Ryan Kohlhagen deals with the 800-pound gorilla – glyphosate-resistant Palmer amaranth, plus resistant marestail and waterhemp. The Jasper County farmer believes Liberty is a tool some overlook. It's a post-emergence herbicide that can be applied over Liberty Link crops which contain tolerance to glufosinate – the active ingredient in Liberty herbicide.

Related: Managing Herbicide Resistant Weeds

"Liberty has worked well for us," Kohlhagen says. "We found Palmer amaranth in 2011, and sprayed a field four times with glyphosate. It was a weird feeling to have weeds Roundup couldn't kill."

Hardy opponent: Ryan Kohlhagen photographed this Palmer seedhead sticking through the snow in a ditch bank. (Photo courtesy of Ryan Kohlhagen)

Kohlhagen recalls that when Palmer showed up in 2011, they pulled out existing Palmer plants by hand. In fact, he gives his mom credit for doing most of that work. Other farmers where Palmer gets a head start have actually hired crews to come in and hand weed and remove the plants from the field.

In 2012 Flexstar didn't kill tall Palmer plants in a field of Roundup Ready beans, Kohlhagen reports. His Liberty Link beans were clean. So he's relied heavily on Liberty Link soybeans ever since. There is no known resistance to Liberty herbicide.

Bill Johnson, Purdue weed specialist, says if you have glyphosate- resistant Palmer amaranth, marestail and/or giant ragweed, it's a good idea to try Liberty Link soybeans.

"We recommend an effective burndown with a residual first, and then Liberty to clean things up when weeds are small," he says.

Kohlhagen's goal is to spray Liberty when weeds are 3 inches tall, although he has taken down taller weeds.

Related: Resistant Weeds Creep Up on Midwestern Farmers

Learn more about Kohlhagen's program at: indianasoybean.com/takeaction. View a video shot for the 'Take Action' campaign against resistant weeds. Johnson notes that Purdue University has also helped support and participate in the Take Action campaign to help make as many people as possible aware of resistant weeds, and what they can do to both fight them, and limit further resistant weeds from developing in the future.