Operation Ranch Hand Operation " Ranch Hand " was a U . S . military operation during the Vietnam War , lasting from 1962 until 1971 . It was part of the overall herbicidal warfare program during the war called " Operation Trail Dust " . " Ranch Hand " involved spraying an estimated 20 million U . S . gallons ( 76 , 000 m ) of defoliant s and herbicide s over rural areas of South Vietnam in an attempt to deprive the Viet Cong of food and vegetation cover . Areas of Laos and Cambodia were also sprayed to a lesser extent . Nearly 20 , 000 sortie s were flown between 1961 and 1971 . The Vietnamese government estimates that 400 , 000 people were killed or maimed and 500 , 000 children born with birth defects as a result of this spraying of what were called by the Americans ' rainbow herbicides ' . The " Ranch Handers " motto was " Only you can prevent a forest " – a take on the popular U . S . Forest Service poster slogan of Smokey Bear . During the ten years of spraying , over of forest and of crops were heavily damaged or destroyed . Around 20 % of the forests of South Vietnam were sprayed at least once . The herbicides were sprayed by the U . S . Air Force flying C - 123 s using the call sign " Hades " . The planes were fitted with specially developed spray tanks with a capacity of of herbicides . A plane sprayed a swath of land that was 80 meters wide and 16 km ( ~ 10 miles ) long in about 4½ minutes , at a rate of about . Sorties usually consisted of three to five airplanes flying side by side . 95 % of the herbicides and defoliants used in the war were sprayed by the U . S . Air Force as part of Operation " Ranch Hand " . The remaining 5 % were sprayed by the U . S . Chemical Corps , other military branches , and the Republic of Vietnam using hand sprayers , spray trucks , helicopter s and boats , primarily around U . S . military installation s . Defoliants . The herbicides used were sprayed at up to 50 times the concentration than for normal agricultural use . The most common herbicide used was Herbicide Orange , more commonly referred to as Agent Orange : a fifty - fifty mixture of two herbicides 2 , 4 - D ( 2 , 4 - dichlorophenoxyacetic acid ) and 2 , 4 , 5 - T ( 2 , 4 , 5 - trichlorophenoxyacetic acid ) . The other most common color - coded " Ranch Hand " herbicides were Agent Blue ( cacodylic acid ) that was primarily used against food crops , and Agent White ( picloram ) which was often used when Agent Orange was not available . The Agents used — known as the Rainbow Herbicides — their active ingredients , and years used were as follows : The herbicides were procured by the U . S . military from Dow Chemical Company ( all but Blue ) , Monsanto ( Orange , Purple and Pink ) , Hercules Inc . ( Orange and Purple ) , Thompson - Hayward Chemical Company ( Orange and Pink ) , Diamond Alkali / Shamrock Company ( Orange , Blue , Purple and Pink ) , United States Rubber Company ( Orange ) , Thompson Chemicals Corporation ( Orange and Pink ) , Agrisect Company ( Orange and Purple ) , Hoffman - Taft Inc . ( Orange ) , and the Ansul Chemical Company ( Blue ) . In April 1967 USA ' s entire production of 2 , 4 , 5 - T was confiscated by the military ; additionally foreign sources where tapped into . 65 % of the herbicides used contained 2 , 4 , 5 - trichlorophenoxyacetic acid that was contaminated with 2 , 3 , 7 , 8 - tetrachlorodibenzodioxin , a " " known human carcinogen " . . . by several different routes of exposure , including oral , dermal , and intraperitoneal " . About 12 million U . S . gallons ( 45 , 000 m ) of dioxin - contaminated herbicides were sprayed over Southeast Asia during American combat operations . In 2005 , a New Zealand government minister was quoted and widely reported as saying that Agent Orange chemicals had been supplied from New Zealand to the United States military during the conflict . Shortly after , the same minister claimed to have been mis - quoted , although this point was less widely reported . From 1962 to 1987 , " 2 , 4 , 5T " herbicide had been manufactured at an Ivon Watkins - Dow plant in New Plymouth . Operations . For most of the war , Operation " Ranch Hand " was based at Bien Hoa Air Base ( 1966 – 1970 ) , for operations in the Mekong Delta region where U . S . Navy patrol boat s were vulnerable to attack from areas of undergrowth along the water ' s edge . Storage , mixing , loading , and washing areas and a parking ramp were located just off the base ' s inside taxiway between the Hot Cargo Ramp and the control tower . For operations along the central coast and the Ho Chi Minh trail regions , " Ranch Hand " operated out of Da Nang Air Base ( 1964 – 71 ) . Other bases of operation included Phu Cat Air Base ( 1968 – 1970 ) , Tan Son Nhut Air Base ( 1962 – 66 ) , Nha