AP Environmental Science: The Pesticide Dilemma
Name: _____
References: Wright, Environmental Science, chapter 13
Raven, The Environment
Readings from Silent Spring and The Lorax
http://on.aol.ca/video/pesticide-poisoning-in-rural-cambodia-502318605
Key Terms and Vocabulary:
Pest, weeds, vectors, herbicides, pesticides, chemical treatment, ecological pest control, integrated pest
management (IPM), endocrine disruptors, bioaccumulation, biomagnification, resurgence, pesticide
treadmill, synergistic effect, cultural control, natural enemies, genetic control, natural chemical control,
hormones, pheromones, economic threshold, insurance spraying, cosmetic spraying, field scouts, organic
food, Organic Foods Protection Act, microbial, plant-incorporated protectants, Delaney clause, Food
Quality Protection Act (FQPA), prior informed consent (PIC).
Different philosophies of pest control
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Chemical treatment of pests: eradicates or decreases pest numbers
Gives only short-term protection
Has highly damaging side effects to other organisms
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Ecological control: long-lasting protection
Based on knowledge of the pest’s life cycle and ecological relationships
May be other organisms or chemicals
May be highly specific to one organism
May manipulate some aspect of the ecosystem
A. Definitions
How are pests defined? Examine the pests on page 319 Fig 13-1 (slide 4)
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Most pests are organisms that directly compete with humans. It could be an
insect or other small animal that destroys garden plants, trees, etc.
Pathogens, wild animals, insects, mold, etc.
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Agricultural pests: feed on crops, ornamental plants, or animals
Insects, fungi, viruses, worms, snails, rats, mice, birds
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Weeds: compete with crops, forests, grasses
How are pesticides defined?
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Pests are named by the activity they affect or what they live on
What are vectors? carry diseases (i.e., malaria, parasites)
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What are Biofouling organisms? They settle in aquatic environments
Interfere with shipping, clog pipes, settle on buoys
Slide 6 borer trap
Slide 7 Khapra
What are Herbicides? kill plants
Where have you seen the use of herbicides on or near the Morven campus?
Japanese Knotweed
Giant Hogweed.
What are Insecticides?
What pest has drastically affected Canadian and North American forestry? (chapter 7)
Pine beetle
The emerald ash borer threatens 7.5 billion U.S. trees
What are Fungicides? Give examples of where these are used. Page 318
What are rodenticides
kill rats, mice
A. What are Broad- and narrow-spectrum pesticides?
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Narrow-spectrum pesticides kill only the organism for which it was intended
and do not harm any other species
Most pesticides are broad-spectrum pesticides, do not degrade readily and/or
break down into compounds as dangerous as or more dangerous than the
original pesticide
B. What are First- and second-generation pesticides? page 322
Pre 1940s, pesticides were either inorganic (contained lead, mercury,
and arsenic) or organic compounds (botanicals and synthetic
botanicals)
i. First-generation pesticides were the first substance used to control
pests, and represent both inorganic and botanical pesticides for
example lead, arsenic, mercury, cyanide. These build up in soils,
inhibit plant growth and poison organisms.
ii. Second-generation pesticides represent the vast arrays of poisons in
use today and were developed through synthetic organic chemistry.
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You must be able to differentiate between botanical pesticides and
synthetics!
B. Major groups of insecticides
1. Chlorinated hydrocarbons were widely used from the1940s
until the 1960s when most were banned
a. Examples include DDT
dichlorodiphenyltrichloroethane (to be discussed in
detail later), endosulfan, lidane, and methoxychlor
b. Synthetic, broad-spectrum insecticides
c. Slow to degrade
d. Persist in the environment and in organisms
2. Organophosphates contain phosphorus and have generally
replaced chlorinated hydrocarbons in large-scale agricultural
use
a. Examples include methamidophos, dimethoate, and
malathion
b. More poisonous than other types of insecticides
c. Highly toxic to terrestrial and aquatic organisms
d. They do not persist in the environment for as long as
chlorinated hydrocarbons
3. Carbamates are derived from carbamic acid
a. Examples include carbaryl and aldicarb
b. Broad-spectrum insecticides
c. Generally not as toxic to mammals
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C. Major groups of herbicides
They tend to be grouped according to how they act and what they kill
1. Selective herbicides kill only certain types of plants
a. Broad-leaf herbicides kill plants with broad leaves but
do not kill grasses
b. Grass herbicides kill grasses but are safe for most other
plants
2. Nonselective herbicides kill all vegetation
D. Inorganic pesticides such as arsenic, copper, mercury and lead are highly
toxic and persistent.
E. Botanical Pesticides such as pyrethrum which is extracted from
chrysanthemum flowers.
