Effect of Growth Stages on Quackgrass (Elytrigia repens) Control in Corn (Zea mays) with Rimsulfuron

Abstract

Experiments were conducted in 1996 and 1997 to determine the effects of postemergence (POST) application of rimsulfuron on quackgrass control. Rimsulfuron applied at 27 g ai/ ha to two-to four-leaf quackgrass controlled 100% of quackgrass 5 wk after treatment (WAT). Rimsulfuron applied to one- to two-leaf quackgrass was not as effective as the same rate applied to two- to four-or four- to six-leaf quackgrass. Stunting and leaf wrinkling of corn were observed 4 WAT when rimsulfuron was applied at 36 g/ha to four- to six-leaf quackgrass. The plants recovered from the stunting as the season progressed and by 12 WAT there was no appreciable stunting. Rimsulfuron (27 g/ha) applied to two- to four-leaf quackgrass increased grain and silage yield of corn by 36% and 45%, respectively, compared to the untreated check. The 27 g/ha rate of rimsulfuron applied to two- to four-leaf quackgrass resulted in 10% more grain yield than the same treatment applied to one- to two- leaf quackgrass. Rimsulfuron at 18 g/ha led to a 17% reduction of sitage yield when applied to the four- to six-leaf quackgrass. At all growth stages of quackgrass, rimsulfuron gave higher grain and silage yields than corn treated with the same rate and timing of nicosulfuron. Rimsulfuron reduced sprouting of quackgrass rhizome nodes, especially at higher rates.