Field studies were conducted from 1997 to 1999 to evaluate the influence of broadleaf herbicides on double-crop glyphosate-resistant soybean injury and yield at Belleville, IL. Diphenylether herbicides applied postemergence (POST) caused 10 to 48% necrosis 7 days after treatment (DAT). POST herbicides caused 0 to 8%, 8 to 37%, and 0 to 12% height reduction 7 DAT in 1997, 1998, and 1999, respectively. In most instances, diphenylether herbicides did not delay soybean maturity, whereas imazethapyr applied POST delayed soybean maturity in 1998 and 1999. Acifluorfen plus bentazon reduced soybean height at maturity in 1997 and 1998, whereas lactofen, imazethapyr, and imazamox reduced height only in 1998. Diphenylether herbicides did not reduce grain yield when compared to the no-herbicide hand-weeded treatment, but imazamox reduced yield by 18%. Furthermore, the soil herbicides applied preemergence and diphenylether herbicides applied POST did not reduce grain yield when compared to glyphosate alone.

Field experiments were conducted in 1997 and 1998 near Rossville in northeast Kansas to evaluate control of imazethapyr-resistant common sunflower with selected herbicides in corn and soybean. In soybean, common sunflower control was unacceptable with imazethapyr, chlorimuron, CGA-277476, and cloransulam applied alone. Lactofen or acifluorfen applied with these herbicides slightly improved control, whereas glyphosate applied with them controlled more than 97% of common sunflower. All herbicides reduced common sunflower populations in the corn. The greatest reductions occurred when atrazine was applied with dicamba, 2,4-D, RPA 201772, or CGA-152005 plus primisulfuron. These herbicide combinations also stunted common sunflower that survived treatment. Several herbicide alternatives are available to control imazethapyr-resistant common sunflower in corn. However, glyphosate was the only herbicide that gave adequate control in soybean.