RE: Best red briar killer
The best non-selective, basal bark application treatment would be a mixture used by tree contractors by your local power company. It consists of Tordon, and stalker and will control any vegetation as long as you apply it completely around the base of the bark of the undesirable species you are trying to control. It is non-selective so it will kill any and all vegetation that it is applied to. You do need a license, but it is very effective.