Herbicide-restant pigweeds (Amaranthus spp.) are in Wisconsin, how serious is it?


  • Thomas Butts
  • Vince Davis
  • UW Madison
Project Media

Pigweeds, specifically common waterhemp (Amaranthus rudis Sauer) and Palmer amaranth (Amaranthus palmeri S. Wats.), are an increasing threat to current agricultural production systems. Common waterhemp and Palmer amaranth are dioecious, small seeded, broadleaf weed species’ known for their prolific growth characteristics and high competitive ability. Exceedingly plastic in nature, common waterhemp and Palmer amaranth can grow at rates of 0.16 and 0.21 cm per growing degree day, respectively (Horak and Loughin, 2000). Furthermore, both species can produce over 250,000 seeds per female plant (Sellers et al., 2003). This intensifies the likelihood and speed that herbicide-resistant biotypes can increase in a population and transfer from one location to another through seed dispersal. Moreover, common waterhemp and Palmer amaranth cause significant yield loss in corn (74 and 91%, respectively) and soybean (56 and 79%, respectively) when left unmanaged (Bensch et al., 2003; Massinga et al., 2001; Steckel and Sprague, 2004).