by Rodrigo Werle (UW-Madison Extension Cropping Systems Weed Scientist)
Under a new emergency rule, Palmer amaranth has been labeled as a prohibited noxious weed seed in Wisconsin. Given Palmer amaranth’s aggressive nature, this is a worthwhile and necessary attempt to keep this troublesome weed species out of the state. For more details, see DATCP article: “Keep an Eye Out for Palmer Amaranth, DATCP Cautions”.
Palmer amaranth’s late and extended emergence window throughout the growing season and vigorous growth rate (up to 2 inches per day under ideal conditions) make control in row crops very difficult. Palmer amaranth is a major weed problem in the US Mid-South and parts of the Midwest. According to University of Wisconsin-Madison Weed Scientists, Palmer amaranth has been reported in 6 Wisconsin counties thus far (see map below).