Herbicide Options for Control of Glyphosate-Resistant Alfalfa in Glyphosate-Resistant Corn.

Glyphosate-resistant corn is planted on over 90% of the acres in the U.S. Glyphosate is also one of the most common herbicides used to terminate an old alfalfa stand. The development and widespread adoption of glyphosate-resistant alfalfa, however, has created a challenge in removing old alfalfa stands and volunteer alfalfa grown in rotation with another glyphosate-resistant crop. The purpose of this study was to determine the effect of different corn herbicides on glyphosate-resistant alfalfa control in glyphosate-resistant corn. Studies were conducted at the UAES Research Farm near Cache Junction, UT in 2012 and 2013. Treatments included common corn herbicides alone and in combination applied when alfalfa was in the vegetative stage or in bloom. Alfalfa percent control and biomass, and corn silage yield were determined at harvest.