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Field Thistle

Cirsium arvense

Summary 5

Cirsium arvense is a species of Cirsium, native throughout Europe and northern Asia, and widely introduced elsewhere. The standard English name in its native area is Creeping Thistle.

Ecological threat in the united states 6

Natural communities that are threatened by Canada thistle include non-forested plant communities such as prairies, barrens, savannas, glades, sand dunes, fields and meadows that have been impacted by disturbance. As it establishes itself in an area, Canada thistle crowds out and replaces native plants, changes the structure and species composition of natural plant communities and reduces plant and animal diversity. This highly invasive thistle prevents the coexistence of other plant species through shading, competition for soil resources and possibly through the release of chemical toxins poisonous to other plants.

Canada thistle is declared a "noxious weed" throughout the U.S. and has long been recognized as a major agricultural pest, costing tens of millions of dollars in direct crop losses annually and additional millions costs for control. Only recently have the harmful impacts of Canada thistle to native species and natural ecosystems received notable attention.

Status as a weed 7

The species is widely considered a weed even where it is native, for example being designated an "injurious weed" in the United Kingdom under the Weeds Act 1959. It is also a serious invasive species in many additional regions where it has been introduced, usually accidentally as a contaminant in cereal crop seeds. It is cited as a noxious weed in several countries; for example Australia, Brazil, Canada, Ireland, New Zealand, and the United States. Many countries regulate this plant, or its parts (i.e., seed) as a contaminant of other imported products such as grains for consumption or seeds for propagation. In Canada, Cirsium arvense is classified as a primary noxious weed seed in the Weed Seeds Order 2005 which applies to Canada's Seeds Regulations.

Control methods include:

Orellia ruficauda feeds on Canada thistle and has been reported to be the most effective biological control agent for that plant. Its larvae parasitize the seed heads, feeding solely upon fertile seed heads.

The rust species Puccinia obtegens has shown some promise for controlling Canada thistle, but it must be used in conjunction with other control measures to be effective. Also Puccinia punctiformis is used in North America and New Zealand in biological control. In 2013 it was demonstrated in four countries in three continents that epidemics of systemic disease caused by this rust fungus could be routinely and easily established. The procedure for establishing this control agent involves three simple steps and is a long-term sustainable control solution that is free and does not involve herbicides. Plants systemically diseased with the rust gradually but surely die. Reductions in thistle density were estimated, in 10 sites in the U.S., Greece, and Russia, to average 43%, 64%, and 81% by 18, 30, and 42 months, respectively, after a single application of spores of the fungus.

Aceria anthocoptes feeds on this species and is considered to be a good potential biological control agent.

Sources and Credits

  1. (c) Cathy McCray, some rights reserved (CC BY-NC-ND), https://www.flickr.com/photos/catmccray/19103029043/
  2. (c) Matt Lavin, some rights reserved (CC BY), http://www.flickr.com/photos/35478170@N08/4972345384
  3. (c) Matt Lavin, some rights reserved (CC BY), https://www.flickr.com/photos/plant_diversity/4972371522/
  4. (c) Matt Lavin, some rights reserved (CC BY), https://www.flickr.com/photos/plant_diversity/4971737905/
  5. Adapted by Kate Wagner from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Cirsium_arvense
  6. (c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22948575
  7. (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Cirsium_arvense

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