Ohio, Indiana, and Illinois are heavily infested with weeds resistant to glyphosate (group 9), PPO inhibitors (group 14), and ALS inhibitors (group 2). This has greatly reduced the number of effective postemergence herbicides for controlling these weeds in Roundup Ready 2 (RR2) soybeans. Adoption of Roundup Ready 2 Xtend (glyphosate and dicamba resistant – RR2 Xtend) soybeans and use of dicamba-based herbicides is one option for managing resistant weed populations. Keep in mind that selection for dicamba resistance occurs each time dicamba is applied, and over reliance on this technology will lead to the development of dicamba-resistant weed populations.
The extension weed science programs at The Ohio State University, Purdue University, and the University of Illinois recently collaborated to revise suggestions and precautions for use of dicamba in dicamba-resistant soybean. The United States Environmental Protection Agency renewed labels of Xtendimax, Engenia, and FeXapan last October, and this updated extension weed science publication offers additional suggestions to help further reduce off-target dicamba movement.