1. Chapter 23 The Pesticide Dilemma

2. Pests
Pest – any organism that interferes in some way with human welfare or activities
grouped by target organism they attack
Insecticides – kills insects
Herbicides – kills plants
Fungicides – kills fungus
Rodenticides – kills rodents

3. Agriculture Sector that uses the most pesticides (85% world wide)
Narrow spectrum pesticides – pesticides that kill only the organism for which it was intended.
Broad spectrum pesticides – pesticides that kill a wide variety of organisms.
Additional problems with pesticides – more in environment, don’t degrade.

4. What is a Pesticide Broad spectrum pesticide
A pesticide that kills a variety of organisms, not just the targeted organisms
First generation pesticide
Inorganic compounds
Lead, mercury and arsenic
Organic compounds (Botanicals- plant derived pesticides)
Nicotine and pyrethrin

5. What is a Pesticide Second generation pesticide Synthetic poison
Ex: DDT

6. Major Groups of Insecticides
Chlorinated Hydrocarbons
Organic compound containing Chlorine
Ex: DDT
Slow to degrade and persist in the environment
Banned or largely restricted
Endosulfan, lindane & methoxychlor still in use
Organophosphates
Organic compounds that contain phosphorus
Most poisonous insecticide
Very poisonous & toxic to birds, bees and aquatic
organisms
Do not persist as long as chlorinated hydrocarbons
Carbamates
Derived from carbamic acid, not toxic to mammals, broad spectrum

7. Major Kinds of Herbicides
Selective Herbicides
Kill only certain types of plants
Can be classified to the type of plant they kill
Broad-leaf herbicides-which kill broad-leaf plants but not grasses
Grass herbicides-kill grasses but not other plants
Ex: 2,4-D
Non selective herbicides-kills all vegetation
Famous example – Agent Orange: mixture of two herbicides that contain dioxins
includes a variety of health effects: tissue cancer, skin diseases, urological disorders & birth defects

8. Benefits and Problems with Pesticides
Benefit: Disease control, crop protection
Fleas, lice and mosquitoes carry disease
Malaria- mosquito born
2.7 million people die each year
Few drugs available, so focus is on killing mosquitoes
DDT

9. Benefits and Problems with Pesticides
Benefit: Crop Protection
Pests eat and destroy 1/3 of world’s crops
Farmers save $3 to $5 for every $1 they invest in pesticides
Problem: Evolution of Genetic Resistance
Pest populations are evolving resistance to pesticides (right)

10. Pesticide Resistance “Pesticide Treadmill”
Cost of applying pesticide increases
Because they must be applied more frequently or in larger doses
While their effectiveness decreases
Because of increased genetic resistance in pests
Resistance Management
Strategies for managing genetic resistance in order to maximize the period in which a pesticide is useful
Delays the evolution of genetic resistance
Refuge of untreated plants-leave some population untouched to prevent resistance

11. Benefits and Problems with Pesticides
Problem: Imbalances the Ecosystem
Spraying to kill insects can affect birds, rabbits, etc.
Despite 33-fold increase in pesticides since the 1940s, crop loss has not really changed

12. Benefits and Problems with Pesticides
Problem: Creation of New Pests
Infestation of red scale insects on lemons after DDT sprayed to control another pest

13. Benefits and Problems with Pesticides
Problem: Persistence, Bioaccumulation, and Biological Magnification
Bioaccumulation
The buildup of a persistent pesticide or other toxic substance in an organisms body
Biological magnification
Increased concentration of toxic chemicals in tissues of organisms at higher trophic levels
Ex: Peregrine falcons (right)

14. Benefits and Problems with Pesticides
Problem: Mobility in the Environment
Do not stay where they are applied
Move through soil, water and air

15. Risk of Pesticides to Human Health
Short-term Effects of Pesticides
Handling food with pesticide residue
Mild case: nausea, vomiting, headaches
Severe case: damage to nervous system
Lead-neurological development
Mercury-biomagnification via fish and crabs

16. Risk of Pesticides to Human Health
Long-term Effects of Pesticides
Cancer- lymphoma
Breast cancer
Sterility
Miscarriage
Birth defects
Decreases body’s ability to fight infection
Potential connection to Parkinson’s disease

17. Alternatives to Pesticides
Using cultivation methods to control pests
Interplant mixtures of plants (alternating rows)
Strip cutting-leaving strips of un-harvested crops
Proper timing of planting, fertilizing, and irrigating
Crop rotation
Biological Control
Use of naturally occurring disease organisms, parasites or predators to control pests (such as lady bugs and praying mantises)
Must take care that introduced agent does not attack unintended hosts

18. Alternatives to Pesticides
Pheromones and Hormones
Can use pheromones to lure pests to traps
By applying insect hormones at wrong time in life cycle, insects can be killed off
Reproductive Controls
Sterilizing some of the members
Sterile male technique
Genetic Controls
Genetically Modified plants (GMOs)
Bt toxin
Potential problem: may affect non-target species (monarch butterfly)
Quarantine
Restriction of the importation of exotic plant and animal material that might harbor pests
Effective, but not foolproof

19. Systems Approach- Integrated Pest Management (IPM)
Combination of pest control methods that keeps pest population low without economic loss
Conventional pesticides are used sparingly when other methods fail
IPM uses 3 premises
Management rather than eradication
Economic injury-don’t take action until this point, use non toxic first
Education-educate farmers as to all the alternatives
Scout and spray-monitor for pests & only spray when they become a problem
Calendar Spraying-regular spraying whether need or not

20. Systems Approach- Integrated Pest Management (IPM)
Rice Production in Indonesia
IPM Introduced

21. Alternatives to Pesticides
Irradiating Food
Harvested food is expose to ionizing radiation, which kills many microorganisms
Predominantly used on meats
Somewhat controversial due to potential for free radicals

22. Laws Controlling Pesticide Use
Food, Drug, and Cosmetics Act (1938)
recognized need to regulate pesticides but had no teeth
Pesticide Chemicals Amendment (1954)
established acceptable levels of pesticides in food
Delaney Cause (1958)
prohibits cancer-causing substances in food (applies only to pesticides)
Federal Insecticide, Fungicide, and Rodenticide Act (1947)
regulated pesticide sale to prevent the sale of lemon (pesticides that don’t work)
requires disclosure of active ingredients but not inert ingredients
Food Quality Protection Act (1996)
Established pesticide residue limits in both raw and processed foods

23. Manufacture and Use of Banned Pesticides
Some US companies still make banned or seriously restricted pesticides
Product is exported
May lead to the importation of food tainted with banned pesticides
Global ban of persistent organic pollutants
Stockholm Convention on Persistent Organic Pollutants (2004)
Stockpiles of banned pesticides, predominantly in developing countries

24. Manufacture and Use of Banned Pesticides