Chapter 23 The Pesticide Dilemma

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Chapter 23The Pesticide Dilemma
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Overview of Chapter 23

• What is a Pesticide?
• Major Kinds of Pesticides
• 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

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What is a Pesticide

• Broad spectrum pesticide
• A pesticide that kills a variety of organisms,
  not just the targeted organisms

• First generation pesticide
• Inorganic compounds
• Lead and mercury
• Botanicals- plant derived pesticides
• Nicotine and pyrethrin

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What is a Pesticide

• Second generation pesticide
• Synthetic poison
• Ex DDT

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Major Groups of Insecticides

• Chlorinated Hydrocarbons
• Organic compound containing Chlorine
• Ex DDT
• Slow to degrade and persist in the environment
• Banned or largely restricted
• Organophosphates
• Organic compounds that contain phosphorus
• Most poisonous insecticide
• Do not persist as long as chlorinated
  hydrocarbons
• Cabamates
• Derived from cabamic acid

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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-D

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Benefits and Problems with Pesticides

• Benefit Disease control
• Fleas, lice and mosquitoes carry disease

• Malaria- mosquito born
• 2.7 million people die each year
• Few drugs available, so focus is on killing
  mosquitoes
• DDT

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Benefits and Problems with Pesticides

• Benefit Crop Protection
• Pests eat and destroy 1/3 of worlds 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)

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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

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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

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Benefits and Problems with Pesticides

• Problem Creation of New Pests
• Infestation of red scale insects on lemons after
  DDT sprayed to control another pest

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Benefits and Problems with Pesticides

• Problem Persistence, Bioaccumulation, and
  Biological Magnification
• Persistence
• Do not degrade readily into less harmful
  compounds
• Linger in the environment
• Bioaccumulation
• The buildup of a persistent pesticide or other
  toxic substance in an organisms body

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Benefits and Problems with Pesticides

• Problem Persistence, Bioaccumulation, and
  Biological Magnification

• Biological magnification
• Increased concentration of toxic chemicals in
  tissues of organisms at higher trophic levels
• Ex Peregrine falcons (right)

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Benefits and Problems with Pesticides

• Problem Persistence, Bioaccumulation, and
  Biological Magnification

• Persistent Organic Pollutants (aka POPs) are
• chemicals that last for years in the environment
• build up in humans and other animals
• move around the world on wind and water currents
• This class of chemicals, which included many
  pesticides, has been targeted for elimination by
  international treaty.

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Benefits and Problems with Pesticides

• Problem Mobility in the Environment
• Do not stay where they are applied
• Move through soil, water and air

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Risk of Pesticides to Human Health

• Short-term Effects of Pesticides
• Handling food with pesticide residue

• Mild case nausea, vomiting, headaches
• Severe case damage to nervous system,

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Risk of Pesticides to Human Health

• Long-term Effects of Pesticides
• Cancer- lymphoma
• Breast cancer
• Sterility
• Miscarriage
• Birth defects
• Decreases bodys ability to fight infection
• Potential connection to Parkinsons disease

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Alternatives to Pesticides

• Using cultivation methods to control pests
• 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

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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
• Reproductive Controls
• Sterilizing some of the members
• Sterile male technique

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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

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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

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Systems Approach- Integrated Pest Management (IPM)

• Rice Production in Indonesia

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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

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Laws Controlling Pesticide Use

• Food, Drug, and Cosmetics Act (1938)
• Pesticide Chemicals Amendment (1954)
• Delaney Cause (1958)
• Federal Insecticide, Fungicide, and Rodenticide
  Act (1947)
• Food Quality Protection Act (1996)

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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)

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Manufacture and Use of Banned Pesticides