Pesticides Pesticides Ch 22Ch 22

PESTPEST = any organism that interferes in = any organism that interferes in some way with human welfare or activities.some way with human welfare or activities.

PESTICIDEPESTICIDE = toxic chemicals used to = toxic chemicals used to reduce the size of and control the pest reduce the size of and control the pest population.population. Grouped by their target organismGrouped by their target organism

InsecticideInsecticide, , HerbicideHerbicide, ,

FungicideFungicide, , RodenticideRodenticide

85% of pesticides worldwide used for 85% of pesticides worldwide used for Agriculture.Agriculture.

““Ideal Pesticides”Ideal Pesticides” Narrow-SpectrumNarrow-Spectrum = kill only target = kill only target

organism.organism. Breaks downBreaks down easily into safe materials easily into safe materials Does not moveDoes not move around in the environment. around in the environment.

““Non-Ideal Pesticides”Non-Ideal Pesticides” Broad-SpectrumBroad-Spectrum = kill more than just = kill more than just

the target.the target. PersistentPersistent or Can degrade into other or Can degrade into other

cmpds that can be cmpds that can be more dangerousmore dangerous Move aroundMove around in the environment. in the environment.

Pre-1940s (Pre-1940s (First-generation pesticidesFirst-generation pesticides)) InorganicsInorganics (Minerals) (Minerals)

Contain lead, mercury, and arsenicContain lead, mercury, and arsenic Very persistent & bioaccumulateVery persistent & bioaccumulate

OrganicsOrganics ( (BotanicalsBotanicals)) Plant-derivedPlant-derived Break down readilyBreak down readily

Post-1940s Post-1940s ((Second-generation pesticidesSecond-generation pesticides)) Synthetic BotanicalsSynthetic Botanicals

Made by altering natural botanicalsMade by altering natural botanicals

Ex: Ex: dichlorodiphenyltrichloroethane (DDT)dichlorodiphenyltrichloroethane (DDT)

INSECTICIDES : INSECTICIDES : Classified by chemical structure Classified by chemical structure

Chlorinated HydrocarbonsChlorinated Hydrocarbons = organic cmpd + Cl = organic cmpd + Cl Broad-spectrum, persistentBroad-spectrum, persistent Most are banned (Most are banned (DDTDDT, endosulfan, etc), endosulfan, etc) Rachel Carson: Rachel Carson: Silent SpringSilent Spring

OrganophosphatesOrganophosphates = organic cmpd + P = organic cmpd + P more poisonous than most othersmore poisonous than most others not persistent, so they’ve replaced most not persistent, so they’ve replaced most

chlorinated hydrocarbonschlorinated hydrocarbons

CarbamatesCarbamates = broad-spectrum, derived from = broad-spectrum, derived from carbamic acidcarbamic acid Less toxic to mammals (Carbaryl, Aldicarb)Less toxic to mammals (Carbaryl, Aldicarb)

HERBICIDESHERBICIDES Classified by how they act & what they killClassified by how they act & what they kill Selective HerbicidesSelective Herbicides = kill only certain types = kill only certain types

of plantsof plants Broad-leaf HerbicidesBroad-leaf Herbicides

2,4-D2,4-D & & 2,4,5-T2,4,5-T common in 1940s common in 1940s 2,4,5-T2,4,5-T banned by EPA in 1979 due to possible banned by EPA in 1979 due to possible

harmful side effects realized after its use in the harmful side effects realized after its use in the Vietnam WarVietnam War

Grass HerbicidesGrass Herbicides

Nonselective HerbicidesNonselective Herbicides = kill all vegetation = kill all vegetation

VIETNAM WAR & HERBICIDESVIETNAM WAR & HERBICIDES US used mixtures of herbicides to kill vegetation US used mixtures of herbicides to kill vegetation

in S.Vietnam to expose hiding places & destroy in S.Vietnam to expose hiding places & destroy crops planted by Vietcong: crops planted by Vietcong: Agent WhiteAgent White, , Agent Agent BlueBlue, & , & Agent OrangeAgent Orange

Negative environmental impacts:Negative environmental impacts: Mangrove forests & hardwood forests destroyedMangrove forests & hardwood forests destroyed Harmed ecology & economy of S.VietnamHarmed ecology & economy of S.Vietnam

