Palmer amaranth

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Palmer amaranth (Amaranthus palmeri) is a dicot weed in the Amaranthaceae family. It is sometimes referred to as 'pigweed.' In many documented cases, Palmer amaranth has evolved resistance to the herbicide glyphosate (Roundup), particularly in fields of genetically engineered Roundup Ready Crops. Palmer amaranth can grow over six feet tall and can grow more than two inches a day. One plant can produce half a million seeds.[1]

Locations of Glyphosate Resistant Palmer Amaranth

Glyphosate resistant palmer amaranth appeared in the following states in the years and crops noted:

  • 2005: Georgia (Cotton, soybean)[2]
  • 2005: North Carolina (Corn, cotton, soybean)
  • 2006: Arkansas (Cotton, soybean)
  • 2006: Tennessee (Corn, cotton, soybean)
  • 2007: New Mexico (Orchards)
  • 2008: Alabama (Soybean)
  • 2009: Missouri (Cotton, soybean)
  • 2010: Illinois (Corn, soybean)
  • 2010: Louisiana (Cotton)
  • 2011: Michigan (Soybean)
  • 2011: Virginia (Soybean)

Palmer Amaranth with resistance to multiple herbicides, including glyphosate, has also emerged:[2]

Note that in each case except for in New Mexico's orchards, the glyphosate resistant palmer amaranth emerged in crops that are primarily grown as genetically engineered Roundup Ready crops (corn, cotton, soybeans).

Articles and resources

Related SourceWatch articles


  1. Herbicide Tolerant Weed Summit, National Academy of Sciences, 2012.
  2. 2.0 2.1 Herbicide Resistant Weeds, Weed Science, Accessed August 9, 2012.

External resources

External articles



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