Palmer amaranth was initially discovered in Harrison County, Iowa in August 2013 in a fallow crop field. Following that discovery, five more infestations were discovered in Page, Fremont, Muscatine, and Lee counties in 2013 and 2014. In July 2016, two landowners, both professional agronomists, detected Palmer amaranth in fields planted this spring to native seed mixes for conservation purposes. One discovery was in a quail habitat (CP 33) conservation planting in Muscatine County and the other was in a pollinator habitat (CP 42) conservation planting in Madison County. Since those initial discoveries in conservation plantings, Palmer amaranth was confirmed in an additional 41 Iowa counties in 2016 (Fig. 1). At least 35 of those counties are on the map as a result of the unintentional seeding of Palmer amaranth with native seed for conservation purposes.
Soil Science Extension
University of Wisconsin Madison