On the back of this worksheet…


Do you think that we should use pesticides?
What applications do you believe pesticides are acceptable for, if any?



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?
Pesticide - any chemical used to kill pests
• insecticide - kills insects
• herbicide - kills plants



Pest management: ways to control pests
History
• 1800 ’ s - used early pesticides containing natural minerals such as sulfur, arsenic, copper, lead, and mercury.




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



Question: Most farms are a monoculture, how could this be a problem?
Growing monocultures attracts many insect pests of that plant. Pesticides were therefore used more often.



Question: What happens to organisms when you spread a pesticide?
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?

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…
Overtime insects became resistant (survived and passed that trait to the next generation) to the pesticide. More pesticide was used.

Problems- What is
Bioaccumulation?

Pesticides bioaccumulate.

This is when pesticides are absorbed and accumulate in the fat of animals through the food chain.



Read the article
Answer the questions




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 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?
Selective pesticide - only kills one pest.
Broad spectrum pesticide - can kill many at once plus everything else.



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 262-
263




EPA sets tolerance levels-
• maximum amount of pesticide residue allowed in or on food.
Maximum contaminant levels (MCLs)
• are tolerance levels for water and are lower than food since more water is consumed
*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 kills more than a million people worldwide each year—90 percent of them in
Africa; 70 percent children under the age of five.


Do the risks out weigh the benefits?