.L.; Talekar, N.S. (1991). Vegetable Soybean Research Needs for Production and Quality Improvement (PDF). Taipei: Asian Vegetable Research and Development Center. pp. 86–87. ISBN 9789290580478. Retrieved 6 February 2016.
  4. ^ Meeker, J. D.; Ryan, L.; Barr, D. B.; Hauser, R. (2006). "Exposure to Nonpersistent Insecticides and Male Reproductive Hormones". Epidemiology. 17 (1): 61–68. doi:10.1097/01.ede.0000190602.14691.70. PMID 16357596.
  5. ^ EXTOXNET (Extension Toxicology Network), Oregon State University
  6. ^ Environmental Fate Of Triclopyr, Carissa Ganapathy, Environmental Monitoring & Pest Management Branch Department of Pesticide Regulation Sacramento, CA

External linksEdit