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DDT 1874-2005

DDT 1874-2005. November 17th, 2005. Paul Jepson Integrated Plant Protection Center Oregon State University jepsonp@science.oregonstate.edu. Pre-1940’s insecticides. Household Clothes moth : camphor, naphalene, p -dichlorbenzene Fumigation : ethylene oxide, hydrocyanic acid

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DDT 1874-2005

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  1. DDT 1874-2005 November 17th, 2005 Paul Jepson Integrated Plant Protection Center Oregon State University jepsonp@science.oregonstate.edu

  2. Pre-1940’s insecticides • Household • Clothes moth: camphor, naphalene, p-dichlorbenzene • Fumigation: ethylene oxide, hydrocyanic acid • Garden and farm • Nicotine, methyl bromide, acetonitrile, calcium copper and lead arsenates, pyrethrins, rotenone Dipping apples in 1% hydrochloric acid for 4 min removes 66-73% of the arsenic residue: 1930 Average arsenic after treatment: 0.006 grains/lb FDA tolerance: 1927: 0.025 grains/lb 1932: 0.01 grains/lb

  3. Experimental hop duster, Corvallis Oregon, 1940 Applying 4,6-dinitro-o-cyclohexyl phenol dust in walnut shell flour for spider mite control

  4. DDT • Highly toxic • Very persistent • Low acute toxicity to humans • 1941, little interest expressed • 1944, use to manage typhus epidemic created high demand in wartime • High use in agriculture from first year of introduction • Impacts on humans and environment overridden by commercial imperatives • Facilitated establishment of modern environmental movement

  5. Chronology of the modern pesticide industry • World War I • Increase in supply of agricultural products to USA and allies • Growth of chemical industry incl. Chemical Warfare Service (PDB) • Development of pest control as a metaphor for war and vice versa • Between wars • Testing of war gases as insecticides • Attempts to establish “Chemical Peace Service” • Entomologists increasingly use war metaphor for pest control • World War II • Total war concept feeds warfare and pest control (annihilation) • Factory capacity for production grows after DDT introduction • US government enables scarce materials to be used to build 14 factories for 11 companies in 1944/4 • 35-100% tax relief given to companies • DuPont awarded post war license for DDT in exchange for production agreement • Wide scale spraying in vector control using chemical warfare equipment • Restrictions on wide use of DDT under war powers legislation, because of side-effects on humans and wildlife, detected at an early stage • Aftermath of war • Organophosphate nerve gases tested as pesticides • No license or patent restrictions on US industry initially • Surplus production capacity directed to agriculture • No legal powers of government to restrict sale of properly labeled chemicals • Wildlife and conservation groups and many entomologists raise concerns by 1945 • War metaphor used nationally to promote DDT use • Efficiency in military use, and for medicine used as an argument for promoting use in agriculture

  6. Introduction and wide-scale use of organochlorine insecticides, 1946 Pyrethrum flower imports peaked at 13 million lbs 1945, but feel sharply in 1946, not resuming until 1955

  7. Early promise, early caution • DDT, HCH: combined contact activity and high toxicity of pyrethrins, with stomach activity and persistence of arsenates • But, were not the universal insecticides that popular accounts made it appear • Toxicity to beneficials (e.g.parasites, bees, beetles, flies) reported in early 1940’s • Research prior to 1946 was more cautious (problems with lack of selectivity in potato, invertebrate loss in carrots, mite outbreaks in apple)

  8. DDT used widely in the house, farm and zoo (Leary, Fishbein & Salter, 1946)

  9. Pesticide treatments by 13 commercial applicators in Oregon, 1957(Mumford, 1959)

  10. Mist blowers, 1952 (Garman, 1953) 50 gals/min, 1mph, gives 11.2 gals per tree, at 20 ft tree spacing The Hale centrifugal sprayer, capable of projecting spray upwards 30ft The Hurst hang-on sprayer Serious drift problems reported in 1950’s literature Application efficiency was not high

  11. Pesticide utilization efficiency(Graham-Bryce, 1977)

  12. Summary • Organochlorines seemed a vast improvement upon what went before • They were inexpensive and often gave high economic return • High persistence and broad spectrum of toxicity did not require them to be used efficiently • Chemists were ignorant of how OC properties impacted ecological processes • Over-optimism and over-marketing led to complacency • Pest outbreaks (caused by loss of natural enemies) were common following OC use • Evidence of wildlife impacts emerged by the late 1950’s but hazard was known in 1945 • The ‘Green Revolution’ relied upon broad spectrum pesticides

  13. Silent Spring byRachel Carson • Main arguments • Pesticides represent new risk, parallel with radioactivity, that deserves to be watched critically • The most severe problems are the long term genetic and ecological ones; ecologists have new responsibilities • The administrative machinery is inadequate • Response in UK: • All scientific claims and statistics checked for accuracy and errors (minor), published in Journal of Ecology, 1963 • Public and parliamentary focus on pollution, ecology, risks and benefits • Gradual restriction of OC’s, 1962-1976

  14. The peregrin falcon(Moriarty, 1999) • 1960, UK racing pigeon owners thought that falcon predation was increasing • Analysis revealed a falcon population decline since 1955 • 1962: 92% of pre-war territories deserted, only 2% of nests successful • pp-DDE and dieldrin seed dressings implicated • Pigeon mortality common, and 2-3 pigeons consumed could prove lethal to falcons • If dieldrin was responsible for the decline, what explains the poor breeding success?

  15. Changes in egg shell thickness index, 1845-1979, for British peregrine falcons (Falco peregrinus)(Ratcliffe, 1993)

  16. DDE implicated in egg shell thinning Shell strength and thickness in Falco peregrinus(Cooke, 1979) Open circles: 1850-1942 Closed circles: 1970-1974 pp-DDE thickens eggs of bengalese finch, hen, quail and pheasant

  17. MAY THRUSH 46.2 (eggs) BLACKBIRDS 52.7 (eggs) THRUSH 119.5 (liver) MAR BLACKBIRDS 87.1 (liver) MOLES 1.78 (liver) Food chain accumulation of pp-DDE in UK orchards after April sprays (ppm) Bailey et al. (1974) EARTHWORMS 1.63 SOIL 0.73 JAN Many equivalent datasets: Clear lake; land and sea bird carcass studies

  18. Epidemiological criteria for inferring causation

  19. Benefits of OC’s? Locust control in Africa Disease vector control

  20. Band spraying with insect growth regulators, using ULV sprayers, replaces OC’s and OP’s Returns to approach used for dieldrin and the OC’s, but without the environmental risk

  21. Alternatives to DDT proving harder to find, but they do exist DDT still used as a wall treatment, and against the vectors of sleeping sickness. Pyrethroid-treated bed nets are just as effective

  22. Impact of the modern insecticide era on biological control?

  23. Numbers of introduced natural enemies by decade (Gurr, et al., 2000)

  24. % Biological introductions leading to success, establishment, failure (or unknown)(Gurr et al., 2000) How can success rate be improved?

  25. The organochlorine legacy • Remaining OC residues and polar accumulation • Human body burdens, declining, but still there • Clean-up and disposal internationally • Gradual shift towards more effective chemicals • Chemophobia among public • Lack of public understanding of agriculture • Regulation improving • Alternative technology suppressed • Recycling of arguments about causation with respect to human disease and environmental impact • POP’s convention permits use in malaria management OC’s in aquatic ecosystems of the Columbia Plateau (USGS)

  26. Continued use of DDT in vector control • Express the trade-offs in terms of costs and benefits • Is lack of DDT the real underlying cause of malaria resurgence? • Do advocacy groups contribute to or detract from progress?

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