Get out your HW & In your notes…
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Do you think that we should use
pesticides?
What applications do you believe
pesticides are acceptable for, if any?
Pesticides
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What is a Pest?
Any organism that is
destructive or
annoying (mostly
weed and insects).
What are some
Examples:
Mosquitoes carry
malaria, grasshopper
destroys crop, rats
carry disease.
What is a Pesticide? What are 2 Types
of Pesticides?
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Pesticide - any chemical used to kill pests
• insecticide - kills insects
• herbicide - kills plants
Pest Management
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Pest management:
ways to control
pests
History
• 1800’s - used early
pesticides
containing natural
minerals such as
sulfur, arsenic,
copper, lead, and
mercury.
History Continued
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World War II - started
using man-made
chemicals called
chlorinated
hydrocarbons in
order to create a
nerve gas. They were
tested on insects.
They worked and
were cheap to make.
Vastly used for
agriculture
EX. DDT
Problems
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Growing monocultures attracts many insect
pests of that plant. Pesticides were therefore
used more often.
Problems- What happens when
you spread a pesticide?
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Kills most things including the organisms that
are helpful (only 1 out of every 8 insect species
are pests).
Problems- Where do the Pesticides go?
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Many pesticides persist (don’t decompose) in
the environment. They stay in soil or runoff
into water.
Problems- Why is it bad if we constantly kill
some of the pests? Think Evolution…
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Overtime insects became resistant (survived
and passed that trait to the next generation) to
the pesticide. More pesticide was used.
Problems- What is
Bioaccumulation?
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Pesticides bioaccumulate- pesticides are
absorbed and accumulate in the fat of animals
through the food chain.
Problems: DDT
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DDT was very
persistent and affects
bird reproduction
through
bioaccumulation.
Some eggs didn’t
develop or the eggs
shells were very thin
causing them to crack.
Bald eagles and
ospreys became
endangered.
Rachel Carson- Silent Spring
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Rachel Carson
writes “Silent
Spring” about the
risks of pesticides DDT is banned.
Other
hydrocarbons were
still used
(Heptachlor and
Chlordane) (read
pgs 269 – 272)
What are 2 Ways Pesticides can be
Used?
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Selective pesticide - only kills one pest.
Broad spectrum pesticide - can kill many
at once plus everything else.
What the EPA does Now…
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Now the EPA and FDA
evaluate the benefits
and risks of pesticides
to all people involved
(workers and
consumers)
EPA requires signal
words and precautions
on labels) – pgs 262263
What the EPA does Now…
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EPA sets tolerance levels• maximum amount of pesticide residue allowed in
or on food.
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Maximum contaminant levels (MCLs)
• are tolerance levels for water and are lower than
food since more water is consumed
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*Even with the EPA regulations, there may
be some risks to you and the environment.
How do the following pictures make
you feel about DDT?
Malaria
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Malaria kills
more than a
million people
worldwide
each year—90
percent of
them in
Africa; 70
percent
children under
the age of
five.
You Decide…
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Do the risks out weigh the benefits?