Triclopyr

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

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Triclopyr is unusually effective on woody plants and is used for brush control in rights of way and defoliation of wooded areas. It is sold under the trade names Garlon and "Release" for these purposes.

Also handy for broadleaf weeds, particularly Creeping Charlie (Glechoma hederacea), upon which it is uncommonly effective. It is sold under the trade names Turflon, Weed-B-Gone (purple label), and Brush-B-Gone ("Poison Ivy Killer") for these purposes. Also the second major ingredient in Confront, which also contains clopyralid, and was withdrawn from most uses due to concerns about compost contamination from the clopyralid.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.

Environmental Issues

Triclopyr breaks down in soil with a half-life of between 30 and 90 days. One of the byproducts of breakdown (trichloro-pyridinol) remains in the soil for up to a year. Triclopyr degrades rapidly in water. It remains active in decaying vegetation for about 3 months.

The compound is slightly toxic to ducks (LD₅₀ = 1698 ppm) and quail (LD₅₀ = 3000 ppm).^[2] It has been found non-toxic to bees and fish.

References

1. ^ Merck Index, 11th Edition, 9572.
2. ^ EXTOXNET (Extension Toxicology Network), Oregon State University