The Pesticide Dilemma
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Transcript of The Pesticide Dilemma
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The Pesticide Dilemma
Chapter 23
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Perfect Pesticide
1.Easily biodegrade into safe elements
1.Narrow Spectrum - kill target species only
1.Remain put in applied location in environment
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Prior to the 1940’s
1st generation
1. Inorganic - lead, mercury, arsenicPersistent and stableToxic to animals
2. Organic (botanicals) - nicotine, pyrethrin, rotenoneEasily biodegradeDo not persistToxic to bees and fish
3. Synthetic Botanicals = second generation
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Second-Generation Pesticides
Synthetic botanicals (DDT) - persistent & stable
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Benefit - Disease Control
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Malaria Snapshot
247 million cases of malaria in 2006, causing about 880,000 deaths, mostly among African children.
Approximately half of the world's population is at risk of malaria – most low income countries
Economic toll
Insecticide-treated nets
Increasing mosquito resistance to insecticides
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The Major Pesticide GroupsChlorinated hydrocarbon (DDT)• Broad-Spectrum persistent – nonpolar
Organophosphates• Broad-spectrum: very toxic to mammals, birds, fish• Nerve agent• Degrades rapidly• More toxic than Chlorinated Hydrocarbons
Carbamates Broad-spectrum similar function to organophosphates
but reversible and less toxic to mammals - degrades rapidly
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Bioaccumulation
•Synthetic substances typically not metabolized - accumulate in fat
Fat soluble (lipophilic) substances cannot be excreted in urine, a water-based medium, and so accumulate in fatty tissues.
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Pull on a star and you find the universe attached
Problems: 1. Mobility
2. Persistence
3. Bioaccumulation
4. Biological Magnification
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Biomagnification
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Biomagnification
Example: Effect of DDT on bald eagles
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Major HerbicidesSelective herbicides - (2,4,5-T & 2,4-D – kills broad-leaved plants)
•Nonselective herbicides
(glyphosate, aka: Round-UpTM)
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Alternatives - GMO’sBacillus thuringiensis (Bt) • Corn & Cotton (roundup ready)• non-target species monarch butterfly• Soil accumulation of Bt
1. Growers plant 80% corn acres with Bt corn - 20% planted with non-Bt corn (refuge area).
2. Refuge area must be within 1/2 mile of Bt field.
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Lawn Care
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Benefits - Initial Returns
Crop production
• Savings of 3-5$ in crops for every $1 invested in pesticides
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Big Business
Problem: Evolution of Genetic Resistance
Creates a pesticide treadmill
Pesticide application
Kills most pests
Resistant survive
Numbers increase
New population genetically resistant
EVEN MORE
INCREASE
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Benefits - Longterm?
Problem: Evolution of Genetic Resistance
# of species exhibiting genetic resistance to pesticides
30 fold increase in insecticide use since 1940
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Problem: Imbalances in the Ecosystem
Creation of New Pests
Lemons
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Alternatives to Pesticides
Integrated Pest Management
1. Management of pest not eradication
2. Education of farmers
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1. Using Cultivation Methods
• Interplant mixtures of plants
• Planting, fertilizing, and irrigating at proper time
• Crop rotation
• Refuge Planting
• Strip or border cutting (see next slide)
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Strip Cutting / Border Cutting1. Lygus bugs love alfalfa like cotton and hay as well
2. Strips 250-300’ wide
3. Alfalfa harvested in two week intervals
4. Drawback - Complicated irrigation and harvesting due to mix
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2. Resistant Crop Varieties
1. Plants have many natural mechanisms to keep insects at bay: repellent or toxic chemicals, thorns, hairs, and tough roots and stems.
2. May reduce need for various “cides”
3. Yields may drop since the plant puts its resources towards its defense.
4. Evolutionary arms race continues and insects may counter plants defense.
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3. Natural Enemies (Biological Controls)
Wasp Invaders 4 Min. http://www.youtube.com/watch?v=vMG-LWyNcAs
1. Predators2. Disease3. Parasites
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4. Pheromone Traps
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5. Other:Alternatives to Pesticides
1. Avoid repeated use of same pesticide
1. Reproductive Controls - Sterile-male technique
1. Quarantine - if foreign pest detected
1. Create a “refuge” (no pesticide applied)
1. Mechanically pull resistant weeds or vacuum bugs: non-chemical methods
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Alternatives to Pesticides
Integrated Pest Management
Rice Production in Indonesia
IPM introduced
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Laws Controlling Pesticide Use
Food, Drug, and Cosmetics Act (1938) - recognized need to regulate pesticides in food
Federal Insecticide, Fungicide, and Rodenticide Act (1947) - regulated effectiveness of pesticides
Pesticide Chemicals Amendment (1954) - set standards & testing for pesticides in food
Delaney Clause (1958) - no cancer causing agent may be used
Food Quality Protection Act (1996) - amended Delaney and reduced time to ban pesticide from 10 years to 14 months
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Stockholm Convention
The Global Ban of Persistent Organic Pollutants