University research supports early weed control

Published on: 17:46PM Jun 08, 2009
Purdue University, Ohio State University and Southern Illinois University recently shared data from a joint 2007-08 glyphosate-tolerant corn timing study. The findings reinforced what many weed scientists (including me) recommend – controlling weeds early in the season protects yield. For example, Iowa State University reports a one day delayed application of glyphosate may cost more than a pre-emergence residual herbicide, depending on crop price and yield potential.
In the study:
  • Plots treated with foundation herbicides early in the season performed better than post-only applications. 
  • The longer weeds were allowed to compete with corn, the less it yielded.

The study showed that applying a pre-emergence herbicide and following up with glyphosate when corn was 12 inches tall yielded 223 bushels per acre. On the opposite end of the spectrum, using no pre-emergence herbicide and waiting until two weeks after corn was 12 inches tall to apply glyphosate yielded more than 40 bushels per acre less.

Corn growers across the Midwest use pre-emergence herbicides for a variety of reasons, including better weed control, yield protection, a wider application window, and to control key problem weeds.  How have pre-emergence herbicides protected your crop so far this season?