Chapter 16 Pests and Pest Control

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Chapter 16Pests and Pest Control

• Environmental Science

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Learning Objectives

• Define pest
• Why do we control pests?
• What are the methods to control pests and the
  philosophies of pest control?
• What are the problems with pesticides?
• Define Integrated Pest Management, is it
  successful?
• Any current revisions?
• How are exportations to developing countries
  regulated?
• How are importations of food to our country
  regulated?

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Vocabulary

• Pest any organism that is noxious, destructive,
  or troublesome
• Agricultural pests
• Insecticide toxin aimed at killing insects
• Herbicide toxin aimed at killing plant or
  fungus
• Pesticide toxin aimed at killing all pests

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PHILOSOPHIES OF PEST CONTROL

• Chemical Treatment
• Ecological Control long-lasting protection
• Against pest or ecosystem
• Integrated Pest Management
• First generation pesticides toxic heavy metals
• Second-generation pesticides synthetic organic
  chemistry

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DDT PART 1 1940s 1950s

• General Consensus at the time
• Toxic to insects and NOT to humans
• Broad spectrum, kills all types of insects, but
  relatively low risk to mammals
• Persistent (sticks around without degradation)
• Saved many lives during WWII to prevent spread of
  body lice and death from typhus fever (sores, ab
  pain,deliria) also used in tropics to stop the
  spread of malaria by mosquitoes
• Used to increase crop production by controlling
  insect pests in agriculture

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DDT Part 1 (continued)

• History of DDT
• DDT (dichlorodiphenyltrichloroethane) is one of
  the most well-known synthetic pesticides
• 1874 - synthesized
• 1939 - DDT's insecticidal properties discovered,
  where it kills by opening sodium ion channels in
  the neurons, causing them to fire spontaneously
  leading to spasms and eventual death
• used with great success in the second half of
  World War II to control malaria and typhus among
  civilians and troops
• after the war, DDT was made available for use as
  an agricultural insecticide, and soon its
  production and use skyrocketed.
• 1948 - Swiss chemist Paul Hermann Müller was
  awarded the Nobel Prize in Physiology or Medicine
  "for his discovery of the high efficiency of DDT
  as a contact poison against several arthropods.

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Pg. 418
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DDT Part 2

• Decline of birds on top of food chain (osprey,
  eagles)
• Eggs breaking before hatched
• Bioaccumulation synthetic organics and breakdown
  products trapped in bodys lipids
• Biomagnification multiplying affect of
  bioaccumulation as you move up food chain,
  negative in this case

Pg. 423
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DDT Part 2 (continued) 1960s - today

• 1962, Silent Spring by American biologist Rachel
  Carson was published, cataloguing the
  environmental impacts of the indiscriminate
  spraying of DDT in the US and questioned the
  logic of releasing large amounts of chemicals
  into the environment without fully understanding
  their effects on ecology or human health.
• The book suggested that DDT and other pesticides
  may cause cancer and that their agricultural use
  was a threat to wildlife, particularly birds.
• Its publication was one of the signature events
  in the birth of the environmental movement, and
  resulted in a large public outcry that eventually
  led to DDT being banned in the US in 1972.

• DDT was subsequently banned for agricultural use
  worldwide under the Stockholm Convention, but its
  limited use in disease vector control (like
  malaria) continues to this day and remains
  controversial.
• the US ban on DDT (and Endangerd Species Act of
  1973) is cited by scientists as a major factor in
  the comeback of the bald eagle from
  near-extinction in the contiguous US.

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Problems with chemical pesticides

• Since the plant eating insects (the pests) are
  part of a dynamic ecosystem, Chemical treatments
  of crops can lead to pesticide treadmill as seen
  on page 418
• Pest problem surpasses economic threshold ? use
  chemical pesticides ? surviving pests develop
  resistance to that dosage leading to resurgence
  of stronger pests
• Thru biomagnification of pesticide effects the
  predator insects are killed off more than actual
  pest ? allowing for resurgence AND secondary
  outbreaks (when other plant eating insects
  previously not pests become pests due to having
  no predators ? higher and more severe pest
  problem ? leads to ever-increasing dosages of
  pesticides and dependence on them ? more
  contamination of food stuffs and ecosystem.YUCK
• Human Health Effects
• Poisoning (toxin)?
• Cancer (carcinogenic)?
• Birth Defects (teratogen)
• Endocrine Disruptors like atrazine and alachor
  weed killers. (increased breast cancer and
  defective or low sperm counts, other sexual
  abnormalities)

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Solution nonpersistent pesticides or IPM
Environmental Effects of Chemical Pesticides

• Toxicity through biomagnification up food chain
• Broad effect on unintended organisms (like us)
• Location of application (in a riparian
  environmental, a watershed or upwind)
• Effect on beneficial insects
• Persistent take a long time to break down esp.
  chlorinated hydrocarbons, long-range danger and
  long term

