Field studies were conducted near Clayton, Goldsboro, Kinston, and Rocky Mount, NC in 2003 to evaluate weed control and cotton response to postemergence (POST) treatments of glufosinate applied alone or in tank mixtures with s-metolachlor, pyrithiobac, or trifloxysulfuron. Late-season control of common lambsquarters, common ragweed, entireleaf morningglory, ivyleaf morningglory, jimsonweed, pitted morningglory, purple nutsedge, and sicklepod with glufosinate early postemergence (EPOST) was ≥90%. The addition of S-metolachlor to glufosinate EPOST improved control of all weeds except sicklepod, ivyleaf morningglory, and entireleaf morningglory. When applied POST, glufosinate provided ≥90% late season control of common lambsquarters, common ragweed, entireleaf morningglory, ivyleaf morningglory, jimsonweed, large crabgrass, pitted morningglory, purple nutsedge, and sicklepod. Control of goosegrass and Palmer amaranth was 81 and 84%, respectively. When pyrithiobac or trifloxysulfuron were added in POST tank mixtures, control of Palmer amaranth improved 6 and 9 percentage points, respectively. Control of goosegrass remained near 80% regardless of herbicide treatment used. The addition of a late post-directed (LAYBY) tank-mixture of glufosinate plus prometryn provided ≥88% late season control of all weeds. Reduced control of goosegrass and Palmer amaranth was observed with the LAYBY tank mixture of glufosinate plus MSMA when compared to other LAYBY tank mixtures. Cotton lint yields in plots receiving any herbicide application were significantly higher than plots receiving no herbicide application for all application timings. Cotton lint yields were ≥ 740 kg/ha where an EPOST was applied and ≥ 680 kg/ha when a POST herbicide was applied. Cotton lint yields were at least 200 kg/ha greater on plots receiving a LAYBY application when compared to plots where no LAYBY treatment was applied.

Nomenclature: Glufosinate, MSMA, prometryn, pyrithiobac, S-metolachlor, trifloxysulfuron, common lambsquarters, Chenopodium album L. CHEAL, common ragweed, Ambrosia artemisiifolia L. AMBEL, entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray IPOHG, goosegrass, Eleusine indica ELEIN, ivyleaf morningglory, Ipomoea hederacea Jacq. IPOHE, jimsonweed, Datura stramonium L. DATST, large crabgrass, Digitaria sanguinalis L. DIGSA, Palmer amaranth, Amaranthus palmeri S. Wats AMAPA, pitted morningglory, Ipomoea lacunosa L. IPOLA, purple nutsedge, Cyperus rotundus L. CYPRO, sicklepod, Senna obtusifolia L. Irwin and Barnaby CASOB, cotton, Gossypium hirsutum L