Photo: Salt cedar & giant cane, Rio Grande, Big Bend National Park. © 2017 Delena Norris-Tull
The History of the Use of Herbicides and Other Pesticides, Prior to and During WW II
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020.
For decades, arsenic, highly toxic to animals and humans, has been used as a pesticide to kill grasshoppers and rodents and as an ingredient in herbicides. ‘Agent Blue’ (dimethylarsinic acid plus sodium cacodylate) has been used as an herbicide, fungicide, and insecticide. It was used in the Vietnam War to kill rice plants, in attempts to starve the North Vietnamese. This chemical is still in use today in the USA as an herbicide in lawns and some crops. ‘Paris green’ is copper acetate triarsenite, a highly toxic material. In the USA, Paris Green was in use beginning in 1867. To make a bait for grasshoppers, the farmers mixed it with grain. The name Paris green came from its use in killing rats in Paris. During World War II, it was sprayed by airplane over Italy to kill the mosquitos that carry malaria. Sodium arsenite was also in use as a pesticide, and has various industrial uses today. It is toxic and also carcinogenic to humans. It is striking that Oregon was the only state, in the 1942 Western Weed Control Conference, to sound the alarm about the use of arsenicals. And in the 1945 Conference, it is one of the few states to express concern about the tendency of most states to focus primarily on the use of chemicals in weed control.
Strychnine is also highly toxic to many animals and to humans. It has been in use in the USA in rangelands since the 1940s. It has been used in Western States to kill rats, mice, prairie dogs, moles, and coyotes.
A variety of additional pesticides were used prior to the advent of petrochemicals. Most of these are described in the minutes from the 1940s of the Western Weed Control Conferences:
- Sinox (dinitro-cresol) was introduced into use in US agriculture in the 1940s. It was used as an herbicide and insecticide until banned by the EPA in 1991. The 1942 minutes of the Western Weed Control Conference include a report on testing the toxicity to sheep in the field. The chemical is highly toxic to humans.
- Diesel oil
- Light industrial fuel oil
- Carbon bisulfide is still used today as a fumigant in grains and a soil disinfectant to kill insects and nematodes. It has various industrial uses, including use as a solvent. It is toxic to humans.
- Sulfamic acid is no longer used in agriculture but is used in various industries. It is toxic to humans.
- Sodium pentachlorophenate is still used as an herbicide and to kill invasive molluscs today.
- Altacide (referenced in the 1942 minutes) (Sodium chlorate) is still used today as an insecticide to kill mosquito larvae.
- Borax - In the 1945 minutes it was reported that Borax caused concern because it was expensive, and it causes soil sterility for three years. It has many uses today, including as an insecticide.
- Copper sulfate (referenced in the 1945 minutes) is still used today as a fungicide and to kill aquatic plants and algae.
- Benoclor (Chlorinated benzene) (referenced in the 1945 minutes) was used as a pesticide, including as a major ingredient in DDT, which was banned by the EPA for use in agriculture in 1972. DDT is still used in other countries, to kill the mosquitos that carry malaria. Chlorinated benzene is still used today in various industrial uses, including in the manufacture of some herbicides. It is moderately toxic to humans.
- Salt – used only on non-agricultural land
- Ammate (ammonium sulphamate) is still used in herbicides today, and has various industrial uses. It is slightly toxic to animals and humans.
Refer to the Western Weed Control Conference minutes, 1942, for reports on the successes and failures of many of these early pesticides. It is striking that little mention is made, in those minutes, of studies of the short- or long-term impact of these chemicals on soils, crops, livestock, wildlife, and humans.
At the end of the 1942 conference, a telegram received from the War Production Board on June 26, 1942, was read:
“ACCOUNT CHLORATE AND ARSENIC SITUATION REQUEST OPINION YOUR CONFERENCE EXTENT TO WHICH BORON COMPOUNDS CAN BE SUBSTITUTED FOR THESE ON PACIFIC COAST. ALSO YOUR OPINION IRREDUCIBLE QUANTITY CHLORATE NECESSARY TO MAINTAIN PRIMARY WEED PROJECTS IN EACH OF YOUR STATES: VICTOR BOUTIN, WAR PRODUCTION BOARD.”
The conference sent this recommendation to the War Production Board: “The Western Weed Conference… cannot approve substitution of Boron compounds for chlorates in treating deep-rooted perennials.”
In the minutes of the 1945 Western Weed Control Conference, reports are included from the first North Central Weed Control Conference. Mr. Ball summarized a report by Mr. A.K. Hepperly, Agricultural Agent of the C.B. & Q. Railroad, who found that the railroads’ use of chlorate to eradicate weeds are “so erratic that it requires so much labor for the original application and the follow-up treatments, and that the seedling problem, together with the fire hazard of sodium chlorate, makes it fall far short of a solution to the railroads’ problem of weed eradication… Considerable Borax has been used on the railroad with good results… inspection during the summer of 1943 showed good kill at most locations, some of which were 100%. Inspection in 1944, however, showed that Borax can be as erratic as sodium chlorate.”
The 1945 conference minutes describe the process of killing weeds using oils, denitro compounds, and phenolic herbicides. The report contained no information on how long the oils remained in the soil, and no information on toxicity to non-target plants and animals.
Slade Franklin, Wyoming Weed and Pest Coordinator, stated in an interview conducted by Becky McMillen: “During World War II sodium chlorate and carbon bisulfide, which had been used as a soil fumigant to kill weeds, were hard to come by. They are both highly flammable and were being used in bombs during the war. After the war, the petrochemical, 2,4-D, became available.” [Refer to the 1945 and 1946 archival minutes of the Western Weed Control Conferences to read details about the emergence of petrochemicals.]
Another concern identified in the minutes from 1942 Western Weed Control Conference was the use of untrained growers who do not know how to manage weeds and are using untested chemicals.
In the California report to the 1946 Western Weed Control Conference, it was stated that, “The last point I wish to stress is my belief that we must give further attention to the question of using commercial pest control operators. Our Agricultural Code provides for registration and is so set up that the individual must know what he is doing or his license will be revoked. I make this statement primarily because I feel that we are going to experience a great deal more trouble in the use of 2,4-D and its mis-handling than we have heretofore unless operators know the material, know how it is applied, and know when to apply it.”
Slade Franklin (Wyoming Weed & Pest Coordinator) told me that: “Rachel Carson published Silent Spring in 1962, which highlighted the toxicity of DDT and other pesticides. The Wyoming Weed and Pest Conference minutes in the 1960s include discussions about the potential toxicity of pesticides and herbicides. In 1963, there was a big fish kill in the Mississippi River. Tordon and Atrazine were developed after 2,4-D. They were more selective than 2,4-D, in regards to which weeds they killed. Today’s herbicides are even more specialized.”