Field studies were conducted at three locations in North Carolina to evaluate clomazone preemergence (PRE) in glyphosate-tolerant cotton. Cotton was injured by fluometuron PRE at one location. Clomazone PRE controlled common ragweed, goosegrass, large crabgrass, and prickly sida better than trifluralin preplant incorporated (PPI). Trifluralin controlled Palmer amaranth better than clomazone. The addition of a late post-directed (LAYBY) treatment of cyanazine plus MSMA improved the control of goosegrass. Glyphosate at 0.8 kg ai/ha, used postemergence as needed, controlled tall morningglory and entireleaf morningglory at least 84%. Common ragweed was controlled with all herbicides, except trifluralin PPI. Prickly sida was controlled 94% or greater in glyphosate-containing systems. Cotton yields and net returns were similar for all glyphosate systems, regardless of soil-applied herbicides and LAYBY treatment options.