Negative health impacts:Negative health impacts: Agent Orange = 2,4-D & 2,4,5-T combined.Agent Orange = 2,4-D & 2,4,5-T combined. Created highly toxic Created highly toxic DioxinsDioxins during creation during creation Birth defects, stillbirths, female reproductive Birth defects, stillbirths, female reproductive

disorders, soft-tissue cancersdisorders, soft-tissue cancers Bioaccumulated in fish = very high levels in Bioaccumulated in fish = very high levels in

Vietnamese peopleVietnamese people

DISEASE CONTROLDISEASE CONTROL Malaria: carried mostly by female mosquitoesMalaria: carried mostly by female mosquitoes Worldwide: 300-500M people currently suffer, Worldwide: 300-500M people currently suffer,

2.7M die each year.2.7M die each year. DDT has helped the malaria problem greatly.DDT has helped the malaria problem greatly. Sri Lanka: went from 2M cases each year to Sri Lanka: went from 2M cases each year to

almost zero with the use of DDT.almost zero with the use of DDT. When spraying stopped, more than 1M cases per When spraying stopped, more than 1M cases per

year within 4 years.year within 4 years. Restarted DDT spraying in 1968Restarted DDT spraying in 1968

DDT still used in at least 20 tropical countries DDT still used in at least 20 tropical countries to control mosquitoes.to control mosquitoes.

CROP PROTECTION- CROP PROTECTION- We already We already knowknow this… this…

1/3 of world’s crops are eaten/destroyed by pests1/3 of world’s crops are eaten/destroyed by pests Pesticides decrease crop loss due to weed Pesticides decrease crop loss due to weed

competition, insect consumption, and plant diseases competition, insect consumption, and plant diseases caused by caused by pathogenspathogens = microorganisms that cause = microorganisms that cause disease.disease.

Many insects are considered pests, and ~200 species Many insects are considered pests, and ~200 species have the potential to cause large economic losses in have the potential to cause large economic losses in agriculture.agriculture.

Pesticide use is justified economically:Pesticide use is justified economically: For every $1 spent by farmers on pesticides, $3-5 For every $1 spent by farmers on pesticides, $3-5

is saved from crop loss.is saved from crop loss. MonocultureMonoculture = one variety of crop species is grown = one variety of crop species is grown

on large tracts of land.on large tracts of land. Causes more pest destruction because it reduces Causes more pest destruction because it reduces

the dangers and accidents that might befall a pest the dangers and accidents that might befall a pest as it searches for food.as it searches for food.

Genetic ResistanceGenetic Resistance any inherited characteristic that decreases the any inherited characteristic that decreases the

effect of a pesticide on a pest.effect of a pesticide on a pest. 520 insect & mite species & 84 weed species 520 insect & mite species & 84 weed species

currently resistantcurrently resistant

EvolutionEvolution causes genetic resistance causes genetic resistance (any (any cumulative genetic change in a population of cumulative genetic change in a population of organisms). organisms). Natural genetic traits protect some individuals from Natural genetic traits protect some individuals from

the pesticide, and their traits move onto the next the pesticide, and their traits move onto the next generation.generation.

Short generation times & large population sizes Short generation times & large population sizes promote rapid evolution & quick adaptation.promote rapid evolution & quick adaptation.

Pesticide TreadmillPesticide Treadmill = the cost of applying = the cost of applying pesticides increases while their effectiveness pesticides increases while their effectiveness decreases (due to genetic resistance)decreases (due to genetic resistance)

Resistance ManagementResistance Management = delay the evolution = delay the evolution of genetic resistance to maximize the time a of genetic resistance to maximize the time a pesticide remains effective.pesticide remains effective. Maintain a nearby “Maintain a nearby “refugerefuge” of untreated plants. Pests ” of untreated plants. Pests

there won’t be affected, and will breed with the newly there won’t be affected, and will breed with the newly resistant pests to keep the gene pool variable.resistant pests to keep the gene pool variable.

Avoid repeated use of same herbicide on the same Avoid repeated use of same herbicide on the same field.field.

Ecosystem ImbalancesEcosystem Imbalances

Pesticides Pesticides affect species other than intendedaffect species other than intended pests. pests. Beneficial insects, birds, and others are often killed.Beneficial insects, birds, and others are often killed.

