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Pesticides and Pest Control
G. Tyler Miller’s
Living in the Environment
13th Edition
Chapter 20
wolf spider
crab spider
Key Concepts
Types and characteristics of pesticides
Pros and cons of using pesticides
Pesticide regulation in the US
Alternatives to chemical pesticides
What is a Pest?
Compete with humans for food
Invade lawns and gardens
Destroy wood in houses
Spread disease
Are a nuisance
May be controlled by natural enemies
Natural Ecosystem (Polyculture)
• Natural enemies of pests control 50 – 90%
of pest species (Earth’s ecological services)
• Natural enemies of pests prevent any one
pest species from taking control for very
long
Pesticides: Types
Chemicals that kill
undesirable organisms
Insecticides
Herbicides
Fungicides
Rodenticides
First Generation Pesticides
Primarily natural substances
Sulfur, lead, arsenic, mercury
Plant extracts:
nicotine, pyrethrum,
rotenone (from tobacco,
chrysanthemums, and tropical forest
legume roots, respectively.)
Plant extracts are degradable
Second Generation Pesticides
Primarily synthetic organic compounds
630 biologically-active compounds
Broad-spectrum agents
Narrow-spectrum agents
Target species
Nontarget species
Major Types of Insecticides
• Chlorinated Hydrocarbons
– DDT
– Highly Persistent (2-15 years)
• Organophosphates
– Malathion
– Moderately Persistent (1-2 weeks)
• Carbamates
– Sevin
– Low Persistence (days-weeks)
• Botanicals
– Rotenone, pyrethrum
– Low Persistence (days-weeks)
The Case for Pesticides
 Save human lives
Malaria (mosquito)
Bubonic plague (rat fleas)
Typhus (body lice and fleas)
Sleeping sickness (tsetse fly)
 Increase supplies and lower cost of food
55% of world’s potential food supply
is lost to pests
Without pesticides it would be worse
The Case for Pesticides
 Work better and faster than alternatives
 Health risks may be insignificant
compared to benefits
 Newer pesticides are becoming safer
 New pesticides are used at lower rates
MAJOR PESTS
Grasshopper
Gypsy moth
caterpillar
MAJOR PESTS
European red mite
MAJOR PESTS
Pink bollworm
ranges overlap
Boll weevil
BOLL WEEVIL
Boll Weevil
• Lay thousands of eggs every 21 days
• 6 generations per growing season
• 25% of pesticide use in US to control the
cotton boll weevil
• Approximately 0.24 pounds of pesticides to
make one cotton T-shirt
Characteristics of an Ideal Pesticide
 Kill only target pests
 Harm no other species
 Break down quickly
 Not cause genetic resistance
 Be more cost-effective than doing nothing
The Case Against Pesticides
 Genetic resistance (directional natural selection)
 Can kill nontarget and natural control species
 Can cause an increase in other pest species
 The pesticide treadmill
 Pesticides do not stay put
 Can harm wildlife (pollinators and insect eaters)
 Potential human health threats
Rise of Genetic Resistance to Pesticides
600
Number of species
500
Gypsy moth
caterpillar
Boll weevil
Insects and mites
400
300
Plant
diseases
200
Weeds
100
0
1950
1960
1970
1980
Year
1990
2000
2010
Pesticide Regulation in the United
States
Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA) (1947, 1972)
 EPA Evaluation of chemicals for toxicity
Tolerance levels: specify the amount of
pesticide residue that can legally remain
on a crop when the consumer eats it
Good News
• Between 1972 and 2001, the EPA banned or
severely restricted the use of 56 active
pesticide ingredients
– Most chlorinated hydrocarbon insecticides
– Several carbamates and organophosphates
– HOWEVER: they may still be
manufactured in US and exported to
other countries…..Circle of Poison
Bad News
• Less than 10% of the 600 active ingredients
used in pesticides have been evaluated fully.
– 165 are suspected human carcinogens
– Missouri study showed a connection between
childhood brain cancer and pesticide use in
home
– Multiple studies have shown connections
between pesticide use and various types of
cancers
Good News
• 1996 Food Quality Protection Act (FQPA)
– Requires new standards for pesticide tolerance
levels
– Requires manufacturers to demonstrate safety
for infants and children
– Allows EPA to apply an additional 10-fold
safety factor
– Requires EPA to consider exposure to more
than one pesticide when setting tolerance levels
Other Ways to Control Pests
 Economic threshold: reduce crop damage
to an economically tolerable level
 Adjusting cultivation practices
 Use genetically-resistant plants
 Biological pest control
 Biopesticides
 Insect birth control
 Hormones and pheromones
 Ionizing radiation (gamma)
Figure 20-8
Page 521
Integrated Pest Management
(IPM)
Ecological system approach
Reduce pest populations to
economic threshold
Field monitoring of pest populations
Use of biological agents
Chemical pesticides are last resort
Effects of IPM