(F) 17 - Organic contaminants Flashcards
Pest vs. Weed
Pest: any organism that damages crops that are valuable to humans
Weed: any plant that competes with crops
- plants are also pests
*Categorization of organisms into these categories is subjective
Pesticide, Herbicide, Insecticide, Fungicide
Pesticide: a poison that targets pest organisms
Herbicide: a poison that kills weeds
Insecticide: a poison that kills insects
Fungicides: a poison that kills fungi
3 main categories of pesticides
- Inorganic
- Organic
- Biological
Inorganic Pesticides: definition and examples
- Usually contain arsenic, copper, lead, or mercury
- Highly persistent in terrestrial enviros
Examples
- Bordeaux Mixture: copper sulfate mixture, used as a fungicide for fruit and veggie crops
- Paris Green: copper and arsenic compound, used as a rodenticide and insecticide
Organic Pesticides: definition and examples
- Many categories: Natural Organic Pesticides, Synthetic Organometallic Pesticides, Phenols, Chlorinated Hydrocarbons, Organophosphorus Pesticides, etc.
- Extracted from organisms (like plants or fungi) when naturally produced OR they can be synthetically produced
- Natural: nicotine, caffeine
- Synthetic: methylmercury, DDT, chlordane, glyphosate
- Some are POPS
Biological Pesticides: definition and examples
- A type of Biological Control that uses other organisms to kill or remove pest organisms
- Example: (Bt-crops) Use of Bacillus thuringiensis (Bt) to kill insect pests
Why do we use pesticides
- Human Health
- increased thanks to pesticides
- some disease that can be controlled through pesticide use: malaria, yellow fever, encephalitis, west nile virus, sleeping sickness, plague, Rickettsia, Schistosomiasis, Lyme disease - Vector Controls
- for diseases spread by vector organisms, the most effective way to control the disease is to remove the vectors
- most are spread by insects, utilize insecticides
- remove breeding grounds - Agriculture
- modern ag exists in part bc of pesticides; targets weeds (herbicides)
- even with pesticides, North America loses 37% of all food and fiber crop production from pests
- fewer pests = fewer losses = increased production = increased profit
Role, pros, and cons of Roundup ready crops
- Genetically modified strains of crops that are resistant to glyphosate, used to kill a wide range of weeds
- Good: spray the field, kill the weeds, keep the crops
- Bad: non-target toxicity, evolution of resistance by weeds, economic monopoly on seeds by Monsanto
3 concerns and potential problems with roundup ready crops
- Roundup Ready crops may crossbreed with weeds to produce glyphosate-resistant weeds
- Roundup Ready plant tissue may be toxic to other organisms in the surrounding ecosystem
- Economic monopoly on these crops by a single company: Monsanto
Negative environmental impacts of pesticides
- Non-target organism impacts
- pesticides often kill organisms other than their targets
- ex. birds can ingest pesticides directly when feeding or indirectly through other food (bioaccumulation —> biomagnification) - Direct and indirect impacts
- direct ex. killing off bark beetles but end up killing the tree, pollinators and other organisms
- indirect ex. loss of production in the Ca2+ shell - Evolution of Resistance
1) Pests eating plants
2) Pesticide application
3) Resistant individuals survive
4) Pests of next generation survive application
5) pesticide application
6) Resistant individuals continue to reproduce
The ‘Refugia’ method as a solution against the evolution of resistance in pests
- Idea is that when spraying a pesticide on a crop, leave an area not sprayed, and then allow for reproduction btw the crop that is sprayed and not sprayed to allow the genetic material to circulate to dilute resistance
- tends to be very effective
How the IPM works (main techniques)
The use of multiple techniques to achieve long-term suppression of pests, including:
1) Bio-controls (biological controls)
- Utilize organisms to eliminate pest organisms
- Predators: ladybugs to control aphids
- Parasites: parasitoid wasps to control many pest insects
- Pathogens: rabbit hemorrhagic disease to control rabbits in Australia and New Zealand
2) Pest-resistant crops
3) Habitat alteration
4) Better pest monitoring
5) Strategic use of pesticides
- Use as a method of last resort
- Try to use botanically-derived compounds
Pesticide use in agriculture and as vector controls against diseases: malaria and DDT example
Malaria
- Problem: mosquitoes are evolving
1) Anti-malarial medication resistance is increasing
2) Insecticide resistance is increasing
3) Climate change is increasing mosquito habitat
Should we bring back DDT to kill mosquitos?
- NO! We can use IPM methods
- Need to use multiple pesticides, with multiple modes of action. Plus, other IPM methods, all combined! In other words, we need to evolve our ways too.
