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Chapter22 Pp Presentation Chapter22 Pp Presentation Presentation Transcript

  • The Pesticide Dilemma Chapter 22
  • What is a Pesticide?
    • Pests are any type of organism that interferes with humans in some way.
    • Pesticides are the toxic chemicals that we use to decrease the numbers of pests.
      • Types: Herbicides, Insecticides, fungicides and rodenticides
      • Some are botanicals (ex: from plants) – nicotine and pyrethrin (ex: from flowers)
      • Some are synthetic – DDT first used in 1939; we didn’t learn of persistence & harm until 1962, Silent Spring.
  • Range of pesticides
    • Narrow-spectrum pesticides :
      • Kills organisms it was intended to.
    • Broad-spectrum pesticides :
      • Kills a variety of organisms.
      • Most pesticides, such as Round-Up
  • Major types of Herbicides
    • Broad Leafed Herbicides
      • Kill plants with broad leaves but leave grasses alone.
        • (Tend to mimic growth hormones & disrupt metabolism.)
    • Grass Herbicides : kill grasses but leave broad leaves alone.
  • Effect of use of Herbicides in Vietnam
      • Agent orange was sprayed over jungles to kill vegetation.
      • It also contained a compound called dioxin , which had severe effects on the Vietnamese and war Veterans.
        • The jungles are about 30% reduced today.
        • Besides birth defects and cancer, the compound is still present within the population; Some Vietnamese have about 1800 ppt.
        • Typically normal people have about 4 ppt.
  • Benefits of Pesticides
    • Disease control
      • Mosquitoes are effective vectors of many diseases, such as malaria in the tropics
      • DDT effectively kills mosquitoes.
        • But the banning of DDT allowed for the return of malaria.
    • Crop production
    • - Farmers save $3-$5 in crops for every $1
    • invested in pesticides
  • Evolution of Genetic Resistance
    • Pesticide treadmill
    • (pest becomes resistant so pesticide needs to be increased &/or it’s chemistry improved)
    • Imbalances in Ecosystems
        • Pesticides also tend to kill the natural predators of the pests by starvation .
      • DDT was sprayed onto lemon trees but allowed a scale insect to proliferate.
    • Bioaccumulation:
      • Most synthetic pesticides are unable to be broken down by bacteria.
        • Slowly this compound will
        • increase in concentration
        • in soil and organisms .
    • Biomagnification:
    • aka Biological amplification
    • - Increase in pesticide concentration as it passes through the food chain.
    • - Many countries subsidize pesticides, hoping for larger crops.
  • Mobility in the Environment (land -> air -> water)
  • Short-term Effects of Pesticides: Handling of food with pesticide residue can result in headache, vomiting, diarrhea etc.
  • Bhopal, India disaster 1984
    • 40 tons of poisonous gas was released from a Union Carbide pesticide plant after water leaked into storage tank, causing a massive explosion
    • covering 30 mi 2 .
    • 600,000 people exposed , many with health problems, especially blindness; 2500 immediately killed.
    • UC paid $500 to each victim but have
    • not cleaned up the land & groundwater.
  • Long-term Effects of Pesticides
    • Higher risk of cancer
    • Sterility
    • Miscarriage / birth defects
    • Higher risk for Parkinson’s disease
    • Acts as an endocrine disrupter , altering reproductive capabilities
    • Suppresses development of intelligence & motor skills of children
  • Alternatives to Pesticides
    • Using Cultivation Methods to Control Pests
    • Intercropping
    • Strip cutting (harvest one segment at a time)
    • Planting, fertilizing & irrigating at proper time
    • Crop rotation
    • Biological Controls
    • Using naturally occurring diseases, parasites, or predators to control a pest.
    • Be careful introducing exotics!
    • Pheromones and Hormones
    • Use pheromones to attract insects to traps
    • Synthetic hormones induce abnormal
    • development
    • Reproductive Controls
    • Sterile-male technique – inundate pest population with large numbers of sterile males
    • Genetic Controls (GMOs) – resistant to pests
    • Quarantine – restriction of the importation of exotic plants & animal materials that might harbor pests.
    • Irradiating foods – especially meat, kills many organisms
    • Integrated Pest Management ( IPM )
    • Identifies the best practices of biological, cultivation & pesticide control for each crop .
    • The pest is managed, not eradicated . Minimal crop damage is expected.
    • Initially requires a lot of money and time for each complete study.
  • IPM & Rice Production in Indonesia IPM introduced 1987 I
    • Rice production good
    • Pests declined
  • Laws Controlling Pesticide Use
    • Food, Drug, and Cosmetics Act (1938) – only recognized the need to regulate pesticides.
    • Pesticide Chemicals Amendment (1954) – established legal limits of pesticidal residue.
    • Federal Insecticide, Fungicide, and Rodenticide Act (1947) (FIFRA) – regulated the effectiveness of pesticides.
    • Food Quality Protection Act – studies all possible negative aspects of pesticides , including
    • smaller legal limits of pesticidal residue
    • injested by children.
  • The Manufacture & Use of Banned Pesticides
    • Some US companies still make banned or seriously restricted pesticides and export the product.
    • This can potentially lead to the importation of food tainted with banned pesticides, known as the Circle of Poison .