Pesticides Pesticides Which one to use by ewghwehws

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									Pesticides




    Which one to use?
What is a pest?

   Organisms that interfere with human welfare
    and activities
    –   Insects
    –   Weeds
Why do we need pesticides?

   Insects eating and destroying crops
   Weeds competing with crops
   Insects carrying disease
Benefits of pesticides

   Allows more food production
   Farmers can save $3-$5 in crops for every
    $1 invested in pesticides
   Protects people from disease
DDT used to fight Malaria

   Sri Lanka in the early 1950’s, more than 2 million
    cases of Malaria
   Began spraying DDT to kill the mosquitos carrying
    the disease
   Cases dropped to 0
   Discontinued spraying and malaria cases jumped up
    to 1 million per year
   Began spraying again and still do in over 20 tropical
    countries
Disadvantages

   Often kill non-target species
   Pesticide residue on crops
   Persistent in environment- affects animals up
    the food chain
   People working closely with pesticide at risk
    of health problems
Types of Pesticides

   Chemical pesticides
    –   Not naturally occuring
    –   Toxic
    –   Persistent in the environment
    –   Affect non-target species
    –   Examples- Crabamate Pesticides, Organochlorine
        pesticides (DDT), Organophosphate pesticides
Chemical Pesticides

   Crabamate Pesticides
    –   Affects non-target species
    –   Affect the nervous system
    –   Effects are usually reversible


   Organophosphate Pesticides
    –   Affect the nervous system
    –   Affects non-target species
    –   Highly toxic
    –   Not as persistent in the environment
   Organocholorine Insecticide
    –   Very persistent in the environment
    –   Affects non-target species
    –   Effects nervous system
    –   Removed from the market due to health effects
    –   Examples include DDT
Organic pesticides

   Naturally occuring in the environment
   Plants have developed natural resistance to pest
    –   Can be used naturally or made synthetically


   Easily degradable in environment
   Not persistent
   Can be toxic to aquatic organisms and pollinators
Biopesticides
–   Microbial pesticides
        Made from microorganisms- fungi and bacteria
–   Plant-incorporated protectants
        Genetically alter plant to produce its own pesticide
–   Biochemical
        Naturally occuring substances that control pests
Major problems with Pesticides

   Pest species (plant and animal) develop resistance
    to pesticides
   Pesticides that don’t degrade easily can cause
    problems for humans and other organisms
   Bioaccumulation- build up of pesticides in body
    Biomagnification- organisms higher up in the food
    web have higher concentrations of pesticides in their
    body
Alternatives

   Integrated Pest management
   Mixing crops- reduce monocultures
   Biological controls
   Genetic controls

								
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