Palmer amaranth

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.

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)
 * 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:
 * 2008: Georgia (soybean), resists glyphosate and imazapic
 * 2009: Mississippi, resists glyphosate and pyrithiobac-Na
 * 2009: Tennessee (Cotton, soybean), resists glyphosate, chlorimuron-ethyl, and pyrithiobac-Na

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).

Related SourceWatch articles

 * Monsanto
 * Glyphosate
 * Biotechnology
 * Genetically Modified Organisms
 * Roundup Ready Crops
 * Glyphosate Resistant Weeds

External resources

 * National Weed Summit, National Academies of Science, May 2012.
 * Vijay K. Nandula, Glyphosate Resistance in Crops and Weeds: History, Development, and Management, John Wiley & Sons, May 25, 2010.
 * Donald B. Pratt, Micheal D. K. Owen, Lynn G. Clark, and Anna Gardner, Identification of the weedy pigweeds and waterhemps of Iowa, Iowa State Extension, April 1999.

External articles
2010s:
 * Dan Charles, "Farmers Face Tough Choice On Ways To Fight New Strains Of Weeds," NPR, March 7, 2012.
 * Jack Kaskey, "Attack of the Superweed: New strains resist Roundup, the world’s top-selling herbicide," Business Week, September 8, 2011.
 * Marcia Ishii-Eiteman, "Monsanto's Superweeds & Superbugs," Pesticide Action Network North America, GroundTruth blog, September 8, 2011.
 * Lynn M. Sosnoskie, Jeremy M. Kichler, Rebekah D. Wallace, A. Stanley Culpepper (2011) Multiple Resistance in Palmer Amaranth to Glyphosate and Pyrithiobac Confirmed in Georgia. Weed Science: July-September 2011, Vol. 59, No. 3, pp. 321-325.
 * Michael J. Coren, "Monsanto-Resistant Weeds Take Root, Raising Food Prices," Fast Company, July 20, 2011.
 * William Neuman and Andrew Pollack, "Farmers Cope With Roundup-Resistant Weeds," New York Times, May 3, 2010.

2000s:
 * Ford Baldwin, "Arkansas rice: History lesson: glyphosate-resistant pigweed," Delta Farm Press, August 10, 2007.