Indirectly responsible for Indirectly responsible for killing many natural killing many natural enemies of the pestsenemies of the pests (may starve/migrate looking (may starve/migrate looking for food after pesticide use)for food after pesticide use) Kill natural enemies directly sometimes Kill natural enemies directly sometimes

eating prey who have pesticides in their bodieseating prey who have pesticides in their bodies

Pest population reboundsPest population rebounds soon due to lack of soon due to lack of predators!predators!

Creation of new pests (Creation of new pests (minor pests become major minor pests become major pestspests)) Pesticide may kill a certain pest’s natural predators, Pesticide may kill a certain pest’s natural predators,

parasites, and competitors.parasites, and competitors.

Persistence, Bioaccumulation & Persistence, Bioaccumulation & BiomagnificationBiomagnification

DDT: falcons, pelicans. bald eagles, DDT: falcons, pelicans. bald eagles, ospreys, and many other birds are very ospreys, and many other birds are very sensitive. Thin shells = chicks die.sensitive. Thin shells = chicks die.

1972 – DDT banned. Bird reproduction 1972 – DDT banned. Bird reproduction increased.increased.

3 characteristics:3 characteristics: PersistencePersistence = natural decomposers haven’t = natural decomposers haven’t

yet evolved ways to degrade synthetic yet evolved ways to degrade synthetic pesticides, so they accumulate in the pesticides, so they accumulate in the environment.environment.

Bioaccumulation / BioconcentrationBioaccumulation / Bioconcentration = = buildup of a persistent pesticide in the body buildup of a persistent pesticide in the body (usually fatty tissues)(usually fatty tissues)

Biological Magnification / AmplificationBiological Magnification / Amplification = = those higher on the food chain have higher those higher on the food chain have higher conc. of pesticides stored.conc. of pesticides stored.

STORY TIME!

WHO’s

Operation Cat Drop

Mobility in the EnvironmentMobility in the Environment Pesticides tend to move through soil, Pesticides tend to move through soil,

water, & air, sometimes long distances. water, & air, sometimes long distances. Wash into rivers & streams to harm fishes Wash into rivers & streams to harm fishes

(death or other health problems like bone (death or other health problems like bone degeneration).degeneration).

14.1M US residents drink water w/ traces 14.1M US residents drink water w/ traces of 5 common herbicides, causing slightly of 5 common herbicides, causing slightly elevated cancer risk elevated cancer risk

Air mobility causes problems as well.Air mobility causes problems as well.

Short Term EffectsShort Term Effects Mild poisoning: nausea, vomiting, headachesMild poisoning: nausea, vomiting, headaches More serious: permanent nervous system damage or More serious: permanent nervous system damage or

other organs.other organs. Globally: more than 3M poisoned, 220,000 die each year.Globally: more than 3M poisoned, 220,000 die each year. Worse in Developing nationsWorse in Developing nations – no safety training & lax – no safety training & lax

laws.laws.

Bhopal (India) Disaster – methyl isocyanate gas Bhopal (India) Disaster – methyl isocyanate gas explosion. Converted to hydrogen cyanide (deadly) in explosion. Converted to hydrogen cyanide (deadly) in the air.the air.

2500 died, survivors had serious respiratory, ophthalmic, 2500 died, survivors had serious respiratory, ophthalmic, intestinal, reproductive, and neurological problems. intestinal, reproductive, and neurological problems. Survivors were paid $500 each. Cleanup still needs to Survivors were paid $500 each. Cleanup still needs to be addressed. be addressed.

Long Term EffectsLong Term Effects

Can cause Can cause cancercancer (lymphoma, leukemia, (lymphoma, leukemia, brain/lung/testicle/breast)brain/lung/testicle/breast)

SterilitySterility possible. possible. Higher rates of Higher rates of miscarriagemiscarriage Greater risk: children of ag.workers (birth Greater risk: children of ag.workers (birth

defects/stunted limbs)defects/stunted limbs) ImmuneImmune system suppression system suppression Potential link to Potential link to Parkinson’sParkinson’s. .

