By Dr. Mark Loux, OSU Extension State Weed Specialist, Adapted from C.O.R.N. 2021-24
We have been screening a random sample of waterhemp populations for herbicide resistance over the past two years. Herbicides used in the screen include mesotrione, atrazine, 2,4-D, fomesafen, and metolachlor.
Results of our research show that it’s possible for Ohio waterhemp populations to have some level of resistance to one, several, or all of these herbicides. Glyphosate is not included because we assume almost all populations are already resistant to this. We are also part of a regional project that has been screening for dicamba and glufosinate resistance with populations that we supply, although none has been identified to date. Our sample size has been small so far, so at this point we are looking to expand our screening to include waterhemp populations submitted by anyone in Ohio looking for more information about their response to herbicides.