•Rachel Carson was a scientist who wrote Silent Spring in 1962.•It addressed the growing use of pesticides (DDT) and their unpredicted effects on song birds.•Original users of pesticides did not know that the poisons used to kill insects would accumulate in other living things and kill them too. BIOACCUMULATION

Pesticides: Types and Pesticides: Types and UsesUsesWhat is a Pest?

A pest is any species that competes with us for food, invades lawns and gardens, destroys wood in houses, spreads disease, or is simply a nuisance

Most of the time nature takes care of the pests through natural enemies (predators, parasites, and disease organisms)

So what’s a Pesticide?So what’s a Pesticide?Pesticides (also known as

biocides) are chemicals that are to kill organisms we consider undesirable Insecticides

Herbicides

Fungicides

Nematocides

Rodenticides

Above: Worker prepares his vehicle for a day of pesticide

spraying

CoevolutionCoevolution For almost 225 million years,

plants have been producing chemicals to ward off or poison herbivores that feed on them…

But, through what is known as coevolution, the predators overcome various plant defenses by natural selection and the plants must develop new defenses

First Attempts at First Attempts at PesticidesPesticidesSulfur (early 500 BC)

Toxic compounds of arsenic, lead, and mercury (1400’s) Abandoned in late 1920’s when

the increasing number of human poisonings increased

Nicotine Sulfate (1600’s)

Pyrethrum and Rotenone (mid-1800’s)

Paul Mueller and the Paul Mueller and the Second Generation Second Generation

In 1939 Paul Mueller discovered that DDT, a chemical known since 1874, was in fact a potent insecticide. DDT became the first pesticide of the so-called Second Generation Pesticides. Mueller went on to win the Nobel Prize in 1948 for his discovery.

Pesticides TodayPesticides TodayChemists have been developing

hundreds of synthetic organic chemicals for use as pesticides

Worldwide about 2.3 million metric tons of pesticides are used yearly 1 lb for each person on earth 75% in developed countries (Latin

America, Asia and Africa on the rise) 1996 world sales = $30 billion($11

billion: US)

Here in the USHere in the USAbout 630 different

biologically active (pest killing) ingredients and about 1,820 inert (inactive) ingredients are mixed to make some 25,000 different pesticide products in the United States

Resistance to pesticidesResistance to pesticidesSome individuals are genetically

immune to a pesticide. They survive and pass these genes to

their offspring.Pesticides stop being effective.

Pesticide Distribution in Pesticide Distribution in USUSCultivation of two crops

Cotton (55%) Corn (35%)

Used about 90% of the insecticides and 80% of the herbicides applied to crops in the United States in 1995

Example of Solid Pesticides

More DistributionMore Distribution25% of the pesticide use in the United

States is for ridding houses, gardens, lawns, parks, playing fields, swimming pools, and golf courses of unwanted pests

Average lawn in US = 10x’s more pesticides per hectare than US cropland

Each year = 250,000 residents become ill

Biological controlBiological control

Biological control (Biocontrol): uses a pest’s natural predators to control the pest Leads to steep

reductions in chemical pesticide use

Cactus moths control invasive prickly pear cactus

Bacillus thuringiensis (Bt): soil bacteria that kills many pests

Biocontrol involves risksBiocontrol involves risks No one can predict the

effects of an introduced species.

The agent may become invasive and harm non-target organisms. Cactus moths are eating

rare Florida cacti.

Removing a biocontrol agent is harder than halting pesticide use. The harm done by

biocontrol agents may be permanent.