Provide some information on DDT. Page 322 onwards and other.
http://www.youtube.com/watch?v=Ipbc-6IvMQI Pesticides DDT Rachel Carson - Silent
Spring. 11min
http://www.youtube.com/watch?v=-UiCSvQvVys DDT let’s put it everywhere 1946
http://www.youtube.com/watch?v=gtcXXbuR244 DDT so safe you can eat it.
Irony in all of these videos.
(slide 15)
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Chemist Paul Müller studied DDT in the 1930s
Dichlorodiphenyltrichloroethane
First synthesized 50 years earlier
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As a pesticide, it was extremely successful
Extremely toxic to insects, not humans or mammals
Very cheap
Broad spectrum: effective against many insect pests
Persistent: provided long-lasting protection
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DDT saved millions of lives
The military used it to control lice (cause typhus fever)
It also controlled dengue fever, mosquitoes (malaria)
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Müller was awarded the 1948 Nobel Prize in medicine
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After World War II, DDT was used to control spruce budworms, mosquitoes,
Dutch elm disease
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Farmers could ignore other pest control methods (crop rotation and destruction of
crop residues)
They grew less resistant crops in more areas
Now, the EPA regulates 18,000 pesticide products
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Rachel Carson’s Silent Spring (1962) documented the effects of uncontrolled use
of pesticides in the U.S.
If use continued, there might be a spring with no birds
With ominous consequences to humans as well
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Agricultural and chemical industries said the book was unscientific and would
stop human progress
Others said it was breakthrough in environmental understanding
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DDT and other hydrocarbons have been banned in the U.S. and other developed
nations
Pesticide use in the US. Examine Fig 13-4 page 321(slide 9)
Read about the Pesticide Expense. Page 320.
II. Benefits and costs of using pesticides
A. Benefits of pesticides
1. Disease control
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2. Crop protection _________higher yields at first.
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B. Problems associated with using pesticides
1. Development of resistance by pests
Refer to page 317 bedbugs and 326 to 327
In 50 years 520 species of insects and 82 species of weeds have become
resistant to pesticides.
The cost of applying pesticides increases while their resistance increases.
How? Every time a pesticide is used some of the pests survive. They pass
on their resistant genes to new generations. This leads to resistant gene
accumulation.
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Chemical pesticides lose their effectiveness
More and more quantities must be used
Newer, more potent pesticides must be developed
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It takes more pesticide to get the same results
In 1946, 2.2 lbs of pesticide resulted in 60,000 bushels of corn being protected; in
1971, it took 141 lbs
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Many pest species have developed resistance
Stored product, medical, and veterinary pests
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Pesticides destroy sensitive individuals
The resistant ones survive
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Resistance develops rapidly in r-selected species
They have high reproductive capacity
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Repeated pesticide applications select for genetic lines that are highly, or totally,
resistant to pesticides
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The Colorado potato beetle developed resistance to 52 compounds (including
cyanide) in 50 years
2. Imbalances in the ecosystem – “Balance of nature”
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Pesticides kill organisms other than the ones they are meant for. eg.
Small species.
This is typical of broad insecticides like Dieldrin. (banned)
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The stress of having the pesticide in the animal’s body may also
make it more vulnerable
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Natural enemies of pests
starve or migrate in
search of food and so
these animals reduce in
number.
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New pests take over. e.g.
Scale insects on lemon
trees when DDT was
used to kill insect pests
which prey on the scale
insect.
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Resurgence: occurs after a pest has almost been eliminated
o The population recovers and even explodes
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Secondary pest outbreak: insects that were originally of no concern
explode and create new problems
o They quickly become resistant to pesticides
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Pesticide treadmill: use of pesticides increases resistance and
secondary-pest outbreaks
3. Persistence, Bioaccumulation, and Biological Magnification

These are all typical of DDT which is a chlorinated hydrocarbon.
Chlorinated hydrocarbons are very stable and breakdown very
slowly (persistence).
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Bioaccumulation is the build up of persistent chemicals in an
organanisms body.
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Biological magnification is the increase in concentration of pesticide
concentrations at successive levels of the food chain.
Refer to page 326 and to Fig 13-8
Fig. 23.9 Biological magnification of DDT in a Long Island Salt Marsh.
What are the problems with nonpersistent pesticides?
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Nonpersistent pesticides are extensively used
Organic phosphates (malathion, parathion, chlorpyrifos)
Carbamates (aldicarb, carbaryl)
They break down into nontoxic products in a few weeks
Nonpersistent pesticides are highly toxic
The EPA must develop health-based standards to address the risk of children’s
exposure to pesticides
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Carbofuran kills 2 million U.S. birds/year
The EPA revoked all uses in 2008
Beneficial insects (bees, butterflies) are highly sensitive
Predatory insects and spiders are also harmed
Resurgencies, secondary-pest outbreaks, and resistance to nonpersistent pesticides
occur
Comment on synergism page 328
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Synergistic effects: multiple factors work together to create an unexpected
outcome
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What is causing the decline of bees?
