Iowa farmers are looking for solutions as they find certain weeds, especially waterhemp, are becoming harder to control. And, with Palmer amaranth — a particularly tough and damaging weed — creeping into the state, those concerns are higher than ever.

"We know (herbicide) resistance is an issue," says Joel DeJong, an Iowa State University (ISU) Extension field agronomist in northwest Iowa. "That’s why there is some renewed interest in how we’re managing weeds."

"Nature is very good about saying you’ve left a void in your management program, and...