Studies were conducted to evaluate weed management systems in nontransgenic, bromoxynil-resistant, and glyphosate-resistant cotton in strip- and conventional-tillage environments. Tillage did not affect weed control, cotton lint yields, or net returns. Early season stunting in strip-tillage cotton was 5% or less, regardless of herbicide system or cultivar and was transient. Excellent (> 90%) control of common lambsquarters, common ragweed, and Ipomoea species, including entireleaf, ivyleaf, pitted and tall morningglories, jimsonweed, prickly sida, and velvetleaf, was achieved with systems containing bromoxynil, glyphosate, and pyrithiobac early postemergence (EPOST). Glyphosate systems provided better and more consistent control of fall panicum and large crabgrass than bromoxynil and pyrithiobac systems. Bromoxynil and pyrithiobac EPOST did not control sicklepod unless applied in mixture with MSMA and followed by (fb) a late postemergence-directed (LAYBY) treatment of prometryn plus MSMA. Palmer amaranth was controlled (> 90%) with all glyphosate and pyrithiobac systems and with the bromoxynil system that included a broadcast soil-applied herbicide treatment. Bromoxynil systems without a broadcast soil-applied herbicide treatment controlled Palmer amaranth 87% or less. Herbicide systems that included glyphosate EPOST controlled sicklepod with or without a soil-applied herbicide treatment. The highest yielding cotton included all the glyphosate systems and bromoxynil systems that contained a soil-applied herbicide treatment. Nontransgenic systems that included a soil-applied herbicide treatment yielded less than a system with soil-applied treatment plus glyphosate EPOST. Net returns from glyphosate systems were generally higher than net returns from bromoxynil or pyrithiobac systems.
Nomenclature: Bromoxynil, fluometuron, glyphosate, MSMA, pendimethalin, prometryn, pyrithiobac, common lambsquarters, Chenopodium album L. CHEAL, common ragweed, Ambrosia artemisiifolia L. AMBEL, entireleaf morningglory, Ipomoea hederacea (L.) var. integriuscula Gray IPOHG, fall panicum, Panicum dichotomiflorum (L.) Michx. PANDI, ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. IPOHE, jimsonweed, Datura stramonium L. DATST, large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA, Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA, pitted morningglory, Ipomoea lacunosa L. IPOLA, prickly sida, Sida spinosa L. SIDSP, sicklepod, Senna obtusifolia (L.) Irwin and Barnaby CASOB, tall morningglory, Ipomoea purpurea L. PHBPU, velvetleaf, Abutilon theophrasti Medik. ABUTH, cotton, G. hirsutum L. ‘Paymaster 1220RR’, ‘Stoneville BXN 47’, and ‘Stoneville 474’