Colony collapse disorder is not caused by one thing
It could be a mixture of pests, pathogens, parasites, viruses, poor nutrition, and stress
Pesticides can interact with these factors
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Bees exposed to pesticides had low growth rates, ate less, and trouble finding
their way back to the hive
They produced fewer queens and danced less
4. Mobility in the environment
Pesticides move through the soil, water and air.
Risks to human health
Refer to table 13-1 and page 324 to 325
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Short-term effects = nausea, vomiting and headaches, abdominal pain, shock,
respiratory failure, allergic reactions, seizures, pneumonia, coma
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About 39 million people/yr suffer acute poisoning
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Most acute cases occur in developing countries
Untrained users have little information on pesticides Fig 13.6
People get sprayed, incorrectly store pesticides, or drink water from contaminated
containers
Chronic health problems
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Pesticides may cause:
Cancer (lymphoma, breast cancer)
Dermatitis, nerve damage, birth defects, infertility
Disruption of the immune and endocrine systems
Parkinson’s disease, low white blood cell counts
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Pesticides as Endocrine Disruptors.
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Many pesticides affect reproductive hormones
Increased breast cancer in humans
Abnormal sexual development in alligators, fish, etc.
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Very low levels mimic or disrupt estrogenic hormones (potent sexual chemicals)
The Use of Herbicides in warfare.
http://www.nytimes.com/video/us/100000002872288/agent-orange.html Agent Orange Dioxin
Bhopal Disaster in India – gas escape from pesticide plant in Bhopal
http://timesofindia.indiatimes.com/india/Make-Union-Carbide-pay-for-Bhopal-tragedyAmnesty-writes-to-Modi-Obama/articleshow/46016416.cms
C. Solutions to the Pesticide Dilemma 13.3 page 329
Alternative pest control methods
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Ecological control: What is this? It manipulates natural factors without damaging
the environment or human health
Depends on understanding the pest and its relationship with its host and
ecosystem
Refer to fig 13-11 Very important
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Insects have complex life cycles
Each stage may be vulnerable to abiotic factors, predators, or parasites. Biological
control recognizes different life stages and attacks the insect using this knowledge
Four categories of ecological pest control are:
Cultural control, natural enemies, genetic control, and natural chemical control
Differentiate between these.
1. Cultural Control Fig 13.12
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A nonchemical change of environmental factors
The pest finds
the area unsuitable or can’t access its target
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Cutting lawns too short results in weeds
Keep grass at least 3 inches high
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Avoid plants that attract pests (e.g., roses)
Plant plants that repel pests (marigolds, chrysanthemums – secrete pyrethrin a natural
insecticide.)
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Hedgerows, fencerows, and shelterbelts provide refuge for pest predators (birds,
amphibians, praying mantises)
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Plowing or burning crop residues decreases diseases
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Example in Fig 13-12 – Wheat rust infests barberry – eliminating this pkant
controls the wheat rust.
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Garden mulch decreases weeds and prevents erosion
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By rotating crops (changing crops each year) pests
of the first crop can’t feed on the second crop
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Controls nematodes in the soil with marigolds
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Monocultures are efficient but allow pest outbreaks
2. Natural enemies/biological controls
Fig 13-14
3. Genetic controls
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Most insects and plant pathogens attack only one or a few closely related species
Incompatible plants are not attacked
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Genetic control strategies: develop genetic traits
in the host species that provide incompatibility
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The hosts are resistant to attack
Potatoes are now resistant to the blight in Ireland that caused a million people to
starve in 1845–1847
Biotechnology and Bacillus thuringiensis page 333
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Incorporating the protein coat of a virus into the plant
The plant becomes resistant to infection by the virus
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Make a gene-silencing chemical that interferes with an insect’s normal cell
function
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A protein from the bacteria Bt can be put into plants
Kills larvae from plant-eating insects
But it is harmless to mammals, birds, other insects
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Resistance to Bt and secondary pests are increasing
Farmers must plant 20% of their fields in non-Bt crops
The resistance genes are diluted
4. Natural chemical control - Pheromones and hormones
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Hormones: chemicals produced in organisms that control development and
metabolic functions
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Pheromones: influence behavior of others of the same species
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Natural chemicals are nontoxic and highly specific
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Juvenile hormone: when sprayed on caterpillars, they do not pupate
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Mimic: a synthetic ecdysone (insect molting hormone) used in moths and
butterflies
Mimic starts the molting process, but doesn’t end it
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Insects use pheromones to attract mates
Pheromones can be identified and synthesized
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Trapping technique: pheromone lures pests into traps
Or they eat poisoned bait
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The confusion technique: a widely dispersed pheromone confuses males so they
can’t find mates
Fig 13-20
6. Integrated pest management (IPM) Fig 13.22
What is this?