Trang Air Base ( 1968 – 69 ) , Phan Rang Air Base ( 1970 – 72 ) , and Tuy Hoa Air Base ( 1971 – 72 ) . Other bases were also used as temporary staging areas for " Ranch Hand " . The Da Nang , Bien Hoa and Phu Cat Air bases are still heavily contaminated with dioxin from the herbicides , and have been placed on a priority list for containment and clean - up by the Vietnamese government . The first aerial spraying of herbicides was a test run conducted on 10 August 1961 in a village north of Đắk Tô against foliage . Testing continued over the next year and even though there was doubt in the State Department , The Pentagon and the White House as to the efficacy of the herbicides , Operation " Ranch Hand " began in early 1962 . Individual spray runs had to be approved by President John F . Kennedy until November 1962 , when Kennedy gave the authority to approve most spray runs to the Military Assistance Command , Vietnam and the U . S . Ambassador to South Vietnam . " Ranch Hand " was given final approval to spray targets in eastern Laos in December 1965 . The issue of whether or not to allow crop destruction was under great debate due to its potential of violating the Geneva Protocol . The president of South Vietnam , Ngo Dinh Diem began to push the U . S . Military Advisory Group in Vietnam and the White House to begin crop destruction in September 1961 , but it was not until October 1962 when the White House gave approval for limited testing of Agent Blue against crops in an area believed to be controlled by the Viet Cong . Soon after , crop destruction became an integral part of the " Ranch Hand " program . Target s for the spray runs were carefully selected to satisfy the strategic and psychological operations goals of the U . S . and South Vietnamese military . Spray runs were surveyed to pinpoint the target area and then placed on a priority list . Due to the low altitude ( ideally ) required for spraying , the C - 123s were escorted by fighter airplanes that would strafe or bomb the target area in order to draw out any ground fire if the area was believed to be ' hot ' . Spray runs were planned to enable as straight a run as possible to limit the amount of time the planes flew at low altitude . Data on the spray runs , their targets , the herbicide used and amount used , weather conditions and other details were recorded and later put into a database called the Herbicide Reporting System ( HERBS ) tapes . The effectiveness of the spraying was influenced by many factors including weather and terrain . Spray runs occurred during the early morning hours before temperatures rose above 85 degrees and the winds picked up . Mangrove s in the Delta region required only one spraying and did not survive once defoliated , whereas dense forests in the uplands required two or more spray runs . Within two to three weeks of spraying , the leaves would drop from the trees , which would remain bare until the next rainy season . In order to defoliate the lower stories of forest cover , one or more follow - up spray runs were needed . About 10 percent of the trees sprayed died from a single spray run . Multiple spraying resulted in increased mortality for the trees , as did following up the herbicide missions with napalm or bomb ing strike s . Scientific community reaction . The use of herbicides in the Vietnam War was controversial from the beginning , particularly for crop destruction . The scientific community began to protest the use of herbicides in Vietnam as early as 1964 , when the Federation of American Scientists objected to the use of defoliants . The American Association for the Advancement of Science ( AAAS ) issued a resolution in 1966 calling for a field investigation of the herbicide program in Vietnam . In 1967 , seventeen Nobel laureates and 5 , 000 other scientists signed a petition asking for the immediate end to the use of herbicides in Vietnam . Press coverage of the controversial use of herbicides in Vietnam increased in the late 1960s . In 1970 , AAAS sent a team of scientists to conduct field tests of the ecological impacts of the herbicide program in Vietnam . A 1969 report authored by K . Diane Courtney and others found that 2 , 4 , 5 - T could cause birth defect s and stillbirths in mice . This and follow - up studies led the U . S . government to restrict the use of 2 , 4 , 5 - T in the U . S . in April 1970 . The Department of Defense followed suit by ' temporarily ' suspending the use of Agent Orange in Vietnam , though they continued to rely on Agent White for defoliation until supplies ran out and the last defoliation spray run took place on 9 May 1970 . Sporadic crop destruction sorties using Agent Blue continued throughout 1970 until the final " Ranch Hand " run was flown on 7 January 1971 .