Soybean growers gain new weapon against weeds

Enlist E3 soybeans have triple-stacked herbicide tolerance, but the technology isn’t a silver bullet for resistant weeds

In January, Corteva Agriscience launched Enlist E3 soybeans in Canada. The technology is a triple-stacked herbicide tolerance, where glyphosate, glufosinate and Enlist Duo herbicides can be applied to the soybeans.

Enlist Duo is a combination of glyphosate and a 2,4-D choline — a low-drift and low-volatility version of 2,4-D.

Enlist E3 will be available this year but mostly in varieties suitable for southwestern Ontario. In 2020 the technology will be broadly available to soybean growers in Canada.

The product launch is positive news for growers struggling with herbicide resistant weeds. But the technology isn’t a cure-all for weeds that are resistant to glyphosate and other herbicides, said Tammy Jones, Manitoba Agriculture weed specialist.

“It’s just another tool,” said Jones, who spoke this January at Ag Days in Brandon. “Continue to rely on your crop rotation (and) competitiveness, all the other things that can enhance the crop’s ability to compete, so you’re not just using herbicides as the solution. They’re part of a management plan, but you can’t get out of a herbicide resistance problem by using herbicides alone.”

A spokesperson for Corteva Agriscience had a similar message. Relying on one herbicide, for multiple in-crop applications and preplanting applications, will increase the risk of weeds developing resistance to the herbicide. A better practice is using different chemistries at different times in the year.

“For example, use of a Group 3 or a Group 14 herbicide mode of action prior to planting Enlist E3 soybeans and using an in-crop application of Enlist Duo would mean that at least three different herbicide modes of action would target weeds,” said Jeff Loessin, marketing category leader for Corteva.

Jones described such an approach as “layering.” Instead of hitting weeds at the same time with multiple herbicides, a grower should apply different weed killers at different times in the season.

“That means maybe doing a pre-seed that has some extended control and then going in with something else that has a different mode of action,” she said.

“We find we get much superior weed control when we go with a layering approach, rather than spraying everything in one tank and (hoping) for the best.”

Loessin added glufosinate can be applied in-crop with Enlist E3 technology, but in a separate application.

“Not in tank mix, (as) there are no registered 2,4-D products that can be used in combination with glufosinate over the top of Enlist E3 soybeans,” he said. “Although Enlist E3 soybeans have tolerance to glyphosate, 2,4-D choline and glufosinate, it is unlikely that all three would be used in a growing season.”

In Manitoba, the Enlist E3 technology may help soybean growers who are coping with kochia. During her talk in Brandon, Jones showed a map of Manitoba illustrating the regions with glyphosate-resistant kochia.

Many of the municipalities in the Red River Valley and south-central Manitoba now have it, along with two rural municipalities in the southwestern corner of the province.

In 2016, only five RMs had glyphosate-resistant kochia.

“With what we’re doing with management techniques, we’re not doing a great job of managing glyphosate-resistant kochia,” Jones said.

One thing growers should be doing is scouting and looking for kochia plants that may be resistant.

If there is a patch in a field, producers should hand pull the kochia or consider spot tillage to remove the weeds.

“Yes, we can spread kochia. It tumbles. But about 90 percent of the seed is right where it grew,” Jones said. “If you’ve got 30,000 seeds per plant, you’ve got a problem in that patch.”

Learning how to manage glyphosate resistant kochia is critical because other herbicide-resistant weeds may soon arrive in Manitoba, Jones added.

Palmer amaranth, a weed that has caused havoc in the southern United States, was found in North Dakota last year. The weed is troublesome because it can reach a height of two metres and a single plant can have one million seeds.

“Palmer amaranth’s prolonged emergence period, rapid growth rate, prolific seed production, and propensity to evolve herbicide resistance quickly makes this the most pernicious, noxious, and serious weed threat that North Dakota farmers have ever faced,” Rich Zollinger, retired North Dakota State University extension weed scientist, said on the university’s website.

If Palmer amaranth becomes established in North Dakota, it’s very likely to move north of the border into Manitoba.

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