Beat Weeds in Small Grains in 2024

Plan for Small Grains Weed Control Success

Ryan Humann, Ph.D., field scientist for Corteva Agriscience, says Tolvera herbicide pairs tolpyralate, a new active ingredient for the cereals market, with bromoxynil to provide effective broadleaf and grass control. It also offers rotational flexibility and is tank-mix friendly. (Provided by Corteva Agriscience)


Tolvera (TM) herbicide from Corteva Agriscience will offer small grain farmers a new active ingredient to battle weed resistance and provide crop rotation flexibility.

Repeating your cereal crop weed control program from 2023 may seem like the smart thing to do, but weeds may have other plans.

To beat weeds in small grains in 2024, repeating a previously successful herbicide plan will eventually cause important herbicide tools to fail as weeds become more resistant.

Diversity becomes critical in cereal grain production to keep weeds off balance. Steps include rotating fields with a broadleaf/pulse crop; using tillage, herbicide burndown or preemergence treatment with varying herbicide classes/modes of action; growing a competitive crop stand; and making timely post applications to keep weeds under control.

"Growers that we see succeeding against weeds in cereals take a program approach with backup plans," says Ryan Humann, Ph.D., field scientist with Corteva Agriscience in Fargo, North Dakota. "As tough weeds like herbicide-resistant kochia, waterhemp, horseweed, narrowleaf hawksbeard and others expand in the Northern Plains, it's going to require numerous practices ahead of postemergence herbicides, so weeds don't go to seed."

An effective weed control plan will track previous weed species and size, severity and field locations. Coupled with crop-specific weed information are herbicide usage by year, group numbers applied, rates, adjuvants, nozzles, weather and yield results.


Depending on initial tillage or burndown herbicide success, initial plans for postemergence control sometimes need to change.

"Growers can map out their crop rotations, early season practice and burndown mixes, but then the environment, crop delays or failed weed control force a shift in plans," Humann says.

He explains numerous postemergence herbicide products currently do a good job controlling broadleaves and grasses.

"But as herbicide-resistant kochia and waterhemp continue to emerge, it's going to get tougher to manage these weeds," Humann points out.

Watch for herbicide resistance. In the western part of the Northern Plains, kochia can resist ALS-inhibiting herbicides, atrazine and, in some areas, even dicamba and fluroxypyr. On the eastern half, waterhemp is showing resistance to glyphosate. Grasses like wild oats and green foxtail have shown resistance to ALS and ACCase-inhibiting herbicides.

"Over the past few years, North Dakota State University weed scientist Brian Jenks has been educating growers about the need to monitor herbicide resistance," Humann says. "It's a scary proposition as growers are running out of herbicide options on resistant weed populations."

Indicators of herbicide-resistant weeds include: the herbicide typically controlling a weed species, poor control on one species while others are controlled normally, poor control confined to isolated spots in a field and dead and alive plants of the same species present in an area. Contact your university weed specialist for further testing.


About five years ago, Corteva began working on a premix concept showing great efficacy and spectrum: bromoxynil, a Group 6 chemistry compound, and an HPPD-inhibitor compound called tolpyralate (a new active ingredient for cereals).

Called Tolvera (TM) herbicide, this new premix recently received registration from the Environmental Protection Agency. With registration, Tolvera herbicide will be available for the 2025 season.

While Corteva has numerous Group 2 and Group 4 chemistries in the cereals market, this Group 6 + Group 27 premix will help round out the company's cereals portfolio. By incorporating Tolvera herbicide into a rotation with other chemistries, the company hopes all herbicide tools will last longer to reduce weed resistance.

"Tolvera herbicide offers a new active ingredient in cereals, giving our Group 2 and Group 4 herbicides a break. It delivers broad-spectrum weed control, including efficacy on critical Northern Plains grasses like green and yellow foxtail," Humann says. "Currently, only Group 1 and 2 chemistries can be used for post control on these grasses, so Tolvera herbicide delivers management flexibility for cereal growers."


For growers who want flexibility in rotating to pulse crops like lentils and chickpeas, Tolvera herbicide offers nine-month plant backs for these and many other common rotational crops, such as sunflower, canola and soybeans.

"Crop rotational flexibility of nine months will set Tolvera herbicide apart from other chemistries," Humann says. "Growers can confidently use the product on cereals and plant other crops the next season without worry of carryover."

Corteva has tested this product across Canada, the Northern and Central Plains, and other wheat-growing areas to determine that Tolvera herbicide has a good rotation profile. Tolvera herbicide is proving successful for growers in the prairie provinces.


Along with crop rotation flexibility, Tolvera herbicide will be labeled for use on most cereal crops: spring wheat, winter wheat, durum wheat and barley. "This premix won't have restrictions on barley and Durham like some products so that growers will have good crop flexibility across the cereals, except oats, triticale and rye," Humann says.

Tolvera herbicide, with two modes of action, will control a broad spectrum of hard-to-control broadleaf weeds and key grasses like foxtail, crabgrass and barnyardgrass. Key broadleaf weed control includes kochia, chickweed, volunteer canola, buckwheat, shepherd's purse, smartweed, mustard, pigweed, waterhemp and lambsquarters.

Aside from being a robust stand-alone premix, it offers good tank-mix flexibility to help growers achieve localized weed spectrum control. Tolvera herbicide is an EC formulation that mixes well with 2,4-D, MCPA or fluroxypyr to achieve greater control of kochia, pigweeds and mustard, or it can be mixed with a graminicide to pick up weeds like downy brome and wild oats that Tolvera herbicide doesn't control.


Like any weed in a post herbicide program, Corteva recommends applying early on three- to four-inch-tall weeds up to the jointing stage for optimum control and crop safety. "Weeds taller than this can begin to metabolize herbicides and reduce control, especially herbicide-resistant weeds like kochia," Humann says.

Other recommendations to optimize control include applying on a warm, sunny day to activate the chemistries within the weed. "We recommend 10 gallons of water per acre with a methylated seed oil (MSO) adjuvant to penetrate the leaf cuticle," he adds.

Optimizing weed control depends on proper planning, adjusting to the environment and rotating chemistries to keep weeds off balance each year. Like a starting pitcher being replaced by a reliever when hitters succeed because they know his stuff, so do weeds resist a herbicide used too often. So, rotate chemistries to keep weed seeds from building up in your soil.


-- For more information about Tolvera herbicide and Corteva Agriscience, visit…


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