Coping with herbicide-resistant weeds, after decades of the easy, sure control afforded by glyphosate (Roundup), will require a multi-pronged approach, Mississippi growers were told at the 2011 Delta Ag Expo.

As glyphosate-resistant pigweed (Palmer amaranth) spreads in the Mid-South, and resistant Italian ryegrass continues to be documented, producers will need to include alternate chemistries — many of which are decades-old active ingredients — in their weed control programs, a panel of specialists noted.

And after wide-scale adoption of no-till and reduced till practices, in many cases, tillage may also be a necessary component for combating resistant weeds.

“There are many farmers who can tell horror stories of the problems we had with insect resistance to pesticides in the 1970s and 1980s,” said Robert Martin, Extension director for Issaquena County, who chaired the forum. “Weed resistance has the potential to be even worse.”

Panel participants were Tom Eubank, assistant research/Extension professor at the Delta Research and Extension Center, Stoneville, Miss.; Darrin Dodds, assistant Extension professor of plant and soil sciences at Mississippi State University; Daniel Stephenson, assistant research/Extension professor of weed science at Louisiana State University; Jason Bond, associate research professor of weed science at the Delta Research and Extension Center; and Erick Larson, associate Extension/research professor of plant and soil sciences at Mississippi State University.

Excerpts from their remarks follow:

Eubank: “We’ve had instances of herbicide resistance since the 1970s. We’ve had a long run with Roundup: 30-plus years before getting resistance. But we’ve used this herbicide continuously on millions of acres, in many cases with no-till, and with fewer alternate chemistries. We need to break that cycle.

“This is an issue that’s not going away. These resistant weeds are going to continue to spread. We’ve got to be proactive and timely in using alternate chemistries in conjunction with glyphosate.