Rainbow Herbicides

The Rainbow Herbicides are a group of chemicals used by the United States military in Southeast Asia during the Vietnam War. Success with Project AGILE field tests with herbicides in South Vietnam in 1961 led to the formal herbicidal program Trail Dust (1961–71). Herbicidal warfare is a form of chemical warfare, in which the objective is destroying the plant-based ecosystem of an agricultural food production and/or destroying foliage which provides the enemy cover.

The Agents used in southeast Asia, their active ingredients and years used were as follow:
 * Agent Pink: 60% - 40% n-butyl: isobutyl ester of 2,4,5-T used in 1961, 1965
 * Agent Green: (n-butyl ester 2,4,5-T) unclear when used but believed to be at the same time as Pink
 * Agent Purple: 50% n-butyl ester of 2,4-D, 30% n-butyl ester of 2,4,5-T, 20% isobutyl ester of 2,4,5-T used 1962–65
 * Agent Blue (Phytar 560G): cacodylic acid and sodium cacodylate used from 1962–71 in powder and water solution
 * Agent White (Tordon 101): 21.2% (acid weight basis) triisopropanolamine salts of 2,4-D and 5.7% picloram used 1966–71.
 * Agent Orange or Herbicide Orange, (HO): 50% n-butyl ester 2,4-D and 50% n-butyl ester 2,4,5-T used 1965–70
 * Agent Orange II:50% n-butyl ester 2,4-D and 50% isooctyl ester 2,4,5-T used after 1968.
 * Agent Orange III: 66.6% n-butyl 2,4-D and 33.3% n-butyl ester 2,4,5-T.
 * Enhanced Agent Orange, Orange Plus, or Super Orange (SO), or DOW Herbicide M-3393: standardized Agent Orange mixture of 2,4-D and 2,4,5-T combined with an oil-based mixture of picloram, a proprietary DOW Chemical product called Tordon 101, an ingredient of Agent White.

In Vietnam, the early large-scale defoliation missions (1962-1964) used 8,208 gallons of Agent Green, 122,792 gallons of Pink, and 145,000 of Purple. These were dwarfed by the 11,712,860 gallons of Orange (both versions) used from 1965 to 1970. Agent White started to replace Orange in 1966; 5,239,853 gallons of White were used. The only agent used on a large scale in an anti-crop role was Blue, with 2,166,656 gallons used.

In addition to testing and using the herbicides in Vietnam, Laos and Cambodia, the US military also tested the "Rainbow Herbicides" and many other chemical defoliants and herbicides in the US, Canada, Puerto Rico, Korea, India, and Thailand from the mid-1940s to the late 1960s. Herbicide persistence studies of Agents Orange and White were conducted in the Philippines. The Philippine herbicide test program which was conducted in cooperation with the University of the Philippines, College of Forestry and was also described in a 1969 issue of The Philippine Collegian, the college's newspaper. Super or enhanced Agent Orange was tested by representatives from Fort Detrick and Dow chemical in Texas, Puerto Rico, and Hawaii and later in Malaysia in a cooperative project with the International Rubber Research Institute. Picloram in Agent White and Super-Orange was contaminated by Hexachlorobenzene (HCB) a dioxin-like carcinogen.