Scientists from both Tennessee and Illinois have confirmed dicamba-resistant waterhemp in their respective states this week.
 
The Illinois weed population, collected from Champaign County, shows 5- to 10-fold levels of resistance to dicamba compared to susceptible populations, said University of Illinois weed scientist Aaron Hager. Overall, it is a 6-way resistant weed population, with resistance to Group 4 (auxins, including dicamba and 2,4-D), Group 2 (ALS-inhibitors), Group 5 (triazines), Group 14 (PPO-inhibitors), Group 27 (HPPD-inhibitors) and Group 15 (VLCFA- synthesis inhibitors, such as S-metolachlor).
 
In Montgomery County, Tennessee, waterhemp collected from fields in the Cumberland River bottoms are showing roughly 4.5-fold levels of resistance to dicamba, said Larry Steckel, University of Tennessee Extension weed scientist, who worked with Purdue University scientists to confirm his findings. The Tennessee waterhemp populations are also resistant to Group 9 (glyphosate), Group 14 (PPO-inhibitors) and Group 2 (ALS-inhibitors), although surprisingly, 2,4-D is still effective on them, Steckel said.
 
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