defoliant

A chemical sprayed or dusted on plants to cause the leaves to fall off.

dēˈfōlēǝnt n. a chemical that removes the leaves from trees and plants and is often used in warfare.

See the Introduction, Abbreviations and Pronunciation for further details.

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Defoliation involves the extermination of plant life that in military operations might conceal enemy armed forces, command centers, supply depots, or, less commonly, fields of crops. Such destruction is accomplished by three principal courses of action: setting fires; dropping napalm or phosphorus bombs; and spraying chemical agents from trucks, helicopters, or fixed-wing aircraft. During World War II and the Korean War the United States employed the former two methods, whereas during the Vietnam War chemical agents, chiefly Agent Orange, tended to be used. Defoliation generally produced the desired military objectives, but the human and ecological consequences remain controversial.

In Vietnam the American attempt to defoliate jungle growth and thus expose the enemy focused on the areas around South Vietnamese and later American base camps; along the Ho Chi Minh Trail; across the Demilitarized Zone separating Northand South Vietnam; up and down rivers, canals, and railways; and on any suspected North Vietnamese or Vietcong concentration. In a July 1999 interview Elmo R. Zumwalt Jr., the commander of naval forces in Vietnam from 1968 to 1970, explained that he had ordered the use of defoliants because his personnel were taking casualties at the rate of 6 percent a month, which meant the average young man would have about a 70 percent probability of being killed or wounded during his year's tour.

The campaign to reduce that casualty figure was designated Operation Ranch Hand, which began officially in January 1962 and lasted until January 1971. During that period U.S. Air Force UC-123 aircraft flew thousands of sorties and sprayed nearly 10,000 square miles with roughly 19 million gallons of herbicide, about 11 million of which were Agent Orange. The nonscientific names for the herbicides—Agent Orange, Agent White, and so forth—were derived from the color codes on the drums that contained the defoliants. These chemicals, mainly those tagged 2, 4-D and 2, 4, 5-T, were combined and sprayed to fatally accelerate plant growth, causing destruction within days of the spraying.

From the outset the military use of herbicides generated negative responses from both Vietnamese and Americans, most particularly when crop destruction was involved. Although the spraying of crops succeeded in reducing the available food supply for the North Vietnamese and Vietcong, it also resulted in the destruction of innocent farmers' crops. State Department officials argued that what little advantage was gained in diminishing the enemy's food supply was vastly exceeded by the ill will generated from the unavoidable damage to non-enemy crops. Since crop destruction never constituted more than 15 percent of Ranch Hand's operations, defoliation advocates in the Defense Department grudgingly accepted sporadic political restrictions placed on crop eradication activities, down to the ending of all chemical operations in January 1971.

Other consequences—chiefly political, ecological, and medical—ensued. During the war many in the American media and scientific communities claimed that the use of herbicides constituted chemical warfare, outlawed by numerous treaties to which the United States was a signatory. At the very least this charge created a public relations problem and added to the opposition that the Vietnam War was generating. It also led to pointed questions about the ecological and human costs of defoliation, compelling the Defense Department to commission studies, the results of which caused further heated debates. One study, begun by the National Academy of Sciences in 1970, asserted in its 1974 report that no long-term damage, including birth defects or environmental degradation, could be attributed to the various herbicidal agents sprayed in Vietnam.

In the 1990s that same organization found connections between herbicides containing dioxin and several ailments, including sarcomas, non-Hodgkin's lymphoma, Hodgkin's disease, and chloracne. Congress, the Air Force, and the Veterans Administration (VA) commenced studies of Vietnam veterans who had possibly been exposed to herbicides. In 1978 the VA began conducting physical examinations, doing laboratory work, and launching a registry to study systematically the latent effects of exposure.

