Researchers from the University of Tennessee report finding dicamba-resistant Palmer amaranth in the state. Results from greenhouse trials and in-field assessment report the level of dicamba resistance is relatively low, about 2.5 times.
The level of infestation in any given field ranges from a small pocket where a mother plant went to seed in 2019 to an area covering several acres in a field.
This would be comparable to the first documented glyphosate-resistant Palmer amaranth found in Tennessee back in 2006, where most were still getting relatively good Palmer amaranth control with glyphosate, while others were noticing escapes in their fields.
Researchers say it’s not time to panic, however, say “it is time to reassess weed management.” Looking forward to 2021, the university says a pre-applied residual that is effective on Palmer amaranth is now a necessity. Moreover, timely applications of Liberty must be used shortly after a dicamba application to remove escapes from coverage.