Waterhemp gaining resistance to dicamba
University of Illinois researchers have discovered another population of waterhemp with resistance to dicamba herbicides.
Co-author of the study Pat Tranel tells Brownfield while it was a low level of resistance, the population had never been sprayed with Dicamba or 2,4D in the past so they did not expect resistance to growth regulator herbicides.
“So it seems to have generalist resistance mechanisms that are not specific to any one herbicide. It really makes resistance management more challenging. In the past we have talked about rotating herbicide sites of action but in a population like this that has metabolic resistance, simply rotating sites of action is not going to resolve resistance problems.”
He says it’s a scary thought, but this population likely has resistance to herbicides that haven’t even hit the market yet.
“A company’s new herbicide might be good on other waterhemp populations but if it’s not effective on this waterhemp population there is a good chance they won’t bring that new herbicide forward. So, this is another challenge to the industry in coming up with new, effective herbicides.”
Tranel says the resistance trait can be passed down from both female and male plants to the next year’s waterhemp seeds.
“This species has incredible reproductive potential. Just a few plants going to seed will create potential for resistance problems next year, so you really want to aim for a clean field at the end of the season with no waterhemp going to seed and really manage that soil seedbank.”
Tranel says herbicides like dicamba and 2,4D are not a silver bullet solution for relatives of waterhemp either as a population of Palmer Amaranth in the US and a foreign population of smooth pigweed have shown resistance.
The first populations of dicamba resistant waterhemp in the US were reported by the University of Tennessee earlier this month. Tranel says this is the first known population in Illinois.
Authors of the University of Illinois study include Lucas Bobadilla (pictured above), Darci Giacominni, Aaron Hager, and Pat Tranel. The work was funded by Bayer Crop Science.