Unit 4: LAND AND WATER USE
PART 1: AGRICULTURE
A. Agriculture
1. Feeding a growing population- Chapter 9
Human nutritional requirements; types of
agriculture; Green Revolution; genetic
engineering and crop production; deforestation;
irrigation; sustainable agriculture
2. Controlling pests- Chapter 10
Types of pesticides; costs & benefits of
pesticide use; integrated pest management;
relevant laws
FOOD AND NUTRITION
• World food supplies have
more than kept up with
human population growth
over the past 2 centuries.
– During the past 40 years,
population growth has
averaged 1.7% per year,
while food production
increased an average 2.2%.
Chronic Hunger and Food Security:
• In 1960, 60% population of developing
countries were considered chronically
undernourished.
– Fallen to less than 14%.
• Poverty is the greatest threat to food
security (Ability to obtain sufficient food on
a daily basis).
– Operates on multiple levels.
– Recognizing role of women in food
production is an important step forward.
Famines are Acute Food
Shortages/Emergencies
• Famines are characterized by large-scale
food shortages, massive starvation,
social disruption, and economic chaos.
• Mass migrations often occur because
productive capacity has been sacrificed.
– Environmental conditions are immediate trigger,
but politics and economics are often underlying
problems.
– Arbitrary political boundaries block historic access
to refuge areas.
Malnutrition and Obesity:
We need the right kinds of food
• Malnourishment Nutritional imbalance
caused by a lack of
specific dietary
components.
– In poorer countries, people
often cannot afford to
purchase an adequate variety
of foods, including meats &
vegetables.
Nutritional Problems
• Iron deficiency is the most
common dietary imbalance
in the world.
– Leads to anemia (low
hemoglobin levels in the
blood)
• Increases risk of death
from hemorrhage in
childbirth and affects
development.
• Red meat, eggs, legumes,
and green vegetables are
all good sources of iron.
Protein Deficiency Diseases
• Kwashiorkor - “Displaced Child” Occurs mainly in children whose
diet lacks high-quality protein.
– Reddish-orange hair, bloated
stomach.
• Marasmus - “To Waste Away” Caused by a diet low in protein and
calories.
– Very thin, shriveled.
Eating a balanced diet is essential for
good health
Obesity
The most common dietary problem
in wealthy countries is over-nutrition.
– According to U.S. Surgeon General:
• 62% of Americans are overweight.
– 33% are obese.
KEY FOOD SOURCES
• 3 crops deliver
majority of world’s
nutrients:
– Wheat, Rice & Corn
• Potatoes, barley, oats
and rye are staples in
cool, moist climates.
• Cassava, sweet
potatoes, and other
roots and tubers are
staples in warm wet
climates.
Meat and Dairy are important protein sources
• Distribution highly
inequitable.
– Developed countries make
up 20% of world
population, but consume
80% of meat and dairy
production.
• 60% of production
occurs in lesser
developed countries.
– More than 1/3 of the total maize, soy, and
coarse grain production are used as
livestock feed.
• However, FAO claims using cereals as
animal feed does not contribute to
hunger and undernutrition.
Seafood
• Seafood is an important
protein source.
• Since 1989, 13/17 major
fisheries have declined or
become commercially
unsustainable.
– FAO estimates operating
costs for the 4 million boats
now harvesting wild fish
exceed fish sales by $50
billion annually.
• Aquaculture is providing an
increasing share of the world’s
seafood.
FARM POLICY
• Farm subsidies in many
countries are protected by
powerful political &
economic interests.
– Agricultural subsidies
encourage surpluses and
allow American farmers to
sell products overseas at
prices below production
costs.
SOIL: A RENEWABLE RESOURCE
• Soil - A complex mixture
of weathered minerals,
partially decomposed
organic materials, & a
host of living organisms.
– At least 15,000 different soil types in the US.
– Vary due to influences of parent material, time,
topography, climate, and organisms.
– Can be replenished & renewed.
Soil Composition
• Particle size affects soil
characteristics.
– Spaces between sand particles
give sandy soil good drainage &
allow aeration  Can easily dry
out.
– Tight packing of small particles
in silty or clay soils makes them
less permeable to air & water.
• Soil exhibits wide range of organic
content.
