CHAPTER 20
PESTICIDES &
PEST CONTROL
WHAT IS A PEST
Any species that does
the following:

-Competes with
humans for food
-Invades lawns and
gardens
-Interferes with
human activity
-Spreads disease
-Nuisance
I. TYPES OF PESTICIDES
1.
2.
3.
4.
5.
Insecticides
Herbicides
Fungicides
Nematocides
(Round worms)
Rodenticides
A. 1st Generation Pesticides
-Generally described as those
first used and that were
derived from natural sources.
Sulfur: Used pre-500B.C.
Toxic Chemicals: (1400’s) Arsenicdoes not break down, Lead and
Mercury
-This approach was abandoned as
late as the1920’s
-Still find measurable levels in
tobacco and other crops grown
on that soil
1st Generation - continued
Natural Pesticides:
(1600’s) Nicotine Sulfate –
from tobacco plants
(1800’s) Pyrethrum,
Rotenone- from
Chrysanthemum flower and
tropical legumes
B. 2nd Generation Pesticides
-Generally described as those that
are chemically produced
-DDT (Dichlorodiphenyltrichloroethane)
*Discovered by Paul Muller
(won the Nobel Prize)
*1st used in 1939
*Use in the U.S. stopped in 1972
as a result of adverse effects on
the environment and population
decreases in unintentional
species.
Biological Magnification
C. Pesticide Use Today
1. TODAY(since 1850)
-50 fold increase in
the use of
pesticides since
the 1950’s
-10x stronger than
the original
pesticides
-2.5 million tons
used per year,
worldwide.
2. IN THE USA
-Around 25,000 pesticide
products
-25% used for homes,
parks, pools, golf courses
-The average lawn receives
10x more synthetic
pesticide than US cropland
-250,000 people become ill
each year
D. Broad vs. Narrow
1. Broad Spectrum Agents:
-Toxic to many species
2. Selective / Narrow Spectrum:
-Specific to a certain species
-Pesticides vary in their
PERSISTANCE
(how long they remain in the
environment)
II. THE CASE FOR PESTICIDES

Those that support the use of
pesticides state that the
benefits outweigh the
potential harmful effects for
many reasons.….

A. Save human lives:

Protection against diseases
like malaria, typhus and
sleeping sickness
B. Increase food supply:
 55%
of food is already
lost to pests
 $65 million / yr
 Helps lower food costs
C. Increased Profit to farmers:
Every
$1
spent on
pesticides
increases
farm profit
by $4
D. They work faster and
better than alternatives:
-Control most pests
at reasonable cost
-Have
a long shelf
life
-Easily
shipped and
applied
-Relatively
when handle
correctly
safe
E. Relatively Safe:

Health risks are
insignificant when used
properly
Today’s
pesticides are
actually safer than those
of the past.
Many
of the new
pesticides are used at a
lower rate than in the
past.
III. THE CASE
AGAINST PESTICIDES
Those
that oppose the use of
pesticides state that they are
harmful for many reasons.….
A. Can cause Genetic Resistance:



Reproduce rapidly and can develop
a resistance in 5-10 years
Surviving organisms come back
stronger.
Leads to Pesticide Treadmill- using stronger
doses, switching to new chemicals, and an
increase in frequency of use
RISE OF GENETIC RESISTANCE TO PESTICIDES
1945-98
600
Number of species
500
Gypsy moth
cateripllar
Boll weevil
Insects and mites
400
300
Plant
diseases
200
Weeds
100
0
1950
1960
1970
1980
Year
1990
2000
2010
Fig. 20.4, p. 507
B. Broad Spectrum insecticides
kill natural predators &
parasites

1/3 of the most destructive
pests are secondary pests
that became widespread
after the use of insecticides
C. Pesticides Do Not
Stay Put



Less than 2% of the
pesticides used
actually reach the
target pests
Less than 5% of
herbicide reaches the
appropriate weeds
Pesticides may end up
in the air, water,
bottom sediments,
food or non-target
organisms.
D. Some Pesticides
Harm Wildlife

Destruction of more than
20% of honeybee colonies
Costing farmers $200
million in lost pollination
Kills 67 million birds
 Kills 6-14 million fish
 Hurt 20% endangered
species

