Triclopyr

Lead Editor

Overview


Triclopyr is a chloropyridinyl compound herbicide used against woody and herbaceous weeds. Most triclopyr is sold as a triethylamine salt (abbreviated TEA) or butoxyethyl ester (abbreviated BEE) derivative of the parent chemical, triclopyr acid. Triclopyr TEA was registered with the EPA in 1979 and triclopyr BEE was registered in 1980 (#EPA). Both chemicals are used for weed control in forests, pastures, and on other grasses including home lawns.

Triclopyr is sold under names such as Access, Crossbow, ET, Garlon, Grazon, PathFinder, Redeem, Rely, Remedy, and Turflon. It is often mixed other herbicides like picloram or 2,4-D to target a greater range of plant pests (#EXTOXNET).

Chemical Description


Technical triclopyr is a white to colorless fluffy crystal (#NIOSH). It does not bond strongly with soil, where is has a half-life ranging from 30-90 days (#EXTOXNET).

Triclopyr BEE has a low solubility in water. It has a tendency to adsorb into soil. It degrades into triclopyr acid within three hours (#CDPR).

Triclopyr TEA is soluble in water (#CDPR).

Triclopyr can be found commercially as soluble or emulsifiable concentrates, ready-to-use liquids, granulars, wettable powders, and pellets (#NIOSH).

Uses


Triclopyr targets broadleaf weeds and brush. It is used on rights-of-way, pasture and rangelands, forests, turf, and residential lawns. Triclopyr TEA is used agriculturally to control weeds affecting rice (#EPA). Over 70,000 pounds of triclopyr are used annually in the United States (#EXTOXNET).

Human Health Effects


Triclopyr BEE, TEA, and acid are slightly toxic in oral and dermal routes of exposure. Inhalation is practically non-toxic. Triclopyr TEA is a corrosive eye irritant and triclopyr BEE is only a slight eye irritant (#EPA). Triclopyr is excreted relatively quickly. A study in which humans ingested triclopyr found more than 80% of the chemical excreted within two days. Tests on animals have found that long term exposure to triclopyr can cause changes in the liver and kidney. An significant increase in breast tumor frequency was observed in female rats and mice that were fed triclopyr (#NPIC).

Exposing the skin and eyes to triclopyr may cause redness. Inhalation may cause coughing (#NIOSH).

Environmental Health Effects


Triclopyr mimics auxin, a natural plant hormone, causing an auxin overdose 1000 times greater than natural levels. This interferes with hormonal balance and normal growth, eventually causing death of the plant. Triclopyr has a low toxicity to grasses, but can harm conifers in high doses (#CDPR).

Triclopyr BEE and triclopyr TEA rapidly degrade into the parent chemical, triclopyr acid, after application. Thus, although triclopyr BEE has a higher affinity for soil, both chemicals are considered to be moderately to slightly mobile in soil (#CDPR).

Triclopyr acid is slightly toxic to birds, and practically non-toxic to most other animals. Triclopyr TEA is only slightly toxic to birds and marine invertebrate organisms. Triclopyr BEE is slightly toxic to birds, and moderately to highly toxic to fish and other marine species (#EPA).

Regulation


Some triclopyr products have restricted use. They can only be purchased and applied by certified applicators. There are products containing triclopyr for unrestricted residential use.

Precautionary Notes


Understand the different risks associated with triclopyr acid, triclopyr TEA, and triclopyr BEE. Be aware that triclopyr derivatives will degrade into triclopyr acid.

References



California Department of Pesticide Regulation. Triclopyr. (January 1997). http://www.cdpr.ca.gov/docs/emon/pubs/fatememo/triclopyr.pdf [Accessed 7-21-10].


Environmental Protection Agency. R.E.D. Facts: Triclopyr. (October 1998). http://www.epa.gov/oppsrrd1/REDs/factsheets/2710fact.pdf [Accessed 7-21-10].


Extension Toxicology Network. Triclopyr. (1996). http://extoxnet.orst.edu/pips/triclopy.htm [Accessed 7-21-10].


National Institute for Occupational Safety and Health. Triclopyr. (April 2006). http://www.cdc.gov/niosh/ipcsneng/neng1100.html [Accessed 7-21-10].


National Pesticide Information Center. Triclopyr. http://npic.orst.edu/factsheets/triclogen.pdf [Accessed 7-21-10].


Pesticide Action Network North America. Triclopyr. http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC36359 [Accessed 7-21-10].
 

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