Environmental Science 1021F/G Lecture Notes - Companion Planting, Pyrethrum, Rodenticide

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Food III
Pests and Pesticides
Pesticides = generic term for all unwanted organisms
Pest - subjective; only a weed/disturbance if unwanted
Eg. Spiel weed is killed in many areas, and grown for food in others
Types of Pesticides
1. Insecticides - block reproduction, breathing, nervous system
2. Herbicides - block photosynthesis
3. Fungicides
4. Rodenticides
Used to control agriculture & negative influences on agriculture
Began w/ herbicides mostly
Before pesticides:
Crop rotation, minimizing input of pest, companion cropping to deter pests
Based on natural relationship of plants
o Many plants have defense mechanisms to keep away pests
o We're now coming back to there methods
1st generation pesticides
Poisons, heavy metals
o Detrimental to human health
o Still present in soils today
Nicotine sulphate (in tobacco plant), pyrethrum (marigold plant)
o Natural pesticide extracts still bottled and sold
o Marigolds are used in companion planting
2nd generation
Away from natural pesticides
Synthetic pesticides (i.e. DDT)
Began w/ broad spectrum (kills everything or many things not necessarily pests - Roundup),
moving toward narrow spectrum (specialized - grasses, broad leafed plants) both in use and future
research
Discovery that non-biodegradable, broad spectrum pesticides are harmful
Biodegradable pesticides w/ no long-term effects on soils, detritivores, plants, insects, water,
ecosystems now found to be ideal
The Case for Pesticides
Protect humans from disease
Plentiful, cheap food supplies require pesticides to be produced
Synthetic pesticides work faster & more effectively than natural
o Also more research in this area; natural pesticides can be improved
We can make synthetic pesticides better so they don't destroy needed life forms
The Case Against Pesticides
Forming superbugs (insects, plants, bacteria)
Kills non-target organisms
o Natural predators, similar organisms
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