Chapter 22 The Pesticide Dilemma
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Transcript of Chapter 22 The Pesticide Dilemma
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What is a Pesticide?Major Kinds of Pesticides
Benefits and Problems With Pesticides Alternatives to Pesticides Laws Controlling Pesticides Use
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Types: InsecticidesHerbicidesFungicidesRodenticides
Regulated by the EPA
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Broad spectrum pesticidekills a variety of organisms, not just the targeted
organismsDoesn’t degrade = doesn’t decompose = persist
and then accumulate in environment or organism.
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o First generation pesticide• Inorganic compounds
• Lead and mercury• Botanicals- plant derived pesticides
• Nicotine
Second generation pesticide Synthetic poison Ex: DDT
for mosquitoesused to controlmalaria
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Chlorinated HydrocarbonsOrganic compound containing Chlorine
Ex: DDTPersist (do not degrade)**Rachel Carson – “Silent Spring” = problems w/
pesticides Organophosphates
Developed during WWIIHIGHLY toxic (bees/humans), but do not persistCurrently used in agriculture
EX: Malathion, diazinon Neurotoxin, especially children
CarbamatesNot as toxic to mammals
Ex: household sprays/traps
RACHEL CARSON…ENVIRONMENTAL GODDESS
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How are organophosphates different than chlorinated hydrocarbons?
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Selective HerbicidesKill only certain types of plantsCan be classified to the type of plant they kill
Broad-leaf herbicidesEx: 2,4-D (2,4 dichlorophenoxyacetic
acid)Ex: 2,4,5 –T (2,4,5,
trichlorophenoxyacetic acid)Used with wheat, corn, rice (cereal
grains = grasses)Grass herbicides
Nonselective – kill all vegetation
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When would you use a broad-leaf herbicide? A grass herbicide
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Sprayed to kill vegetation – Agent White, Blue, Orange
Ecological damage – decades to repair – destroyed mangroves (habitat for fish and coast protection from erosion), forests destroyed
Human effectsAgent Orange = (combination of broad leaf
herbicides + dioxins) birth defects, stillbirths, cancer
Dioxin in breastmilk – Vietnamese = 1800 ppt, US = 4 ppt
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Benefit 1. : Disease controlFleas, lice and mosquitoes carry disease
• MalariaMalaria- mosquito born
• 2.7 million people die each year
• Few drugs available, so focus is on killing mosquitoes
• DDT
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Benefit 2. : Crop ProtectionPests eat and destroy 1/3
of world’s cropsFarmers save $3 to $5 for
every $1 they invest in pesticides
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Name the 2 reasons why pesticides are used?
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Problem: Evolution of Genetic ResistancePest populations are evolving resistance to
pesticides (right)Pesticide TreadmillCost of applying pesticide increases
Because they must be applied more frequently or in larger doses
While their effectiveness decreases Because of increased genetic resistance in pests
Resistance Management Refuge of untreated plants: allows mating of
treated/untreated pests to delay resistance Remove surviving weeds after herbicide application
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Problem: Kills non-target organismsSpraying to kill insects can kill birds, fish, beesDespite 33-fold increase in pesticides since the
1940s, crop loss has not really changed
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Problem: Creation of New PestsPesticide kills predator or competitor of minor pest
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Problem: Persistence, Bioaccumulation, and Biological Magnification Bioaccumulation
The buildup of a persistent pesticide or other toxic substance in an organisms body
Biological magnification• Increased concentration
of toxic chemicals in tissues of organisms at higher trophic levels, stored in fat• Ex: Peregrine falcons (right),• Bald Eagles
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Problem: Mobility in the Environment Do not stay where they are applied harm non-
target organisms. Move through soil, water (run-off) and air
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Effects of PesticidesHandling food with pesticide residue
• Mild case: nausea, vomiting, headaches
• Severe case: damage to nervous system (neurotoxin!!!)
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Long-term Effects of Pesticides:Cancer- lymphoma and breastSterilityMiscarriageBirth defectsHarms immune system
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1984 Bhopal, India Explosion at pesticide plant released
toxic gas (cyanide) Many died immediately Others: problems to respiratory,
reproductive, nervous systems
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Using cultivation methods to control pests Interplant mixtures of plants (alternating rows):
polyculture !!Crop rotation
Biological ControlUse of naturally occurring disease organisms,
parasites or predators to control pestsMust take care that introduced agent does not
attack unintended hosts
CANE TOADS
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Pheromones and HormonesCan use pheromones to lure pests to traps
Reproductive ControlsSterilizing some of the membersSterile male technique: sterilize in lab and then
release
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IPMCombination of pest
control methods that keeps pest population low without economic loss
Controls pests, not eradicate
Cons: requires a lot of knowledge
Conventional pesticides are used sparingly when other methods failHOW DOES IPM DIFFER FROM
ORGANIC FARMING?
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Farmers MONITOR pests and act when injury threshold is reached.
EX: Cotton – 1% of land; 50% of pesticide use in US. – WOW!! Organic cotton helps reduce pesticide use.
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Rice Production in IndonesiaPredators of pests normally kept in check
by pesticides
IPM IPM IntroduceIntroduce
dd
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Food, Drug, and Cosmetics Act (1938) –FDCA – determined pesticides need regulation!
Delaney Clause (1958) – no cancer causing substances; not cover raw foods.
Federal Insecticide, Fungicide, and Rodenticide Act (1947) – FIFRA – regulates what pesticides are sold based on safety.
Food Quality Protection Act (1996) – stricter guidelines on pesticide limits, covers raw food, reduce time to ban harmful pesticide.
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Some US companies still make banned or seriously restricted pesticidesProduct is exported
Importation of food tainted with banned pesticides from other countries
Global ban of persistent organic pollutantsStockholm Convention on Persistent
Organic Pollutants (2004) – requires countries to eliminate usage of the 12 most toxic chemicals.
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