The invasive weed Palmer amaranth has been found in Goodhue County, according to the Minnesota Department of Agriculture which positively identified it.

According to a press release from the MDA, after a crop consultant reported a suspected plant to the department, staff conducted a site visit and found the weed in two corn fields managed by one farmer.

The MDA scouted fields surrounding the documented infestations and did not find any additional Palmer plants. It is unknown at this time how Palmer amaranth got into the two fields. The MDA reported that it is continuing to investigate potential sources.

An herbicide application stunted but did not kill the plants, and a crew hand pulled weeds in the two fields to eliminate any chance of seed production.

“This is a good example of the limits of herbicide on Palmer amaranth,” said Denise Thiede, MDA’s seed unit supervisor. “If plants are allowed to reach a certain size, an herbicide application may not control them. That’s why we’re counting on farmers and crop consultants to report suspected plants. They are our best line of defense against Palmer amaranth.”

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The MDA will continue to work with the farmer, crop consultants, University of Minnesota Extension and county agricultural inspector to manage the infestations, said the press release.

Palmer amaranth is listed as a noxious weed in Minnesota and was first discovered in the state in 2016. All above and below ground parts of the plant must be destroyed, and it cannot be moved. The invasive weed is also listed as a prohibited weed seed in the state. This means no Palmer amaranth is allowed in any seed offered for sale in Minnesota.

Palmer amaranth has been found in 11 Minnesota counties, including Goodhue County. However, most of the sites have been successfully eradicated and the remaining are being closely monitored, according to the MDA.

Left uncontrolled, a single female Palmer amaranth plant typically produces 100,000 to 500,000 seeds. It is resistant to multiple herbicides, can cause substantial yield losses, and greatly increase weed management costs in soybeans and corn.

The MDA is asking farmers and agronomists to take photos of suspicious plants, pull them out, and save them in plastic bags for genetic testing if needed. Report the find to the Minnesota Department of Agriculture’s Arrest the Pest line at 1-888-545-6684 or arrest.the.pest@state.mn.us.