Pesticide & Endocrine DisruptorsPesticide & Endocrine Disruptors Reproductive problems in animals (endocrine disrupters)Reproductive problems in animals (endocrine disrupters) River Otters: abnormally small penisesRiver Otters: abnormally small penises Female sea gulls: behavioral changes – pair with other Female sea gulls: behavioral changes – pair with other

females.females. Our Stolen FutureOur Stolen Future = 1996 book by = 1996 book by

Colburn/Dumanoski/MyersColburn/Dumanoski/Myers Suggested human hormone systems may be disrupted, as well Suggested human hormone systems may be disrupted, as well

as other health problems (breast/testicular cancer, male birth as other health problems (breast/testicular cancer, male birth defects, low sperm counts).defects, low sperm counts).

Cause-Effect relationship still not established.Cause-Effect relationship still not established. Should DDT be banned immediately worldwide??Should DDT be banned immediately worldwide?? May internationally ban 9 pesticides suspected of May internationally ban 9 pesticides suspected of

endocrine disruption. endocrine disruption.

PROS/CONS of DDT

Research the pros & cons of DDT Research the ban on DDT by the World

Health Organization Make a list of arguments for & against a

potential worldwide ban on DDT. We’ll discuss next class.

Pesticides & ChildrenPesticides & Children

Household Pesticides greater threat to childrenHousehold Pesticides greater threat to children Play on floors/lawns w/ more pesticide exposure.Play on floors/lawns w/ more pesticide exposure. Bodies still developingBodies still developing May cause brain cancer & childhood leukemia.May cause brain cancer & childhood leukemia.

EPA estimate: EPA estimate: 84% of US homes using pesticide 84% of US homes using pesticide products.products. Pest strips, bait boxes, flea collars, bug bombs, etc.Pest strips, bait boxes, flea collars, bug bombs, etc.

Pesticide residue on foodPesticide residue on food May affect dev.of intelligence & motor skills of May affect dev.of intelligence & motor skills of

young children.young children.

Cultivation MethodsCultivation Methods

InterplantingInterplanting = alternating rows of different = alternating rows of different plantsplants

Strip CuttingStrip Cutting = harvest one crop at a time, = harvest one crop at a time, leaving habitat for natural predators of the leaving habitat for natural predators of the pests.pests.

Planting around marginsPlanting around margins to keep habitat to keep habitat for natural predators.for natural predators.

Proper timing & crop rotationProper timing & crop rotation

Genetic ControlsGenetic Controls Create a pest-resistant crop by Create a pest-resistant crop by crossing pest-crossing pest-

resistant plants w/ non-resistantresistant plants w/ non-resistant.. Problems: fungi/bacteria/pathogens evolve Problems: fungi/bacteria/pathogens evolve

quickly = must keep ahead!quickly = must keep ahead!

Genetically Modified (GM)Genetically Modified (GM) Plants can be created quickly Plants can be created quickly ! ! It could harm other parts of the environment It could harm other parts of the environment !!

Many varieties are selective. Modify the gene = Many varieties are selective. Modify the gene = more general & more widely effective! more general & more widely effective!

Biological ControlsBiological Controls use naturally occurring disease use naturally occurring disease

organisms/ parasites/ predators to control organisms/ parasites/ predators to control pests.pests.

>300 species have been introduced.>300 species have been introduced. Careful that new control Careful that new control

agents don’t become pests! agents don’t become pests! (weevil/thistle)(weevil/thistle)

BtBt = soil bacterium that’s = soil bacterium that’s a great natural insecticide. a great natural insecticide.

QuarantineQuarantine restrict import of exotic plants/animals that restrict import of exotic plants/animals that

may harbor pests.may harbor pests. Effective, but not foolproof.Effective, but not foolproof. Ex: Mediterranean Fruit Flies (medflies) in Ex: Mediterranean Fruit Flies (medflies) in

California… it’s worked, but they keep California… it’s worked, but they keep coming back! coming back!

Pheromones & HormonesPheromones & Hormones

PheromonesPheromones = natural = natural substances produced by substances produced by animals to stimulate a animals to stimulate a response within their response within their species.species. Use to lure insects into trapsUse to lure insects into traps!!

HormonesHormones = natural = natural chemicals produced by chemicals produced by insects to regulate their own insects to regulate their own growth/metamorphosis.growth/metamorphosis. Given at wrong time: abnormal Given at wrong time: abnormal

development & possible death.development & possible death.

Integrated Pest Integrated Pest Management (IPM)Management (IPM)

Combine many methods of pest mgmt.Combine many methods of pest mgmt. Pesticides are a last resort, and weak ones are Pesticides are a last resort, and weak ones are

used in low amts.used in low amts. Important for Important for Sustainable agricultureSustainable agriculture.. Used to Used to MANAGEMANAGE, not , not ERADICATEERADICATE..

