Chapter 23 The Pesticide Dilemma

1. Chapter 23The Pesticide Dilemma

2. Pests • Pest – any organism that interferes in some way with human welfare or activities grouped by target organism they attack • Insecticides – kills insects • Herbicides – kills plants • Fungicides – kills fungus • Rodenticides – kills rodents

3. Agriculture • Sector that uses the most pesticides (85% world wide) • Narrow spectrum pesticides – pesticides that kill only the organism for which it was intended. • Broad spectrum pesticides – pesticides that kill a wide variety of organisms. • Additional problems with pesticides – more in environment, don’t degrade.

4. What is a Pesticide • Broad spectrum pesticide • A pesticide that kills a variety of organisms, not just the targeted organisms • First generation pesticide • Inorganic compounds • Lead,mercury and arsenic • Organic compounds (Botanicals- plant derived pesticides) • Nicotine and pyrethrin

5. What is a Pesticide • Second generation pesticide • Synthetic poison • Ex: DDT

6. Major Groups of Insecticides • Chlorinated Hydrocarbons • Organic compound containing Chlorine • Ex: DDT • Slow to degrade and persist in the environment • Banned or largely restricted • Endosulfan, lindane & methoxychlor still in use • Organophosphates • Organic compounds that contain phosphorus • Most poisonous insecticide • Very poisonous & toxic to birds, bees and aquatic organisms • Do not persist as long as chlorinated hydrocarbons • Cabamates • Derived from cabamic acid, not toxic to mammals, broad spectrum

7. 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-which kill broad-leaf plants but not grasses • Grass herbicides-kill grasses but not other plants • Ex: 2,4-D • Non selective herbicides-kills all vegetation • Famous example – Agent Orange: mixture of two herbicides that contain dioxins includes a variety of health effects: tissue cancer, skin diseases, urological disorders & birth defects

8. Benefits and Problems with Pesticides • Benefit: Disease control, crop protection • 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

9. Benefits and Problems with Pesticides • Benefit: Crop Protection • Pests eat and destroy 1/3 of world’s crops • Farmers save $3 to $5 for every $1 they invest in pesticides • Problem: Evolution of Genetic Resistance • Pest populations are evolving resistance to pesticides (right)

10. Pesticide Resistance • “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 • Strategies for managing genetic resistance in order to maximize the period in which a pesticide is useful • Delays the evolution of genetic resistance • Refuge of untreated plants-leave some population untouched to prevent resistance

11. Benefits and Problems with Pesticides • Problem: Imbalances the Ecosystem • Spraying to kill insects can affect birds, rabbits, etc. • Despite 33-fold increase in pesticides since the 1940s, crop loss has not really changed

12. Benefits and Problems with Pesticides • Problem: Creation of New Pests • Infestation of red scale insects on lemons after DDT sprayed to control another pest

13. Benefits and 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 • Ex: Peregrine falcons (right)

14. Benefits and Problems with Pesticides • Problem: Mobility in the Environment • Do not stay where they are applied • Move through soil, water and air

15. 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 • Lead-neurological development • Mercury-biomagnification via fish andcrabs

16. Risk of Pesticides to Human Health • Long-term Effects of Pesticides • Cancer- lymphoma • Breast cancer • Sterility • Miscarriage • Birth defects • Decreases body’s ability to fight infection • Potential connection to Parkinson’s disease

17. Alternatives to Pesticides • Using cultivation methods to control pests • Interplant mixtures of plants (alternating rows) • Strip cutting-leaving strips of un-harvested crops • Proper timing of planting, fertilizing, and irrigating • Crop rotation • Biological Control • Use of naturally occurring disease organisms, parasites or predators to control pests (such as lady bugs and praying mantises) • Must take care that introduced agent does not attack unintended hosts

18. Alternatives to Pesticides • Pheromones and Hormones • Can use pheromones to lure pests to traps • By applying insect hormones at wrong time in life cycle, insects can be killed off • Reproductive Controls • Sterilizing some of the members • Sterile male technique • Genetic Controls • Genetically Modified plants (GMOs) • Bt toxin • Potential problem: may affect non-target species (monarch butterfly) • Quarantine • Restriction of the importation of exotic plant and animal material that might harbor pests • Effective, but not foolproof

19. 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 IPM uses 3 premises • Management rather than eradication • Economic injury-don’t take action until this point, use non toxic first • Education-educate farmers as to all the alternatives Scout and spray-monitor for pests & only spray when they become a problem Calendar Spraying-regular spraying whether need or not

20. IPM Introduced Systems Approach- Integrated Pest Management (IPM) • Rice Production in Indonesia

21. 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 radicals

22. Laws Controlling Pesticide Use • Food, Drug, and Cosmetics Act (1938) recognized need to regulate pesticides but had no teeth • Pesticide Chemicals Amendment (1954) established acceptable levels of pesticides in food • Delaney Cause (1958) prohibits cancer-causing substances in food (applies only to pesticides) • Federal Insecticide, Fungicide, and Rodenticide Act (1947) regulated pesticide sale to prevent the sale of lemon (pesticides that don’t work) requires disclosure of active ingredients but not inert ingredients • Food Quality Protection Act (1996) Established pesticide residue limits in both raw and processed foods

23. 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) • Stockpiles of banned pesticides, predominantly in developing countries

24. Manufacture and Use of Banned Pesticides