How Managing Herbicide Resistance Is Not Futile for Crop Protection Companies
It has been 40 years since a new weed-killing chemical mechanism has been introduced into the crop protection marketplace. The decades since have seen weeds become resistant to existing herbicides, resulting in these problematic plants escaping growers’ best efforts to neutralize them.
“We’ve been giving weeds a herbicide diet, and they keep finding ways to get around that diet,” says Ron Geis, a Market Development Specialist with Corteva Agriscience. “There’s been nothing waiting in the wings when one process fails, so herbicides should have multiple modes of action to keep weeds off balance.”
As weeds are staving off typical glyphosate herbicides, agricultural chemical companies like Corteva are developing new modes of action that target invasive plants before their tolerance can evolve. New herbicide combinations should sustain product life and limit the overuse of pesticides in the battle against resilient weeds, says Geis.
Companies are increasing their R&D efforts to create handy formulations, offering varied solutions that can tackle farmer pain points this year and down the road. Corteva’s Vorceed Enlist, for example, is a corn rootworm stopper with the added benefit of curtailing late-season emerged broadleaf weed pressures. Enlist’s corn trait overcomes weed tolerance to 2,4-D choline, glyphosate, glufosinate, and FOP herbicides.
When applied according to label instructions, Enlist solutions feature near-zero volatility as well as reduced potential for physical drift. A wide application window further enables the use of Enlist in the mitigation of late-season broadleaf weeds, says Geis.
“Our Resicore herbicide is good for corn as well,” says Geis. “It has three modes of action to manage weed resistance. Combining Resicore with other resistance products gives farmers a wide application window throughout the operating season.”
Ongoing U.S. drought conditions accentuated the importance of multiple applications and modes of action. Additives included in existing herbicides increased uptake in moisture-deprived weeds where closed stomata and thickened cuticles had reduced product effectiveness. Corteva also emphasizes attacking post-emergent weeds like water hemp when at small stature, or about one to three inches in height.
Riding a successful 2023 into a full launch next year is Kyro, a corn herbicide combining three modes of action effective against 65 different types of broadleaf and grass weeds.
“It’s been an educational process,” says Geis. “We got complacent with our glyphosate program. Glyphosate was more formidable when weeds were out of control. You could just up the rate and you’d end up good before resistance kicked off. Farmers understand that they must have multiple modes of action, because one and done won’t cut it.”
A Push For Long-Lasting Activity
Yield monitors are an essential component of any contemporary field management strategy, delivering feedback on cultural practices as well as inputs like herbicides, notes Kip Jacobs, Technical Services Manager for UPL.
When deliberating UPL’s herbicide portfolio, farmers should first determine what weeds are present in their field, as each chemical mode of action is only effective against certain species. Jacobs’ customers must also determine application timing, which includes pre-plant, pre-emergence and post-emergence windows throughout the year.
“Regardless of the timing, it is always recommended to have a residual component in the tank, because the easiest weed to control is the one you never see,” says Jacobs.
The environment comes into play as well — not only weather, but field characteristics such as water solubility and chemical absorption rates. After all, a herbicide that binds to organic matter rather than weeds is not much use to producers, says Jacobs.
UPL has a suite of distinguished products aimed at easing its customers’ real-world challenges. For example, the company’s Preview 2.1SC herbicide is gaining marketplace traction for its efficacy against tough-to-control weeds such as waterhemp, kochia, redroot pigweed, and palmer amaranth. As its name suggests, Preview 2.1SC has a unique 2:1 ratio of metribuzin to sulfentrazone — a pairing designed for a lasting residual effect along with best-in-class incorporation into soil. Jacobs points to an innovative co-crystal formulation that provides consistency across a vast range of soil types.
“Generally, growers have to choose between crop safety and acceptable weed control,” says Jacobs. “The co-crystal formulation provides exceptional crop safety on high pH soils where we typically see herbicide injury occur. It also offers prolonged residual effectiveness in high organic matter soils where we see herbicides bind to OM, which can then result in shortened residual timings.”
UPL is not resting on its past successes, adds Jacobs. The recently launched Batalium Amped herbicide — championed by the company for its high active ingredient load — will continue to deliver multiple modes of action to the wheat market. Next year will see UPL add to its wheat portfolio through the release of IronGate and Audit 9:1, with these solutions aiming to control broadleaf and grass weed species.
In the meantime, Imiflex is a strong post-emergence option for mitigation of lambsquarters and velvetleaf in soybean. In the corn market, UPL is introducing Intrava DX as a foundational pre-emergence offering.
“All of UPL’s products are developed to fill a niche in the marketplace,” says Jacobs. “We pay especially close attention to the driving biological factors in target weed species that favor the evolution of resistance to herbicides. With these factors in mind, we develop incredibly specific herbicide combinations in concentrated formulations so we can maximize activity and coverage of those target species.”
More Power in One Jug
Whether already established or new to market, the best herbicides limit pesticide overuse for even the hardiest weeds, says Belchim Crop Protection USA President and General Manager Tom Wood. Although Belchim offers a host of agricultural products, the current climate has pushed the company mainly into the resistance marketplace.
As weeds become immune to previously dependable dicamba, glyphosate, and HPPD chemistries, Belchim is having customers incorporate its Tough herbicide into their tank mixes. Tough 5EC, for instance, is a pyridate-based product that enhances post-emergence control of broadleaf weeds with a wide application window.