• Humus - Insoluble residue from
partially decomposed plants &
animals  Most significant factor
in soil structure
Soil Organisms
• Activity of
organisms living in
the soil help create
structure, fertility, &
tilth (cultivation
suitability)
• Micorrhizal
symbiosis between
plants roots &
specific fungal
species.
Soil Profiles/Layers
• Soils are stratified into
horizontal layers called soil
horizons
• Together make up soil
profile
• O Horizon (Organic layer)
–Leaf litter, partially
decomposed
organisms.
• A Horizon (Topsoil)
–Mineral particles
mixed with organic
material.
Soil Profiles/Layers
• E Horizon (Leached)
– Depleted of soluble
nutrients.
• B Horizon (Subsoil)
– Often dense texture
from accumulating
nutrients.
• C Horizon (Parent Material)
– Weathered rock
fragments with little
organic material.
WAYS WE USE AND ABUSE SOILS
• Approximately 12.5% of
the earth’s land area is
currently in agricultural
production.
– Up to 4x as much could
potentially be
converted to
agricultural use.
– Much of this additional
land suffers from
constraints.
Agriculture
• 1. Wheat, rice, corn & potatoes make up over ½ of
world’s food production
• We now produce more than enough food to feed
everyone on earth if there were no political
restraints & people ate less meat.
• Industrial agriculture uses 8% of world’s oil but
saves virgin land.
• If animals included, it takes on average, 3 Calories
of fossil fuel energy to produce 1 Calorie of food
energy.
Agriculture
• If you include transportation along with animals it
take 10 Calories of energy input to produce 1
Calorie of food energy.
• Livestock eat up to 38% of world’s grain production
(70% in USA).
• Livestock responsible for 14% of US topsoil loss.
• If everyone became a vegetarian, world oil reserves
would last another 260 years instead of the
projected 40-80 years.
Agriculture
• Cattle produce 12-15% of world’s methane.
• Livestock are producing 21x more feces than
people, but fortunately ½ is recycled back into
soil.
• Agriculture is world’s #1 reason for habitat
loss.
• Causes water pollution from herbicide
fertilizer, oil runoff & sediments.
• Air pollution from particulates (disturbed soil)
& diesel exhaust (tractors).
Agriculture
• Salinization of soil from inorganic fertilizers.
• Loss of species diversity  increased
pestilence, pests can move quickly through
crop exhausts (monoculture)  loss of genetic
resources.
• Depletion of surface & subsurface (aquifer)
water supplies uses up more than ½ of water
in US.
• Use of fossil fuel, 17% of US total energy use.
Major Types of Food Production
• Industrialized– Industrialized High Input Agriculture
• Uses large amounts of fossil fuel energy, water, commercial
fertilizers, & pesticides
– Plantation Agriculture
• Practice in developing countries in which cash crops such as
bananas & coffee are grown by large corporations
Major Types of Food Production
• Traditional– Traditional Subsistence Agriculture
• Uses human labor or draft animals to produce only
enough food for a farm family’s survival.
1. Family farms
2. Shifting (slash & burn) cultivation
(#1 cause of rainforest loss)
3. Nomadic herding of livestock
– Traditional Intensive Agriculture
• Farmers increase their inputs of human & animal labor,
fertilizer, & water to get a higher yield per area of
cultivated land to produce enough food to feed their
families & to sell for income
Land Resources
• In developed countries,
95% of recent agricultural
growth has been from
altered agricultural
practices (pesticides fertilizer).
– Less land cultivated in
NA now than 100 years
ago.
• Many developing
countries are reaching
limit of lands that can be
exploited for agriculture
without unacceptable
social & environmental
costs.
Land Degradation
• Estimated nearly 3
million ha of cropland
ruined annually via
erosion, 4 million ha
transformed into deserts,
& 8 million ha converted
to non-agricultural uses
Land Degradation
• Based on both biological
productivity & expectations
of what land should be like.
• Generally, land is considered
degraded when soil is
impoverished or eroded, runoff is contaminated, or
biodiversity is diminished.
• Water & wind are the
driving forces for vast
majority of soil degradation.
Global Soil Degradation
Erosion
• Erosion is an important
natural process, resulting in
redistribution of the products
of geologic weathering, & is
part of both soil formation &
soil loss.
– Tends to begin subtly.
– Worldwide, erosion
reduces crop production by
equivalent of 1% of world
cropland per year.
Mechanisms of Erosion
• Sheet Erosion - Thin layer of surface removed.
