Download Chapter 23: The Pesticide Dilemma

Chapter 23
The Pesticide Dilemma
Overview of Chapter 23
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What is a Pesticide?
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Major Kinds of Pesticides
Benefits and Problems With Pesticides
Risks of Pesticides to Human Health
Alternatives to Pesticides
Laws Controlling Pesticides Use
The Manufacture and Use of Banned
Pesticides
What is a Pesticide
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Broad spectrum pesticide
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A pesticide that kills a variety of organisms, not just
the targeted organisms
First generation
pesticide
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Inorganic compounds
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Lead and mercury
Botanicals- plant
derived pesticides
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Nicotine and pyrethrin
What is a Pesticide
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Second generation pesticide
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Synthetic poison
Ex: DDT
Major Groups of Insecticides
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Chlorinated Hydrocarbons
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Organophosphates
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Organic compound containing Chlorine
Ex: DDT
Slow to degrade and persist in the environment
Banned or largely restricted
Organic compounds that contain phosphorus
Most poisonous insecticide
Do not persist as long as chlorinated
hydrocarbons
Carbamates
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Derived from carbamic acid
Major Kinds of Herbicides
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Selective Herbicides
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Kill only certain types of plants
Can be classified to the type of plant they kill
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Broad-leaf herbicides
Grass herbicides
Ex: 2,4-D
Benefits and Problems with Pesticides
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Benefit: Disease control
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Fleas, lice and mosquitoes carry disease
Malaria- mosquito
born
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2.7 million people
die each year
Few drugs
available, so
focus is on killing
mosquitoes
DDT
Benefits and Problems with Pesticides
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Benefit: Crop
Protection
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Pests eat and destroy
1/3 of world’s crops
Farmers save $3 to $5
for every $1 they invest
in pesticides
Problem: Evolution of
Genetic Resistance
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Pest populations are
evolving resistance to
pesticides (right)
Pesticide Resistance
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Pesticide Treadmill
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Cost of applying pesticide increases
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While their effectiveness decreases
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Because they must be applied more frequently or in
larger doses
Because of increased genetic resistance in pests
Resistance Management
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Strategies for managing genetic resistance in
order to maximize the period in which a
pesticide is useful
Delays the evolution of genetic resistance
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A refuge of untreated plants works well
Benefits and Problems with Pesticides
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Problem: Imbalances the Ecosystem
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Spraying to kill insects can affect birds,
rabbits, etc.
Despite 33-fold increase in pesticides since
the 1940s, crop loss has not really changed
Benefits and Problems with Pesticides
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Problem: Creation of New Pests
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Infestation of red scale insects on lemons
after DDT sprayed to control another pest
Benefits and Problems with Pesticides
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Problem: Persistence, Bioaccumulation, and
Biological Magnification
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Bioaccumulation
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The buildup of a persistent pesticide or other toxic
substance in an organisms body
Biological magnification
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Increased concentration
of toxic chemicals in
tissues of organisms at
higher trophic levels
Ex: Peregrine falcons
(right)
Benefits and Problems with Pesticides
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Problem: Mobility in the Environment
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Do not stay where they are applied
Move through soil, water and air
Risk of Pesticides to Human Health
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Short-term Effects of Pesticides
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Handling food with pesticide residue
Mild case:
nausea,
vomiting,
headaches
Severe case:
damage to
nervous
system,
Risk of Pesticides to Human Health
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Long-term Effects of Pesticides
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Cancer- lymphoma
Breast cancer
Sterility
Miscarriage
Birth defects
Decreases body’s ability to fight infection
Potential connection to Parkinson’s disease
Alternatives to Pesticides
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Using cultivation methods to control pests
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Interplant mixtures of plants (alternating rows)
Strip cutting (harvesting only one segment of the
crop at a time; leaves a refuge for pests and their
predators)
Proper timing of planting, fertilizing, and
irrigating
Crop rotation
Biological Control
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Use of naturally occurring disease organisms,
parasites or predators to control pests
Must take care that introduced agent does not
attack unintended hosts
Alternatives to Pesticides
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Pheromones and Hormones
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Can use pheromones to lure pests to traps
By applying insect hormones at wrong time in life
cycle, insects can be killed off
Reproductive Controls
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Sterilizing some of the members
Sterile male technique
Alternatives to Pesticides
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Genetic Controls
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Genetically Modified plants (GMOs)
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Bt toxin
Potential problem: may affect non-target species (monarch
butterfly)
Quarantine
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Restriction of the importation of exotic plant and
animal material that might harbor pests
Effective, but not foolproof
Systems Approach- Integrated Pest
Management (IPM)
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IPM
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Combination of pest
control methods that
keeps pest population
low without economic
loss
Conventional
pesticides are used
sparingly when other
methods fail
Systems Approach- Integrated Pest
Management (IPM)
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Rice Production in Indonesia
IPM
Introduced
Alternatives to Pesticides
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Irradiating Food
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Harvested food is expose to ionizing radiation, which
kills many microorganisms
Predominantly used on meats
Somewhat controversial due to potential for free
radicals
Laws Controlling Pesticide Use
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Food, Drug, and Cosmetics Act (1938)
Pesticide Chemicals Amendment (1954)
Delaney Cause (1958)
Federal Insecticide, Fungicide, and Rodenticide
Act (1947)
Food Quality Protection Act (1996)
Manufacture and Use of Banned Pesticides
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Some US companies still make banned or
seriously restricted pesticides
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Product is exported
May lead to the importation of food tainted
with banned pesticides
Global ban of persistent organic pollutants
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Stockholm Convention on Persistent Organic
Pollutants (2004)
Manufacture and Use of Banned Pesticides