Four field experiments were conducted in Louisiana and Mississippi in 2009 and 2010 to evaluate POST herbicides treatments with tembotrione applied alone or as a prepackaged mixture with thiencarbazone for weed control in corn. Treatments included tembotrione at 92 g ai ha−1, thiencarbazone : tembotrione at 15 : 76 g ai ha−1, atrazine at 2,240 g ai ha−1, glufosinate at 450 g ai ha−1, glyphosate at 860 g ae ha−1, and coapplications of tembotrione or thiencarbazone : tembotrione with atrazine, glufosinate, or glyphosate. All treatments were applied to 26-cm corn in the V4 growth stage. Treatments containing thiencarbazone : tembotrione and those with tembotrione controlled barnyardgrass, browntop millet, entireleaf morningglory, hophornbeam copperleaf, johnsongrass, Palmer amaranth, and velvetleaf 85 to 96% and 43 to 97% 28 d after treatment and at corn harvest, respectively. Corn yield ranged from 9,200 to 10,420 kg ha−1 and was greater than the nontreated control following all herbicide treatments, except atrazine alone. Results indicated that thiencarbazone : tembotrione or tembotrione POST is an option for weed management in corn, and applications of thiencarbazone : tembotrione would be strongly encouraged where rhizomatous johnsongrass is problematic.

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.