Palmer amaranth is a hard-to-control noxious weed that can significantly reduce crop yields. It was first introduced in Minnesota in 2016 through contaminated seed mixes used for conservation plantings.
Fortunately, Minnesota regulators were prepared. They had already declared Palmer amaranth a prohibited noxious weed in 2015, and they quickly added the weed's seed to their prohibited list by emergency order. As a result, they were able to take prompt action to identify and eradicate newly emerged infestations.
A research paper featured in the journal Weed Technology documents Minnesota's experiences, including the timeline to eradication, best practices and lessons learned.
Of the sites sown with contaminated seed mixes, Palmer amaranth was found at eight. With intensive scouting, torching, prescribed burning and herbicide application in 2016 and 2017, those infestations were eradicated. Similar results were achieved in 2018, 2019 and 2020 when populations of Palmer amaranth were discovered at new locations across the state.
The authors point to several success factors, including broad cooperation among the commissioner of agriculture, legislative committees, commodity groups and farmers. Once an aggressive protocol to address Palmer amaranth was established, critical information could be quickly disseminated across the agricultural community and to the public. One example: When officials determined that manure from livestock could contain viable Palmer amaranth seeds, they were able to quickly share the information with growers and take steps to eliminate the risk.
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