Download Pesticides and ag

The Pesticide Dilemma ch 10
Salad Vac:
This machine controls
insect pests without
the use of chemical
pesticides
Overview
• What is a Pesticide?
– Major Kinds of Pesticides
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Benefits and Problems With Pesticides
Risks of Pesticides to Human Health
Alternatives to Pesticides
Laws Controlling Pesticides Use
The Manufacture and Use of Banned
Pesticides
What is a Pesticide
• Any organism that interferes with Human
welfare is called a “pest”
• Pesticides: toxic chemicals that kill pests
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Types:
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Insecticide = kills insects
Herbicide = kills plants
Fungicide = kill fungi
Rodenticide = kills rodents
(careful when using around household
pets)
What is a Pesticide
• Broad spectrum pesticide
– A pesticide that kills a variety of organisms, not just the targeted
organisms (ideally we would use “narrow spectrum”
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First generation pesticide
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Inorganic compounds
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Lead and mercury
Botanicals- plant derived
pesticides
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Nicotine and pyrethrin
Chrysanthemum flowers are
used to make pyretherine
(insecticide)
What is a Pesticide
• Second generation pesticide
– Synthetic poison
– Ex: DDT
– dichlorodiphenyltrichloroethane
Major Groups of Insecticides
• Chlorinated Hydrocarbons
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Organic compound containing Chlorine
Ex: DDT (used during 1940’s – 1960’s)
Slow to degrade and persist in the environment
Banned or largely restricted (US still uses endosulfane, lindane,
methoxychlor)
– Rachel Carson’s “Silent Spring” raised awareness regarding problems
with the use of these broad spectrum pesticides
• Organophosphates
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Organic compounds that contain phosphorus
Most poisonous insecticide
Do not persist as long as chlorinated hydrocarbons
Toxic to humans: methamidophos, dimethoate, and malathion still used today
• Carbamates
– Derived from cabamic acid
– Not as toxic to humans; carbaryl and aldicarb are most commonly used
Major Kinds of Herbicides
• Selective Herbicides
– Kill only certain types of plants
– Can be classified to the type of plant they kill
• Broad-leaf herbicides
• Grass herbicides
– Ex: 2,4-Dichlorophenoxyacetic acid
Use of Herbicides in the Vietnam
War
– Carried out from 1962-1971
– Sprayed more than 12 million gallons of herbicides
– Agent Orange
– Dioxin
– Breast milk of vietnamese women 1800 ppm
compared to that of US = 4 ppm
– Bioaccumulation
– Birth defects/cancer/tumors/nervous system
damage
Benefits and Problems with Pesticides
• Benefit: Disease control
– Fleas, lice and mosquitoes carry disease
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MalariaAnophelese
mosquito
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2.7 million people
die each year
Few drugs available,
so focus is on killing
mosquitoes
DDT used
Benefits and Problems with Pesticides
• Benefit: Crop Protection
– Pests eat and destroy 1/3
of world’s crops
– Farmers save $3 to $5 for
every $1 they invest in
pesticides
• Problem: Evolution of
Genetic Resistance
– Pest populations are
evolving resistance to
pesticides (right)
Pesticide Resistance
• Pesticide Treadmill
– Cost of applying pesticide increases
• Because they must be applied more frequently or in
larger doses
– While their effectiveness decreases
• Because of increased genetic resistance in pests
• Resistance Management
– Strategies for managing genetic resistance in order
to maximize the period in which a pesticide is
useful
– Delays the evolution of genetic resistance
• Refuge of untreated plants
Benefits and Problems with Pesticides
• Problem: Imbalances the Ecosystem
– Spraying to kill insects can affect birds, rabbits,
etc.
– Despite 33-fold increase in pesticides since the
1940s, crop loss has not really changed
Benefits and Problems with Pesticides
• Problem: Creation of New Pests
– Infestation of red scale insects on lemons after
DDT sprayed to control another pest
Benefits and Problems with Pesticides
• Problem: Persistence, Bioaccumulation, and
Biological Magnification
– Bioaccumulation
• The buildup of a persistent pesticide or other toxic
substance in an organisms body
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Biological magnification
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Increased concentration of
toxic chemicals in tissues of
organisms at higher trophic
levels
Ex: Peregrine falcons (right)
Benefits and Problems with Pesticides
• Problem: Mobility in the Environment
– Do not stay where they are applied
– Move through soil, water and air
Risk of Pesticides to Human Health
• Short-term Effects of Pesticides
– Handling food with pesticide residue
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Mild case: nausea,
vomiting, headaches
Severe case: damage
to nervous system,
death
3-million humans
exposed and 220,000
die annually
Risk of Pesticides to Human Health
• Long-term Effects of Pesticides
– Cancer- lymphoma
– Breast cancer
– Sterility
– Miscarriage
– Birth defects
– Decreases body’s ability to fight infection
– Potential connection to Parkinson’s disease
Alternatives to Pesticides
• Using cultivation methods to control pests
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Interplant mixtures of plants (alternating rows)
Strip cutting
Proper timing of planting, fertilizing, and irrigating
Crop rotation
• Biological Control
– Use of naturally occurring disease organisms, parasites or
predators to control pests
– Must take care that introduced agent does not attack
unintended hosts (Ex:Vedalia beetle feeding on cottonycusion scale; also lady bugs and aphids)
Alternatives to Pesticides
• Pheromones and Hormones
– Can use pheromones to lure pests to traps
– By applying insect hormones at wrong time in life
cycle, insects can be killed off ( Ex: cause pre
mature molting in caterpillars)
• Reproductive Controls
– Sterilizing some of the members
– Sterile male technique
Alternatives to Pesticides
• Genetic Controls
– Genetically Modified plants (GMOs)
• Bt toxin
• Potential problem: may affect non-target species
(monarch butterfly)
• Quarantine
– Restriction of the importation of exotic plant and
animal material that might harbor pests
– Effective, but not foolproof
– USDA has blocked the importation of medflies on more than 100
separate occasions
Systems Approach- Integrated Pest
Management (IPM)
• IPM
– Combination of pest
control methods that
keeps pest population
low without economic
loss
• Conventional pesticides
are used sparingly when
other methods fail
Systems Approach- Integrated Pest
Management (IPM)
• Rice Production in Indonesia
IPM
Introduced
Alternatives to Pesticides
• Irradiating Food
– Harvested food is expose to ionizing radiation,
which kills many microorganisms
– Predominantly used on meats
– Somewhat controversial due to potential for free
radicals
Laws Controlling Pesticide Use
• Food, Drug, and Cosmetics Act (1938)-recognized need
to regulate pesticides found in food but did not address “how”
• Pesticide Chemicals Amendment (1954)established acceptable/unacceptable levels of pesticides
• Delaney Cause (1958)- no chemical that has been proven to
cause cancer in test animals can be used in processed food
• Federal Insecticide, Fungicide, and
Rodenticide Act (1947)- prevented the purchase of pesticides
that did not work
• Food Quality Protection Act (1996)- (ammended FDCA
and FIFRA) established reisdue pesticide limits that pose a threat to infiants.
Finally, BMI was taken into consideration for LD’s
Manufacture and Use of Banned Pesticides
• Some US companies still make banned or
seriously restricted pesticides
– Product is exported
• May lead to the importation of food tainted
with banned pesticides
• Global ban of persistent organic pollutants
– Stockholm Convention on Persistent Organic
Pollutants (2004)
Manufacture and Use of Banned Pesticides