After reviewing research on late-season weed control in soybeans, Bob Hartzler of Iowa State University says the benefits are limited. He says, by late July, weeds poking their heads above the canopy have little impact on yield. And killing the weeds late may have little impact on weed seed production. Once weed seed fill has initiated, a sprayed weed can still produce plenty of viable seeds. The biggest benefit of late-season control may be in making harvest easier. But because the weeds have already done their damage to yield and produced viable seeds, the presence of substantial late-season weed populations might indicate that an earlier, mid-season glyphosate treatment or a residual herbicide might have been justified. Read more about the study at