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Pest Control. Chapter 12 APES 2008. What are pesticides?. Chemicals that kill pests Biocides- kill wide range of pests Herbicides- kill plants Insecticides- kill insects Fungicides- kill fungi. History of Pesticides. Every culture has used pesticides

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Pest control l.jpg

Pest Control

Chapter 12 APES

2008


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What are pesticides?

  • Chemicals that kill pests

    • Biocides- kill wide range of pests

    • Herbicides- kill plants

    • Insecticides- kill insects

    • Fungicides- kill fungi


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History of Pesticides

  • Every culture has used pesticides

  • Modern era of pesticides began in 1934 with development of DDT (Dichloro-Diphenyl-Trichloroethane)

  • Used in WWII to control parasites & tropical disease

  • Was cheap, stable, soluble in oil, easily spread over wide areas.

  • High toxicity for target organisms- kills 90% of target organisms in single application

  • It was the “magic bullet”- the answer to our prayers… or was it?


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History of Pesticides

  • Indiscriminate & excessive use of pesticides has caused

    • Damage to ecosystems

    • Harm to human health

    • Creation of “superbugs”

  • ¾ of all pesticides are used in Most Developed Countries (MDC) but rates in LDC are on the rise by 7-8%.

  • DDT was banned in US in the 1970’s. We can now only use it in emergencies.

  • DDT is still used in many other countries- especially for control of mosquitoes.

Children playing in DDT clouds at beach.


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History of Pesticidesclassified based on chemical structure

1st stage included Inorganic Pesticides

  • Arsenic, copper, lead, mercury

  • Highly toxic & indestructable

Arsenic poisoning from infected water sources in Bangladesh


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History of Pesticides

2nd stage included petroleum based sprays and natural organic pesticides

  • Nicotine, rotenone

  • Botanicals

  • From plants


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History of Pesticides

3rdstage included chlorinated hydrocarbons

  • DDT, chlordane, aldrin, dieldrin, toxaphene

  • Block nerve signals

  • Fast & toxic, carcinogenic

  • Biomagnify- stay in ecosystem

  • Dieldrin 50X as toxic to people as DDT

  • Toxaphene kills goldfish at 5 ppb- one of the highest toxicities for any compound


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History of Pesticides

4th stage: Biological controls-

  • using live organisms or their toxins instead of pesticides

  • Bacillus thuingiensis (Bt)- kills beetles, caterpillars by destroying their digestive tract

  • Parasitic wasps

  • Ladybugs eat aphids

  • Viruses


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Alternatives to Pesticides

  • Biological controls- natural predator

    • Bacillus thuringiensis (Bt)- kills beetles & caterpillars

    • Ladybugs, praying mantises, wasps

    • Ducks & geese in fields will eat insects & weed seed.

    • Planting garlic or marigolds can deter pests.

    • Release of artificial hormones can disrupt life cycles (sex phermones)


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Alternatives to Pesticides

  • Integrated Pest Management (IPM)- use a combination of methods, including biological control, chemical pesticides, and methods of crop planting.

  • Vacuuming bugs off crops

  • Move away from monoculture- grow several crops to confuse the pest.

  • No till or low till agriculture- helps natural enemies to build up in the soil

  • Trap crops- mature before rest of field to attract pests, then sprayed heavily, destroy trap crop to prevent spread to people or “real” crop.


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IPM continued

  • Crop rotation keeps pest population low.

    • Using cover crops keeps weeds down

    • Provide habitat for natural predators (plant trees along edge of farm for birds which will eat bugs & provide windbreak which prevents erosion)


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Benefits of Pesticides

  • Reduce disease transmission by insect vectors (DDT sprayed to kill mosquitoes & prevent malaria, when stopped in 1964, malaria reappeared immediately)

    • Which is more important? Protecting people or the environment?

    • If you had to choose between contracting masses of worms that will make you go blind before the age of 30 or a small chance of cancer due to pesticide exposure it you live to 50 or 60, which would you choose?

  • Reduce crop losses by two-thirds.

    • Farmers save $3-$5 for every $1 they spend on pesticides.

    • Lowers costs and increases crop quality


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Problems with Pesticides

  • Non-target organisms affected

    • Potato aphid spraying killed migrating robins

    • Insecticide spraying in CA killed salmon

    • Honeybees disappearing

  • Resistant individuals will develop due to natural selection

  • Pesticide is killing off natural predators that help control bad populations

  • Limited useful lifespan- can move far from original application spot (next slide)

  • Persistant organic pollutants (POP’s) are very long lasting and dangerous. Banned in most countries but persistent in soil & water

  • Affect Human Health

    • Acute- poisoning & illness

    • Chronic- cancer, birth defects, degenerative diseases

Pest resurgence leads to the use of higher doses or more toxic chemical use


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The Grasshopper Effect

  • Many chemicals like chlorinated hydrocarbons evaporate from water & soil in warm areas & condense & precipitate in colder regions.

  • This happens over & over, “hopping” northward until it collects in polar regions.

  • Affecting top predators (polar bears, whales, & humans)

  • Some carcasses have to be treated as toxic waste they are so “infected” with pesticide.

  • Be familiar with “The Dirty Dozen”- from toxicity handout


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About Human Health…

  • Yaqui children in Mexico tested…

    • Foothills children age 4-5 not exposed to much pesticide

    • Valley children age 4-5 repeatedly exposed


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Who regulates pesticide usage?

  • Environmental Protection Agency (EPA)

    • Regulates sale & usage under Federal Insecticide, Fungicide, & Rodenticide Act (FIFRA) which mandates the “registration” of all pesticide products.

    • Determines which pesticides are safe to use for humans & environment

    • Sets tolerance levels for residues that may remain in or on foods marked in U.S. This falls under the Federal Food, Drug, and Cosmetic Act (FFDCA).

  • Department of Agriculture (USDA) & Food & Drug Administration (FDA) enforce pesticide use & tolerance limits set by EPA. Can seize & destroy food shipments that violate.


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