• Rill Erosion - Small rivulets of running water gather
together and cut small channels.
• Gully Erosion - Rills enlarge to form bigger
channels too large to be removed by normal
tillage.
• Streambank Erosion - Washing away of soil from
established streambanks.
Mechanisms of Erosion- Wind/Water
• Wind can equal or
exceed water as an
erosive force,
especially in a dry
climate & on flat land.
• Intensive farming practices:
• Row crops leave soil exposed.
• Weed free-fields.
• Removal of windbreaks.
• No crop-rotation or resting
periods.
• Continued monocultures.
Desertification
• Conversion of productive
lands to desert
• threatens 1/3 of the earth’s surface
• Rangelands and pastures are highly
susceptible (overgrazing, soil degradation)
• Africa & China are of particular concern
– rapid population growth & poverty
create unsustainable pressures
Desertification
OTHER AGRICULTURAL RESOURCES
A. Water
– Agriculture accounts for largest
single share of global water
use.
• As much as 80% of water
withdrawn for irrigation
never reaches intended
destination.
–Cheap cost encourages
over-use.
»Waterlogging
»Salinization
Fertilizer
• Lack of nitrogen, potassium, &
phosphorus often limits plant growth.
• Adding nutrients via fertilizer usually
stimulates growth and increases crop
yields.
• 1950 - Average of 20 kg/ha
fertilizer used.
• 1990 - Average of 91 kg/ha
fertilizer used.
• Manure & nitrogen-fixing
bacteria are alternative methods
of replenishing soil nutrients.
Energy
• Farming in industrialized countries is
highly energy-intensive.
– Between 1920-1980, energy use rose directly
with mechanization of agriculture, and
indirectly with spraying of chemicals.
– Altogether, US food system consumes 16% of
total energy use.
– Most foods require more energy to
produce, process, & transport than
we yield from them.
Agriculture & Domestication of Animals
• 10,000 years ago
• Major turning point in human
race’s relationship with planet
earth
NEW CROPS & GENETIC ENGINEERING
• Most of world food comes from
16 widely grown crops.
– At least 3,000 species of plants
have been used for food at some
point in time.
– Many new or unconventional
varieties might be valuable food
supplies.
Green Revolution
• Most major improvements in farm
production have come from technological
advances and modification of a few wellknown species.
– Corn yields jumped from 25 bushels per acre to
130 per acre in last century.
• Most of gain accomplished through
conventional plant breeding.
– Also seen rise of dwarf varieties.
• Green Revolution - Spread of new varieties
around the world.
Agriculture Revolutions
• 1st Green Revolution– 1950-1970 Industrialized Agriculture
– Using petroleum products, pesticides &
inorganic fertilizers
– Developed countries were able to greatly
increase their food production
– Excess food was exported to developing
countries
Agriculture Revolutions
• 2nd Green Revolution– 1970-2000
– Faster growing, higher yielding crops were
developed & exported to developing countries
• 3rd Green Revolution– Presently taking place as bioengineers splice
designer genes into food crops in an effort to
make them higher yielding, tastier, easier to
transport, more drought resistant, & more pest
resistant.
Genetic Engineering
• Genetically Modified Organisms
(GMO’s)
– Contain DNA possessing genes
borrowed from unrelated species.
• Can produce crops with pestresistance and wider tolerance
levels.
• Opponents fear traits could
spread to wild varieties, and
increased expense would
largely hurt smaller farmers.
– Estimated that 60% of all processed
foods in NA contain transgenic
products.
Pest Resistance & Weed Control
• Biotechnologists have recently
created plants containing genes
for endogenous insecticides.
– Concern has arisen over several
points.
• Spread of genes into wild
populations leading to
resistance in pests.
• Effect on nontarget species.
Is Genetic Engineering Safe ?
• Environmental and consumer
groups have campaigned against
transgenic organisms.
– “Frankenfoods”
• U.S. Food & Drug Administration
declined to require labeling of
foods containing GMO’s.
– New varieties are “substantially
equivalent” to related
traditionally-bred varieties.
SUSTAINABLE AGRICULTURE
A. Soil Conservation
– Managing Topography
• Contour Plowing - Plowing across
slope to slow flow of water.
• Strip Farming - Planting different
crops in alternating strips along land
contours.
