The Pesticide Dilemma

Chapter 22

What is a Pesticide? Pests are any type of organism that interferes with humans in

some way. Pesticides are the toxic chemicals that we use to decrease the

numbers of pests. Types: Herbicides, Insecticides, fungicides and rodenticides Some are botanicals (ex: from plants) – nicotine and

pyrethrin (ex: from flowers) Some are synthetic – DDT first used in 1939; we didn’t learn

of persistence & harm until 1962, Silent Spring.

Range of pesticides Narrow-spectrum pesticides:

Kills organisms it was intended to.

Broad-spectrum pesticides: Kills a variety of organisms. Most pesticides, such as Round-Up

Major types of Herbicides Broad Leafed Herbicides

Kill plants with broad leaves but leave grasses alone. (Tend to mimic growth hormones & disrupt

metabolism.)

Grass Herbicides: kill grasses but leave broad leaves alone.

Effect of use of Herbicides in Vietnam Agent orange was sprayed over jungles to kill vegetation. It also contained a compound called dioxin, which had

severe effects on the Vietnamese and war Veterans. The jungles are about 30% reduced today. Besides birth defects and cancer, the compound is still present within

the population; Some Vietnamese have about 1800 ppt. Typically normal people have about 4 ppt.

Benefits of Pesticides Disease control

Mosquitoes are effective vectors of many diseases, such as malaria in the tropics

DDT effectively kills mosquitoes. But the banning of DDT allowed for the return of malaria.

Crop production - Farmers save $3-$5 in crops for every $1 invested in pesticides

Evolution of Genetic Resistance

Pesticide treadmill

(pest becomes resistant so pesticide needs to be increased &/or it’s chemistry improved)

Imbalances in Ecosystems Pesticides also tend to kill the natural

predators of the pests by starvation.

DDT was sprayed onto lemon trees but allowed a scale insect to proliferate.

Bioaccumulation: Most synthetic pesticides are

unable to be broken down by bacteria.

Slowly this compound will

increase in concentration

in soil and organisms.

•Biomagnification:

aka Biological amplification

- Increase in pesticide concentration as it passes through the food chain.

- Many countries subsidize pesticides, hoping for larger crops.

Mobility in the Environment (land → air → water)

Short-term Effects of Pesticides:Handling of food with pesticide residue

can result in headache, vomiting, diarrhea etc.

Bhopal, India disaster 1984

40 tons of poisonous gas was released from a Union Carbide pesticide plant after water leaked into storage tank, causing a massive explosion

covering 30 mi2. 600,000 people exposed, many with health

problems, especially blindness; 2500 immediately killed.

UC paid $500 to each victim but have

not cleaned up the land & groundwater.

Long-term Effects of Pesticides

Higher risk of cancer Sterility Miscarriage / birth defects Higher risk for Parkinson’s disease Acts as an endocrine disrupter, altering

reproductive capabilities Suppresses development of intelligence & motor

skills of children

Alternatives to Pesticides

1. Using Cultivation Methods to Control Pests

Intercropping Strip cutting (harvest

one segment at a time) Planting, fertilizing &

irrigating at proper time Crop rotation

2. Biological Controls Using naturally occurring diseases, parasites, or

predators to control a pest. Be careful introducing exotics!

3. Pheromones and Hormones Use pheromones to attract insects to traps Synthetic hormones induce abnormal

development

4. Reproductive Controls Sterile-male technique – inundate pest population

with large numbers of sterile males

5. Genetic Controls (GMOs) – resistant to pests

6. Quarantine – restriction of the importation of exotic plants & animal materials that might harbor pests.

7. Irradiating foods – especially meat, kills many organisms

8. Integrated Pest Management (IPM)

•Identifies the best practices of biological, cultivation & pesticide control for each crop.

•The pest is managed, not eradicated. Minimal crop damage is expected.

•Initially requires a lot of money and time for each complete study.

IPM & Rice Production in Indonesia

IPM introduced 1987 I

-Rice production good

-Pests declined

Laws Controlling Pesticide Use

Food, Drug, and Cosmetics Act (1938) – only recognized the need to regulate pesticides.

Pesticide Chemicals Amendment (1954) – established legal limits of pesticidal residue.

Federal Insecticide, Fungicide, and Rodenticide Act (1947) (FIFRA) – regulated the effectiveness of pesticides.

Food Quality Protection Act – studies all possible negative aspects of pesticides, including

smaller legal limits of pesticidal residue injested by children.

The Manufacture & Use of Banned Pesticides

Some US companies still make banned or seriously restricted pesticides and export the product.

This can potentially lead to the importation of food tainted with banned pesticides, known as the Circle of Poison.