Some Quick FactsSome Quick FactsBroad-Spectrum agents : toxic

to many species

Selective or Narrow spectrum agents : effective against a narrowly defined group of organisms

Pesticides vary in persistence (length of time they remain deadly in environment)

The ProsThe Pros Pesticides save human lives: has

prevented premature births due to malaria, bubonic plague, typhus, sleeping sickness (all carried by pests)

Pesticides increase food supplies and lower food costs: 55% of crop lost before harvest due to pests

Pesticides increase profits for farmers: every $1 spent on pesticides yields worth approximately $4 (although dropped to $2 if harmful effects)

More ProsMore ProsPesticides work faster and better than

alternatives: Pesticides can control pests quickly and at a reasonable cost. Long shelf life and easily shipped and applied

Health risks insignificant when compared to their benefits Safer more effective pesticides are being

developed

New pesticides are being used in less rates per unit when compared to older products

Ultimate Goal of PesticidesUltimate Goal of PesticidesKill only the target pest

Harm no other species

Disappear or break down into something harmless after doing its job

Not cause genetic resistance in target

Be cheaper than doing nothing

The ConsThe ConsGenetic Resistance: pest organisms

develop resistance to the pesticide after a short period of being exposed to it

Broad-Spectrum insecticides kill natural predators and parasites that may have been maintaining the population of a pest species at a reasonable level Ex. Wolf spiders, wasps, predatory beetles…

Cons continued…Cons continued…

Because natural predators can be wiped out; this may unleash new pests whose populations the predators had previously held in check

In Our WaterIn Our WaterTesting in rivers

and water reveal that pesticides have strayed away from there targets and found there way into the waters

Pesticide TreadmillPesticide TreadmillAs pests become resistant to the

pesticides, sales reps for the pesticide recommend larger doses or more frequent application As a result farmers end up on a

pesticide treadmill where they end up paying more and more for a pest control program that often becomes less and less effective

Pesticide TreadmillPesticide Treadmill Pesticides become less effective over time Genetic resistance to pesticides develops in pest

species – natural selection Some individuals have a gene that makes them

resistant to a pesticide, they pass the gene onto their offspring so that the entire population becomes resistant

This requires a more frequent sprayings, larger doses or a switch to new pesticides

Yields have decreased because of pesticide resistance since second generation pesticides have come into use

Example of Pesticide Example of Pesticide TreadmillTreadmill In Central America, cotton

growers increased the frequency of insecticide applications from 10 to 40 times per growing season. Still, declining yields and falling profits forced many of the farmers into bankruptcy

Figure 13.1

Insecticideapplication

Chromosome with gene conferring resistance to insecticide

Survivors

Additional applications of the same insecticide will be less effective, and the frequency of

resistant insects in the population will grow

Where does it all go?Where does it all go?

Only about 2% of the sprayed insecticide by air reaches target pests

Less than 5% of herbicides applied reach target weed

Pesticides that don’t reach there target end up in the air, surface water, groundwater, bottom sediments, food and other non-target organisms

ContinuedContinued

Still, pesticide waste can be reduced by using re-circulating sprayers, covering spray booms, and using rope-wick applicators

DDTDDTBanned in 1972 by US

1980 high levels in peregrine falcon and the osprey

EPA found DDT in 99% of the freshwater fish it tested

DDT drifts from other countries still using it

DDT accumulates in fat body tissues of animals

DDT was not used for handling weeds

DDT is, persistent, synthetic organic compound and a subject to biomagnifications in food chains

World’s Worst Industrial World’s Worst Industrial AccidentAccident Bhopal, India

Occurred December 2, 1984

Union Carbide (a pesticide manufacturer)

MIC (methyl isocyanate) gas leaked

the cooling system malfunctioned and the tank exploded

Gas affected 30 square miles and an estimated 600,000 people were exposed

BhopalBhopal

Officially 5,100 people were killed (probably anywhere from 7,000 – 15,000 died)

50,000 – 60,000 sustained permanent injuries, blindness or lung injuries

The Cause?The Cause?

