PesticidesPesticides

OverviewOverview

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What Are Pesticides?What Are Pesticides?

Chemicals designed and used to kill Chemicals designed and used to kill “pests” (as defined by humans)“pests” (as defined by humans)

These chemicals are hard to get rid These chemicals are hard to get rid of and cycle through ecosystemsof and cycle through ecosystems

Types of PesticidesTypes of Pesticides

Early pesticides included arsenic, Early pesticides included arsenic, lead, mercury, and plant extracts lead, mercury, and plant extracts (such as nicotine).(such as nicotine).

In the early 20In the early 20thth century, we started century, we started manufacturing synthetic chemicals, manufacturing synthetic chemicals, such as DDT.such as DDT.

The more organisms that were The more organisms that were considered “pests” to humans, the considered “pests” to humans, the more we created different pesticides.more we created different pesticides.

Types of PesticidesTypes of Pesticides

Pesticide TypePesticide Type Target PestTarget Pest

InsecticideInsecticide InsectsInsects

HerbicideHerbicide WeedsWeeds

FungicideFungicide Moulds, Mildew, and Moulds, Mildew, and FungiFungi

BactericideBactericide BacteriaBacteria

Forms of PesticidesForms of Pesticides

Taken many forms, Taken many forms, such as sprays, such as sprays, lotions, powders, lotions, powders, pet collars, kitchen, pet collars, kitchen, laundry, and laundry, and bathroom bathroom disinfectants and disinfectants and sanitizers, sanitizers, swimming pool swimming pool chemicals…chemicals…

Pesticides in AfricaPesticides in Africa

http://http://www.youtube.com/watch?vwww.youtube.com/watch?v=fUrTnpTP3Wk&feature=related=fUrTnpTP3Wk&feature=related

Why Use Pesticides?Why Use Pesticides?

Protect crops from weeds, insects and Protect crops from weeds, insects and mouldsmoulds

Prevent disease (eg West Nile Virus and Prevent disease (eg West Nile Virus and Malaria)Malaria)

Cosmetic reasons (lawns and golf Cosmetic reasons (lawns and golf courses)courses)

BioamplificationBioamplification

Is the increase of concentration of a Is the increase of concentration of a substance that occurs in a food chain substance that occurs in a food chain as a consequence of:as a consequence of:– Persistence (can’t be broken down by Persistence (can’t be broken down by

environmental processes)environmental processes)– Low rate of internal degredationLow rate of internal degredation– Low rate of excretion of the substanceLow rate of excretion of the substance

Bioamplification Occurs Bioamplification Occurs Because:Because:

Consumers ingest toxic Consumers ingest toxic preyprey

The concentration of The concentration of the pesticide increases the pesticide increases the higher up the food the higher up the food chainchain

RESULT:RESULT:

The more trophic levels The more trophic levels in a food web, the in a food web, the greater the greater the amplification of the amplification of the pesticide toxinpesticide toxin

Mercury in Our FishMercury in Our Fish

http://http://www.youtube.com/watch?vwww.youtube.com/watch?v=UCy0eC8Lldk&feature=related=UCy0eC8Lldk&feature=related

ddichloroichloroddiphenyliphenylttrichloroethanrichloroethane (DDT)e (DDT)

DDT was banned in North DDT was banned in North America in the 1970’s, but America in the 1970’s, but it is still used in many it is still used in many developing countries in the developing countries in the world.world.

Newer pesticides are Newer pesticides are somewhat safer:somewhat safer:– Water-soluble – can be Water-soluble – can be

excreted and broken down excreted and broken down in soil in soil

– Less bioamplificationLess bioamplification BUTBUT

– More doses needed to be More doses needed to be effectiveeffective

– Not selective – will Not selective – will kill/harm anythingkill/harm anything

Pesticide ResistancePesticide Resistance

http://http://www.youtube.com/watch?vwww.youtube.com/watch?v=f6sup-gNS54=f6sup-gNS54

Pesticide ResistancePesticide Resistance Organisms can adat to Organisms can adat to

changes and/or threats in changes and/or threats in order to ensure their order to ensure their survival.survival.

Pests have developed a Pests have developed a resistance to pesticides.resistance to pesticides.

The surviving pests pass The surviving pests pass those resistant genes on to those resistant genes on to their offspring, and soon their offspring, and soon the entire population is the entire population is resistant to the pesticides.resistant to the pesticides.

New pesticides have to be New pesticides have to be createdcreated

With each ne pesticide, With each ne pesticide, resistant pests will surviveresistant pests will survive

Pesticide Movement in Pesticide Movement in EcosystemsEcosystems

Not only do Not only do pesticides pesticides travel through travel through an ecosystem an ecosystem by the biotic by the biotic factors, but by factors, but by abiotic factors abiotic factors as well.as well.

Environmental LawEnvironmental Law

It is interesting that we humans It is interesting that we humans seem to only stop using pesticides seem to only stop using pesticides when they affect or pose a threat to when they affect or pose a threat to us. us.

We are finally now seeing laws put We are finally now seeing laws put into place in Ontario prohibiting the into place in Ontario prohibiting the purchase of cosmetic pesticidespurchase of cosmetic pesticides