Picloram is a systemic herbicide used for general woody plant control. It also controls a wide range of broad-leaved weeds, but most grasses are resistant.
Pesticide Management Education Program,

Cornell University Cornell University is a Private university, private Ivy League research university based in Ithaca, New York, United States. The university was co-founded by American philanthropist Ezra Cornell and historian and educator Andrew Dickson W ...

. A

chlorinated In chemistry, halogenation is a chemical reaction which introduces one or more halogens into a chemical compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. ...

derivative of

picolinic acid Picolinic acid is an organic compound with the formula . It is a derivative of pyridine with a carboxylic acid (COOH) substituent at the 2-position. It is an isomer of nicotinic acid and isonicotinic acid, which have the carboxyl side chain at th ...

, picloram is in the

pyridine Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weak ...

family of herbicides. Picloram 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. Herbicides containing picloram are sold under a variety of brand names.

Dow Chemicals The Dow Chemical Company is an American multinational corporation headquartered in Midland, Michigan, United States. The company was among the three largest chemical producers in the world in 2021. It is the operating subsidiary of Dow Inc., a ...

and now

Dow AgroSciences Dow AgroSciences Limited liability company, LLC was a wholly owned subsidiary of the Dow Chemical Company specializing in not only agricultural chemicals such as pesticides, but also seeds and biotechnology solutions. The company was based in ...

sell herbicides containing it under the brand name Tordon. During the

Vietnam War The Vietnam War (1 November 1955 – 30 April 1975) was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam w ...

, picloram and other herbicides were combined to make

Agent White Agent White is the code name for a herbicide used by the U.S. military in its herbicidal warfare program during the Vietnam War. The name comes from the regulatory requirements of identifying each container of the various herbicides through the a ...

(commercially available as Tordon 101) and enhanced

Agent Orange Agent Orange is a chemical herbicide and defoliant, one of the tactical uses of Rainbow Herbicides. It was used by the U.S. military as part of its herbicidal warfare program, Operation Ranch Hand, during the Vietnam War from 1962 to 1971. T ...

, which was previously conducted by the British military during the

Malayan Emergency The Malayan Emergency, also known as the Anti–British National Liberation War, was a guerrilla warfare, guerrilla war fought in Federation of Malaya, Malaya between communist pro-independence fighters of the Malayan National Liberation Arm ...

. Large quantities of these herbicides were sprayed by U.S. forces in areas where they considered its long-term persistence desirable, such as inland forests. In 1974, of picloram were used in the US, mainly by government and industry.

Safety

Picloram is of moderate toxicity to the eyes and only mildly toxic on the skin. No history of human intoxication by picloram has been documented, so symptoms of acute exposure are difficult to characterize. Picloram is the most persistent of its family of herbicides. It does not adhere to soil, so may leach to groundwater, and has in fact been detected there. It is degraded in soil and water mainly by microbes. Picloram has very little tendency to accumulate in aquatic life. Gardeners who use dung as fertilizer should check to make certain that the animal source has not grazed on picloram-treated hay, as the dung still has broadleaf-killing potency. In regards to occupational exposures, the U. S.

Occupational Safety and Health Administration The Occupational Safety and Health Administration (OSHA; ) is a regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. The United States Congress established ...

has established a

permissible exposure limit The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agents such as high level noise. Permissible exposure limits were established by the Occupational ...

of 15 mg/m³ total exposure and 5 mg/m³ for respiratory exposure, over an eight-hour workshift.NIOSH Pocket Guide to Chemical Hazards
Centers for Disease Control and Prevention

References

External links

* {{Herbicides Auxinic herbicides Chloropyridines 4-Aminopyridines Aromatic acids Herbicides Beta-Amino acids Group 4 herbicides