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

DDT - http://www.youtube.com/watch?v=LQ64sV0nSVU

DDT -

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

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

•Nonselective herbicides

(glyphosate, aka: Round-UpTM)

Lawn Care

Benefits - Initial Returns

Crop production

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

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

Benefits - Longterm?

Problem: Evolution of Genetic Resistance

# of species exhibiting genetic resistance to pesticides

30 fold increase in insecticide use since 1940

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

Resistance Management

Create a “refuge” (no pesticide applied)

Avoid repeated use of same pesticide

Mechanically pull resistant weeds or vacuum bugs: non-chemical methods

IPM

Problem: Imbalances in the Ecosystem

Creation of New Pests

Lemons

Pull on a star and you find the universe attached

Problems: 1. Mobility

2. Persistence

3. Bioaccumulation

4. Biological Magnification

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.

Biomagnification

Biomagnification

Example: Effect of DDT on bald eagles

Using Cultivation Methods to Control Pests

• Interplant mixtures of plants

• Strip cutting or leaving margins

• Planting, fertilizing, and irrigating at proper time

• Crop rotation

• Refuge Planting

Strip Cutting / Border CuttingStrip cutting was developed as a management tool to reduce the migration of lygus bugs from forage

alfalfa into cotton. It consisted of harvesting alternate strips (250 to 300 ft wide) of alfalfa at two-week intervals throughout the summer to assure that some alfalfa was always available to attract lygus bugs.

This system worked well as an insect management strategy, it created operational constraints, since the strips had to be managed as separate fields within a field thus complicating irrigation and harvesting operations.

An alternative strategy called border cutting. Narrow (10-ft) strips of uncut alfalfa were left. At the following harvest, these strips ("old hay") were cut. The old hay was blended with new growth alfalfa. There were concerns about the nutritional quality of the blended bales, so border cutting was not readily adopted.

Alternatives to Pesticides

• Biological Controls

Naturally occurring diseases, parasites, & predators• Pheromone and Hormone Traps• Reproductive Controls - Sterile-male technique• Quarantine - if foreign pest detected

http://www.youtube.com/watch?v=vMG-LWyNcAs

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.

Alternatives to Pesticides

Integrated Pest Management

1. Management of pest not eradication

2. Education of farmers

Alternatives to Pesticides

Integrated Pest Management

Rice Production in Indonesia

IPM introduced

Laws Controlling Pesticide UseFood, Drug, and Cosmetics Act (1938) - recognized need to regulate

pesticides in foodFederal Insecticide, Fungicide, and Rodenticide Act (1947) - regulated

effectiveness of pesticidesPesticide Chemicals Amendment (1954) - set standards & testing for

pesticides in foodDelaney 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

Estimates of Risk of Cancer from Pesticide Residue 8.8 deaths per 10,000 people

The Manufacture and Use of Banned Pesticides

The Global Ban of Persistent Organic Pollutants - Stockholm Convention