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Environmental Science
Course Code
Carl Mitchell

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Chapter 21:
Pesticides: A substance used to poison pests.
oCommonly used to protect crop plants, livestock, domestic animals, and
humans from damage and diseases caused by microorganisms, fungi, insects,
rodents, and other pests, to defend crops from competition with unwanted but
abundant plants (i.e., weeds)
Humans have acquired important benefits from many uses of pesticides, including:
oIncreased yields of crops, because of protection from diseases, competition,
defoliation, and parasites
oPrevention of much spoilage and destruction of stored food
oPrevention of certain diseases, thereby conserving health and saving the lives of
millions of people and domestic animals
Non-target organism (or non-target damage): Damage caused by a pesticide to non-
target organisms. Organisms that are not pests, but which may be affected by a pesticide
Broad-spectrum pesticide: A pesticide that is toxic to other organisms as well as the pest.
The Nature of Pesticides
oThey are defined by their usefulness in causing more mortality to or otherwise
managing the abundance of species that are deemed to be pests. [pests = any
organism judged to be significantly interfering with some human purpose]
oThey are an extremely diverse group of chemicals.
Their classification is based of pesticides is based on their targets:
Fungicide: A pesticide used to protect crop plants and animals from fungi that cause
diseases or other damages.

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Herbicide: A pesticide use to kill weeds. [weeds are unwanted plants that interfere with
some human purpose]
Insecticide: A pesticide used to kill insects that are considered pests.
Mollusicides: are used to kill snails and slugs in agriculture and gardens, and aquatic snails
that can be vectors of diseases such as schistosomiasis.
Inorganic Pesticides
oThey are compounds that contain arsenic, copper, lead, or mercury. They are
highly persistent in terrestrial environments, being slowly dispersed by leaching,
and erosion by wind and water.
oMajor use of fungicide, herbicides and insecticides.
Organic Pesticides:
oThese are artificially synthesized chemicals, but some are natural toxins
produced by certain species of plants and certain species of plants and extracted
and used as pesticides. Examples are:
oNatural organic pesticides: extracted from plants. Nicotine and related
alkaloids, for example, are extracted from tobacco and used as insecticides,
usually applied as nicotine sulphate. These can be extracted from flowers,
shrubs, and denticides such as the sea onion.
oSynthetic organometallic pesticides: used mainly as fungicides. They include
organomercurials such as methylmercury and phenylmercuric acetate.
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