Environmental Science Chapter 20 Review
How can spiders help control insect pests?
Spiders kill more insects every year than insecticides do.
What is a pest?
Any species that (1) competes with us for food, (2) invades lawns and gardens, (3) destroys wood in houses, (4) spreads disease, or (5) is simply a nuisance.
How are species we consider pests controlled in nature?
In natural ecosystems and many polyculture agroecosystems, natural enemies (predators, parasites, and disease organisms) (1) control the populations of 50-90% or pest species as part of the earth’s ecological services and (2) help keep any one species from taking over for very long.
What happens to this natural pest control service when we simplify ecosystems?
When we replace polyculture agriculture with monoculture agriculture and spray fields with large amounts of pesticides, we upset many of these natural population checks and balances. Then we must devise ways to protect our monoculture crops, tree plantations, and lawns from insects and other pests that nature once controlled at no charge.
How have plants evolved to protect themselves from herbivores?
Plants have been producing chemicals to ward off or poison herbivores that feed on them for about 225 million years. Herbivores overcome various plant defenses through natural selection; then the plants use natural selection to develop new defenses.
A substance used to kill nematodes (roundworm).
Pesticides that kill rodents.
They were mainly natural substances, chemicals borrowed from plants that had been defending themselves from insects for eons. Ex. Pyrethrum, obtained from the heads of chrysanthemum flowers and Rotenone, from the roots of various tropical forest legumes.
They are generally the synthetic pesticides used today. Ex. DDT.
They are toxic to many species.
Selective or narrow-spectrum agents are effective against a narrowly defined group of organisms.
List 7 benefits of relying on chemical pesticides.
(1)They save human lives. (2) They increase food supplies and lower food costs. (3) They increase profits for farmers. (4) They work faster and better than alternatives. (5) When used properly, their health risks are insignificant compared with their benefits. (6) Newer pesticides are safer and more effective than many older pesticides. (7) Many new pesticides are used at very low rates per unit area compared with those of older products.
List 5 traits of the ideal pest-killing chemical.
(1) Kill only the target pest. (2) Harm no other species. (3) Disappear or break down into something harmless after doing its job. (4) Not cause genetic resistance in target organisms. (5) Be more cost effective than doing nothing.
Summarize the harmful effects of pesticides in terms of development of genetic resistance among pests.
Because of genetic resistance, many insecticides (such as DDT) no longer protect people from insect-transmitted diseases, such as malaria, in some parts of the world. It also puts famers on the pesticide treadmill, whereby they pay more and more for a pest control program that often becomes less and less effective.
With respect to pesticides, what is the circle of poison? How might it affect you?
Residues of some of these banned or unapproved chemicals exported to other countries can return to the exporting countries on imported food. Persistent pesticides such as DDT can also be carried by winds from other countries to the United States.
How are pesticides regulated in the United States?
The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), established by Congress in 1947 and amended in 1972, requires EPA approval for use of all commercial pesticides.
List major strengths and weaknesses in pesticide control laws.
The EPA does not regulate pesticides very well. They can not be sued and they do not have a time-limit to test and pass pesticides, therefore dangerous ones can be on the market for up to 10 years before they are done away with.
According to the U.S. National Academy of Sciences, what four things should be done to minimize the harmful effects of pesticides?
(1) Make human health the primary consideration for setting limits on pesticide levels allowed in food. (2) Collect more and better data on pesticide exposure for different groups, including farm workers, adults, and children. (3) Develop new and better test procedures for evaluating the toxicity of pesticides, especially for children. (4) Consider cumulative exposures of all pesticides in food and water, especially for children, instead of basing regulations on exposure to a single pesticide.
List 6 cultivation practices that can be used to help control pests.
(1) Rotating the types of crops planted in a field each year. (2) Adjusting the planting times so major insect pest either starve or get eaten by their natural predators. (3) Growing crops in areas where their major pests do not exist, (4) planting trap crops to lure pests away from the main crop, (5) planting rows of hedges or trees around fields to hinder insect invasions and provide habitats for their natural enemies (with added benefit of reduced soil erosion). (6) Increasing the use of polyculture, which uses plant diversity to reduce losses to pests.
List the pros and cons of using the pest control method of genetic engineering to speed up the development of pest- and disease-resistant crop strains.
However, there is controversy over whether the projected advantages of the increasing use of genetically modified plants and foods outweigh their projected disadvantages.
List the pros and cons of using the pest control method of biological control.
It is costly and very specified, making it a good method, just time-consuming and complicated.
List the pros and cons of using the pest control method of insect birth control through sterilization.
One would have to isolate the species and there would have to be a huge amount of males sterilized in order for it to work. But it would be a chemical free method that would not poison the food in any way.
List the pros and cons of using the pest control method of insect sex attractants.
It is another method that would have isolate the pest or predator. The only thing would be that it wou
List the pros and cons of using the pest control method of insect hormones (pheromones).
Another good method, but it would have to be released just at the right maturity time of the pest and it could take weeks to actually do away with the pest.
List the pros and cons of using the pest control method of food irradiation.
Small amounts of radiation are claimed to be harmless, but we do not know the actual long-term effects and consequences of this method.
List the pros and cons of using integrated pest management (IPM).
Combined use of biological, chemical, and cultivation methods in proper sequence and timing to keep the size of a pest population below the size that causes economically unacceptable loss of a crop or livestock animal.
Summarize the harmful effects of pesticides in terms of the killing of natural predators and parasites that help control pest species.
Currently 100 of the 300 most destructive insect pests in the United States were secondary pests that became major pests after widespread use of insecticides. Crop losses have not reduced with the use of pesticides in the U.S.
Summarize the harmful effects of pesticides in terms of creation of new pest species.
Pesticides create new pest species that are genetically resistant to the current pesticide, therefore worsening the situation altogether.
Summarize the harmful effects of pesticides in terms of migration of pesticides into the environment.
Pesticides are generally applied in a way in which only around 2-5% of the substance actually reach their target pest and weeds. The remaining gets released into the air, surface water, groundwater, bottom sediments, food, and non-target organism such as humans and wildlife.
Summarize the harmful effects of pesticides in terms of effects on wildlife.
The can (1) wipe about 20% of U.S. honeybee colonies and damage another 15%, costing farmers at least $200 million per year from reduced pollination of vital crops, (2) kill more than 67 million birds and 6-14 million fish, and (3) menace about 20% of the endangered and threatened species in the United States.
Summarize the harmful effects of pesticides in terms of effects on the health of pesticide and farm workers and the general public.
Pesticides could prove to have chemicals in them that are carcinogens, therefore being extremely toxic and posionous for human health.