Chapter 23 The Pesticide Dilemma

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Chapter 23The Pesticide Dilemma
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Pests

• Pest any organism that interferes in some way
  with human welfare or activities
• grouped by target organism they attack
• Insecticides kills insects
• Herbicides kills plants
• Fungicides kills fungus
• Rodenticides kills rodents

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Agriculture

• Sector that uses the most pesticides (85 world
  wide)
• Narrow spectrum pesticides pesticides that kill
  only the organism for which it was intended.
• Broad spectrum pesticides pesticides that kill
  a wide variety of organisms.
• Additional problems with pesticides more in
  environment, dont degrade.

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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, mercury and arsenic
• Organic compounds (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
• Endosulfan, lindane methoxychlor still in use
• Organophosphates
• Organic compounds that contain phosphorus
• Most poisonous insecticide
• Very poisonous toxic to birds, bees and aquatic
• organisms
• Do not persist as long as chlorinated
  hydrocarbons
• Carbamates
• Derived from carbamic acid, not toxic to mammals,
  broad spectrum

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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-which kill broad-leaf
  plants but not grasses
• Grass herbicides-kill grasses but not other
  plants
• Ex 2,4-D
• Non selective herbicides-kills all vegetation
• Famous example Agent Orange mixture of two
  herbicides that contain dioxins
• includes a variety of health effects tissue
  cancer, skin diseases, urological disorders
  birth defects

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Benefits and Problems with Pesticides

• Benefit Disease control, crop protection
• 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-leave some population
  untouched to prevent resistance

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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
• Bioaccumulation
• The buildup of a persistent pesticide or other
  toxic substance in an organisms body

• 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 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
• Lead-neurological development
• Mercury-biomagnification via fish and crabs

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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-leaving strips of un-harvested
  crops
• Proper timing of planting, fertilizing, and
  irrigating
• Crop rotation
• Biological Control
• Use of naturally occurring disease organisms,
  parasites or predators to control pests (such as
  lady bugs and praying mantises)
• 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
• 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
• IPM uses 3 premises
• Management rather than eradication
• Economic injury-dont take action until this
  point, use non toxic first
• Education-educate farmers as to all the
  alternatives
• Scout and spray-monitor for pests only spray
  when they become a problem
• Calendar Spraying-regular spraying whether need
  or not

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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)
• recognized need to regulate pesticides but
  had no teeth
• Pesticide Chemicals Amendment (1954)
• established acceptable levels of pesticides in
  food
• Delaney Cause (1958)
• prohibits cancer-causing substances in food
  (applies only to pesticides)
• Federal Insecticide, Fungicide, and Rodenticide
  Act (1947)
• regulated pesticide sale to prevent the sale
  of lemon (pesticides that dont work)
• requires disclosure of active ingredients but
  not inert ingredients
• Food Quality Protection Act (1996)
• Established pesticide residue limits in both
  raw and processed foods

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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)
• Stockpiles of banned pesticides, predominantly in
  developing countries

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Manufacture and Use of Banned Pesticides