When harvesting crops now and into the fall, it is a great opportunity to scout fields one last time for the effectiveness of your weed management plans. If a single weed species (or additional species known to be resistant) is present at least at 40 percent to 60 percent of normal height, then herbicide-resistant biotypes are likely present.

If redroot pigweed and/or Powell amaranth and another species is present at the end of the season following two glyphosate applications, then resistance is likely not the case, although it can’t be ruled out unless seeds are collected and tested. If a single weed species is present following two or three glyphosate applications and a continuum of plant responses from dead to near-normal in appearance is observed, then glyphosate resistance is likely present in the field. Visit the following web address to learn more about the response of individual plants to glyphosate: http://www.ag.ndsu.edu/glyphosateresistance.

If herbicide-resistant weeds are present, pull/cut them, bag them, carry them out of the field and destroy them to stop weed seed production in order to reduce the build-up of resistant biotypes in soil seed bank.  The most important reason to scout now is to determine one last time this season the reason why the annual weeds escaped management practices.

Record the location of all perennial weed patches in order to return to apply herbicides this fall if possible or to target the patches next season.