Controlling herbicide-resistant weeds like waterhemp and Palmer amaranth is becoming more of a puzzle every year as growers battle weeds that are tolerant to three, four or even five different herbicide groups.
A 2013 survey indicated 70 percent of Iowa’s waterhemp population was resistant to three herbicide groups, and the problem is worsening, said Iowa State University weed scientist Bob Hartzler.
“We probably have as many four-way resistant populations as we have three-way resistant populations, and it’s going to continue to shift that way,” he said.
However, Hartzler insists farmers can hold their own in the battle against weeds by getting back to basics regarding weed management. That means basing control efforts based on the specific weed ...