Multiple vs. Effective Modes Of Action

Interest in using multiple modes of herbicide action in weed management programs is increasing, according to Aaron Hager, University of Illinois associate professor of weed science.

However, each component of a herbicide premix or tankmix with multiple modes of action is not necessarily effective for every weed or under all application conditions.

For example, giant ragweed, a large-seeded, summer annual, broadleaf weed species, can be difficult to control with a single herbicide. Because of its extended germination and emergence characteristics, farmers may have to use more than one herbicide or multiple herbicide applications.

While herbicide resistance has been found in the Illinois giant ragweed populations, it is not as common or widespread as herbicide resistance in other weed species. Many soil-residual–herbicide premixes containing two or more active ingredients are available to farmers who want to be proactive and use multiple modes of action to reduce the selection for herbicide resistance in giant ragweed.

However, “To effectively reduce the selection intensity for resistance to a particular active ingredient, each component of the premix or tankmix should have similar efficacy against the target weed species,” Hager said. “In addition, each component should demonstrate similar soil persistence.” Few commercial soil-applied herbicide premixes satisfy these criteria when giant ragweed is the target species.

The timing of a herbicide premix or tankmix application can also influence the effectiveness of each component. For example, a farmer may choose to use Harness Xtra (or any other premix of a chloroacetamide and atrazine) to control waterhemp, a small-seeded summer annual broadleaf weed species that has developed resistance and is becoming a serious problem in Illinois fields.

If it is applied before waterhemp seed has germinated, each component of this premix (acetochlor and atrazine) provides effective residual control. However, if the Harness Xtra is not applied until after waterhemp emerges, only the atrazine can effectively control the emerged waterhemp plants.

Similarly, said Hager, “A tankmix of a chloroacetamide herbicide and glyphosate applied after waterhemp emergence does not contain more than one effective mode of action to control emerged waterhemp, nor does it contain more than one effective mode of action for soil-residual control of later-germinating waterhemp.”

Illinois waterhemp populations have evolved resistance to herbicides from at least five herbicide site-of-action families, including inhibitors of acetolactate synthase (ALS), photosystem II (PSII), protoporphyrinogen oxidase (PPO), enolpyruvyl shikimate-3-phosphate (EPSPS) and hydroxyphenyl pyruvate dioxygenase (HPPD). “While not every individual waterhemp plant is resistant to one or more herbicides, most field-level waterhemp populations contain one or more types of herbicide resistance,” said Hager.

Perhaps even more daunting is the occurrence of multiple herbicide resistances within individual plants or fields. Waterhemp plants and populations demonstrating multiple herbicide resistance are becoming increasingly common, can be more difficult to manage, and few herbicide modes of action are effective for their control.

For example, most Illinois waterhemp populations have developed resistance to ALS-inhibiting herbicides, which is often “stacked” with resistance to herbicides from other mode-of-action families. Soil- and foliar-applied herbicide premixes containing various ALS-inhibiting herbicides are numerous. While many of these products do have multiple modes of action, the ALS inhibitor component cannot control ALS-resistant plants.

In a postemergence scenario, applying a premix or tankmix of a diphenylether (PPO inhibitor) and glyphosate (EPSPS inhibitor) provides two effective modes of action against sensitive waterhemp, one effective mode of action against waterhemp resistant to either PPO inhibitors or glyphosate, and no effective modes of action against waterhemp resistant to both PPO inhibitors and glyphosate.

In summary, using herbicides from multiple mode-of-action groups may help reduce the selection intensity for resistance to a particular active ingredient of a herbicide. However, many factors determine the effectiveness of each premix or tankmix ingredient against the weed species of concern.

