FARGO, N.D. -- It's too late to be proactive on glyphosate resistance in weeds. Everybody is reacting, said experts addressing a Northern Weed Resistance Forum on March 8, sponsored by Peterson Farms Seed.

Keynote speakers
From left: Bryan Young, weed specialist from Southern Illinois University, and Jeff Stachler, the North Dakota State University/University of Minnesota sugar beet/weed specialist, were keynote speakers about glyphosate resistance at an event in Fargo on March 8. (Mikkel Pates, Agweek)

FARGO, N.D. -- It's too late to be proactive on glyphosate resistance in weeds. Everybody is reacting, said experts addressing a Northern Weed Resistance Forum on March 8, sponsored by Peterson Farms Seed.

Jeff Stachler, North Dakota State University/University of Minnesota sugar beet weed specialist in Fargo, said there were more glyphosate resistant weeds in 2011 than in 2010.

"The Red River Valley had its "break-out" year with resistance in waterhemp in Minnesota and the Red River Valley," Stachler said. "Most importantly, we have glyphosate resistance in horseweed in North Dakota, as well as kochia. Those are going to be weeds with serious ramifications," Stachler said.

"From a management standpoint, I know it's not popular, but if we hand-remove those few (resistant) survivors that are out in the field, they can't cause a future problem," Stachler said. "We're going to have to get back to scouting and scouting and scouting, and be diligent in what we're doing. We need to be as diverse in our management strategies as possible."

This is the second weed resistance seminar sponsored by Peterson Farms Seed, a company that deals in Roundup Ready products, but also is promoting LibertyLink technology, which has a different chemistry that can be used to rotate with Roundup ready crops.


Stachler said that promoting LibertyLink crops is a slow process because it had problems when it was first introduced in the early days in corn, Stachler said. "People had some disappointments, or failures. They've been hesitant to switch."

David Carruth, an agronomist from C-W Cooperative in Comstock and Wolverton, Minn., said for the past two years several growers have switched from Roundup Ready to the LibertyLink program. "I think we have about 6,000 units sold this year, and it's about 40 to 45 sales that are LibertyLink so far this year." Customers in his area were having problems with waterhemp and common ragweed, but other weeds are "closing in on us as well."

Carruth said LibertyLink is more effective on broadleaf and weaker on grass, which is the opposite of glyphosate. He said there were no complaints about the company's LibertyLink acres last year, and no one who switched has gone back. He said with all crops except wheat being glyphosate-resistant, there are "six or seven passes of glyphosate in three years, possibly. We can't be doing that, we're going to wear out glyphosate in no time if we keep doing that. We've got to be putting out pre-emerge herbicides, changing the mode of action, if we're still using a glyphosate system we have to be adding (an additive herbicide) to the tank."

Comparing costs

One consideration is cost. LibertyLink soybean seed is retailing for about $41 to $42 per unit, while Roundup Ready II seed is $49 to $50 per unit, Carruth said. On top of that, Bayer is throwing in a $4 per unit rebate with a minimum purchase of 250 units.

One challenge is trying to make sure growers who have switched to LibertyLink technology inform their neighbors, to avoid spray drift problems, Carruth said. Last year the co-op encouraged putting up signs -- at "field entrances, anywhere we could, to try to get that neighbor's attention that, 'Hey, we've got LibertyLink beans here.'"

Stachler said soybeans is the "preferred crop to have LibertyLink in" especially for the sugar beet grower "because we know we're getting something different" in chemistry on a crop where there are limited tools to control resistant weeds.

"The one thing is, and I understand it's economics, and I'm not asking people to go broke, but where are the wheat acres?" Stachler asked. "Especially in the southern valley, we've replaced it with corn and soybeans. Wheat is a wonderful tool and for those of us in sugar beets, we know that the research shows we get higher sugar beet yields following a cereal crop. We've got to get as much wheat in the rotation as we can afford."


On the horizon, the speakers noted that Bayer is developing a LibertyLink-Roundup Ready canola, that is "stacked" which would be detrimental to sugar beet growers, because they're not going to control resistant weeds with glyphosate in sugar beets and they're not going to be able to control it with Liberty in the soybeans.

No optimism

Bryan Young, a weed specialist from Southern Illinois University, talked about Roundup resistance problems in Illinois and surrounding states. "Optimism has no place in weed management," Young says. "Assume the worst, and plan for the worst."

Young showed attendees photographs of farm fields where weed resistance had gotten so bad that there was no solution.

In 2011, Iowa had a "benchmark year" for glyphosate resistance, Young says. There is a lot of waterhemp resistance, as well as HPPD-resistant waterhemp, also causing problems in corn management. HPPD is short for hydroxyphenylpyruvate dioxygenase. "This is the epiphany, we need to change ways moving forward -- both corn and beans. There's no (being) proactive about it. They're all reacting in Iowa," Young said.

One audience member half-jokingly asked how to get neighbors to switch to another mode of action. Young suggested doing more scouting in the neighbor's field and knowing where water and wind are coming from. "Know where the problems are so that you can be prepared to handle it," he said. Another option is to try to demonstrate on your own field or on the neighbor's field, with permission, how to improve weed control. "The only other thing I can think of is peer pressure," or perhaps telling the neighbor's landlord his renter doesn't correctly handle weeds.

In response to an audience question, Young said it is possible to use cover crops to help control Roundup Ready resistance.

"If you're trying to control marestail in a no-till situation, for example, using something like cereal rye can work fairly well, but in some other cover crop combinations it depends on the stand that you get, the weed species you're trying to target and when you might terminate that cover crop," Young says. "It is a complete management system, a different way of producing a crop, and it can be more difficult to manage than some of the plain-old herbicide resistant weeds." Cover crops can also tie up some of the herbicides, and create drawbacks.

Mikkel Pates is an agricultural journalist, creating print, online and television stories for Agweek magazine and Agweek TV.
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