Pesticides in the Environment Monoculture demand Pesticides Families DDT Biomagnification Alternatives to Pesticides

Monocultures One species of land cover or crop Examples: Cornfield Residential Lawn No diversity results in unbalanced ecosystem

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

Broad vs. Selective

Synthetic vs. Organic

Synthetic 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

1. 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 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 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.

DDT 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 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.

Bioaccumulation

Biomagnification

Biomagnification 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 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

OSPREY Pandion haliaetus

Peregrine Falcon

Solution: Integrated Pest Management Breed and release natural predators: Spiders Ladybugs Wasps Mixed crop farms Organic pesticides Mechanical removal of pests Vaccum Wash plants

Natural Predators

Organic farming: Basic Practices

GM: A new world of possibilities?

Quiz 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 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