The Pesticide Dilemma

Chapter 22

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, arsenic Persistent and stable Toxic to animals

2. Organic (botanicals) - nicotine, pyrethrin, rotenone Biodegradable Toxic to bees and fish

3. Synthetic Botanicals = second generation Persistent and stable (DDT) Toxic and nonpolar

Second-Generation Pesticides

Synthetic botanicals (DDT) - persistent & stable

DDT - https://www.youtube.com/watch?v=v2EtxYxEKww

The Major Pesticide Groups

Chlorinated hydrocarbon (DDT)• Broad-Spectrum persistent – nonpolar

Organophosphates• Broad-spectrum: very toxic to mammals, birds, fish• Nerve agent• Biodegradable

Carbamates Broad-spectrum similar to organophosphates but 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

Malaria Snapshot247 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 – mostly low income countries

Control:1. DDT2. Insecticide-treated nets3. Increasing mosquito resistance to insecticides and drugs

Benefit - Disease Control

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

Problem: Imbalances in the Ecosystem

Lemons

Pull on a star and you find the universe attached

Problems: 1. Mobility

2. Persistence

3. Bioaccumulation

4. Biological Magnification

Fat soluble (lipophilic - nonpolar) substances cannot be excreted in urine, a water-based medium, and so accumulate in fatty tissues. Metabolized polar molecules are excreted.

Biomagnification

Biomagnification

Example: Effect of DDT on bald eagles

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

Alternatives to Pesticides

Integrated Pest Management

1. Management of pest not eradication

2. Education of farmers

Alternatives to Pesticides

1. Biological Controls Naturally occurring diseases, parasites, &

predators

2. Pheromone and Hormone Traps

3. Reproductive Controls - Sterile-male technique

4. Quarantine - if foreign pest detected

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

Using Cultivation Methods to Control Pests

1. Crop rotation

2. Interplant mixtures of plants

3. Planting, fertilizing, and irrigating at proper time

4. Strip cutting or leaving margins

5. 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 - 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.

Resistance Management

1. Create a “refuge” (no pesticide applied)

2. Avoid repeated use of same pesticide

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

4. IPM