Leave a Reply

Herbicides Stories

Soybean Plant closeup
Crop InputsDow Launching New Soybean Burndown Herbicide
June 30, 2016
With the 2016 growing season nearing the halfway mark, many growers are scouting soybean fields to find unwelcome marestail plants Read More
glyphosate
Crop InputsWHO: Glyphosate ‘Unlikely’ To Cause Cancer
May 16, 2016
Via Reuters.com reporter Kate Kelland: The weed-killing pesticide glyphosate, made by Monsanto and widely used in agriculture and by gardeners, Read More
dicamba, Roundup Ready 2 Xtend
Crop InputsASA: No Dicamba On Roundup Ready 2 Xtend In 2016
May 16, 2016
While Roundup Ready 2 Xtend (RR2X) are tolerant to dicamba and glyphosate herbicides, no dicamba herbicides will be approved for Read More
CPP, glyphosate, dicamba, atrazine,
Crop InputsReport: Congress Pressing EPA On Glyphosate Review Handling
May 16, 2016
Via Reuters.com reporter P.J. Huffstutter: U.S. lawmakers have asked EPA to explain why it published – and then withdrew – Read More
Trending Articles
The Andersons Waterloo
ManagementFirst Indiana Facility Certified Under 4R Nutrient Stewardship Certification Program
June 27, 2016
The 4R Nutrient Stewardship Certification Program has announced that The Andersons, Inc.’s Waterloo, IN, facility has been added to its Read More
Food IT
Industry NewsCalifornia Event Will Mix Ag And Tech Professionals To Explore IT Solutions
June 20, 2016
Silicon Valley is hot on agriculture, and an upcoming event in California will bring together the food and tech industries Read More
Monsanto Luling Plant
Eric SfiligojWhat’s Next For Monsanto?
May 31, 2016
For the folks at Monsanto’s headquarters in St. Louis, MO, it has been an eventful few weeks. Back on May Read More
Soybean Plant closeup
Industry NewsMonsanto Rejects Bayer Bid; Open To More Talks
May 25, 2016
Monsanto Co, the world’s largest seed company, turned down Bayer AG’s $62 billion acquisition bid as “incomplete and financially inadequate” Read More
Eric SfiligojPity The Monsanto Haters
May 23, 2016
An old saying goes thus: “Be careful what you wish for. You just might get it.” Given current events, there Read More
Monsanto Luling Plant
Crop InputsReport: Bayer Eyeing Monsanto For Possible Mega-Merger
May 16, 2016
Bayer AG is exploring a potential bid for U.S. competitor Monsanto Co. in a deal that would create the world’s Read More
Latest News
CHS-Wayland Exterior Dry Fertilizer storage
Retail FacilitiesCHS Expands Michigan Location With New Dome Blending Fa…
July 1, 2016
When CHS wanted to update its Wayland, MI, facility to better serve its customers, it called on Dome Corp. of Read More
Heritage Cooperative
CropLife 100Heritage, Agland Co-op Explore Mutual Merger Interest
June 30, 2016
According to a report in The Ohio Country Journal, Heritage Cooperative and Agland Co-op have entered into negotiations to consider Read More
Soybean Plant closeup
Crop InputsDow Launching New Soybean Burndown Herbicide
June 30, 2016
With the 2016 growing season nearing the halfway mark, many growers are scouting soybean fields to find unwelcome marestail plants Read More
ManagementUpdates on Glyphosate Use in the EU and Bayer/Monsanto
June 29, 2016
Editors Paul Schrimpf and Eric Sfiligoj discuss the latest important developments on these crop protection fronts. Read More
Industry NewsCompass Minerals Names Protassium+ Sales Director
June 28, 2016
Compass Minerals, the producer of Protassium+ sulfate of potash, has named Scott Johnson director of sales for Protassium+ North America. Read More
Eric SfiligojThe British Leave Vote Impact On EU Agriculture
June 27, 2016
Like virtually everyone else in the world this past week, I’ve watched the global reaction to Britain’s vote to exit Read More
Valent David Nothmann
Crop InputsValent Names David Nothmann Vice President Of Marketing
June 27, 2016
Valent U.S.A. Corp. has announced the appointment of David Nothmann as vice president of marketing. Nothmann will be responsible for Read More
The Andersons Waterloo
ManagementFirst Indiana Facility Certified Under 4R Nutrient Stew…
June 27, 2016
The 4R Nutrient Stewardship Certification Program has announced that The Andersons, Inc.’s Waterloo, IN, facility has been added to its Read More
CropLife 100BRANDT Contributes To Mayo Clinic
June 27, 2016
BRANDT, a leading agriculture retailer and manufacturer of specialty agriculture products, has pledged a sizable donation to the Mayo Clinic Read More
ManagementReport: U.S. Farmland Values On Average Continue Gradua…
June 27, 2016
Land price movement has been in the forefront for farmers, landowners, lenders and land brokers for a decade now during Read More
AdjuvantsPrecision Laboratories Introduces Intact Xtra For Use W…
June 27, 2016
Precision Laboratories announces the launch of Intact Xtra, an adjuvant designed for applicators who want to maximize spray applications and Read More
Key Cooperative’s new liquid fertilizer, crop chemical, and seed facility in Grinnell, IA stores 1.5 million gallons of liquid fertilizer and 120,000 gallons of crop chemicals.
Retail FacilitiesKey Cooperative Facility Features The Latest In Murray …
June 27, 2016
When Key Cooperative wanted to improve the overall efficiency at its new state-of-the-art facility in Grinnell, IA, it turned to Read More
Allen Summers Asmark Institute PSM Training
EmployeesAsmark Institute Sponsors 25 ResponsibleAg Auditor Trai…
June 21, 2016
The Asmark Institute has announced plans to provide 25 scholarships through their affiliated State fertilizer and agrichemical associations to help encourage Read More
Kennebec Elevator
CropLife 100Wheat Growers Celebrates Kennebec Elevator Grand Openin…
June 21, 2016
Over 250 patrons and guests were on hand to celebrate Wheat Growers’ Kennebec Elevator grand opening. South Dakota Secretary of Read More
Land O Lakes
Industry NewsLand O’Lakes To Acquire Ceres
June 20, 2016
Land O’ Lakes, Inc. and Ceres, Inc. have announced that they have signed a definitive merger agreement under which Land O’Lakes Read More
Food IT
Industry NewsCalifornia Event Will Mix Ag And Tech Professionals To …
June 20, 2016
Silicon Valley is hot on agriculture, and an upcoming event in California will bring together the food and tech industries Read More
LegislationVilsack Christens WinField Crop Adventure, Talks Monsan…
June 17, 2016
The WinField Crop Adventure grand opening ceremonies at Fair Oaks Farms (near Winemac, IN) welcomed USDA Secretary of Agriculture Tom Read More