CHAPTER 20PESTICIDES &
PEST CONTROL
-Competes with humans for food
-Invades lawns and gardens-Interferes with human activity -Spreads disease-Nuisance
WHAT IS A PESTAny species that does the following:
I. TYPES OF PESTICIDES1. Insecticides 2. Herbicides3. Fungicides4. Nematocides
(Round worms)5. 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) Arsenic- does 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
Natural Pesticides: (1600’s) Nicotine Sulfate – from tobacco plants
1st Generation - continued
(1800’s) Pyrethrum, Rotenone- from Chrysanthemum flower and tropical legumes
-Generally described as those that are chemically produced
-DDT (Dichlorodiphenyl-trichloroethane)*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.
- It is still sold to foreign countries
B. 2nd Generation Pesticides
Biological Magnification
C. Pesticide Use Today
-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.
1. TODAY(since 1850)
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. Narrow1. 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
55% of food is already lost to pests
$65 million / yr Helps lower food costs
B. Increase food supply:
Slide 2
Grasshopper
Gypsy mothcaterpillar
Fig. 20.2a, p. 505
Slide 3
Fig. 20.2b, p. 505
European red mite
Slide 4
Fig. 20.2c, p. 505
Boll weevilPink bollworm
ranges overlap
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 safe when handle correctly
E. Relatively Safe: Health risks are insignificant when
used properly
Many of the new pesticides are used at a lower rate than in the past.
Today’s pesticides are actually safer than those of the past.
III. THE CASE AGAINST PESTICIDES
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
Those that oppose the use of pesticides state that they are harmful for many reasons.….
Fig. 20.4, p. 507
600
500
400
300
200
100
01950 1960 1970 1980 1990 2000 2010
Year
Num
ber o
f spe
cies
Boll weevilGypsy moth cateripllar
Insects and mites
Weeds
Plant diseases
RISE OF GENETIC RESISTANCE TO PESTICIDES 1945-98
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 disorders, immune system problems
Bhopal India
http://www.bhopal.org/testimony/index.html
Bhopal, India, 2-3 Dec. 1984On 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.
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 non-Hodgkin’s lymphoma.
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
C. HOW TO IMPROVE PESTICIDE REGULATIONS (519)
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
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
V. OTHER WAYS TO CONTROL PESTS
1. Cultivation Practices; crop rotation changing planting times planting trap crops increasing habitat for natural
predators
2. Create Genetically Resistant Plants;
B. Alternatives to Pesticides
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 of research & development
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