PESTICIDES !!!!!
Chapter 22
1. What are pest? Any organism that interferes in some
way with human welfare or activities.
2. What are pesticides? Toxic chemicals designed to
eliminate pest.
- Two types of pesticides
Narrow spectrum --- kills only one organism
Broad spectrum ---- kills a variety of organisms
(good and bad)
- 4 groups of pesticides
Insecticide --- kills insects
Herbicides ---- kills plants
Fungicides ---- kills fungi
Rodenticides --- kills rodents (such as rats and mice)
- Two generations of pesticides
1st generation --- mostly botanicals (made from plants)
Examples: nicotine from tobacco, pyrethrin from chrysanthemum flowers (figure 22.1), Arsenic
2nd generation --- synthetic poisons
DDT was the first --- 1939 (figure 22.2)
Table 22.1 --- pay attention to the toxicity to
mammals, ecological effects, and
persistence/bioaccumulation.
3. Rachel Carson --- Silent Springs -- book documenting
evidence of pesticide problems
4. 3 major groups of insecticides are
- Chlorinated hydrocarbons --- DDT broad spectrum, persistence,
- Organophosphates --- broad spectrum, low persistence
- Carbamates---- broad spectrum, low persistence
5. Benefits of pesticides
- Disease control – typhus, malaria,
- Crop protection –
Monoculture – only one variety of one crop species is grown on large tract of land.
- Problems with pesticides
- Pest species evolve a resistance to pesticides after repeated exposure
Genetic resistance – any inherited characteristic that decreases the effect of a pesticide on a pest.
Evolution – any cumulative genetic change in a population of organisms
Subsequent pest populations contain larger percentages of pesticide-resistant pests than before.
r-strategists ---- short generation time --- constantly evolving (Figure 22.5)
pesticide treadmill – the cost of applying pesticides increases while their effectiveness decreases. RESULTS in increased pesticide use, higher production costs, declines in crop yields.
- Affect numerous species other than the target species generating imbalances in the ecosystem or agriculture fields and can pose a threat to human health (malaria – figure 22.4)
Indirect effect – predators starve or migrate in search of food
Direct effect – predators consume a lot of pesticide by consuming the pests
Figure 22.6
Table 22.2 --- things have gotten worse!!
Soon pest will rebound because of resistance or
no predators!!!!
- Creation of new pests – turning minor pest into major pest (figure 22.7)
- Persistence -- time it takes for the pesticide to be broken down by nature. (figure 22.8)
- Bioaccumulation --- the buildup of a persistent pesticide in an organism’s body over time
- Biomagnificataion --- the increase in pesticide concentrations as the pesticide passes through successive levels of the food web. (figure 22.9)
- Mobility in the environment—pesticides move through the soil, water, and air (figure 22.10)
- Risks of pesticides to human health
- Permanent damage to nervous system and other body organs.
- Nausea, vomiting, headaches
- Death (highest # in developing countries)
- Cancer (lymphoma, leukemia, brain, lungs, testicles)
- Disrupt the human endocrine (hormone) system (sterility, higher rates of miscarriage, birth defects, reduces ability to fight infection (Table 22.3)
- Our Stolen Future –book about how the persistent toxic chemicals in the environment are disrupting human hormone systems.
- Parkinson’s disease ????
- Children are at greater risk from household pesticides (figure 22.11)
8. Circle of Poison (page 538) Other countries used pesticides that are banned in the U.S. They return to the U.S. on imported produce!!! Only about 1% of the food shipments that enter the United States each year are inspected!
What is our ATTITUDE about Pesticides? What is the Risk????
Now the Good News!!!!
Alternatives to Pesticides
- Cultivation methods
- Biological controls
- Pheromones and Hormones
- Reproductive Control
- Genetic Controls
- Quarantine
- Scout- and - Spray
- Integrate Pest Management (IPM)
- Irradiating Foods
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