Environmental Science 1021F/G Lecture Notes - Apple Sauce, Biological Pest Control, Sport Utility Vehicle

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Food and land 3 2/27/2013 6:17:00 PM
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
(subjective)
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
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2) Herbicides disrupt plant growth and metabolism
meant to harm plants not to kill but to suppress the growth
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 hasn’t 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)
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New pesticides are safer and used at lower rates than older pesticides
The Case Against Pesticides:
What are the true costs?
Genetic resistance insects and plants
Kill non-target organisms, incl. natural predators
85-90% sprayed don’t hit target
Can increase other pests
Harm wildlife
Pesticide movement
Human health threat; 20,00040,000 deaths
Environmental health threat
Still 6% decrease in yield loss to pests
Economic threshold of use
Use reduced without yield decrease
Economic thresh hold use is it more expensive for farmer to buy it
and then lose it to spraying and missing then affects rest of farm (ie soil) if
soil get affected then would have to use fertilizer its about looking at the
big picture.
Alternatives to Synthetic Chemical Pesticides
Some based on biomimicry, part of Integrated Pest Management
(IPM)
1) Change cultivation practices (cultural)
2) Biological pest control altering insects in some way ie insect birth
control, using radiation (capture males and get rid of fertility) so controlling
population but not decreasing population
Insect birth control (hormones/pheromones) insects are stimulated
to reproduce, so some of these traps to catch the males is to put the
pheromone in the trap (they think there is a mating female there)
Predators
3) Hot water
4) Genetically-resistant plants
Recall: associated problems
plants develop many toxic chemicals to deter insects = biomimicry
before using chemical pesticides you should use ever alternative first =
intergarted pet managment
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