• Terracing - Shaping land to create
level shelves of earth to hold water
and soil.
• Plant perennial species.
Sustainable Agriculture
Soil Conservation
• Providing Ground Cover
– Annual row crops cause highest rates of erosion
because they leave soil bare for much of the year.
• Leave crop residue after harvest.
• Plant cover crops after harvest.
Soil Conservation
• Reduced Tillage
– Minimum Till - Chisel plow
– Conserv-Till - Coulter (Disc)
– No-Till - Drilling
• Often farmers using conservation tillage must
depend relatively heavily on pesticides.
– Traditional tillage helped control weeds and pests.
Low-Input Sustainable Agriculture
• Do not depend on chemical fertilizers and
pesticides, and use antibiotics only to combat
illness.
– Typically do not produce as high quality product as
intensive farmers, but production costs are lower,
and often obtain higher prices.
Pest Management Notes
Pests
Any organism that interferes in
some way with human welfare
or activities
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.
Figure 13-27
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.
PROTECTING FOOD RESOURCES: PEST
MANAGEMENT
• Advantages and disadvantages of conventional
chemical pesticides.
Figure 13-28
Classification of Pesticides
Specific Types:
Herbicides
• A toxic chemical that kills plants
Insecticides
• A toxic chemical that kills insects
Rodenticides
• A toxic chemical that kills rodents
Fungicides
• A toxic chemical that kills fungi
Nematicides
• A toxic chemical that kills
nematodes (roundworms)
Algaecides
• A toxic chemical that kills algae
Bactericides
• A toxic chemical that kills bacteria
Piscicides
• A toxic chemical that kills fish
(unwanted species)
Hard/Persistent Pesticides
Characteristics:
• Composed of compounds that retain their
toxicity for long periods of time. They work
their way up the food chain through
animals and may accumulate in their fatty
tissues and stay indefinitely.
Examples
DDT and many other chlorinated hydrocarbons.
Soft Pesticides
Characteristics
• Reduced-risk pesticides. They are
short-term and don’t harm the
environment or man.
Examples
soaps, oils, plant extracts,
baking soda, and dish liquid.
Chemical Classes of Pesticides
Organochlorines (chlorides)
•
•
•
•
Hard/persistent
Toxic in the long term
Not very toxic in the short-term
Ex. DDT
Organophosphates
• Soft/not persistent
• Highly toxic in the short term
• They require very specific safety equipment
for application.
• Ex. Parathion
Carbamates
• Soft/not persistent
• Not as toxic as the other two
• Most of the over-the-counter
pesticides.
• Ex. Sevin Dust
Historical Use of Pesticides
• Natural Pesticides – pyrethrins (from
chrysanthemums); sulfur and garlic
• Synthetic Pesticides – Used during and
after WWII and today.
Benefits of Pesticide Usage
Disease Control
• Save human lives
• Prevent insect-transmitted diseases, such
as malaria (anapheles mosquito), bubonic
plague (rat fleas), typhus (body lice &
fleas), & sleeping sickness (tsetse fly).
Food Production
• Increase food supplies
and lower food costs.
• About 55% of the world’s
food supply is lost to
pests before (35%) and
after (20%) harvest.
• These losses would be
worse and food prices
would rise.
Fiber Production
• Crops such as cotton
• Kills pests like the cotton boll weevil.
Efficiency When Compared to
Alternatives
• Pesticides control most pests quickly and at
a reasonable cost.
• They have a long shelf life
• Easily shipped and applied
• Are safe when handled properly.
• When genetic resistance occurs, farmers
can use stronger doses or switch to other
pesticides.
• Proponents feel they are safer than the
alternative
Development of Safer Pesticides
• such as botanicals and micro-botanicals
• safer to users and less damaging to the
environment.
• Genetic engineering holds promise in
developing pest-resistant crop strains.
• It is very expensive to develop these, so
they are only doing it for large-market
crops like wheat, corn, and soybeans.
Problems Associated with
Pesticide Usage
Impact on Non-target Organisms
• Pesticides don’t stay put.
• The USDA says that only 2% of the
insecticides from aerial or ground spraying
actually reaches the target pests
• Only 5% of herbicides applied to crops
reaches the target weeds.
• They end up in the environment
Superbugs
• Genetic resistance to pesticides.
• Insects breed rapidly; within 5-10 years (sooner in
tropics) they can develop immunity to pesticides and
come back stronger than before.
