Giant ragweed populations vary in their emergence patterns and herbicide resistance depending on management history. Group 2 (ALS-inhibitors) resistance is most likely to occur in fields with a history of non-GMO soybeans that depended heavily on Group 2 herbicides (ALS-inhibitors) for control. Farmers should evaluate the performance of previous herbicide applications, scout and understand emergence patterns in order to determine the best management practices.
Farmers managing populations of weeds with Group 2 (ALS) and Group 9 (glyphosate) resistance have limited options and will likely have to emphasize the use of Group 14 (PPO-inhibitor) herbicides and Group 10 (glufosinate) in LibertyLink® soybeans. Rotating to corn and taking advantage of effective corn herbicides may be the best option for dense infestations of Group 2 (ALS)- and Group 9 (glyphosate)-resistant populations.
Follow the steps below for the best management of herbicide-resistant giant ragweed.
Photo: Ohio State Weed Lab, The Ohio State University, Bugwood.org