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Noxious weeds

Noxious weeds

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A noxious weed is an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 of a plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 that has been designated by country, state or provincial, or national agricultural authorities as one that is injurious to agricultural and/or horticultural crops, natural habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

s and/or ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

s, and/or humans or livestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

. Most noxious weeds are introduced species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...

 (non-native) and have been introduced into an ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

 by ignorance, mismanagement, or accident. Occasionally some are native. Typically they are plants that grow aggressively, multiply quickly without natural controls (native herbivores, soil chemistry, etc.), and adversely affect native habitats, croplands, and/or are injurious to humans, native fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...

, and livestock through contact or ingestion. Noxious weeds are a large problem in many parts of the world, greatly affecting areas of agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

, forest management
Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...

, nature preserves and parks
Regional park
Regional park is a term used for an area of land preserved on account of its natural beauty, historic interest, recreational use or other reason, and under the administration of a form of local government.-Definition:...

, and other open space lands.


These weeds are typically agricultural pests, though many also have impacts on natural areas. Many noxious weeds have come to new regions and countries through contaminated shipments of feed and crop seeds
SEEDS is a voluntary organisation registered under the Societies Act of India....

 or intentional introductions such as ornamental plants for horticultural use. For a proportional example, the Idaho Department of Agriculture (U.S.) has around 300 introduced or exotic species listed with 36 classified as noxious weeds (invasive species).

The legal designation of noxious weed for a plant species can use these four criteria:
  1. It is present in but not native to state-province-ecosystem.
  2. It is potentially more harmful than beneficial to that area.
  3. Its management, control, or eradication is economically and physically feasible.
  4. The potential adverse impact of it exceeds the cost of its control.


There are types of noxious weeds that are harmful or poisonous to humans, domesticated grazing animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, and wildlife. Open fields and grazing pastures with disturbed soils and open sunlight are often more susceptible. Protecting grazing animals from toxic weeds in their primary feeding areas is therefore important.


Some guidelines to prevent the spread of noxious weeds are:
  1. Avoid driving through noxious weed-infested areas.
  2. Avoid transporting or planting seeds and plants that one can't identify.
  3. For noxious weeds in flower or with seeds on plants, pulling 'gently' out and placing in a secure closable bag is recommended. Disposal such as hot composting or contained burning is done when safe and practical.
  4. Using only certified weed-free seeds for crops or gardens.

Maintaining control of noxious weeds is important for the health of habitats, livestock, wildlife and native plants, and of humans of all ages. How to control noxious weeds depends on the surrounding environment and habitats, the weed species, the availability of equipment, labor, supplies, and financial resources. Laws often require that noxious weed control funding from governmental agencies must be used for eradication, invasion prevention, or native habitat and plant community restoration project scopes.

Further reading

  • "Noxious weed free forage and straw certification program." 2006. State of Idaho. Nov. 2008 http://www.agri.idaho.gov
  • Taylor, Ronald. Northwest Weeds. Montana: Mountain Press Publishing Company, 1990.
  • U.S. Department of Agriculture Forest Services. Notes on Western Range Forbs. Washington: U.S. Government Printing Office, 1996.
  • Sheley, Roger, James Jacobs, and John Martin. "Integrating 2,4-D and sheep grazing to rehabilitate spotted knapweed infestations." Journal of Range Management (2004): Academic Search Premier. EBSCO Albertson's Library, Boise, ID. 04 Nov. 2008 http://www.jstor.org/stable/4003861
  • Roché, C T, et al. "Tracking an invader to its origins: the invasion case history of Crupina vulgaris." Weed Research 43.3 (June 2003): 177-189. Academic Search Premier. EBSCO. Albertson's Library, Boise, ID. 4 Nov. 2008 .

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