Determine when pest pop reaches an Determine when pest pop reaches an economic economic injury thresholdinjury threshold when benefit of taking action when benefit of taking action exceeds cost.exceeds cost.

Requires education on good strategies.Requires education on good strategies. Overall, IPM use is low. Knowledge to use pesticides Overall, IPM use is low. Knowledge to use pesticides

is less than to use IPM. is less than to use IPM.

Reproductive ControlsReproductive Controls Sterile Male TechniqueSterile Male Technique = sterilize males = sterilize males

w/ radiation or chemicals.w/ radiation or chemicals. Disadvantages: Disadvantages:

Must be done Must be done continuallycontinually to be effective - if to be effective - if discontinued, pest pop will rebound very discontinued, pest pop will rebound very quickly.quickly.

Expensive! Expensive! $$$$$$$$$$$$

Irradiating FoodsIrradiating Foods Use ionizing radiation (gamma rays Use ionizing radiation (gamma rays

from cobalt 60) on harvested food from cobalt 60) on harvested food to kill harmful microorganismsto kill harmful microorganisms

First used in US: 1992First used in US: 1992 Controversial, yet mostly Controversial, yet mostly safesafe.. Can cause Can cause free radicalsfree radicals

(carcinogenic), but they normally (carcinogenic), but they normally occur produced by frying and occur produced by frying and boiling.boiling.

Don’t know the long-term effects Don’t know the long-term effects yet. yet.

FOOD, DRUG, and COSMETICS ACT (1938)FOOD, DRUG, and COSMETICS ACT (1938)

Recognized the need to regulate pesticides Recognized the need to regulate pesticides found in foodfound in food

NO MEANS FOR REGULATION!NO MEANS FOR REGULATION! Made more effective in 1954: Made more effective in 1954: Pesticide Pesticide

Chemicals Amendment (AKA Miller Chemicals Amendment (AKA Miller Amendment)Amendment) required establishment of required establishment of acdeptable and unacceptable levels of acdeptable and unacceptable levels of pesticides in food.pesticides in food.

Delaney ClauseDelaney Clause (1958): no substance capable (1958): no substance capable of causing cancer in test animals or in humans of causing cancer in test animals or in humans would be permitted in processed food.would be permitted in processed food. Didn’t cover raw foods, & lacked data on older Didn’t cover raw foods, & lacked data on older

pesticides.pesticides. Almost impossible for newer pesticides to pass Almost impossible for newer pesticides to pass

standards standards

Federal Insecticide, Fungicide, and Rodenticide ActFederal Insecticide, Fungicide, and Rodenticide Act (1947): (1947): regulate effectiveness of pesticidesregulate effectiveness of pesticides (restrict use (restrict use

of ineffective pesticides).of ineffective pesticides). Now requires testing and registration of active Now requires testing and registration of active

ingredientsingredients Don’t meet FDCA standards? No registration with Don’t meet FDCA standards? No registration with

FIFRA.FIFRA. 1972: EPA gets regulatory authority, and has now 1972: EPA gets regulatory authority, and has now

banned or restricted use of many chlorinated banned or restricted use of many chlorinated hydrocarbons (DDT)hydrocarbons (DDT)

Amended FIFRA in 1988 to require registration of older Amended FIFRA in 1988 to require registration of older pesticides, so now must face the same standards of new pesticides, so now must face the same standards of new pestic.pestic.

Didn’t address groundwater cont., establish standards Didn’t address groundwater cont., establish standards for residues on food or farm worker safety, require for residues on food or farm worker safety, require companies to disclose potentially harmful companies to disclose potentially harmful inertinert ingredients ingredients

Food Quality Protection ActFood Quality Protection Act

1996: amended FDCA & FIFRA. 1996: amended FDCA & FIFRA. Established identical pesticide residue limits for Established identical pesticide residue limits for

raw produce and processed foods.raw produce and processed foods. Must consider child susceptibility when Must consider child susceptibility when

considering pesticide residue limits.considering pesticide residue limits. Must set limits for all health risks, not just Must set limits for all health risks, not just

cancer.cancer. Must test for endocrine-disrupting propertiesMust test for endocrine-disrupting properties. .