Aaron Hager, University of Illinois Extension weed science specialist, discusses how the weed management practices of farmers across much of the Midwest have, in many ways, been altered dramatically.
Aaron Hager, University of Illinois Extension weed science specialist, discusses how the weed management practices of farmers across much of the Midwest have, in many ways, been altered dramatically.

CHICAGO — Farmers are dealing with more than just weeds that are resistant to herbicides. They also have challenges with weed shifts.

“A great example is the geographic expansion of Palmer amaranth,” said Damon Palmer, U.S. commercial leader for Enlist with Dow AgroSciences.

“This weed has been a real pest for farmers in the Southeast for years, and now we see it moving into the Midwest, including Illinois and the eastern Corn Belt in states like Indiana, Michigan and Ohio,” added Palmer during a presentation at the Corn, Sorghum and Soybean Research Conference hosted by the American Seed Trade Association.

“When I started at the U of I 20 years ago, there were about two people in the state who knew what waterhemp was,” said Aaron Hager, University of Illinois Extension weed science specialist. “In a relatively short amount of time, this has gone from a species of obscurity to one that is the driver species of the majority of our acres in Illinois.”

Now, Hager said, for some fields in Illinois, “we have a weed species that when it comes out of the ground, we may not have a chemical option for its control.”

And, he added, there is no evidence it will go away in the foreseeable future.

One of the biological characteristics that has facilitated the spread of the waterhemp problem is the number of seed produced by the plants.

“Female waterhemp plants are capable of producing in excess of 1 million seeds per plant,” the specialist reported.

Another aspect of weed resistance is how weeds are changing.

“Marestail is evolving from a winter annual to a weed that is starting to germinate in the summer,” Palmer noted.

“Another complicating factor is herbicide innovation has hit a stalemate — from 1940 to 2000, there were 10 new modes of action introduced,” he said. “And from 2000 to 2010, there were no new modes of action introduced in the U.S.”

Looking forward over the next five to eight years, Palmer said there’s an “innovation cliff.”

“Patents have decreased for herbicide innovation, so we are looking at the technology we’ve got to use in the future,” he said.

“The foundation of the Enlist weed control system is 2,4-D,” the Dow AgroSciences spokesman explained. “It’s complimentary to glyphosate, systemic, and it has strong broadleaf control.”

In addition, 2,4-D has a regulatory package that is accepted in more than 60 countries, Palmer noted.

“This herbicide has been rigorously tested and used for many years,” he said.

The Enlist weed control system currently is being developed for corn, soybeans and cotton.

“The Enlist Duo herbicide will contain two modes of action, and the Enlist soybeans will have a trait to provide tolerance to 2,4-D,” the spokesman explained. “Depending regulatory approval, the trait will allow post-emerge application of Enlist Duo up to R2.”

Enlist Ahead is a management program that will support the weed control system.

“It is designed for the grower and applicator, to help them succeed while promoting the responsible use of the Enlist weed control system,” Palmer said. “It is focused on recommendations and label requirements, herbicide application parameters and weed resistant management to help sustain this technology in the future.”

With the herbicide weed resistant problem continuing to grow, Jon Fischer, U.S. corn and soybean licensing manager for Bayer CropScience, noted the importance for all farmers to become proactive about keeping the utility of the herbicides currently being used.

“We’ve seen the greatest increase in LibertyLink soybeans in the areas where resistant weeds have developed to glyphosate,” Fischer said.

Over the past three years, Bayer has conducted surveys with 300 growers.

“The data from the 2012 survey for the Midwest and South showed 65 percent of the growers are using pre-emergence or residual herbicides with LibertyLink soybeans and 48 percent of growers are using both a burndown and pre-emergence residual product,” Fischer reported.

And on 33 percent of the acres, a residual tank mix was used with Liberty.

“Something else is going in the tank, and producers are using more than one mode of action to control target weeds,” the Bayer spokesman said. “The survey reported 87 percent of the producers were very satisfied or satisfied with the weed management of the LibertyLink program.”

“Residual herbicide usage in the U.S. has increased from one out of three acres in 2010 to 55 percent in 2012,” reported Matt Helms, U.S. launch lead for the Roundup Ready Xtend Crop System for Monsanto Co. “Monsanto is building on our current platform of Roundup Ready PLUS with the Roundup Ready Xtend system for tomorrow.”

For the Roundup Ready Xtend system, Helms said, “we will stack dicamba tolerance on top of the high-yielding Genuity, and our recommendations will have pre-emergence products to ensure we have at least two modes of action.”

This system will deliver additional benefits and tools to farmers by broadening the spectrum of weed control.

“Farmers are searching for more effective, broad-spectrum weed control, and dicamba is a proven herbicide that when used in conjunction with a diversified weed management program, including residual herbicides, can deliver that effective weed control,” Helms said.

“That enables our customers to focus on what they do best — maximize the yields of those fields.”