Pesticides in the Environment

Pesticides in the Environment

Monoculture demandPesticides Families

DDTBiomagnification

Alternatives to Pesticides

MonoculturesMonocultures

One species of land cover or crop

Examples: Cornfield Residential Lawn

No diversity results in unbalanced ecosystem

Monocultures continued…Monocultures continued… Without diversity, monoculture plant is over run with

insects that feed on that particular species.

Normally, biodiversity would maintain small populations of plant, pest, and predator.

Because of crop damage, pesticides are applied

Natural predators of pest insects die off with application of pesticides

Pesticide Treadmill begins

What is a pesticide?What is a pesticide?

any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest.

Broad vs. Selective Broad vs. Selective

Synthetic vs. Organic Synthetic vs. Organic

Synthetic PesticidesSynthetic Pesticides

Pesticides which do NOT naturally occur in the environment

Have carbon and hydrogen atoms as the basis of their molecule

Includes chlorinated hydrocarbons, organophosphates, carbamates, synthetic pyrethroids, and phenoxy acids

Persistent vs. Not persistent Persistent vs. Not persistent

1. Organophosphates1. Organophosphates

Most are NOT persistent and will break down to non-toxic materials in 1-30 days

Do NOT accumulate in food chains

Includes malathion, chlorpyrifos (Dursban), diazinon, dichlorvos (Vapona), acephate (Orthene), and propetamphos (Safrontin)

2. Chlorinated Hydrocarbons2. Chlorinated Hydrocarbons

Most are persistent and accumulate in food chains.

Range from moderately to very toxic towards mammals

Includes DDT, dieldrin, chlordane, aldrin, BHC, endrin, heptachlor, and methoxychlor

Effects of Chlorinated Hydrocarbon UseEffects of Chlorinated Hydrocarbon Use

Non-lethal effects in fish include lower reproductive rates, liver and kidney damage, damaged gills, modified metabolism, and changes in behavior

Non-lethal effects in birds include lower reproductive rates, show changes in feeding habits and metabolism, and they may have some liver damage.

Lethal exposure in fish, birds, and mammals include symptoms of respiratory difficulty, sluggishness, and neurological complications eventually leading to death.

DDTDDT Dichlorodiphenyltrichloroethane (C14H9Cl15) A chemical colorless pesticide which is used by

spraying it on crops and livestock First used heavily during World War II. Is persistent Was approved for public use in 1947 and banned in

1972 in the U.S.. It did reduce Malaria from 75 million cases to 5

million case in ten year.

DDT continuedDDT continued Natural predators to the pests were being killed by this

pesticide while the pests were becoming resistant to it.

It caused the destruction of reproductive maturation in wildlife:

demasculinizing of alligators, converting some male fish into females which bear viable young, thinned the eggshells in some birds which results in the inability for the birds to hatch.

Rachel Carson’s book ”Silent Spring” first aroused public awareness and suspicion of the negative effects of DDT on the environment . Resulted in the formation of the Environmental Protection Agency.

BioaccumulationBioaccumulation

BiomagnificationBiomagnification

BiomagnificationBiomagnification

DDT is fat soluble Accumulated concentrations are magnified at

each higher trophic level For example: If each phytoplankton in the Long

Island Sound retains one unit of DDT, a small fish feeds on thousands of zoo/phytoplankton, the fish will store thousands of units of DDT in fatty tissues. A large fish will eat 10 small fish and store tens of thousands of DDT units, etc.

Case Study: Raptors and DDTCase Study: Raptors and DDT Ospreys, Bald Eagles, Peregrine Falcons

Prior to 1970, these birds of prey were near extinction on the east coast because of biomagnification of DDT.

DDT disrupted the reproductive system of adult birds. Eggs formed, but eggshells were paper thin and crushed when incubated.

Ban of DDT and aggressive wildlife management techniques brought all three species back to the region.

Bald Eagle Haliaeetus leucocephalus

Bald Eagle Haliaeetus leucocephalus

OSPREY Pandion haliaetus OSPREY Pandion haliaetus

Peregrine FalconPeregrine Falcon

Solution: Integrated Pest ManagementSolution: Integrated Pest Management

Breed and release natural predators:

SpidersLadybugsWasps

Mixed crop farms Organic pesticides Mechanical removal of

pestsVaccumWash plants

Natural PredatorsNatural Predators

Organic farming: Basic PracticesOrganic farming: Basic Practices

GM: A new world of possibilities?GM: A new world of possibilities?

QuizQuiz What is a monoculture? DDT was first heavily used during which time period?

(WWI, WWII, Vietnam, or Civil War) Name at least two of the different groups of synthetic

pesticides. What group is most persistent in the environment? What disease did the use of DDT reduce in number of

occurrences? What happens to chemical pesticides as they travel

through the food web? Explain IPM as an alternative to chemical pesticides.

For More InformationFor More Information http://www.chm.bris.ac.uk/webprojects2000/aroshier/whatare.html http://www.chm.bris.ac.uk/webprojects2000/aroshier/history.html http://www.chm.bris.ac.uk/webprojects2000/aroshier/mainpest.html http://www.chm.bris.ac.uk/webprojects2000/aroshier/human.html http://www.chm.bris.ac.uk/webprojects2000/aroshier/environment.html http://www.chm.bris.ac.uk/webprojects2000/aroshier/danger.html http://www.chm.bris.ac.uk/webprojects2000/aroshier/laws.html http://www.chm.bris.ac.uk/webprojects2000/aroshier/future.html