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Chapter 16 Pests and Pest Control


CHAPTER 16 PESTS AND PEST CONTROL Environmental Science DDT Part 1 (continued) History of DDT: DDT (dichlorodiphenyltrichloroethane) is one of the most well-known ... – PowerPoint PPT presentation

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Title: Chapter 16 Pests and Pest Control

Chapter 16Pests and Pest Control
  • Environmental Science

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
  • Any current revisions?
  • How are exportations to developing countries
  • How are importations of food to our country

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

  • 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

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

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.

Pg. 418
DDT Part 2
  • Decline of birds on top of food chain (osprey,
  • 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
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
  • 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.

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

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

  • Since persisent pesticides are banned now,
    Agrochemical industry has created nonpersistent
    organic phosphates (malathion, parathion,
    chlorpyrifos) and carbamates (aldicarb and
  • 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
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)

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

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
  • 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)

SOCIOECONOMIC ISSUESbalancing crop yield,
nutrition, cosmetics and cash
  • Economic
  • Threshold
  • Insurance
  • Spraying
  • Cosmetic
  • Spraying
  • Snow white
  • syndrome
  • Organic
  • growing

Pg. 433
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

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
  • 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

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

  • DDT was not used for handling weeds but has saved
    millions of lives by controlling disease-causing
  • 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

  • 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
  • Lack of access to safe drinking water is a major
    cause of disease transmission in developing