Pesticide Notes
Pest - Any organism that is destructive or annoying (mostly
weeds and insects).
EX. mosquitoes carry malaria, grasshopper destroys crop, rats
carry disease.
Pesticide - any chemical used to kill pests
EX. 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.
arsenic paste used as a pesticide in the early 1900’s
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
- Growing monocultures attract many insect pests of that plant.
Pesticides were therefore used more often.
1) kills most things including the organisms that are helpful
(only 1 out of every 8 insect species are pests).
2) Many pesticides persist (don’t decompose) in the
environment. They stay in soil or runoff into water.
3) Overtime insects became resistant (survived and passed that
trait to the next generation) to the pesticide. More pesticide was
used.
4) Pesticides bioaccumulate - pesticides are absorbed and
accumulate in the fat of animals through the food chain.
(see diagram)
*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 - limited and
Chlordane - banned) (read pgs 269 – 272)
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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 262263
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.
Do the risks out weigh the benefits?
IPM - Integrated Pest Management - uses several methods to
control insect pests
1) Development of varieties of crops that are resistant to insects
by using their use of natural pesticides or physical barriers (EX.
hairy leaves).
2) Beneficial Insects - uses predatory insects to kill pests
EX. parasitic wasps for the gypsy moth, lady bugs
3) Microbial Pesticides – using bacteria, viruses, fungus or
predators to control insects.
EX. bacterial spray – Bt – Baccillus thuringiens - nonpersistant
- expensive and companies don’t make money on it.
- takes more planning than pesticides
- takes time to be effective
4) Birth control - sterilize UV male insects and release them to
mate w/females. Female do not lay eggs or eggs don’t hatch.
5) Biochemical - natural chemical to repel or attract pests deer
off. Sex attractants - chemicals (pheromones) that attract insect
to a trap. EX. Jap. beetle bags.
6. Cultivation practices - Crop rotation and time planting after
insect is no longer present.
7. Computer program – technology used to plant crops around
pest and to use pesticides efficiently
8. Synthetic pesticides - Proper use of pesticides