Currently approved for corn, lentils, mint and chickpeas, this unique Group 6 offering is a photosynthesis inhibitor used in the management of grass and broadleaf weeds. Wood recommends combining Tough with HPPDs including Callisto or Impact for the strongest control.
“When you’re thinking about resistant weeds, this will reduce or eliminate the weed seed bank that is going to cause problems down the road,” says Wood. “In addition, (this process) provides more modes of action, and offers good return on investment that retailers can include in their programs.”
Along with the currently available Spin-Aid — designed to kill broadleaf weeds in spinach and red garden beets — Belchim is readying the 2024 release of Tough R, which Wood calls “the next step in the brand ladder.”
“Tough R is Tough plus Callisto in one jug,” says Wood. “This product provides dual modes of action, bringing all the benefits of Tough, plus what mesotrione brings without any resistance issues. It also provides the residual benefits that pyridate does not have.”
Meanwhile, farmers accustomed to Valent’s work in soybean are utilizing the company’s products to address their weed-control needs in corn. In 2023, Valent entered the corn market with Maverick, a broad-spectrum herbicide in development since 2017, says Asset Strategy Team Lead Joseph Short.
Grasses, waterhemp, and Palmer amaranth are Maverick’s natural enemies, with the product offering application flexibility from the pre-plant stage to full-grown stalks. Low use rates for easy in-field handling — alongside compatibility with fertilizer, atrazine, and 2,4-D — make Maverick a premium season-long solution for corn growers, says Short.
“Many corn herbicide use rates only effective at quarts per acre, but Maverick’s use rates are ounces per acre,” says Short. “This helps from a convenience standpoint, because you’re handling less material and improving sustainability.”
Valent is taking a holistic approach to the marketplace via a portfolio that encompasses broad, season-long control options for broadleaves and grasses.
“We want to expand that footprint across retailers and to new geographies throughout the Midwest,” says Short. “Whether on the corn or soybean side, our products are answering the challenge on being proactive around herbicide resistance. Growers need tools for managing the whole season. For us, we are moving forward on these solutions.”
A Tool in the Toolbox
Considering soil moisture plays a key role in chemical activation and uptake, the Midwest’s unusually dry weather caused residual herbicides to lose much of their efficacy, says Liam Vincent, Technical Marketing Manager for BASF.
With HPPD resistance in corn another unfortunate agricultural trend, BASF has reformulated an established active ingredient that expands the herbicide application window. New herbicide Surtain supercharges the BASF-patented Kixor AI to hinder broadleaf weeds such as kochia and Palmer amaranth before they emerge from the soil.
Kixor is now teamed with pyroxasulfone for top-notch grass control. Bringing a reputable active ingredient into a longer application window allows producers to swap their control methods when combatting any manner of weed, says Vincent.
Now being reviewed for registration by the EPA, Surtain will enter the market next year with a full launch scheduled for 2025. BASF is also introducing its Liberty ULTRA herbicide in 2024, giving farmers a broad-spectrum tool for glufosinate-tolerant canola, corn, cotton, and soybean.
Powered by Glu-L technology – named for the activation of D-glufosinate ammonium – Liberty ULTRA offers significant weed control while allowing growers to use less of the product.
“By transforming that D isomer to L, we are able to achieve a 25% reduction in use rate,” says Vincent. “We are packing 32 ounces of our Liberty herbicide into 24 ounces of Liberty ULTRA. Liberty is already in a leadership position from an efficacy perspective – we needed to make sure that we were improving on the product.”
Residual activity continues to be the watchword for Syngenta, notes company agronomist Phil Krieg.
“Our motto is the easiest weed to control is the one we don’t allow to emerge,” says Krieg.
“So, our entire portfolio of products across crops gives growers flexibility in how those herbicides are applied.”
Earlier this year, Syngenta unveiled its Storen corn herbicide for the 2024 growing season. According to the company, Storen will give producers up to three weeks longer residual weed control than other leading corn herbicides.
Storen combines four residual active ingredients in one premix — BIR, mesotrione, S-metolachlor, and pyroxasulfone — plus the crop safener benoxacor. The mixture works together to impede emergence of barnyard grass, foxtail, waterhemp, Palmer amaranth, giant ragweed, and more.
“What we’ve done is to offer flexibility to growers who are battling the wild weather swings we’ve had,” says Krieg. “The four active ingredients compliment each other in physical properties such as rainfall activation and how they bind with soil.”
Although FMC does not have any new products on the immediate horizon, its Authority Supreme and Authority Edge offerings remain its two most popular soil-applied residual herbicides. By combining the longest lasting Group 14 and Group 15 active ingredients — sulfentrazone and pyroxasulfone, respectively — these dual-mode-of-action properties deliver the best pre-plant and pre-emergence residual weed control for soybean crops, says FMC Regional Technical Manager Gail Stratman.
Equally popular are FMC’s Anthem brand herbicides — Anthem Maxx and Anthem Flex. Maxx is a premier companion product with the company’s Authority lineup, while Flex merges burndown activity with robust residual control.
“Each product with its particular label fits different crops and application timings, but both bring excellent weed control in their respective crops,” says Stratman.
Most farmers know that chemistry is not the only answer for strong weed management, Stratman adds.
“Growers can start the season with soil residual herbicides, but they also should be employing other tools like row spacing, cover crops and tillage to help herbicides be more successful,” says Stratman. “Herbicides are one tool, but should never be viewed as the only tool. To be successful, they have to be part of a larger management system to reduce overall weed populations.”
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