Involves a combination of pest control strategies – chemical and nonchemical – that are unique to the crop and the location.
Non chemical involve the use of natural predators, the use of sex
pheromones to attract bugs to a place
away from the crops, the introduction
of sterile breeding partners and crop
rotation.
If chemical products are used they are
used on specific targets reduce their
use.
Would you buy rice from Indonesia? Explain your reasoning. Page 336
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The economic and environmental benefits have been remarkable
The government saved millions by not buying pesticides
Farmers have not had to buy pesticides and equipment
Thousands of tons of pesticides did not enter the environment
Fish are thriving in the rice paddies
Farmers, consumers, and wildlife have increased health benefits from reduced
pesticide use
Irradiating foods
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Organically grown food
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Many farmers are turning away from pesticides, chemical fertilizers, antibiotics,
and hormones
For grains, vegetables, and livestock
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Organic farms are small and use traditional farming methods to grow diverse
crops
They are tied to local economies
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Organic foods in the U.S. bring in $26 billion/year
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Organic crops have lower yields and higher costs
But also lower expenses
Crops lack, or have much smaller, pesticide residues
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II. Legislation and international issues
Three agencies are involved in protecting consumers from pesticides on food:
A. EPA: sets allowable tolerances for residues
B. FDA: monitors and enforces tolerances on most foods
C. Food Safety and Inspection Service (USDA): monitors and enforces
tolerances on meat, poultry, and eggs
A. U.S. Federal pesticide legislation
1. Food, Drug, and Cosmetics Act, FDCA.
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2. Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA, 1947) page
338 _regulates the manufacture and use of pesticides.
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3. Food Quality Protection Act (FQPA) page 339
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4. Plant Protection Act page 338
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5, Organic Food Protection Act 1990 page 337
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Established the National Organic Standards Board (NOSB) under the
USDA
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Standards for certifying organic foods prohibits:
Genetically engineered or irradiated food
Fertilization with sludge or chemicals
Conventional pesticides, antibiotics, growth hormones
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What does the USDA symbol on food represent? This symbol on food
signals that the food or crop was produced on a certified organic farm
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Farmers must be inspected to use the organic seal
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If food is at least 95% organic, they can use the seal
But they cannot claim to be 100% organic
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What is APHIS?
The USDA’s Animal and Plant Health Inspection Service (APHIS) monitors and
controls pests. APHIS regulates the movement of ash tree products
To allow commerce but prevent infestation of the emerald ash borer in 2012
It monitors pests that might attack wildlife and monitors bioengineered species
The EPA adds a 10-fold safety factor in assessing children’s risks from pesticides
Children eat more fruits and vegetables per unit of body weight
They are more susceptible to carcinogens and neurotoxins
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Tolerances: limits set by the EPA on the amounts of a pesticide that can remain in
or on foods
Malathion’s tolerance on crops is 8 ppm
But in milk, it is 0.5 ppm because children drink it
B. Global pesticide issues
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U.S. agencies collaborate with other nations to prevent the spread of pest
organisms
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The International Plant Protection Convention (IPPC)
Set up an international system to quarantine products to prevent pest spread
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The 1995 United Nations Convention on the Law of the Sea (UNCLOS)
Prevents the introduction of marine species to new areas
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The Rotterdam Convention: an international treaty
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Promotes open exchange of information about hazardous chemicals between
countries (including pesticides)
What does POP stand for?
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Look up the “Dirty Dozen” on the table
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What is the Stockholm Convention on Persistent Organic Pollutants?
Stockholm convention eliminates or restricts persistent organic pollutants (2004)
Nations will ban 9 of the 12 most dangerous chemicals
DDT will only be used for malaria control
Accidental releases of two pesticide breakdown products (dioxins, furans) will be
limited
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What would you include in a persuasive article in the Georgia Strait or
North Shore newspaper in an attempt to encourage people to reduce the
use of pesticides? (5 marks)
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How are Persistant Organic Pesticides, POPs, linked to climate change? Page 320
In summary
1. With new farming practices in place, food production has increased dramatically, and
with it, the need for pest control has increased dramatically in the past 50–60 years.
Pest control has taken on two basic forms: chemical treatment or integrated pest
management.
2. Use of chemical pesticides, including DDT have simultaneously allowed for higher
food production and for increased pest resistance, human health conditions, and
effects on the broader environment. Recently, we have focused on the use of
synthetic organic chemical pesticides with little resolution to our long standing issues
with pesticides.
3. Ecological control of pests is a way of using natural factors to control pests in such a
way that is not harmful to humans and allows for sustainable agriculture.
4. Agriculture is moving away from pesticides and towards integrated pest management
and organically grown food as consumer concern over pesticides increases.
5. Policies have been put in place that address the effect of pesticides on human health,
the need for proper training for those who work with pesticides, and the need to keep
food free of pesticide residues.
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