Iowa farmers need a new approach to counteract the growing number of herbicide-resistant weeds and fend off new species like Palmer amaranth from taking over their corn and soybean fields, according to Iowa State University (ISU) Extension weed scientists.

"We need to refocus on weed seedbank management," ISU weed scientist Mike Owen said Nov. 30 at the Integrated Crop Management Conference. "Once you have the problem, particularly with resistance, it ain’t going away."

Many farmers seem to be turning a blind eye to late-season weeds, figuring the latecomers don’t impact yields like early-season weeds do, Owen said. That’s just asking for problems in the future, since weed seeds can remain viable in the soil...