Here is an update from answer-line person, Richard Jauron, on his nimblewill control demonstration with the herbicide Tenacity (mesotrione). You will find posts on the application from last summer and updates during the fall of 2011 and spring of 2012 . The following pictures are from June 2012.
The work is going well, and he feels that he has achieved at least 75% control at this time.
Nimblewill can come back later in the season from plant parts. It can also come back from seed. Richard will continue to monitor this. He also plans to keep at it until he has beat the nimblewill.
Here are some comments from Richard.
Nimblewill is present in the center of this photograph. Area was treated with Tenacity in summer of 2011.
--- Nimblewill is present in photograph, but at a reduced level.
Overall view of the backyard. This area contained several areas of nimblewill in 2011. Nimblewill-infested areas were treated with Tenacity in the summer of 2011. Seventy-five to eighty percent of the nimblewill appears to have been destroyed.