MDA encourages farmers and agronomists to scout fields before harvest
St. Paul, MN: The Minnesota Department of Agriculture (MDA) has positively identified the invasive weed Palmer amaranth in Houston County.
The MDA was contacted by the Houston County Ag Inspector after discovering several hundred plants in a small hay field. The field has since been mowed and burned off to destroy any plants, seedlings, and seeds produced this season. The MDA Palmer amaranth team will monitor the site for up to three years for any new plants.
The source of the infestation is still under investigation.
“While we’re still trying to determine how Palmer amaranth got into the field, we’re asking farmers to scout for the weed now before harvest,” said Denise Thiede, MDA’s Seed Unit Supervisor. “The plants will be identifiable with flowering and fruiting structures. Seedhead spikes can get up to three feet long and are pricklier than waterhemp or other pigweed spikes.”
If you suspect Palmer amaranth on your property, collect the whole plant and contain any seed produced. Contact the Minnesota Department of Agriculture’s Arrest the Pest line at 1-888-545-6684 or email@example.com, the University of Minnesota Extension, or your local crop consultant.
Palmer amaranth is listed as a noxious weed in Minnesota. All above and below ground parts of the plant must be destroyed, and it cannot be moved. The weed is also listed as a prohibited weed seed in Minnesota as well as in Iowa, North Dakota, South Dakota, and Wisconsin. This means no Palmer amaranth is allowed in any seed offered for sale in the state. A zero-tolerance approach to this weed is essential to protect agriculture in our region.
Since it was first discovered in the state in 2016, Palmer amaranth has been found in eight Minnesota counties, including Houston. It was discovered in conservation plantings in Lyon and Yellow Medicine counties in 2016, and Todd and Douglas counties in 2017. The MDA confirmed the weed in row crop fields in Redwood and Jackson counties in 2018. Palmer amaranth has been eradicated from all those sites. The weed was also found in a proso millet field in Lincoln County in August 2019. The Lincoln and Houston sites will be monitored to determine if further management is needed to eradicate these newly introduced populations.
Details of previous finds are on the MDA website.
This work on Palmer amaranth is supported by the Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizens Commission on Minnesota Resources.
Click to download photo of Palmer amaranth plant – Caption: Palmer amaranth flowering in Houston County. Note how the leafstalk is longer than the leaf blade on lower leaves.
Click to download photo of multiple Palmer amaranth plants – Caption: Palmer amaranth has long flowering spikes that are spiny. The plant can produce hundreds of thousands of seeds in a short time frame. Seeds mature within 10-12 days after pollination.
Click to download photo of close-up Palmer amaranth plant – Caption: This close-up of the flowering spike of a Palmer amaranth plant shows the spiny flower head and leafstalk longer than the leaf blade.
Click to download photo of torching of Palmer amaranth plants – Conservation Corps Minnesota staff torch the area infested with Palmer amaranth in Houston County. Flame torching is an effective management strategy to kill Palmer amaranth plants, seedlings, and seeds on the soil surface.
Click to download photo of torched area – Flame torching destroys all the vegetation and exposes planting rows and Palmer amaranth skeletons.
Source: Minnesota Department of Agriculture