Glyphosate Resistance Management: A Brave New World

When he came to America a year ago to make presentations on glyphosate resistance, Stephen Powles said he was met at times with utter skepticism.

“In some conversations (at ag meetings), people asked, ‘Is that right, weeds can gain resistance to glyphosate? Is that really possible?’”

A year later, the Australian weed scientist is back in the U.S., and attitudes are different. “Nobody asks those kinds of questions now," he said. "They now understand the reality (of the situation)."

The difference between last year and this year is that Georgia weed scientists announced finding glyphosate-resistant Palmer amaranth in the state, and weed scientists in North Carolina and Tennessee also said they found what appeared to be similar cases in their states.

Powles made that observation this morning during a teleconference on glyphosate resistance. The conference was arranged by Syngenta, and Powles was one of three panelists who answered questions for ag writers during the teleconference, which focused on cotton. (A similar conference was planned this afternoon for Midwest ag writers.)

Powles, a professor at the University of Western Australia and director of the Western Australia Herbicide Resistance Initiative, has become an authority on the subject of herbicide resistance. As he joked, ag technology and information usually start in the U.S. and flow to Australia. In this case, Australians are supplying the initial information because they’ve lived with resistance issues longer.

Australia has had all manner of problems with herbicide resistance, including glyphosate-resistant ryegrass in its wheat belt.

Other panelists this morning were:

• Chris Main, South Carolina Extension weed specialist. Main studied glyphosate-resistant horseweed while working on his PhD at the University of Tennessee.
• Chuck Foresman, Syngenta’s technical brand manager for herbicide resistance.

A number of my colleagues participated in the conference, including David Bennett with Delta Farm Press, who wrote some of the initial articles about this looming problem. David and others will likely have expanded coverage in upcoming issues.

What I’m passing along today are the high points:

The bottom line first: Growers will have to break away from total reliance on glyphosate. Panelists admitted that nobody wants to hear such talk in a farm economy that’s already squeezed by weak commodity prices and escalating input costs. “Farmers are simply farming in 2006 in a way that allows them to possibly make a profit so they can farm again in 2007,” Main observed. “But they need to be planning now for the next three to five years and do things that allow us to preserve this technology (Roundup Ready) for as long as possible.”

No “silver bullets” are on the horizon. Main said that no new or significant herbicides or weed-control technologies are likely to be available over the next several years. The overwhelming adoption of Roundup Ready created a research gap several years ago, Powles explained. With a fading herbicide market, a number of companies merged, so there are now fewer corporate research programs, overall. Companies mothballed projects that would have easily gone forward before Roundup Ready’s introduction. While some products are in various stages of development, it will be late in the decade before you’ll see anything that might help.

The key is “diversity.” Both Powles and Main used the word to describe the mixture of chemical, mechanical and agronomic tools growers will have to resurrect in order to stall further resistance development. Think tankmixes, residual herbicides, tillage, cultivation, postemergence materials, rotation, etc.

Roundup Ready technology still has a place. But, Main said, its price may decline as resistance becomes more of a factor. “Glyphosate still controls 95% or more of the weed species out there,” he said. “But where resistance is a factor, you’ll have to add something else. As more weeds become resistant, the amount the market is willing to pay for this technology will likely decrease because there’s less utility with the glyphosate option.”

Related item: Our Beltwide coverage this month included a related article, Herbicide Resistance: Don't Panic, But Be Proactive.

On the wire: Cotlook Ups 2005-06 World Cotton Output Estimate

And we quote: "The man who has confidence in himself gains the confidence of others." -- Hasidic Saying