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Preventing Palmer amaranth in Minnesota

Palmer amaranth is on the Minnesota Noxious Weed List in the "prohibited-eradicate noxious weeds" category. This legal status means the plant must be destroyed and that no transportation, propagation or sale of this plant species is allowed.

Report possible infestations to the Minnesota Department of Agriculture (MDA). You can use their online reporting form, email them at reportapest@state.mn.us, or call 1-888-545-6684.

View MDA information on Palmer amaranth in Minnesota.

Palmer amaranth in a Tennessee field.

Palmer amaranth (Amaranthus palmeri) has been confirmed in Minnesota. Efforts to eradicate this weed are critical to Minnesota’s commodity crop producers.

Palmer amaranth isn’t native to the northern United States but has spread northward from southern states. It’s been confirmed in Wisconsin, Iowa, Illinois, Nebraska, South Dakota and other northern states.

In August 2016, it was discovered in newly seeded Conservation Reserve Program (CRP) land in Iowa, and confirmed in Yellow Medicine County in Minnesota, that September.

Why Palmer amaranth is a threat

Palmer amaranth is the most competitive and aggressive pigweed species. It’s related to waterhemp and, like waterhemp, it emerges throughout the growing season, from May to August. However, Palmer amaranth is much more aggressive than waterhemp, growing 2 to 3 inches a day.

Herbicide resistance

Palmer amaranth can quickly adapt to herbicide management tactics that don’t include diverse effective sites of action (SOAs), ultimately limiting control options. In the northern states, Palmer amaranth is expected to be resistant to multiple herbicides, including glyphosate (SOA group 9) and acetolactate synthase (ALS) inhibitors (SOA group 2).

  • Palmer is dioecious, with male and female plants. Outcrossing results in the rapid spread of herbicide resistance.
  • It’s a prolific seed producer, with a single female plant typically producing 100,000 to 500,000 seeds.
  • Timing of herbicide application is critical. Effective preemergence herbicides must be followed by timely (plants less than 3 inches tall) and effective postemergence herbicides.

Threat to crop production

Palmer amaranth infestations have caused substantial yield losses and greatly increased weed management costs in cotton, soybeans and corn in the southern states. Once established in the northern corn and soybean states, it’ll likely do the same and significantly increase costs and decrease yields.

How to handle infestations

Palmer amaranth’s legal status as a state-prohibited noxious weed on the “Eradicate” list means the plant must be destroyed and that no transportation, propagation or sale of this plant species is allowed.

This law gives MDA, county, city and township officials the right to inspect land areas believed to be affected by this weed and ask owners to destroy the plants. It also allows MDA officials to investigate where potential seed lot contamination sources are occurring.

How to report

If you suspect a weed is a Palmer amaranth, email the following to reportapest@state.mn.us.

  • Your location.

  • The plants’ location. Be as specific as possible.

  • A description of the area where the plant was found.

  • Your contact information.

  • Seed source (if known).

  • Photos (similar to those under Identifying).

    • Entire plant

    • Petiole (where the leaf connects to the stem)

    • Seed head

After photographing and reporting, an MDA staff member will review and contact you if more information is needed.

  • Do not let the plants in question go to seed in the field. See below for tips on destroying the plants.
  • Do remove and save some plant material until the species has been confirmed.
    • Live plant material can be placed in a paper bag and refrigerated while dead material can be placed in a paper bag and stored at room temperature.
  • The MDA may request some plant tissue for genetic testing to confirm identification. 

Destroy the plants

Destroy the plants after photographing and reporting them to MDA. 

Note: The timeframe is very short to eradicate the plant. Due to the economic significance of this invasive weed, it’s worth our collective effort to try.

Small populations

If the Palmer amaranth population is small in number:

  • Weed plants by hand.

  • Place them in a large paper bag.

  • Remove them from the field to a site suitable for burning the plants.

  • Burn the plants.

Larger populations

For a larger population of plants at the mature stage of the weed’s life cycle, particularly when the seed is being set:

  • Mow the area.

  • Clean off the mower on-site. This prevents the spread of any weed seed shed onto the mower.

Mowing doesn’t kill the entire plant, but it’ll keep the seed on the ground in the affected area where insects and rodents can feed on it. Mowing will reduce movement away from the affected area. Plus, any seed that germinates the following year will have to compete with the more established plants that surround it.

It’s important to closely monitor the affected and surrounding area the following year to make sure there are no weeds that escaped detection or seeds that have moved into adjacent lands. By reporting your affected site to the MDA, they’ll be able to assist you with this monitoring procedure.

Why report?

This information helps the MDA understand the weed’s current distribution and its potential to spread to your fields and adjacent lands. Reporting also allows local officials to help monitor the site in subsequent years to make sure there are no escapes. This is particularly important if land ownership changes.

Handling Palmer amaranth


Authors: Jeff Gunsolus, Extension weed scientist;  Lisa Behnken, Chryseis Modderman, and Lizabeth Stahl, Extension educators; Fritz Breitenbach, former Extension integrated pest management specialist; Phyllis Bongard, Extension communications specialist 

Reviewed in 2024

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