DDT 1874-2005Paul JepsonIntegrated Plant Protection CenterOregon State Universityjepsonp@science.oregonstate.eduNovember 17th, 2005

Pre-1940s insecticidesHouseholdClothes moth: camphor, naphalene, p-dichlorbenzeneFumigation: ethylene oxide, hydrocyanic acidGarden and farmNicotine, 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: 1930Average arsenic after treatment: 0.006 grains/lbFDA tolerance:1927: 0.025 grains/lb1932: 0.01 grains/lb

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

DDTHighly toxicVery persistentLow acute toxicity to humans1941, little interest expressed1944, use to manage typhus epidemic created high demand in wartimeHigh use in agriculture from first year of introductionImpacts on humans and environment overridden by commercial imperativesFacilitated establishment of modern environmental movement

Chronology of the modern pesticide industryWorld War IIncrease in supply of agricultural products to USA and alliesGrowth of chemical industry incl. Chemical Warfare Service (PDB)Development of pest control as a metaphor for war and vice versaBetween warsTesting of war gases as insecticidesAttempts to establish Chemical Peace ServiceEntomologists increasingly use war metaphor for pest controlWorld War IITotal war concept feeds warfare and pest control (annihilation)Factory capacity for production grows after DDT introductionUS government enables scarce materials to be used to build 14 factories for 11 companies in 1944/435-100% tax relief given to companiesDuPont awarded post war license for DDT in exchange for production agreementWide scale spraying in vector control using chemical warfare equipmentRestrictions on wide use of DDT under war powers legislation, because of side-effects on humans and wildlife, detected at an early stageAftermath of warOrganophosphate nerve gases tested as pesticidesNo license or patent restrictions on US industry initiallySurplus production capacity directed to agricultureNo legal powers of government to restrict sale of properly labeled chemicalsWildlife and conservation groups and many entomologists raise concerns by 1945War metaphor used nationally to promote DDT useEfficiency in military use, and for medicine used as an argument for promoting use in agriculture

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

Early promise, early cautionDDT, HCH: combined contact activity and high toxicity of pyrethrins, with stomach activity and persistence of arsenatesBut, were not the universal insecticides that popular accounts made it appearToxicity to beneficials (e.g.parasites, bees, beetles, flies) reported in early 1940sResearch prior to 1946 was more cautious (problems with lack of selectivity in potato, invertebrate loss in carrots, mite outbreaks in apple)

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

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

The Hale centrifugal sprayer, capable of projecting spray upwards 30ftThe Hurst hang-on sprayerMist blowers, 1952(Garman, 1953)50 gals/min, 1mph, gives 11.2 gals per tree, at 20 ft tree spacing

Serious drift problems reported in 1950s literatureApplication efficiency was not high

Pesticide utilization efficiency (Graham-Bryce, 1977)

SummaryOrganochlorines seemed a vast improvement upon what went beforeThey were inexpensive and often gave high economic returnHigh persistence and broad spectrum of toxicity did not require them to be used efficientlyChemists were ignorant of how OC properties impacted ecological processesOver-optimism and over-marketing led to complacencyPest outbreaks (caused by loss of natural enemies) were common following OC useEvidence of wildlife impacts emerged by the late 1950s but hazard was known in 1945The Green Revolution relied upon broad spectrum pesticides

Silent Spring by Rachel Carson

Main argumentsPesticides represent new risk, parallel with radioactivity, that deserves to be watched criticallyThe most severe problems are the long term genetic and ecological ones; ecologists have new responsibilitiesThe administrative machinery is inadequateResponse in UK:All scientific claims and statistics checked for accuracy and errors (minor), published in Journal of Ecology, 1963Public and parliamentary focus on pollution, ecology, risks and benefitsGradual restriction of OCs, 1962-1976

The peregrin falcon(Moriarty, 1999)1960, UK racing pigeon owners thought that falcon predation was increasingAnalysis revealed a falcon population decline since 19551962: 92% of pre-war territories deserted, only 2% of nests successfulpp-DDE and dieldrin seed dressings implicatedPigeon mortality common, and 2-3 pigeons consumed could prove lethal to falconsIf dieldrin was responsible for the decline, what explains the poor breeding success?

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

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

SOIL0.73EARTHWORMS1.63BLACKBIRDS87.1 (liver)BLACKBIRDS52.7 (eggs)THRUSH119.5 (liver)THRUSH46.2 (eggs)MOLES1.78 (liver)JANMARMAYFood chain accumulation of pp-DDE in UK orchards after April sprays (ppm)Bailey et al. (1974)Many equivalent datasets: Clear lake; land and sea bird carcass studies

Epidemiological criteria for inferring causation

Benefits of OCs?Locust control in Africa

Disease vector control

Band spraying with insect growth regulators, using ULV sprayers, replaces OCs and OPsReturns to approach used for dieldrin and the OCs, but without the environmental risk

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

Impact of the modern insecticide era on biological control?

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

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

The organochlorine legacyRemaining OC residues and polar accumulationHuman body burdens, declining, but still thereClean-up and disposal internationallyGradual shift towards more effective chemicalsChemophobia among publicLack of public understanding of agricultureRegulation improvingAlternative technology suppressedRecycling of arguments about causation with respect to human disease and environmental impactPOPs convention permits use in malaria management

OCs in aquatic ecosystems of the Columbia Plateau (USGS)

Continued use of DDT in vector controlExpress the trade-offs in terms of costs and benefitsIs lack of DDT the real underlying cause of malaria resurgence?Do advocacy groups contribute to or detract from progress?