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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.
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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