Differential susceptibility of Iowa waterhemp (<i>Amaranthus tuberculatus</i>) populations to 2,4-D, dicamba, and glufosinate

Multiple herbicide-resistant waterhemp ( Amaranthus tuberculatus (Moq.) J.D. Sauer) has limited herbicide options for Iowa row crop production. Soybean Glycine max (L.) Merr.) cultivars and corn Zea mays L.) hybrids resistant to 2,4-D, dicamba, glufosinate have provided more management. A probability-based survey of fields was conducted in fall 2019 wherein seeds were collected their susceptibility determined. The average survival all populations treated with 1× 17%, 5%, 4%, respectively. Seven percent exhibited ≥50% rates 2,4-D.