Abstract: 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.

Nomenclature: Acifluorfen; bentazon; glyphosate; imazamox; imazethapyr; lactofen; soybean, Glycine max (L.) Merr. ‘Asgrow 3601 RR’, ‘Asgrow 4501 RR’, and ‘Bergmann-Taylor 369 CR’.

Additional index words: Herbicide injury, preemergence, postemergence, CGA-248757, CGA-277476, cloransulam, flumiclorac, fomesafen, imazaquin, pendimethalin.

Abbreviations: DAT, days after treatment; POST, postemergence; PRE, preemergence.