FAIRMOUNT, N.D. — Some soybean acres may shift to Enlist technology this year, as farmers press their ongoing vigilance against herbicide resistance in weeds, an expert said.

Greg LaPlante, who owns G.L. Crop Consulting of Wahpteton, N.D., has been scouting fields for nearly 40 years in the southern Red River Valley, making recommendations to farmers on pest control, as well as crop planning, including advice on varieties, fertilizer and inputs. He currently has five farmer-customers, growing cereal grains, sugar beets, soybeans, sunflowers, and corn.

When LaPlante started consulting in the region in 1981, he went through the programs of conventional herbicide programs to the advent of glyphosate (Roundup)-resistant varieties.

“We’ve seen the evolution of weed species shift, and also selection resistant species of different weeds,” said LaPlante, who became one of the foremost prophets against weed resistance.

30-year trend

Greg LaPlante, of Wahpeton, N.D., has been crop consulting for nearly 40 years in the southern Red River Valley, scouts a soybean field near Fairmount, N.D., on May 29, 2020. He said farmers need to watch resistance to the pre-emerge herbicide programs that are based on Dual-type chemistry.  Photo taken May 29, 2020, at Fairmount, N.D. Mikkel Pates / Agweek
Greg LaPlante, of Wahpeton, N.D., has been crop consulting for nearly 40 years in the southern Red River Valley, scouts a soybean field near Fairmount, N.D., on May 29, 2020. He said farmers need to watch resistance to the pre-emerge herbicide programs that are based on Dual-type chemistry. Photo taken May 29, 2020, at Fairmount, N.D. Mikkel Pates / Agweek
Weed resistance — where weeds would adapt to new herbicide chemistry — started happening 30 years ago, and gets more challenging all of the time.

“We’d come out with a new herbicide. We’d use it really hard. Growers would adapt to it very quickly. It would get on 90% to 100% of the acres. The weed resistance would start developing to that particular chemistry within a few years,” LaPlante said.

Bruce Potter, an Extension Service integrated pest management specialist with the University of Minnesota at its Lamberton, Minn., Southwest Research and Outreach Center, said weed resistance in that part of the state started with ALS-resistant waterhemp in the 1980s, and now issues are predominant in corn-soybean rotations.

Bruce Potter, an integrated pest management specialist at the University of Minnesota Southwest Research and  Outreach Center at Lamberton, Minn., says scientists in his area studying -- but have not  yet confirmed -- resistance to 2-4,D resistance in giant ragweed. Photo taken Jan. 25, 2018, in Mankato, Minn.  Mikkel Pates / Agweek
Bruce Potter, an integrated pest management specialist at the University of Minnesota Southwest Research and Outreach Center at Lamberton, Minn., says scientists in his area studying -- but have not yet confirmed -- resistance to 2-4,D resistance in giant ragweed. Photo taken Jan. 25, 2018, in Mankato, Minn. Mikkel Pates / Agweek
Waterhemp is the “poster child” for resistance issues, although issues have extended to glyphosate-resistant giant ragweed. He said researchers are monitoring suspected but unconfirmed 2-4,D resistance in giant ragweed. One of the crop consultants in the area sprayed a patch and suspected it, but Potter says there are no greenhouse grow-outs to determine test rates. He noted giant ragweed resistance to Roundup (glyphosate) is difficult to judge because of different resistance characters within a single plant.

Potter, who is primarily an entomology specialist, says the Lamberton center has hired a new weed scientist to replace Jeffrey Gonsolus, who retired in October.

Northward ho

LaPlante and other consultants and farmers at the intersection of North Dakota, South Dakota and western Minnesota have watched these issues travel northward.

As waterhemp became resistant to glyphosate, LaPlante tried to make growers realize the problem, even if they had “just a few plants here and there.” Within five years they had large-scale resistance problems to glyphosate.

“It was all about getting them to start to understand that that chemistry was pretty much broken for them and start having to change herbicide and weed control,” he said.

The advent of the weed Palmer amaranth coming into Minnesota and North Dakota was a game changer. Palmer amaranth has an especially large seed load.

“The stories that a lot of growers heard about Palmer amaranth made them start thinking that they needed to step up their game,” he said. “They knew they could stop Palmer amaranth if they did a good job of controlling waterhemp.”

Suddenly, more farmers were listening more closely to Extension Service agronomists and others who were trying to talk them into new techniques for weed control. Most farmers have adopted the primary tools — more pre-emerge herbicide and longer-residual herbicide products.

Cotton’s lesson

“We’ve kind of adopted what they started doing down South in the cotton industry — a pre-emerge, and maybe one or two lay-by applications of a residual herbicide, besides the primary post-emerge herbicide,” LaPlante said. This “layering” of the herbicides to give better control came first in sugar beets, and growers are starting to see a benefit in other crops, too.

