The Pesticide Dilemma

Chapter 23

Perfect Pesticide

1.Easily biodegrade into safe elements

1.Narrow Spectrum - kill target species only

1.Remain put in applied location in environment

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

Second-Generation Pesticides

Synthetic botanicals (DDT) - persistent & stable

Benefit - Disease Control

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

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

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.

Pull on a star and you find the universe attached

Problems: 1. Mobility

2. Persistence

3. Bioaccumulation

4. Biological Magnification

Biomagnification

Biomagnification

Example: Effect of DDT on bald eagles

Major HerbicidesSelective herbicides - (2,4,5-T & 2,4-D – kills broad-leaved plants)

•Nonselective herbicides

(glyphosate, aka: Round-UpTM)

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.

Lawn Care

Benefits - Initial Returns

Crop production

• Savings of 3-5$ in crops for every $1 invested in pesticides

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

Benefits - Longterm?

Problem: Evolution of Genetic Resistance

# of species exhibiting genetic resistance to pesticides

30 fold increase in insecticide use since 1940

Problem: Imbalances in the Ecosystem

Creation of New Pests

Lemons

Alternatives to Pesticides

Integrated Pest Management

1. Management of pest not eradication

2. Education of farmers

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)

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

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.

3. Natural Enemies (Biological Controls)

Wasp Invaders 4 Min. http://www.youtube.com/watch?v=vMG-LWyNcAs

1. Predators2. Disease3. Parasites

4. Pheromone Traps

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

Alternatives to Pesticides

Integrated Pest Management

Rice Production in Indonesia

IPM introduced

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

Stockholm Convention

The Global Ban of Persistent Organic Pollutants