This fall, Palmer amaranth was discovered for the first time in soybean fields in Redwood and Jackson counties, writes Jeff Gunsolus, Extension Agronomist – Weed Science, University of Minnesota. In Redwood County, one female and three male plants were found and in Jackson County, one female plant was found. All plants were destroyed, no seed was discovered and no additional plants were found within a 5-mile radius. The seed source is under investigation but likely routes would include contaminated field equipment and water and manure transport. North Dakota is experiencing a similar situation.
Past Detections in 2016 and 2017
Our first detections of Palmer amaranth in Minnesota occurred in 2016 in CRP plantings in Yellow Medicine and Lyon Counties. Contaminated CRP seed was also responsible for Palmer amaranth detection in Todd and Douglas counties in 2017. At this time six other counties in Minnesota were found to be planted with CRP contaminated seed lots but no plants have been found in the field.
To date, the reporting triangle of farmer and crop consultant – U of MN Extension – Minnesota Department of Agriculture (MDA) has been responsible for maintaining the Palmer amaranth infestation to very low levels. Early detection prevents the potential for seed spread via combines and other field equipment and allows the MDA time to investigate the potential source, stop recurrence (if possible) and to assess the infested site.
Reporting to the MDA will not identify a farm field location but if Palmer amaranth is confirmed then the county where the infestation occurred will be reported.
Identification Characteristics of Palmer Amaranth
Palmer amaranth is challenging to identify as many of the amaranth species look similar. However, at this time of the year identification is easier when the plants are in their reproductive phase of development. For help in identification, click here.
Key characteristics to look for would include: rapid growth that can reach over 6 feet in unmown areas, plant is smooth with no hairs on stems or leaves, leaf petiole (the stalk connecting the leaf to the stem) is often longer than the leaf and seed and pollen heads can reach 1 to 3 feet in length. However, the most consistent characteristic is the spiny bracts found on the female seed head.