•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