Indian government claims it was caused by company negligence

The company claims sabotage by a disgruntled former worker

Regulation in the USRegulation in the US All commercial pesticides must be

approved by EPA EPA reviews each pesticide EPA sets tolerance levels : amount of

toxic pesticide residue that can legally remain on crop

No longer has to test on birds and fish 55 active pesticides banned in US, but

may be used and shipped elsewhere

More RegulationsMore Regulations

National Academy of Sciences says that the federal laws are not adequate

98% of potential risk of cancer would be eliminated if pesticide residue on food eliminated by government

Approximately $1 Billion spent on regulating pesticides each year

FIFRA and the EPAFIFRA and the EPA Federal Insecticide, Fungicide, Rodenticide

Act All commercial pesticides must be

approved for use The pesticide companies evaluate the

biologically active ingredients in their products and the EPA reviews the data

When a pesticide is approved for use on fruits or vegetables, a tolerance level is set that can legally remain on a crop when a consumer eats it

1996 Food Quality 1996 Food Quality Protection ActProtection Act Requires food to have only reasonable

levels of pesticide tolerance

It requires manufacturers to demonstrate that the active ingredients in there products are safe for infants and children

Requires EPA to consider exposure to more thatn one pesticide when setting pesticide tolerance levels

EPA develops program to screen ingredients

From AboveFrom Above

Just one of the many ways that pesticides are being applied are through aerial drops of the chemicals

Other SolutionsOther SolutionsCrop rotations

Planting times can be adjusted

Plowing at night (reduces weeds)

Plant where major pests do not exist

Switch away from monoculture to intercropping, agroforestry, and polyculture

More SolutionsMore Solutions Plants and animals that are genetically

resistant to certain pest insects, fungi and diseases can be developed

- downside: costly

Biological control: predators and pathogens

300 biological pest control successful in China and Cuba

Biological Control: non-toxic to humans Downside: timely

We depend on insects to We depend on insects to pollinate cropspollinate cropsMost insects do not harm agriculture,

and some are absolutely vital. 800 cultivated plant species rely on insect

pollinators.Pollination: male plant sex cells (pollen)

fertilize female sex cells By wind or animals

Pollinators include: Hummingbirds Bats Insects

Colony Collapse Colony Collapse DisorderDisorder Populations of native

pollinators have plummeted.

Honeybees pollinate more than 100 crops — 1/3 of the U.S. diet. Recently, introduced

parasitic mites have devastated hives.

To conserve pollinators: Reduce or eliminate

pesticide use Plant gardens of

flowering plants

Even more Solutions…Even more Solutions…Plant toxins

Bt toxin used to kill thousands of strain of common soil bacterium

Insect Birth Control (sterile male approach)

Aqua heat: spray boiling water on crops

Fish or frankenfish? Fish or frankenfish? FDA weighs altered salmonFDA weighs altered salmon

Yes… more Yes… more solutionssolutions

Some crops can be exposed to gamma rays after harvest Extends shelf life

Critics say irradiating food destroys vitamins and other nutrients

Increases death from botulism poisoning

Picowaved stickers on food that has been

Integrated Pest Integrated Pest Management (IPM)Management (IPM)IPM uses multiple techniques to

suppress pests. Biocontrol Chemicals, when necessary Population monitoring Habitat alteration Crop rotation and transgenic crops Alternative tillage methods Mechanical pest removal

Integrated Pest Integrated Pest Management (IPM)Management (IPM)Each specific crop and its pest(s)

are evaluated

It requires a mix of biological, cultivation and chemical practices

Pests populations are not eradicated, but carefully managed so that crop destruction is minimized

IPMIPMBiological methods – predators,

parasites, disease organisms, sterilization, sex attractants, hormones

Cultivation – vacuuming, planting times, trap crops, polyculture, intercropping, agroforestry

Development of genetically resistant plants, genetically engineered plants

Chemical pesticides in small amounts are used as a last resort

IPMIPM Integrated Pest Management

Goal is reduction of crop damage to an economically tolerable level Carefully monitor damage levels of

pests

When reached, farmers first use biological methods

Small amounts of insecticides are used as a last resort

Pesticides in PoliticsPesticides in PoliticsPesticides

have been a big issue with environmentally safe activists. It is a big topic the EPA has to deal with