pesticides farming

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Pesticides andOrganic Farming



Pesticides

• Herbicides

• Insecticides

• Fungicides

• Bactericides



•Pests, DDT and biomagnification

•DDT, eagles and falcons•Endangered Species Act•Organic farming

Overview of Lesson



Domestic crops wereselected for maximum

productivity and had littlenatural pest resistance



Blight hitspotatoes, 1845

Based on: Population Reports , May 1992

Potato famine of Ireland was caused bygenetically uniform crops and lack of

pesticides to protect them



Pests attack andeat our food crops

This problem isdue, in part, to notselecting for pestresistance duringdomestication

Today‟s Pests

Based on: National Geographic , February 1980



DDT was invented in the1940‟s and viewed as: - miracle for farmers- and safe



“The most discussed of the new insecticides is

dichloro-diphenyl-trichloroethane, shortened to

DDT but also called Guesarol. This compound hasremarkable power to kill insects, particularly bodylice-the „cooties‟ of World War I. The prevalence of

typhus, carried by body lice, in the Mediterranean

theater of this war has emphasized its value.DDT‟s effectiveness in war may well be

overshadowed by its value in peace. Painstakinginvestigations have shown it to be signally

effective against many of the most destructiveinsects that feed upon crops.”

Scientific American , July 1944.



Arial crop sprayerswere used to spray

tons of DDT oncrops across theU.S.

Photo courtesy of Texas Parks and Wildlife Department



Pests became resistant to DDT

Based on: National Geographic



Pesticide Resistance

In the beginning, mostpests were sensitive toDDT but a few were

resistant

The resistant forms

survived and reproduced

In the end, most pestswere resistant to DDT

Based on: National Geographic , February 1980



Biomagnification

The concentration ofpesticides in higher levels of

food chains



Pesticides

Persistence+ Lipid solubility

= Bioacculmulation



Bioaccumulation

waterzooplanktonsmallfishlri

E.g DDT



Most food chains consist of four trophic levels

Based on: Mader, S., Inquiry Into Life , McGraw-Hill

Trophic Levels



Energy Availableto Consumers at

Next Trophic Level

Energy Lost byRespiration

Energy Lost byDeath and Decay

Energy Lost byExcretion

Energy Lost by

Egestion of Feces

Energy Ingested



DDT is concentrated asit moved up food chain

This is because energyis lost (from respiration)as you go up the foodchain but DDT is not

Based on: Campbell et al, Biology: Concepts

and Connections , Benjamin Cummings

DDT in Food Chain



•Pests, DDT and biomagnification•DDT, eagles and falcons •Endangered Species Act•Organic foods

Overview of Lesson



Bald Eagle

•

Once was widelydistributed over U.S.

•As a top carnivore itfeeds on fish

•Swoops down and

captures fish off thesurface of the water

Photo courtesy of Texas Parks and WildlifeDepartment



•Scientists discovered that DDT wasconcentrated in the bald eagle

•DDT affected the eagle‟s ability to reproduce

Photos courtesy of Texas Parks and Wildlife Department



Scientists foundthat the eagle eggshad thin egg shellsand broke easily

Nests containedbroken, rotten eggs

The number of

young producedper breedingpair was reduced



Population of adulteagles declined to 4,000and the eagle was listedas “Endangered”




The Environmental Protection Agency (EPA)banned DDT in 1972




Eagle reproduction before and after DDT ban

Based on: Grier, J., Science, 1982



Eagle populations increased rapidly andthe eagle is now listed as “Threatened”

From: Time , July 11, 1994



Peregrine Falcon •Occurred naturallyover most of

continental U.S.

•Nests on cliffs

•Keen eyesight(if human, could readnewspaper print at 110 yards)

•Feeds on other birds,knocking them out ofthe sky at 200 m.p.h.




•After DDT was introducedin 1940s, DDT weakened

the birds‟ egg shells, devastating the population

•By early 1970s, the entire

U.S. population was downto 12 breeding pairs

•Peregrines were declaredfederally endangered and

DDT banned

•Peregrines were bred incaptivity and reintroduced

successfully in cities

DDT & Peregrine

Photos courtesy of Texas Parks and Wildlife Department



•Pests, DDT and biomagnification•

DDT, eagles and falcons•Endangered Species Act•Organic foods

Overview of Lesson



“In the United States at least 500 species and subspecies of plantsand animals have become extinct

since the 1500s.”

Douglas Chadwick, H., National Geographic , March 1995



Endangered Species Act of 1973

• The Secretary of the Interiordetermines whether a species is

endangered or threatened

• The Secretary develops and

implements recovery plans for theconservation of endangered species



Definitions - Endangered

Species Act • Endangered Species - Any species that is

in danger of extinction throughout all or a

significant portion of its range

• Threatened Species - Any species that is

likely to become an endangered specieswithin the foreseeable future



OTHER COMEBACKSESA is having

somesuccess

2009 StatsAnimals 613Plants 747

endangeredspecies in the

U.S.

Gray whale(California population)

Aleutian Canadagoose

American alligator

Brown pelicanUtah prairie dot

Greenback cutthroattrout

1994

1985

1990

1987

1984

1978

date ofchange

Species removed from

endangered list orreclassified as threatened

Based on: Time , July 11, 1994



•Pests, DDT and biomagnification•

DDT, eagles and falcons•Endangered Species Act•Organic foods

Overview of Lesson



Defining “Organic”

Foods produced withouthormones, antibiotics,herbicides, insecticides,

chemical fertilizers,genetic modification orgerm-killing radiation

The USDA labels suchfoods “certified organic”

From: Newsweek , Sept. 30, 2002



Availability of Organic Products

Based on: Newsweek , Sept. 30, 2002



Unanswered Questions about

Certified Organic FoodsAre organic food safer than other foods?

Do organic foods taste better?

Are organic foods worth the extra costs?

Are people eating organic diets healthier thanpeople with conventional diets?



Can organic farming help

the environment?

Pesticides now kill 67 million American

birds per year

The Mississippi River dumps enoughfertilizer into the Gulf of Mexico to maintain

a 60 mile “dead zone” devoid of fish



Pesticides and Human Health

India suffering from human healthconsequences of pesticide use

•

Infertility•Cancer related deaths increasing•Childhood cancers•Mental retardation

Research shows pesticides and fertilizersin the groundwater.

pesticides farming

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