For technical information on this herbicide, see
www.epa.gov/safewater/dwh/c-soc/picloram.html and
www.epa.gov/safewater/dwh/c-soc/24-d.html

See also notes by David Mackenzie

The following information is from forests.org/ric/good_wood/tox_herb.htm

Picloram (Tordon), a picolenic acid herbicide, is the type of herbicide a chemical company loves to sell and those concerned only with killing vegetation love to buy: it is persistent and can be used to kill a large variety of woody plants and annual and perennial broadleaved weeds.

A mixture of picloram and 2,4-D, known as Agent White during the Vietnam War, was sprayed by the US military on those plants that survived the initial onslaught of Agent Orange (2,4,5-T and 2,4-D). That mixture is sold in Australia as Tordon.

Picloram/Tordon can be sprayed on foliage, injected into plants, applied to cut surfaces, or placed at the base of the plant where it will leach to the roots. Once absorbed by the foliage, stem, or roots, picloram is transported throughout the plant, where it is quite stable (ie, just sits there, waiting...).

The very characteristics of Picloram that ensure the killing of a wide variety of plants, however, are also the one ones that cause trouble in the wider environment: persistence, leaching, and broad toxicity to plants in small amounts.