Published online by Cambridge University Press: 12 June 2017
A field experiment of 2 yr duration at two locations was conducted to determine the effectiveness of glyphosate [N-(phosphonomethyl)glycine] and vernolate (S-propyl dipropylthiocarbamate) as single or combination treatments for quackgrass [Agropyron repens (L.) Beauv.] control in a soybean [Glycine max (L.) Merr.]-corn [Zea mays (L.)] rotation. Vernolate applied preplant incorporated at 3.36 kg/ha gave 30 to 58% and 28 to 34% quackgrass control at the end of the first and second growing seasons, respectively. Spring applications of glyphosate at 1.12 and 1.68 kg/ha before plowing gave 53 to 90% quackgrass control at the end of the second growing season. Glyphosate at 1.12 and 1.68 kg/ha followed by vernolate preplant incorporated at 3.36 kg/ha gave 85 to 99% quackgrass control at the end of the second growing season. Although vernolate did not provide effective long term quackgrass control, it did effectively augment quackgrass control when applied as a sequential treatment to glyphosate applied at 0.56 or 1.12 kg/ha.