Several herbicide-based weed management programs for glyphosate-tolerant cotton were compared in eight field studies across Alabama during 1996 and 1997. Weed management programs ranged from traditional, soil-applied residual herbicide programs to more recently developed total postemergence (POST) herbicide programs. Pitted morningglory and sicklepod control was best achieved with fluometuron applied preemergence (PRE) followed by (fb) a single POST over-the-top (POT) application of glyphosate fb a POST-directed application of glyphosate. Annual grass control was better with the preplant incorporated (PPI) programs at two of three locations in both years. Treatments that included at least one glyphosate POT application gave increased grass control over no glyphosate or pyrithiobac POT. Velvetleaf control was improved with the addition of glyphosate POT. A herbicide program using no POST herbicides yielded significantly less seed cotton than any program using POST herbicides at one location. PRE- and POST-only weed management programs at another location produced more seed cotton and gave greater net returns than PPI programs. Similarly, net returns at that same location were equivalent for both PRE- and POST-only programs, and less for PPI programs. POST-only programs yielded highest amounts of seed cotton and netted greater returns.

Military bases in the United States were mandated to reduce the amount of pesticide used to 50% of 1993 levels by 2000. Historically, 2,4-D was applied to control common sunflower, which establishes itself in disturbed soils and obstructs gunners' views of targets. A 25-ha lowland field in Camp Forsyth was selected to compare efficacy of alternative herbicides with that of 2,4-D low-volatile ester (LVE), with the goal of reducing the amount of herbicide applied by at least half. Site vegetation was mostly native tallgrass prairie dominated by warm-season C4 grasses (e.g., big bluestem, Indiangrass, little bluestem, and switchgrass) and including less abundant C3 species in the Asteraceae, Fabaceae, Brassicaceae, and other families. Initially, the site had a high population of common sunflower. All herbicide treatments from 3 yr of field trials were highly and equally effective at reducing common sunflower, decreasing stem density by 83 to100%. Treatments that offer substantial reductions in the amount of herbicide applied are chlorimuron (0.01 kg ae/ha), dicamba + 2,4-D amine (0.07 kg ae/ha + 0.20 kg ae/ha), clopyralid + 2,4-D amine (0.06 kg ae/ha + 0.28 kg ae/ha), 2,4-D LVE (0.56 kg ae/ha), and metsulfuron + 2,4-D amine (0.002 kg ai/ha + 0.28 kg ae/ha). Use of these herbicides at Ft. Riley would reduce total active ingredient applied by 73 to 99% and lower chemical costs for this particular use by as much as 88%.