Vigilance urged against Palmer amaranth spread

By Scout Nelson

Palmer amaranth remains a major concern for Minnesota agriculture. Added to the Minnesota Noxious Weed List in 2015, this aggressive weed falls under the prohibited-eradicate category. This means any Palmer amaranth found in the state must be destroyed because of its potential threat to crop production.

In 2016, Palmer amaranth entered Minnesota through contaminated conservation seed mixes sourced from Texas and Kansas. Its rapid growth and competitive nature make it even more challenging than water hemp. The weed is also known for its resistance to herbicides, which makes controlling more difficult.

This issue led the Minnesota Department of Agriculture, along with the University of Minnesota Extension and crop consultants, to set up a monitoring and eradication program.

Since that time, 121 sites have been reported across the state. Fortunately, Palmer amaranth established itself in 44 locations. Continuous surveillance and control efforts have kept most areas clear, with only seven counties still under active monitoring. Palmer is considered eradicated at a site after three years without sightings. However, in 2025, four new sites are under investigation.

“If you suspect a new Palmer infestation, please take time to report it through the report a pest website.”

The main source of introduction remains contaminated seed. Farmers are advised to purchase from trusted Minnesota suppliers to reduce risk. Equipment, especially harvest machinery from other states, can also spread seeds and must be cleaned before use. Additionally, hay, livestock feed, and manure from infested regions can introduce the weed to new areas. Monitoring fields where such products are used is essential.

Palmer amaranth belongs to the pigweed family and can be mistaken for other pigweeds like water hemp. Identifying it correctly is important, and resources are available for this purpose. Continued awareness and management remain key to controlling this invasive weed in Minnesota.

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