Biological pest control - SchoolRack

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14 Δεκ 2012 (πριν από 7 χρόνια και 6 μήνες)

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PROTECTING FOOD RESOURCES: PEST
MANAGEMENT


Organisms found in
nature (such as
spiders) control
populations of most
pest species as part of
the earth’s free
ecological services.

PROTECTING FOOD RESOURCES: PEST
MANAGEMENT


We use chemicals to repel or kill pest organisms
as plants have done for millions of years.


Chemists have developed hundreds of chemicals
(pesticides) that can kill or repel pests.


Pesticides vary in their persistence.


Each year > 250,000 people in the U.S. become ill
from household pesticides.

Type of Pesticide

Examples

Biomagnified?

Chlorinated
hydrocarbons

DDT, dieldrin,
chlordane

Yes

organophosphates

Malathion, parathion,
diazinon

No

Botanicals

Rotenone, camphor

No

Contact Herbicides

Paraquat

No

Systemic Herbicides

2,4
-
D, Roundup

No

Fungicide

Methyl bromide

No

Fumigant

Carbon tetrachloride,
ethylene dibromide

Yes

Major Types of Pesticides

PROTECTING FOOD RESOURCES: PEST
MANAGEMENT


Advantages and disadvantages of conventional
chemical pesticides.

Individuals Matter: Rachel Carson


Wrote
Silent Spring

which introduced the
U.S. to the dangers of
the pesticide DDT and
related compounds to
the environment.

The ideal Pesticide and the
Nightmare Insect Pest


The ideal pest
-
killing chemical has these
qualities:


Kill only target pest.


Not cause genetic resistance in the target organism.


Disappear or break down into harmless chemicals
after doing its job.


Be more cost
-
effective than doing nothing.

Superpests


Superpests are
resistant to
pesticides.


Superpests like the
silver whitefly

(left)
challenge farmers as
they cause > $200
million per year in
U.S. crop losses.

Pesticides Kill Natural Pest Enemies and Create New
Pests


Broad
-
spectrum
pesticides kill natural
predators


New pests are unleashed
once natural predators
eliminated


Currently 100 of the 300
most destructive insect
pests in the U.S. were
secondary pests

When genetic resistance develops, pesticide
sales representatives usually recommend :


More frequent application of pesticides


Larger doses of pesticides


A switch to new chemicals to keep the
resistant species under control

The result is a pesticide treadmill, whereby the farmer may pay more and more for a
pest control program

Where do pesticides go?


Bottom sediments


Surface water


Groundwater


Air


Food


Humans


Wildlife


Each Year in the United States Pesticides Applied
to Cropland


Wipe out 20% of the U.S. honeybee colonies
and damages another 15%


Kill more than 67 million birds


Kill 6


14 million fish (runoff from croplands)


Menace about 20% of the endangered and
threatened species in the U.S.

Pesticide Protection Laws in the U.S.


Government regulation has banned a number
of harmful pesticides but some scientists call
for strengthening pesticide laws.


The Environmental Protection Agency (EPA), the
Department of Agriculture (USDA), and the Food
and Drug Administration (FDA) regulate the sales
of pesticides under the Federal Insecticide,
Fungicide and Rodenticide Act (FIFRA).


The EPA has only evaluated the health effects of
10% of the active ingredients of all pesticides.

Other Ways to Control Pests


There are cultivation, biological, and
ecological alternatives to conventional
chemical pesticides.


Fool the pest through cultivation practices.


Provide homes for the pest enemies.


Implant genetic resistance.


Bring in natural enemies.


Use pheromones to lure pests into traps.


Use hormones to disrupt life cycles.

Other Ways to Control Pests


Biological pest
control
:
Wasp
parasitizing a gypsy
moth caterpillar.

Advantages of Biological Control


Focuses on selected
target species


Is nontoxic to other
species


Can be self
-
perpetuating


Minimizes genetic
resistance

Disadvantages of Biological Control Agents


Can take years of research


Cannot always be mass
-
produced


Often are slower acting and more difficult to
apply


Must be protected from pesticides sprayed
close by


Can multiply and become pests themselves

Other Ways to Control Pests


Genetic engineering
can be used to
develop pest and
disease resistant
crop strains.


Both tomato plants were exposed to destructive
caterpillars. The genetically altered plant (right)
shows little damage.

Using Birth Control to help control pests

1.
Males of some insect
species are raised in the
laboratory

2.
They are sterilized by
radiation or chemicals

3.
The sterilized males are
released into an infested
area to mate
unsuccessfully with
fertile wild females

NO

LONGER

USED

Case Study: integrated Pest
Management: A Component of
Sustainable Agriculture

An ecological approach to pest control uses a mix
of cultivation and biological methods, and small
amounts of selected chemical pesticides as a last
resort
.

Why is IPM important?

Case Study: integrated Pest
Management: A Component of
Sustainable Agriculture


Many scientists urge the USDA to use three
strategies to promote IPM in the U.S.:


Add a 2% sales tax on pesticides.


Establish federally supported IPM demonstration
project for farmers.


Train USDA personnel and county farm agents in IPM.


The pesticide industry opposes such measures.