Importance of Managing Perennial Weeds in the Fall: Quackgrass

We in the weed science business are pretty good at telling producer’s to manage perennial weeds in the fall because they are controlled much better.  Although its nice to believe without question, quantitative proof is always better. I recently came across a University of Guelph research report from 1977 (I was still in diapers) that nicely demonstrates the reduction in quackgrass re-growth the following spring after a fall glyphosate application.Although a spring application of glyphosate will reduce quackgrass re-growth the next spring (compared to doing nothing),  waiting until the fall to apply the glyphosate resulted in an additional 80% reduction in re-growth.