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Lecture 5

Environmental Science 1021F/G Lecture Notes - Lecture 5: Biomimetics, Environmental Health, Biological Pest Control

Environmental Science
Course Code
Christie Stewart

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Food and Land III
Pests and Pesticides
Pest unwanted organism that interferes with human activities; subjective "A
weed is a plant whose virtues have not yet been discovered" Waldo Emerson
for the farmer any plant that is not the crop is a pest
pest = very broad general term
pest to western farmers, but in Africa it is a crop
Pesticide kills or controls undesirable organisms
100 species (1%) cause 90% of the damage
Disturbs predator-prey cycles in natural ecosystems and polyculture Pesticide is
disruptive to predator prey cycles when you disrupt one species it affects whole
food chain
when you kill the prey, the predator decreases (lost its food source) if pesticide is
for predator the prey will increase in numbers
Pesticides: Types
1) Insecticides block reproduction, airways, nervous system to kill insects
2) Herbicides disrupt plant growth and metabolism meant to harm plants not to
kill but to suppress the growth
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3) Fungicides: attack fungus
4) Rodenticides: kill rodents
Pesticide History
Before pesticides
- Crop rotation, vary planting times, plant diversity, hedgerows. Based on plants
natural instincts
First generation
-Sulphur, lead, arsenic, mercury problem b/c poisonous to humans
-Nicotine sulphate, pyrethrum, rotenone naturals=come from plants
Second generation
- Synthetic organic compounds (eg DDT), broad- and narrow-spectrum,
persistence reduction, some natural
persistence reduction major problem is they persist in soil for a very long time
even after say DDT was banned it still is present in soil
- second generation try to create pesticides that breakdown in the soil
- reduces that persistence has been the goal
broad spectrum = roundup, partnered with GMO crops and will kill any plant that
hasnt been modified to resist
narrow spectrum = opposite, would only affect one specific species
DDT = banned but not everywhere because used to kill mosquitos with malaria
therefore use of pesticides does help save lives so not completely banned
If stopped using pesticides half of global food production would decrease, so there
would be famine and a giant increase on price of food
The Case For Pesticides
-Saves human lives Malaria, bubonic plague, typhus Increase food supplies and
profits; lower costs
Work faster and better than alternatives
Health risk *may* be insignificant compared to benefits 3000-6000 death/yr (EPA)
-New pesticides are safer and used at lower rates than older pesticides
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