Field studies were conducted in Louisiana and Mississippi in 2009 and 2010 to evaluate PRE herbicide treatments containing isoxaflutole or a prepackaged mixture of thiencarbazone-methyl ∶ isoxaflutole (TCM ∶ isoxaflutole) for weed control in corn. PRE treatments included the premix of TCM ∶ isoxaflutole alone (30 ∶ 80 g ai ha−1) and with atrazine (1,120 g ai ha−1), isoxaflutole alone (90 g ai ha−1) and with atrazine (1,120 g ai ha−1), and the premix of atrazine plus S-metolachlor (1,820 plus 1,410 g ai ha−1). POST treatments included glufosinate (450 g ai ha−1) or glyphosate (870 g ae ha−1) applied to 30-cm corn along with a no POST treatment. All PRE treatments controlled barnyardgrass, entireleaf morningglory, rhizomatous johnsongrass, Palmer amaranth, and velvetleaf 87 to 95% 4 wk after planting (WAP) and browntop millet and hophornbeam copperleaf were controlled 86 to 95% 8 WAP. Weed control was improved 8 and 20 WAP when either POST treatment was applied. TCM ∶ isoxaflutole plus atrazine controlled barnyardgrass, entireleaf morningglory, Palmer amaranth, and velvetleaf at least 90% 20 WAP regardless of POST treatment. TCM ∶ isoxaflutole plus atrazine provided greater control of browntop millet (90%) than isoxaflutole alone or with atrazine and atrazine plus S-metolachlor where control was 86% 20 WAP. Pooled across POST treatments, all PRE treatments containing isoxaflutole or TCM ∶ isoxaflutole controlled rhizomatous johnsongrass better (74 to 76%) than atrazine plus S-metolachlor (67%). Corn yield following herbicide treatments ranged from 9,280 to 11,040 kg ha−1 compared with 9,110 kg ha−1 for the nontreated. Results indicate that TCM ∶ isoxaflutole or isoxaflutole PRE is an option for use in a corn weed management program and may prolong the use of atrazine where weed resistance may be an issue. Where rhizomatous johnsongrass is a problem, TCM ∶ isoxaflutole or isoxaflutole PRE can provide better control than atrazine plus S-metolachlor PRE. Without PRE treatments, glufosinate or glyphosate was needed for season-long weed control.
Nomenclature: Atrazine; glufosinate; glyphosate; isoxaflutole; S-metolachlor; thiencarbazone-methyl, methyl 4-[(4,5-dihydro-3-methoxy-4-methyl-5-oxo-1H-1,2,4-triazol-1-yl)carboxamidosulfonyl]-5-methylthiophene-3-carboxylate; barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG; browntop millet, Urochloa ramosa (L.) Nguyen PANRA; entireleaf morningglory, Ipomoea hederacea (L.) Jacq. var. integriuscula Gray IPOHG; hophornbeam copperleaf, Acalypha ostryifolia Riddell ACCOS; johnsongrass, Sorghum halepense (L.) Pers. SORHA; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; velvetleaf, Abutilon theophrasti Medik ABUTH; corn, Zea mays L.