• Weeds and plant-disease organisms also become
resistant.
• 520 insect and mite species, 273 weed species, 150
plant diseases, and 10 rodent species (mostly rats)
have developed genetic resistance to pesticides.
• At least 17 insect pest species are resistant to all
major classes of insecticides
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.
Figure 13-29
Case Study: Growing Germ
Resistance to Antibiotics
• Rabidly producing infectious bacteria are
becoming genetically resistant to widely used
antibiotics due to:
– Genetic resistance: Spread of bacteria around the
globe by humans, overuse of pesticides which
produce pesticide resistant insects that carry
bacteria.
– Overuse of antibiotics: A 2000 study found that
half of the antibiotics used to treat humans were
prescribed unnecessarily.
Persistence
• Many pesticides stay in the
environment for a very long time. Ex.
DDT
Bioaccumulation
• Increase in the concentration of a chemical
in specific organs or tissues at a level higher
than normal.
• Stored in body fat and can be passed along
to offspring.
• Usually a concern to organisms higher on
the food chain.
Formation of New Pests
• Turning of minor pest into major pests.
• The natural predators, parasites, & competitors
of a pest may be killed by a pesticide it allows
the pest population to rebound.
• EX. DDT to control insect pests on lemon trees
caused an outbreak of a scale insect (a sucking
insect that attacks plants) that had not been a
problem.
Food/Water Contamination
• Pesticides run off into our water as
we spray for bugs & stay on our food.
Pesticide Poisoning
• (Read Raven pg. 553) Shortterm exposure to high levels
of pesticides can result in
harm to organs and even
death
• Long-term exposure to lower
levels of pesticides can cause
cancer.
• Children are at a greater risk
than adults.
Pesticide Poisoning
Symptoms
• Nausea, vomiting, and headaches.
• More serious can result in damage to the
nervous system & other body organs.
Examples
The W.H.O. estimates that more than 3
million people are poisoned by pesticides
each year, & about 220,000 die.
National Cancer Institute
• Pesticides have been shown to cause
lymphomas, leukemia, brain, lung, and
testicular cancers.
• The issue of whether certain pesticides
cause breast cancer remains unresolved
• Researchers have noted a correlation
between a high level of pesticides in the
breast's fatty tissue and cancer.
How Pesticides Function
LD-50 (Median Lethal Dose)
• The LD-50 is the amount of pesticide it will
take, in one dose, to kill ½ of all the target
organisms.
• It is usually referring to rats & mice in a
laboratory experiment.
Nervous System
• Some interfere with the nervous system,
cause uncontrollable muscle twitching or
paralysis.
• Some are nervous system poisons.
Ex.
Spectracide, Nicotine, DDT, Dursban, &
Diazinon.
Photosynthesis
• Some pesticides inhibit
photosynthesis and prevent
chlorophyll formation.
• Ex. Stampede, Pyrazon.
Smothering
• The vapors kill the pest by suffocating the
animal. Soap can smother soft bodies of
insects.
• Ex. flea collars, pest strip, and soap.
Dehydration
• Dehydration uses the
fossilized remains of
tiny, one-celled
organisms called
diatoms. It kills
insects by scratching
their wax outer
covering and causing
them to dehydrate.
This is a soft
pesticide.
Inhibition of Blood Clotting
• Other types of pesticides cause
animals (especially rats) to bleed to
death by preventing their blood from
clotting.
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.
The Perfect Pesticide
Characteristics
• The ideal pesticide would kill only the
organism for which it was intended to
harm, and not any other species. It
would be broken down by natural
chemical decomposition or by
biological organisms.
Examples
• The perfect pesticide would break down
into safe materials such as water, carbon
dioxide, and oxygen. It would stay
exactly where it was put and not move
around in the environment. There is no
such thing!
Pesticides and the Law
EPA
• The EPA & USDA are responsible for
the overseeing the laws.
Research
• Pesticide companies must use 3 methods to
determine pesticides health threats:
– Case Reports – (made to physicians) about people
suffering from adverse health effects
– Laboratory Investigations – (usually on animals) to
determine toxicity, residence time, what parts of
the body are affected and how the harm takes
place.
– Epidemiology – (in populations of humans
exposed) used to find why some people get sick
while others do not
Days to Harvest
• The last day you can spray crops
before you harvest them for human
consumption.
