Field experiments were conducted to evaluate weed control provided by glyphosate, glufosinate, and MSMA applied alone or in mixture with residual and nonresidual last application (LAYBY) herbicides. Herbicide treatments included glyphosate early postemergence (EPOST) alone or followed by glyphosate, glufosinate, or MSMA late-postemergence (LPOST) alone or tank-mixed with one of the following LAYBY herbicides: carfentrazone-ethyl at 0.3 kg ai/ha, diuron at 1.12 kg ai/ha, flumioxazin at 0.07 kg ai/ha, fluometuron at 1.12 kg ai/ha, lactofen at 0.84 kg ai/ha, linuron at 0.56 kg ai/ha, oxyfluorfen at 1.12 kg ai/ha, prometryn at 1.12 kg ai/ha, or prometryn trifloxysulfuron at 1.12 kg ai/ha 10 g ai/ha. Residual herbicides were also applied alone LPOST. Weeds evaluated included barnyardgrass, broadleaf signalgrass, coffee senna, entireleaf morningglory, hemp sesbania, ivyleaf morningglory, johnsongrass, large crabgrass, Palmer amaranth, pitted morningglory, prickly sida, redroot pigweed, sicklepod, smooth pigweed, spiny amaranth, and velvetleaf. Treatments containing MSMA provided lower average weed control compared to those containing glyphosate or glufosinate, and residual herbicides applied alone provided inadequate weed control compared to mixtures containing a nonresidual herbicide. Across 315 of 567 comparisons (55%), when a LAYBY herbicide was added, weed control increased. The most difficult to control weed species at all locations was pitted morningglory. Barnyardgrass and hemp sesbania at the Mississippi location and hemp sesbania at the Louisiana location were collectively difficult to control across all treatments as well.
Nomenclature: carfentrazone-ethyl; diuron; flumioxazin; fluometuron; glufosinate; glyphosate; lactofen; linuron; MSMA; oxyfluorfen; prometryn; trifloxysulfuron; barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG; broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash BRAPP; coffee senna, Cassia occidentalis L. CASOB; entireleaf morningglory, Ipomoea hederacea var. integruiscula Grey IPOHG; hemp sesbania, Sesbania exaltata (Raf.) Rydb.ex A. W. Hill SEBEX; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq IPOHE; johnsongrass, Sorghum halepense L. Pers. SORHA; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; Palmer amaranth, Amaranthus palmeri L. AMAPA; pitted morningglory, Ipomoea lacunosa L. IPOLA; prickly sida, Sida spinosa L. SIDSP; redroot pigweed, Amaranthus retroflexus L. AMARE; sicklepod, Senna obtusifolia (L.) Irwin & Barnaby CASOB; smooth pigweed, Amaranthus hybridus L. AMACH; spiny amaranth, Amaranthus spinosus L. AMASP; velvetleaf, Abutilon theophrasti Medik. ABUTH; cotton, Gossypium hirsutum L