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NONPERSISTENT PESTICIDES

• Since persisent pesticides are banned now,
  Agrochemical industry has created nonpersistent
  organic phosphates (malathion, parathion,
  chlorpyrifos) and carbamates (aldicarb and
  carbaryl)
• Typically inhibit enzyme cholinesterase essential
  for proper functioning of nervous system in
  insects, and all animals (us too)
• Dangers
• Persistent enough to ride the food supply from
  farmer to consumer (few weeks to break down)
• Many are more toxic to mammals than older
  chlorinated hydrocarbons varieties like DDT
  (higher LD50) and require more applications
  (higher dosage)
• Still kill beneficial insects and have
  biomagnification effect see Argentina Hawk
  problem pg 421

Dupont Agrosciences
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4 Categories of natural or biological PEST CONTROL

• 1. Cultural nonchemical alteration of
  environmental factors (import restrictions, grass
  lawn of at least 3 inches high keeps away most
  crabgrass noxious weeds, crop rotation)
• 2. Control by natural enemies/predators
  (parasitic wasp uses gypsy moth pupa
• or tomato hornworms, or less pesticide
• spraying to allow natural return predators
• to control brown planthoppers on rice)
• 3. Genetic Control
• Chemical Barriers (crossbreeding of plants to
  enhance toxic chemical production by plant like
  with Hessian fly and wheat leaves)
• Physical Barriers (hooked sticky hairs on stems
  to trap small larva)

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4 Categories of natural or biological PEST CONTROL

• 3. Genetic Control (cont.)
• Sterile Males so no successful offspring
• Biotechnology to introduce genes from bacteria,
  virus or other plant species (GMOs like
  engineering Bt, a bacillus thuringienis protein,
  into plants which kills larva of plant eating
  insects,but harmless to mammals birds) (Roundup
  herbicide resistant gene in crops, 90 of US
  soybean crop is Roundup Ready)
• 4. Natural Chemical Controls
• Use of hormones (chemical signals) like
  pheromones to cause physiological issues or stunt
  development cycle (Juvenile hormone prevents
  pupation, or Mimic emulates ecdysone hormone
  causing molting to begin but not finish

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Integrated Pest Management (IPM)

• Coordinated use of pest environmental
  information to develop the best feasible control
  methods, often using natural pathways to promote
  sustainable control when possible
• In a way that is the least harmful to people,
  property and environment and still cost effective
• Emphasis is on pest control not eradication
• Targeted, finely tuned common-sense methods as
  opposed to indiscreminate toxification of
  EVERYTHING
• A return to old-school, pre-chemical industry
  methods of pest management
• 4 Tiered Approach Pest Action Threshold,
  Information Building, Prevention First, Control
  and Reduction (biological first, then narrow
  range synthetic, then broad spectrum synthetic
  (see IPM Notes ppt for more details)

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SOCIOECONOMIC ISSUESbalancing crop yield,
nutrition, cosmetics and cash

• Economic
• Threshold
• Insurance
• Spraying
• Cosmetic
• Spraying
• Snow white
• syndrome
• Organic
• growing

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Pg. 433
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Concerns when regulating pesticide

• Evaluated for intended use and impacts on
  environmental health
• Proper training and safety of agricultural
  workers using it
• Risk of pesticide residue on our food

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PUBLIC POLICY (pg 432 433)

• FFDCA 1938 (Federal Food, Drug, and Cosmetic Act)
  is a piece of legislation that first started the
  control pesticide residues left on food eaten in
  the US the Delaney Clause was controversial
  because it prevented any trace of a pesticide
  that had evidence of being carcinogenic in lab
  animal tests (too restrictive?)
• 3 agencies involved EPA sets allowable
  tolerances ? FDA monitors and enforces all food
  except meat while USDA (US Dept of Ag) enforces
  meat, poultry and eggs
• FIFRA 1947 1972 (Federal Insecticide,
  Fungicide, and Rodenticide Act)
• Must register pesticide, label lists active
  ingredients
• FQPA 1996 (Food Quality Protection Act)
• The new law regulating safe amounts of pesticide
  residue on food, requiring reasonable certainty
  of no harm, especially in chronic cause of cancer
  or exposure to children
• Developing Countries and Importing Foods
• Prior informed consent (PIC) managed by FAO
  importers and exporters inform each other of
  practices

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New Policy Needs

• Reduction of pesticide use
• Develop methods that rely on biological control
  and use of natural processes
• Adopt IPM practices
• Adopt precautionary principle (like European
  Union has) of requiring burden of proof on
  manufacturers not consumers, meaning a new
  chemical must be proven safe rather than assumed
  safe until long term problems develop

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DDT

• DDT was not used for handling weeds but has saved
  millions of lives by controlling disease-causing
  pests
• The 1948 Nobel prize was awarded to Paul Muller
  for discovering DDT
• DDT is a cheap, persistent, synthetic, organic,
  compound is subject to biomagnifications in
  food chains

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Diseases

• Lyme disease can be transferred to humans through
  a bite from an infected tick (vector)
• Mosquitoes are the vector for Malaria
• The protozoan of the genus Plasmodium is the
  causative agent of malaria
• DDT is great at killing mosquitoes should we use
  it?
• Lack of access to safe drinking water is a major
  cause of disease transmission in developing
  countries.