Glyphosate-resistant waterhemp has recently been confirmed in a small area of Richland County, North Dakota. Glyphosate-resistant waterhemp was confirmed in southern Minnesota in 2007 and has continued to increase over time. In 2010, based on visual observations, a high percentage of fields in Renville and Swift counties in Minnesota had some frequency (> 1 plant/field) of glyphosate-resistant waterhemp present at harvest. The frequency of glyphosate-resistant waterhemp has continued to increase due to the continued planting of Roundup Ready crops and the exclusive use of glyphosate.

Where glyphosate-resistant biotypes are known to be present in fields, waterhemp must be properly managed using reactive management strategies. Proactive management strategies will be necessary in other fields in order to attempt to prevent glyphosate-resistant biotypes from developing. Often the level of weed-control inputs will be lower in fields where proactive strategies are employed due to lower weed seed bank populations. Proper management requires managing waterhemp across the entire cropping system over time. Many growers have begun using pre-emergence residual herbicides. Increasing crop rotation diversity in the cropping system and focusing on the use of Roundup Ready crops in the rotation where the fewest alternative herbicides to glyphosate exist will also reduce the selection pressure for glyphosate-resistant waterhemp. To illustrate, wheat, corn and LibertyLink corn and soybean provide more chemical weed control options and should be considered.