“This year I think there are going to be more acres of the Enlist soybean — basically a 2-4,D-resistant component,” LaPlante said. There had been dicamba-resistant soybeans the past several years, but growers are starting to look at the Enlist to avoid severe application restrictions to off-target “drift” damage, especially in the presence of all-too-common temperature inversion.

A pallet of Enlist soybeans sits, wrapped in cellophane on a pallet in a warehouse in southeast North Dakota on May 29, 2020. Crop consultant Greg LaPlante expects more of this technology to be used in 2020, because of fewer application restrictions compared to some dicamba-resistant beans. Photo taken May 29, 2020, at Fairmount, N.D. Mikkel Pates / Agweek
A pallet of Enlist soybeans sits, wrapped in cellophane on a pallet in a warehouse in southeast North Dakota on May 29, 2020. Crop consultant Greg LaPlante expects more of this technology to be used in 2020, because of fewer application restrictions compared to some dicamba-resistant beans. Photo taken May 29, 2020, at Fairmount, N.D. Mikkel Pates / Agweek
“Last year, with the real late spring we had, some growers planted dicamba-resistant beans but weren’t able to use the herbicide,” he said. “The Enlist gives them more time, and gives them another mode of action.”

LaPlante thinks about 20% to 30% of the soybeans in his area will be Enlist beans.

“We don’t have all the varieties that we need to be able to do a complete job on the agronomic end of things,” LaPlante said. “Soybean cyst nematodes have gotten to be a very serious problem in southeastern North Dakota.”

Some Enlist varieties don’t have very strong tolerance to soybean cyst nematodes, which are second only to weed resistance as an economic problem for growers.

Last year, when the beans were being raised for seed for 2020, the contracts were signed well ahead of market traumas from COVID-19 and the latest impacts from Chinese trade disruptions. Seed costs didn’t come down, he said. “As a new technology, most of those companies are looking at recouping some of that investment.” Farmers are best to select crop protection according to their particular weed programs.

Beet vigilance

Sugar beets haven’t added much for new technology since the crop was genetically modified to be tolerant to Roundup. Roundup-resistant beets came out in 2008.

“We’re pretty much limited to the pre-emerge and residual type of products,” LaPlante said. “We use the Roundup to take care of the weeds that it will control. And then we’ll have to hope we get the rain, and timely rains, for the residual products to work.”

Beet growers and dry edible bean growers understand that controlling weeds in rotation crops are extremely important in controlling waterhemp and other resistant weeds.

Some fields that were harvested late or haven’t been harvested at all change how farmers handle residue.

“In some situations, rather than a pre-emerge, we might look at an early post-emerge product with a residual-type of product to get the burn-down and then the residual (effect) after that," he said. "That’s where Enlist herbicide gives one more tool in the toolbox to control a strictly post-emerge weed problem.”

PP after corn

Weeds are germinating now on cornfields that are still standing, LaPlante said. “There’s an open canopy because those crops have been dead for eight to nine months. The sun is getting into them. As soon as they can get those harvested, they may have to look at killing the weeds. If they can’t get them harvested for another three or four weeks, they may to try and do something while the corn is still out there.”

That gets to be a problem because farmers generally aren’t used to making applications to a mature crop that is 180 days past the harvest date.

“Some fields probably won’t get harvested. They’ll just have to destroy them out in the field and go from there,” LaPlante said.

Some fields in 2019 where unharvested fields became an “incredible weed mess,” with waterhemp and other weeds getting out of control. It makes it very expensive for the next year, to control that weed population, he said.

Fortunately, in southeast North Dakota there wasn’t the anticipated flooding that many had worried about.

“We didn’t have a lot of spring runoff, and a lot of seed movement heading up the valley,” he said.

Crop consultant Greg LaPlante of Wahpeton, N.D., on May 29, 2020, studies soybean seedlings and indicates damage is due to insects or some kind of herbicide or other injury. Photo taken May 29, 2020, at Fairmount, N.D. Mikkel Pates / Agweek
Crop consultant Greg LaPlante of Wahpeton, N.D., on May 29, 2020, studies soybean seedlings and indicates damage is due to insects or some kind of herbicide or other injury. Photo taken May 29, 2020, at Fairmount, N.D. Mikkel Pates / Agweek
Looking ahead, farmers are starting to see the break-down in control for some their pre-emerge and residual herbicides. Some farmers in Iowa, Indiana have seen some resistance to Dual-type products — one of the foundation herbicides for soybeans, corn and sugar beets — so farmers up farther north need to remain diligent.

He said some of the herbicides have been applied but haven’t gotten the needed rain to activate them.

“It’s tough to distinguish whether it’s resistance or (lack of) activation of that herbicide,” he said.

“What we rely on are those one- or two-modes of action,” he said. “We need to stay on top of that and I think growers need to be listening to what Extension Service has to say.” Looking ahead, he urges farmers to budget time to go to winter meetings and learn about the latest developments.