Chapter 23 The Pesticide Dilemma - PowerPoint PPT Presentation

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Chapter 23 The Pesticide Dilemma


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Title: Chapter 23 The Pesticide Dilemma

Chapter 23The Pesticide Dilemma
Defining Pests
  • Organism that is oxious, destructive
  • Competes with us for food, invades lawns/gardens,
    destroys houses, spreads disease
  • Injurious plant or animal

Defining Pests
  • Typical Characteristics
  • Reproduce rapidly
  • Migrate quickly
  • Pioneers in ecological succession
  • Compete aggressively against more specialized
  • Generalists

Defining Pests
  • Categories
  • Agricultural pests feed on crops or ornamental
  • Arachnids spiders, ticks, flour/grain/cheese
  • Crustaceans woodlice/pill bugs,
    flour/grain/cheese mites
  • Pathogens bacteria, viruses, fungi
  • Rodents house mouse, common rat
  • Insect pest examples

Types of Pesticides
  • Pesticides (Biocides) Chemicals developed to
    kill organisms that we consider undesirable.
  • 1. Insecticides - Insect-killers
  • 2. Herbicides - Weed-killers
  • 3. Fungicides Fungus-killers
  • 4. Nematocides Roundworm-killers
  • 5. Rodenticides Rat- and Mouse-killers

Pesticide Types
  • First-generation pesticides
  • Sulfur used as an insecticide since 500 BC
  • Arsenic (As), lead (Pb) and mercury (Hg) by the
  • Nicotine sulfate extracted from tobacco leaves
    in the 1600s
  • Pyrethrum obtained from the heads of
    chrysanthemum flowers
  • Rotenone from the root of the derris plant
  • Resistant pest populations developed

Types of Pesticides
  • Second-generation
  • Since 1950 pesticide usage has increased 50 fold
    and toxicities have increased 10 fold.
  • 10X more synthetic pesticides are used on the
    average home than on croplands in the US.
  • 75 of synthetic pesticides are used in the
    developed countries

Types of Pesticides
  • About 2.5 million tons of pesticides are used
    yearly, worldwide.
  • In the United States, about 630 different
    biologically active (pest-killing) ingredients
    and 1,820 inert (inactive) ingredients are mixed
    to make 25,000 different pesticide products.
  • DDT 1939, Entomologist Paul Mueller discovered
    that DDT (dichlorodiphenyltrichloroethane) was a
    potent insecticide. It soon became the worlds
    most-used pesticide. Awarded a Nobel Prize in
  • Broad-spectrum agents toxic to many species
  • Selective-spectrum agents effective against a
    narrowly defined group of organisms.

Types of Pesticides
Types of Pesticides
  • 1. Persistence the length of time in which
    pesticides remain deadly in the environment this
    may vary from days to years.
  • 2. Biomagnification the process by which toxins
    accumulate the higher you go in the food chain
    (generally because the toxin is not water soluble
    and therefore not easily excreted).

Pesticide Types Chemical Structure
  • o Inorganic pesticides (e.g. arsenic, copper,
    lead and mercury)
  • Generally highly toxic
  • Remain in soil forever
  • Generally neurotoxins

Types of Pesticides
  • Natural organic pesticides (botanicals)
  • Extracted from plants
  • Nicotine toxic to a broad spectrum of organisms
  • Rotenone used to kill fish
  • Turpentine and phenols effective pesticides

Types of Pesticides
  • Fumigants (e.g. carbon tetrachloride, carbon
  • Generally small molecules
  • Gasify easily
  • Penetrate rapidly into a variety of materials
  • Used to sterilize soil
  • Prevent decay or rodent and insect infestations
    of stored grain
  • Very dangerous to workers who apply them
  • Use has been curtailed or banned altogether

Types of Pesticides
  • - Chlorinated Hydrocarbons (organochlorines)
    (e.g. DDT, chlordane, aldrin)
  • Inhibit nerve membrane ion transport and block
    nerve signal transmission
  • Fast acting and highly toxic in sensitive
  • Highly persistent in soil
  • Stored in fatty tissues of a variety of organisms
  • Become concentrated through food chains

Types of Pesticides
  • Organophosphates (e.g. parathion, malathion)
  • Inhibit cholinesterase which is an enzyme
    essential for removing excess neurotransmitter
    from synapses in peripheral nervous system
  • Extremely toxic to mammals, birds, and fish
  • Less persistent in environment than

Types of Pesticides
  • Carbamates (e.g. carbaryl, aldicarb)
  • Share many organophosphate properties
  • Extremely toxic to bees

Types of Pesticides
  • Microbial agents and biological controls
  • Living organisms or toxins derived from them
    used in place of pesticides
  • Some species of bacteria kill caterpillars or
    beetles by releasing a toxin that ruptures that
    digestive tract.
  • Some parasitic wasps attack moth and caterpillar

Benefits of 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
  • DDT

Benefits of Pesticides
  • Disease Control
  • Insects and ticks serve as vectors in the
    transmission of a number of disease-causing
    pathogens and parasites
  • Diseases spread by biting insects
  • o Malaria
  • o Yellow fever
  • o Encephalitis
  • o Sleeping sickness
  • Diseases can be reduced by judicious use of

