Chapter 23 The Pesticide Dilemma

1
Chapter 23The Pesticide Dilemma
2
Overview of Chapter 23

• What is a Pesticide?
• Major Kinds of Pesticides
• Benefits and Problems With Pesticides
• Risks of Pesticides to Human Health
• Alternatives to Pesticides
• Laws Controlling Pesticides Use
• The Manufacture and Use of Banned Pesticides

3
What is a Pesticide

• Broad spectrum pesticide
• A pesticide that kills a variety of organisms,
  not just the targeted organisms

• First generation pesticide (pre 1940s)
• Inorganic compounds
• Lead and mercury
• Botanicals- plant derived pesticides
• Nicotine and pyrethrin

4
What is a Pesticide

• Second generation pesticide (synthetic)
• Synthetic poison
• Ex DDT

5
Major Groups of Insecticides

• Chlorinated Hydrocarbons
• Organic compound containing Chlorine
• Ex DDT (dichlorodiphenyltrichloroethane)
• Banned in USA in 1972
• Slow to degrade and persist in the environment
• Banned or largely restricted
• Organophosphates
• Organic compounds that contain phosphorus
• Most poisonous insecticide
• Do not persist as long as chlorinated
  hydrocarbons
• Cabamates
• Derived from cabamic acid

6
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
• Grass herbicides
• Ex 2,4-D

7
Benefits and Problems with Pesticides

• Benefit Disease control
• 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
• Sri Lanka 1950s
• 2 million cases/year
• Dropped to near zero with DDT use

8
Benefits and Problems with Pesticides

• Benefit Crop Protection
• Pests eat and destroy 1/3 of worlds 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)

9
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

10
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
• Genetic resistance
• Destruction of natural enemies
• Poor agricultural pracitces

11
Benefits and Problems with Pesticides

• Problem Creation of New Pests
• Infestation of red scale insects on lemons after
  DDT sprayed to control another pest

12
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)

13
Benefits and Problems with Pesticides

• Pesticides do not stay where they are applied but
  tend to move through the soil, water, and air
• Pesticide mobility is a problem for both wildlife
  and humans
• It can be lethal to aquatic organisms (i.e.,
  fish), and/or cause bone degeneration, decrease
  their competiveness and increase their chances of
  being preyed upon
• 14.1 million U.S. residents drink water
  containing traces of five widely used herbicides
• Herbicides can elevate cancer risk in humans

14
Benefits and Problems with Pesticides
Problem Mobility in the Environment
15
Risk of Pesticides to Human Health

• Short-term exposure can harm organs and even
  cause death
• A person with a mild case of pesticide poisoning
  may exhibit symptoms such as nausea, vomiting,
  and headaches
• Pesticides poison approximately 67,000 Americans
  each year
• Globally, 4 million people are poisoned by
  pesticides, 300,000 die
• Almost any pesticide can kill a human if the dose
  is large enough

16
Risk of Pesticides to Human Health

• Long-term Effects of Pesticides
• Cancer- lymphoma
• Breast cancer
• Sterility
• Miscarriage
• Birth defects
• Decreases bodys ability to fight infection
• Potential connection to Parkinsons disease

17
Alternatives to Pesticides

• Alternative ways to control pests include
  cultivation methods, biological controls,
  pheromones and hormones, reproductive controls,
  genetic controls, quarantine, and irradiation
• Integrated pest management (IPM), which combines
  various alternative methods of pest control, is
  the most effective way to control pests
• Using cultivation methods to control pests
• Using an insect vacuum, interplanting mixtures of
  plants, and strip cutting are effective
  cultivation methods used to control pests
• The proper timing of planting, fertilizing, and
  irrigating promote healthy, vigorous plants that
  are more resistant to pests, because they are not
  stressed by other environmental factors

18
Alternatives to Pesticides

• Biological controls
• A method of pest control that involves the use of
  naturally occurring disease organisms, parasites
  or predators to control pests is referred to as a
  biological control
• More than 300 species have been introduced as
  biological control agents to North America
• Finding an effective parasite or predator is
  difficult
• The pest species typically does not evolve
  genetic resistance to the biological control
  agent the same way it does to pesticides
• Nematodes and fungi as biological control agents
• Nematodes are effective against mosquitoes, corn
  borers, weevils, grasshoppers, and locusts
• Fungal spores can target desert locusts
• Problems with biological control
• Attack of an unintended host
• Make sure it does not become a pest itself

19
Alternatives to Pesticides

• Pheromones and hormones
• Pheromones can be used to control individual pest
  species
• Synthetic hormones have been used to trigger
  abnormal molting in insect larvae
• Reproductive controls
• Reproductive control strategies suppress pests by
  sterilizing some of its members
• The sterile male technique helps to control the
  reproductive potential of the pest population so
  that the population of the next generation is
  much smaller

20
Alternatives to Pesticides

• Genetic controls
• Many varieties of crops have been selectively
  breed to be genetically resistant to disease
  organisms or insects
• Through traditional selective breeding techniques
  this can take as long as 10-20 years
• Plant breeders are in a continual race to keep
  one step ahead of plant pathogens
• Genetic engineering can produce genetically
  modified (GM) plants that are pest-resistant in
  fewer generations
• Quarantine
• Restriction of the importation of exotic plant
  and animal material that might harbor pests
• Effective, but not foolproof

21
Systems Approach- Integrated Pest Management (IPM)

• IPM
• Combination of pest control methods that keeps
  pest population low without economic loss
• Conventional pesticides are used sparingly when
  other methods fail

22
Systems Approach- Integrated Pest Management (IPM)

• Rice Production in Indonesia

23
Systems Approach- Integrated Pest Management (IPM)

• The systems approach integrated pest management
  (IPM)
• IPM is a combination of control methods is often
  more effective than controlling pests with a
  single technique
• IPM combines a variety of biological,
  cultivation, and pesticide controls tailored to
  the conditions and crops of an individual farm,
  campus, city, or greenhouse
• IPM requires a thorough knowledge of the system,
  including life cycles, feeding habits, travel,
  and nesting habits of the pests as well as their
  interactions with their hosts and other organisms
• IPM is the management rather than the eradication
  of pests it requires that farmers be educated

24
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 (carcinogens)

25
Laws Controlling Pesticide Use

• Food, Drug, and Cosmetics Act (FDCA 1938)
• Pesticide Chemicals Amendment (1954), aka the
  Miller Amendment, requires the establishment of
  acceptable and unacceptable levels of pesticides
  in food
• The Delaney Clause (1958) states that no
  substance capable of causing cancer in test
  animals or in humans would be permitted in
  processed food
• The Federal Insecticide, Fungicide, and
  Rodenticide Act (FIFRA 1947)
• Regulates the effectiveness of pesticides
• A 1988 amendment required reregistration of older
  pesticides and subjected them to the same
  toxicity tests that new pesticides face
• Food Quality Protection Act (1996)
• This Act amended both the FDCA and FIFRA
• It requires that the increased susceptibility of
  infants and children to pesticides be considered
  when establishing pesticide residue limits for
  some 9,700 pesticide uses on specific crops
• It also reduces the time it takes to ban a
  pesticide considered dangerous from 10 years to
  14 months

26
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
• Some of the food imported into the U.S. contains
  traces of banned pesticides such as DDT,
  dieldrin, chlordane, and heptachlor
• The FDA inspect only about 1 of the food
  shipments that enter the U.S. each year

27
Manufacture and Use of Banned Pesticides
Global ban of persistent organic
pollutants Stockholm Convention on Persistent
Organic Pollutants (2004) (US needs to
participate actively)