Restrictions
• The EPA sets a tolerance level specifying
the amount of toxic pesticide residue that
can legally remain on the crop when the
consumer eats it.
FFDCA
• Federal Food, Drug, and Cosmetic
Act
• Strengthened in 1996
• Sets pesticide tolerance levels
Label Requirements
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
the brand name
the ingredient statement
the percentage or amount of active ingredient(s) by weight
the net contents of the container
the name and address of the manufacturer
Registration and establishment numbers
Signal words and symbols
Precautionary statement
Statement of practical treatment
Environmental hazard statement
Classification statement
Directions for use
Re-entry statement
Harvesting and/or grazing restrictions
Storage and disposal statement.
FIFRA
• The Federal Insecticide,
Fungicide & Rodenticide Act
• It was first established in
1947 & revised as recently as
1996.
• States what must be on a
pesticide label & requires
registration of all pesticides.
FQPA
• Food Quality Protection Act
• Established in 1996
• Amends both FIFRA and FFDCA.
Rachel
Carson
Time
• Rachel Carson lived from 1907 to
1964.
• She published her famous work
Silent Spring in 1962.
Contributions
• “Pesticide sprays, dusts, and aerosols are
now applied almost universally to farms,
gardens, forests, and homes - non selective
chemicals that have the power to kill every
insect, the good and the bad, to still the
song of birds and the leaping of fish in the
streams, to coat the leaves with a deadly
film and to linger on soil - all this though
the intended target may be only a few
weeds or insects. Can anyone believe . . .
Contributions
. . . it is possible to lay down such a barrage of
poisons on the surface of the earth without
making it unfit for life? They should not be
called insecticides, but biocides.”
• Silent Spring heightened public awareness and
concern about the dangers of uncontrolled use
of DDT and other pesticides, including poisoning
wildlife and contaminating human food supplies.
Integrated Pest
Management (IPM)
Definition:
• A limited use of pesticides along with
other practices.
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.
Cultural Methods
Physical
• This includes rotating between different
crops, selecting pest-resistant varieties,
planting pest-free rootstock, and
vacuuming up harmful bugs.
Traditional “EcoFarmer”
• Each crop is evaluated as parts of an
ecological system.
• A control program is developed that
includes a mix of cultivation, biological, and
chemical methods applied in proper
sequence with the proper timing.
Biological Methods
Other Ways to Control Pests
• Biological pest
control: Wasp
parasitizing a
gypsy moth
caterpillar.
Figure 13-31
Predators/Parasites
• Using natural predators & parasites
to control population of pests.
Diseases
• Using disease organisms (bacteria
and viruses) to control pests.
Natural Repellants
• Garlic, sulfur, pyrethrins (from
chrysanthemums) to help control
pests.
Microbials
• Used for insect wars, especially by organic
farmers.
• EX. The Bacillus thruingensis (Bt) toxin is a
registered pesticide sold commercially as a
dry powder.
• Each of the thousands of strains of this
common soil bacteria kills a specific pest.
Timing of Application
• Adjusting planting times so that
major insect pests either starve or
get eaten by their natural predators.
Type of Crops
• Switching from vulnerable monocultures
to intercroping, agroforestry, and
polyculture, which use plant diversity to
reduce losses to pests.
Photodegradable Plastics
• Using plastic that
degrades slowly in
sunlight to keep
weeds from
sprouting between
crops.
Pheromones
• Synthesized bug sex attractant used to lure
pests into traps or attract their predators.
Genetic Methods
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.
Figure 13-32
Resistant Crops
• Plants and animals that are
resistant to certain pest
insects, fungi, and diseases
can be developed.
• This can take 10 to 20 years.
• Genetic engineering is now
helping to speed up this
process through the
development of transgenic
crops.
Sterilization
• Males of some insect species can be raised
in the laboratory, sterilized by radiation or
chemicals, and released into an infested
area to mate unsuccessfully with fertile
wild females.
• Males are sterilized rather than females
because the male insects mate several
times, whereas the females only mate
once.
What Can You Do?
Reducing Exposure to Pesticides
• Grow some of your food using organic methods.
• Buy organic food.
• Wash and scrub all fresh fruits, vegetables, and wild foods you pick.
• Eat less or no meat.
• Trim the fat from meat.
Fig. 13-30, p. 299