  • Crop Protection
  • Plant diseases, insect and bird predation, and
    competition by weeds reduce crop yields worldwide
    by at least 1/3.
  • Without modern chemical pesticides, losses might
    be much higher.
  • Farmers may save 3 to 5 for every 1 spent on
  • o Lower costs and generally better quality for
  • Cosmetic damage can greatly reduce the economic
    value of crops

Pesticide Problems
  • Effects on Nontarget Species
  • Estimated that up to 90 of the pesticides we use
    never reach their intended targets.
  • Many beneficial organisms are poisoned
    unintentionally as a result
  • o Sometimes effects are immediate
  • o Sometimes effects are not immediate and thus
    difficult to pin down
  • A 1999 study linked insecticide (4-nonylphenol)
    spraying on Canadian forests with dramatic
    declines in Atlantic salmon

Pesticide Problems
  • Pesticide Resistance and Pest Resurgence
  • Pesticides almost never kill 100 of a target
    species even under the most ideal conditions
  • The most resistant members of a population
    survive pesticide treatment and produce more
    offspring like themselves with genes that enable
    them to withstand further chemical treatment.
  • Pest resurgence because most pests propagate
    rapidly and produce many offspring, the
    population will quickly rebound with pesticide
    resistant individuals.
  • Pesticide treadmill due to pesticide resistance,
    it takes constantly increasing doses to get the
    same effect

Pesticide Problems
  • Creation of New Pests
  • Broadcast pesticide spraying may kill beneficial
    predators that previously kept a number of pests
    under control
  • Higher trophic levels are more likely to be
    knocked out than lower ones.

Pesticide Problems
  • Persistence and Mobility in the Environment
  • The qualities that make DDT and other chlorinated
    hydrocarbons so effective (stability, high
    solubility, and high toxicity), also make them
    environmental nightmares.
  • o Some of the compounds have been discovered far
    from any possible source and long after they were
  • o Can accumulate in polar regions through a
    series of evaporation, condensation, and
    precipitation events.
  • o Have a high affinity for fat

Pesticide Problems
  • Breakdown by-products may still be present in the
  • In a 1999 study, breakdown by-product of DDT,
    p,p'-DDE , is found in the amniotic fluid of 30
    of a sample of pregnant women in Los Angeles, CA.
  • o Atrazine and alochlor are widely used
  • 30 of all community wells and as much as 60 of
    all private wells in the mid-western corn belt
    are contaminated with atrazine and alochlor.
  • o Because of the ubiquity of these persistent
    organic pollutants (POPs), there is a widespread
    movement to ban them.

Human Health Problems
  • Pesticide effects on human health can be divided
    into 2 categories
  • Short-term effects, including acute poisoning
    and illnesses caused by relatively high doses and
    accidental exposures.
  • Long-term effects suspected to include cancer,
    birth defects, and immunological problems, and
    other chronic degenerative diseases.

Health Problems
  • The World Health Organization (WHO) estimates
    that between 2.5 and 5million people suffer from
    acute pesticide poisoning.
  • o At least 2/3 of this illness and death results
    from occupational exposures in developing
  • Long-term health effects difficult to document
    conclusively, however, links have been
  • o Significant learning and attention problems in
    children whose mothers at Lake Michigan fish
  • o Children from farming communities where
    pesticide use is high had diminished growth and
    development as compared to children with minimal
    pesticide exposure

  • In many cases, improved management programs can
    cut pesticide use between 50 and 90 with
    reducing crop production or creating new diseases

  • Behavioral
  • Crop rotation (growing a different crop in a
    field each year in a 2-to6-year cycle) keeps pest
    populations from increasing.
  • Mechanical cultivation can substitute for
    herbicide treatment, but can increase erosion
  • Flooding fields before planting can suppress
    both weeds and insect pests.
  • Burning crop residues and replanting with cover
    crop can suppress weeds and insect pests.

  • Behavioral
  • Habitat diversification
  • Growing crops where pests are absent
  • Adjusting planting times can avoid pest
  • Switching from monoculture to mixed polyculture
  • Tillage at certain times

  • Biological predators or pathogens that can
    control many pests more cheaply and safely than
    broad-spectrum, synthetic chemicals
  • o Bacteria can be sprayed on crops to control
  • o Ducks, chickens, and gees can rid fields of
    both insects and weeds.
  • o Insects including mantises and ladybugs protect
    against a multitude of pests.

  • Biological
  • Plants with insect-repelling properties such as
    garlic and marigolds.
  • Herbivorous insects can be used to control
  • Genetics and bioengineering
  • Breeding livestock that tolerate pests well
  • Hormones can be used to upset development or as
    sex attractants to bait traps containing toxic

Integrated Pest Management
  • Integrated pest management (IPM) flexible,
    ecologically based pest-control strategy that
    uses a combination of techniques applied at
    specific times, aimed at specific crops and
  • Does not give up pest controls entirely.
  • Enhances growth and diversity of beneficial
  • Enhance plant defenses

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

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

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

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

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)

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
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