Unit 4: LAND AND WATER USE PART 1: AGRICULTURE A. Agriculture 1. Feeding a growing population-...

Unit 4: LAND AND WATER USEPART 1: AGRICULTURE

A. Agriculture1. Feeding a growing population- Chapter 9 Human nutritional requirements; types of agriculture; Green Revolution; genetic engineering and crop production; deforestation; irrigation; sustainable agriculture2. 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 healthObesity

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 farms2. 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, run-off 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 RESOURCESA. 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 well-known 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 pest-

resistance 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 AGRICULTUREA. 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.

Pests

Any organism that interferes in some way with human welfare

or activities

Pest Management Notes

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)

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.

Hard/Persistent Pesticides

DDT and many other chlorinated hydrocarbons.

Examples

Characteristics• Reduced-risk pesticides. They are

short-term and don’t harm the environment or man.

Soft Pesticides

soaps, oils, plant extracts, baking soda, and dish liquid.

Examples

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) Short-term 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.

Symptoms• Nausea, vomiting, and headaches.• More serious can result in damage to the

nervous system & other body organs.

Pesticide Poisoning

The W.H.O. estimates that more than 3 million people are poisoned by pesticides each year, & about 220,000 die.

Examples

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.

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.

The Perfect Pesticide

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!

EPA

• The EPA & USDA are responsible for the overseeing the laws.

Pesticides and the Law

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.

Time

• Rachel Carson lived from 1907 to 1964.

• She published her famous work Silent Spring in 1962.

Rachel Carson

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.

Definition:• A limited use of pesticides along with

other practices.

Integrated Pest Management (IPM)

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.

Fig. 13-30, p. 299

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.