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Chapter 22 The Pesticide Dilemma

Chapter 22 The Pesticide Dilemma. Overview of Chapter 22. What is a Pesticide? Major Kinds of Pesticides Benefits and Problems With Pesticides Alternatives to Pesticides Laws Controlling Pesticides Use. What is a Pesticide. Types: Insecticides Herbicides Fungicides Rodenticides

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Chapter 22 The Pesticide Dilemma

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  1. Chapter 22The Pesticide Dilemma

  2. Overview of Chapter 22 • What is a Pesticide? • Major Kinds of Pesticides • Benefits and Problems With Pesticides • Alternatives to Pesticides • Laws Controlling Pesticides Use

  3. What is a Pesticide • Types: • Insecticides • Herbicides • Fungicides • Rodenticides • Regulated by the EPA

  4. What is a Pesticide • Broad spectrum pesticide • kills a variety of organisms, not just the targeted organisms • Doesn’t degrade = doesn’t decompose = persist and then accumulate in environment or organism.

  5. What is a Pesticide • First generation pesticide • Inorganic compounds • Lead and mercury • Botanicals- plant derived pesticides • Nicotine • Second generation pesticide • Synthetic poison • Ex: DDT for mosquitoes used to control malaria

  6. What is an herbicide for?

  7. What is a fungicide for?

  8. What is an insecticide for?

  9. Major Groups of Insecticides • Chlorinated Hydrocarbons • Organic compound containing Chlorine • Ex: DDT • Persist(do not degrade) • **Rachel Carson – “Silent Spring” = problems w/ pesticides • Organophosphates • Developed during WWII • HIGHLY toxic (bees/humans), but do not persist • Currently used in agriculture • EX: Malathion, diazinon • Neurotoxin, especially children • Carbamates • Not as toxic to mammals • Ex: household sprays/traps RACHEL CARSON… ENVIRONMENTAL GODDESS

  10. How are organophosphates different than chlorinated hydrocarbons?

  11. 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 • Ex: 2,4-D (2,4 dichlorophenoxyacetic acid) • Ex: 2,4,5 –T (2,4,5, trichlorophenoxyacetic acid) • Used with wheat, corn, rice (cereal grains = grasses) • Grass herbicides • Nonselective – kill all vegetation

  12. When would you use a broad-leaf herbicide? A grass herbicide

  13. Case study: Vietnam War and herbicide use • Sprayed to kill vegetation – Agent White, Blue, Orange • Ecological damage – decades to repair – destroyed mangroves (habitat for fish and coast protection from erosion), forests destroyed • Human effects • Agent Orange = (combination of broad leaf herbicides + dioxins)  birth defects, stillbirths, cancer • Dioxin in breastmilk – Vietnamese = 1800 ppt, US = 4 ppt

  14. Benefitsof Pesticides • Benefit 1. : 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 mosquitoes • DDT

  15. Benefitsof Pesticides • Benefit 2. : Crop Protection • Pests eat and destroy 1/3 of world’s crops • Farmers save $3 to $5 for every $1 they invest in pesticides

  16. Name the 2 reasons why pesticides are used?

  17. Problems with Pesticides:Pesticide Resistance • Problem: Evolution of Genetic Resistance • Pest populations are evolving resistance to pesticides (right) 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 • Refuge of untreated plants: allows mating of treated/untreated pests to delay resistance • Remove surviving weeds after herbicide application

  18. Problemswith Pesticides • Problem: Kills non-target organisms • Spraying to kill insects can kill birds, fish, bees • Despite 33-fold increase in pesticides since the 1940s, crop loss has not really changed

  19. Problemswith Pesticides • Problem: Creation of New Pests • Pesticide kills predator or competitor of minor pest

  20. 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, stored in fat • Ex: Peregrine falcons (right), • Bald Eagles

  21. Problemswith Pesticides • Problem: Mobility in the Environment • Do not stay where they are applied  harm non-target organisms. • Move through soil, water (run-off) and air

  22. Risk of Pesticides to Human Health • Effects of Pesticides • Handling food with pesticide residue • Mild case: nausea, vomiting, headaches • Severe case: damage to nervous system (neurotoxin!!!)

  23. Risk of Pesticides to Human Health • Long-term Effects of Pesticides: • Cancer- lymphoma and breast • Sterility • Miscarriage • Birth defects • Harms immune system

  24. Case Study: Bhopal Disaster • 1984 Bhopal, India • Explosion at pesticide plant released toxic gas (cyanide) • Many died immediately • Others: problems to respiratory, reproductive, nervous systems

  25. Alternatives to Pesticides • Using cultivation methods to control pests • Interplant mixtures of plants (alternating rows): polyculture !! • Crop rotation • Biological Control • Use of naturally occurring disease organisms, parasites or predators to control pests • Must take care that introduced agent does not attack unintended hosts CANE TOADS

  26. Alternatives to Pesticides • Pheromones and Hormones • Can use pheromones to lure pests to traps • Reproductive Controls • Sterilizing some of the members • Sterile male technique: sterilize in lab and then release

  27. Systems Approach- Integrated Pest Management (IPM) • IPM • Combination of pest control methods that keeps pest population low without economic loss • Controls pests, not eradicate • Cons: requires a lot of knowledge • Conventional pesticides are used sparingly when other methods fail HOW DOES IPM DIFFER FROM ORGANIC FARMING?

  28. Farmers MONITOR pests and act when injury threshold is reached. • EX: Cotton – 1% of land; 50% of pesticide use in US. – WOW!! Organic cotton helps reduce pesticide use.

  29. IPM Introduced Systems Approach- Integrated Pest Management (IPM) • Rice Production in Indonesia • Predators of pests normally kept in check by pesticides

  30. Laws Controlling Pesticide Use • Food, Drug, and Cosmetics Act (1938) –FDCA– determined pesticides need regulation! • Delaney Clause (1958) – no cancer causing substances; not cover raw foods. • Federal Insecticide, Fungicide, and Rodenticide Act (1947) – FIFRA – regulates what pesticides are sold based on safety. • Food Quality Protection Act (1996) – stricter guidelines on pesticide limits, covers raw food, reduce time to ban harmful pesticide.

  31. Manufacture and Use of Banned Pesticides • Some US companies still make banned or seriously restricted pesticides • Product is exported • Importation of food tainted with banned pesticides from other countries • Global ban of persistent organic pollutants • Stockholm Convention on Persistent Organic Pollutants (2004) – requires countries to eliminate usage of the 12 most toxic chemicals.

  32. Manufacture and Use of Banned Pesticides

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