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

Abstract

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, and glufosinate have provided more herbicide options for waterhemp management. A probability-based survey of Iowa fields was conducted in fall 2019 wherein waterhemp seeds were collected and their susceptibility to 2,4-D, dicamba, and glufosinate was determined. The average survival of all populations treated with 1× 2,4-D, dicamba, and glufosinate was 17%, 5%, and 4%, respectively. Seven percent of treated populations exhibited ≥50% survival to 1× rates of 2,4-D.