E. Threat to Human Health






3 million agricultural workers
are harmed each yr (300,000 in
USA)
Most not reported due to the
majority of farm workers
being illegal immigrants
18,000 deaths (probably
underestimated)
165 of the approved active
ingredients are carcinogenic
Exposure in food is related to
4-20,000 cases of cancer / year
Birth defects, genetic
mutations, nervous system
Bhopal India
Bhopal, India, 2-3 Dec. 1984
On the night of 2-3 December 1984, a sudden
release of about 30 tons of methyl isocyanate
(MIC) occurred at the Union Carbide pesticide
plant at Bhopal, India. The accident was a
result of poor safety management practices,
poor early warning systems, and the lack of
community preparedness. The accident led to
the death of over 2,800 people living in the
vicinity and caused respiratory damage and
eye damage to over 20,000 others. At least
200,000 people fled Bhopal during the week
after the accident. Estimates of the damage
vary widely between US $350 million to as
high as US $3 billion.
http://www.bhopal.org/testimony/index.html
IV. PESTICIDE
REGULATIONS IN THE U.S.
A. USE IN THE U.S. (518)
 All commercial pesticides
require EPA approval for
general and/or restricted
use. (Based on FIFRA)
-Evaluated for
biologically active
ingredients + affects
-If approved the EPA
sets acceptable tolerance
levels
Between 1972-2000, EPA
banned or restricted 56
active pesticide
ingredients in U.S. – may
be used elsewhere.
 EPA asked to reevaluated
600 pre-1972 active
ingredients used in
pesticides. (by 2000 less
than 10% completed)

-weak enforcement

-weak laws for pre 1972
toxins

B. OTHER DISTURBING FACTS




165 active ingredients in U.S.
approved pesticides are known
to be carcinogens
Missouri study showed
increased childhood brain
cancer with use of various
pesticides.
Also, associated with immune
and endocrine disorders
Swedish report showed,
exposure to glyphosate tripled
chances of getting nonHodgkin’s lymphoma.
C. HOW TO IMPROVE PESTICIDE
REGULATIONS (519)
Need to make human
health the primary
consideration for
setting pesticide limits.
 New tests for evaluating
toxicity of pesticides
 Consider the cumulative
exposures of all
Pesticides

D. HOW TO IMPROVE
PESTICIDES
Kill only target species
would be ideal
 Harm no other species
 Break down into
something harmless after
doing its job
 Not cause genetic
resistance in target
organisms
 Be more cost effective
than doing nothing

The War Against Insects
V. OTHER WAYS TO CONTROL
PESTS
A.


Goals of Pesticide Control
One of the biggest problems with the use
of pesticides is in determining the
ECONOMIC THRESHOLD.
This is point where cost of damage due
to not applying pesticides outweighs the
cost of application of pesticides.

To protect themselves, farmers often
practice

INSURANCE SPRAYING
COSMETIC SPRAYING- Making its
appearance more desirable

B. Alternatives to Pesticides
1. Cultivation Practices;




crop rotation
changing planting times
planting trap crops
increasing habitat for
natural predators
2. Create Genetically Resistant
Plants;
A Fungus Among Us
3. Biological Pest Control;
Pro’s
-focus on
target
-are nontoxic
-save money
-minimize
resistance
Con’s
-no mass
reproduction
-slow
-must be
protected from
spraying
-can multiply
faster than
pest
-requires a lot
4. Insect Birth Control;





Sterilization of insects, used
with screwworms, fruit flies
Involves irradiating males
Disadvantages include…
-high cost
-estimating mating
times/behaviors
-need large # of males
-males must be reintroduced
5. Sex Attractants;
The use of
pheromone baited
traps.
Pheromone- is a
species-specific
chemical sex
attractant.
6. Hormones to
stunt growth;
7. Spraying with hot
water;
8. Exposing food
to gamma
radiation
C. INTEGRATED PEST MANAGEMENT
 Approach
where crops
and pests are examined
as part of an ecological
system.



Overall aim is to reduce crop damage
and economic losses but not
complete eradication of the pest.
Requires more expert knowledge and
multiple approaches to pest
controlSlower acting than
pesticides
Only small amounts of pesticide are
used at critical times
IPM is ?

A chemical program

A ecological program

A biological program
Ways to Reduce Threat to
Pesticides in the Food We Eat.

Scrub all food in soapy water

Grow own fruits and vegetables using
organic gardening methods

Purchase organically grown foods
Did you know?

Flea collars are linked to brain tumors

Pre-1972 pesticides may still have
untested chemicals as ingredients

Round-Up is linked to Non-Hodgkins
type Lymphoma