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University of Minnesota Extension

Scouting for Palmer amaranth

Source: Kaitlyn Albers, University of Minnesota Extension - Wright, McLeod and Meeker Counties, alber877@umn.edu 612-394-5229

Palmer amaranth

Palmer amaranth, although native to the southwest region of the United States and northwestern region of Mexico, has been listed on Minnesota’s Prohibited Noxious Weed Eradicate List since 2014. It has been spreading east and north across the states and was first reported in Yellow Medicine County, Minnesota in 2016. Palmer amaranth is very difficult and expensive to control due to its rapid growth rate, seed production, resistance to multiple classes of herbicides and its competitive nature. It grows two to three inches per day, commonly reaches heights of six to eight feet and can produce up to 500,000 seeds per plant!

It is important for landowners to regularly scout for Palmer amaranth in order to control its spread by reporting and eradicating weed populations. It is crucial for farmers to be surveying their fields and pastures. If present, Palmer amaranth can significantly increase production costs as well as impact crop yields. In some states, yield losses have been up to 91% in corn and 79% in soybeans. To date, Palmer amaranth has never been reported in Wright, McLeod or Meeker counties. Keep in mind that even though it hasn’t been reported, does not mean that it isn’t present. Reports are documented by the Minnesota Department of Agriculture (MDA) for each county and are available to view here. Be on the lookout for Palmer amaranth this fall during harvest in your crop fields, borders, ditches, conservation lands and around dairies. 

Identifying Palmer amaranth: 

When scouting for Palmer amaranth it is important to know what you are looking for. Palmer amaranth, Amaranthus palmeri, looks similar to Minnesotas’ native pigweeds such as tall waterhemp (A. tuberculatus), Powell's amaranth (A. powellii) and redroot and smooth pigweeds (A. retroflexus and A. hybridus respectively). Some distinguishing characteristics include:

  • Lack of fine hairs on stems and leaves (present on redroot and smooth pigweeds)
  • Petiole (stalk connecting the leaf to the stem) is longer than the length of the leaf
  • Tall seed head spikes on female plants (up to three feet long) and are more prickly than water hemp or redroot and smooth pigweed spikes.

To learn more about identifying Palmer amaranth, contact MDA's Weed Team, U of M Extension Crops Educator, or your crop consultant. If you suspect Palmer amaranth on your property, immediately visit the MDA's Report A Pest page and enter the location of the suspected plants and your contact information into the online reporting form. For identification assistance and control techniques, residents of Wright, McLeod, and Meeker counties can contact Kaitlyn Albers, the Interim Crops Extension Educator at 612-394-5229 or email alber877@umn.edu 

For more information on preventing the spread of Palmer amaranth visit: https://extension.umn.edu/annual-broadleaf-weeds/preventing-palmer-amaranth-minnesota Visit the Minnesota Department of Agriculture for reporting and additional information: https://www.mda.state.mn.us/plants-insects/palmer-amaranth-minnesota

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