Perhaps the most notable case of an American soldier's illness being attributed to Agent Orange is that of Elmo R. Zumwalt III. His sickness and eventual death from cancer at age forty-two in 1988 attracted much attention, since his father had ordered the spraying of herbicides in areas where the son served from 1969 to 1970. Although a causal relationship could not be established, Elmo III believed one existed, particularly since his son, Elmo IV, had been diagnosed with a genetic disorder. In 2001 a University of Texas researcher, Arnold J. Schecter, produced a public health report on Bien Hoa, where seven thousand gallons of Agent Orange had spilled in 1970. His study revealed high levels of dioxin in children born after the war and in adults who moved to the city from locations where no herbicides containing dioxin were sprayed. Schecter concluded that the toxic substance migrated from soil to the groundwater to waterways, from which fish were caught and eaten. One gathers that some relationship exists between exposure to the various herbicidal agents and numerous health problems, since the VA has provided compensation to nearly two thousand veterans and because the various chemical companies that manufactured the agents settled a class-action lawsuit out of court that provided almost $200 million in damages to veterans.

Bibliography

Buckingham, William A., Jr. Operation Ranch Hand: The Air Force and Herbicides in Southeast Asia, 1961–1971. Washington, D.C.: Office of Air Force History, United States Air Force, 1982.

Schuck, Peter H. Agent Orange on Trial: Mass Toxic Disasters in the Courts. Cambridge, Mass.: Harvard University Press, 1986.

Texas Technical University. "Vietnam Archive." Burch and Pike collections. Available from http://archive.vietnam.ttu.edu/vietnamarchive.

Wilcox, Fred A. Waiting for an Army to Die: The Tragedy of Agent Orange. New York: Random House, 1983.

Zumwalt, Elmo R., Jr., and Elmo R. Zumwalt III. My Father, My Son. New York: Macmillan, 1986.

—Thomas Reins

A chemical used to remove the leaves from plants to facilitate mechanical harvesting. The early defoliants, especially arsenical compounds, presented serious hazards if the plants were later fed to livestock or if the spray drifted to nearby pasture paddocks. Modern defoliants are nontoxic if used according to manufacturer's recommendations. See mcpa, tributyl triphosphorotrithioite, thidiazuron.

A chemical that causes leaves to be shed. One use for defoliants is in the cotton fields, where fewer leaves make it easier to harvest the cotton bolls.

This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. (April 2007)

A helicopter sprays defoliant on a dense jungle area in the Mekong delta (07/26/1969).

A defoliant is any chemical sprayed or dusted on plants to cause its leaves to fall off. A classic example of a highly toxic defoliant used for tactical purposes is Agent Orange, which was used widely by the U.S. military during the Vietnam War from 1961 to 1970.

Defoliants differ from herbicides in that the former seeks mainly to strip leaves from plants, and the latter is used to destroy or inhibit the growth of plants. Defoliation is not always caused by defoliants. It can be many different environmental factors that cause a plant's leaves to fall off.

See also

• List of environment topics

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Dansk (Danish)
n. - afløvningsmiddel

Nederlands (Dutch)
ontbladeringsmiddel

Français (French)
n. - défoliant

Deutsch (German)
n. - Entlaubungsmittel

Ελληνική (Greek)
n. - αποφυλλιστική χημική ουσία

Italiano (Italian)
defogliante

Português (Portuguese)
n. - desfolhante (m)

Русский (Russian)
дефолиант

Español (Spanish)
n. - defoliante, defoliado

Svenska (Swedish)
n. - avlövningsmedel

中文（简体）(Chinese (Simplified))
脱叶剂, 落叶剂

中文（繁體）(Chinese (Traditional))
n. - 脫葉劑, 落葉劑

한국어 (Korean)
n. - 고엽제

日本語 (Japanese)
n. - 落葉剤, 枯葉剤

العربيه (Arabic)
‏(الاسم) رذاذ أو غبار كيميائي يرش على النباتات لجعل الأوراق تتساقط قبل أوانها‏

עברית (Hebrew)
n. - ‮משיר עלים (כימיקל)‬

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