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

Crop InputsEU Glyphosate Controversy Heating Up Yet Again
August 17, 2016
The battle over glyphosate rages on in Europe, creating a lot of question marks over whether the herbicide will continue Read More
Winter Wheat
HerbicidesNew Wheat Herbicide Helps Growers Manage Resistant Weeds
August 2, 2016
Quelex herbicide from Dow AgroSciences is now registered by the U.S. EPA, providing wheat growers a new solution for advanced Read More
Palmer pigweed seedhead in cotton
HerbicidesStudy: Fall Weed Controls Can Make Significant Impact On Glyphosate-Resistant Palmer Amaranth
July 28, 2016
An article published in the latest issue of the journal Weed Science shows that adopting harvest-time and post-harvest weed controls Read More
Palmer pigweed in soybean stubble
HerbicidesSpecial Issue Of Weed Science Explores Human Aspects Of Herbicide Resistance
July 27, 2016
Weeds that evolve resistance to herbicides are a serious threat to global agricultural production. In this Special Issue of Weed Science, Read More
Trending Articles
Bayer Monsanto
Crop InputsBayer-Monsanto Mega-Merger: 6 Things You Need To Know
September 14, 2016
Mega mergers have become almost routine in the agricultural industry. Right on the heels of Monday’s news that fertilizer giants Potash Read More
Potash Corp Agrium
Crop InputsAgrium, Potash Corp To Merge To Create $36 Billion Company
September 12, 2016
Canada’s Agrium Inc. and Potash Corp of Saskatchewan Inc. have agreed to combine in a deal that would create a Read More
Osage Co-op Elevator Osage, IA Finished Building
OpinionAre We Crazy?
September 8, 2016
At some point in the first few months of my employment here at CropLife® magazine, I started getting curious about Read More
ManagementMAGIE 2016 Highlights and Deere Anti-Trust
September 1, 2016
CropLife Editor Eric Sfiligoj discusses the recent Midwest AG Industries Exposition and the Department of Justice’s objection to John Deere Read More
ASMARK 2016 Retailers Live! Tour - CPS
CropLife 100CPS Acquires Texas Retail Operation
August 23, 2016
Crop Production Services (CPS) has acquired the assets of Larry’s Chemical and Spray, Inc., for an undisclosed amount in an Read More
Key Cooperative Marcus Construction Steel Building
Retail FacilitiesMarcus Construction Builds High-Speed Agronomy Center For Key Cooperative
July 7, 2016
Key Cooperative in Grinnell, IA, wanted a state-of-the-art Agronomy Center to better serve its customers. Marcus Construction delivered exactly that. Read More
Latest News
Syngenta Seedcare Institute
Seed/BiotechSyngenta Opens New North America Seedcare Institute In …
September 23, 2016
Syngenta unveiled its new Seedcare Institute in Stanton, MN, during a recent grand opening celebration. More than 150 industry leaders, Read More
StewardshipMonsanto Invests $1.6 Million In System To Quantify Gre…
September 23, 2016
The USDA – Natural Resources Conservation Service (USDA-NRCS) recently awarded the National Corn Growers Association (NCGA) and its Soil Health Read More
Pipe rack
LegislationCourt Sides With Ag Retailers On PSM
September 23, 2016
The D.C. Court of Appeals has ruled the Occupational Safety and Health Administration violated the Occupational Safety and Health Act when Read More
ManagementPacific Coast Fertilizer Announces Interest In Longview…
September 22, 2016
Pacific Coast Fertilizer LP (PCF) announced at the Cowlitz Economic Development Council board of directors meeting its interest in developing Read More
Young corn plants in soil
UncategorizedCool Planet Raises Additional $9 Million To Commerciali…
September 22, 2016
Cool Planet has announced the first close of a new financing round to commercialize the company’s Cool Terra Engineered Biocarbon Read More
Crop InputsJim Loar Promoted To President And CEO Of Cool Planet
September 22, 2016
In a move that reflects and reinforces the company’s commitment to the agricultural market, the Cool Planet board of directors Read More
BlendersNorth Dakota Coop Debuts Dry Fertilizer Plant
September 22, 2016
North Central Grain Cooperative has begun operations at a new dry fertilizer plant at its Rolla, ND, site. It is Read More
Crop InputsMonsanto, Bayer Officials Defend Proposed $66 Billion M…
September 21, 2016
Top officials for Monsanto and Bayer defended their proposed $66 billion merger before skeptical senators on Tuesday, insisting that the Read More
ManagementUpcoming Shows & Recent Events
September 19, 2016
Editors Paul Schrimpf and Eric Sfiligoj talk about upcoming trade shows and events and review the Mid America CropLife Association Read More
Industry NewsVerdesian Life Sciences Appoints New CEO
September 19, 2016
Verdesian Life Sciences, a plant health and nutrition company, today announced that its board of directors has named Kenneth M. Avery Read More
Corn
Crop InputsEPA Settles With Syngenta For Alleged Multi-Regional Pe…
September 19, 2016
The U.S. EPA has announced a multi-region settlement with Syngenta Crop Protection, LLC (Syngenta) in Greensboro, NC, for alleged violations of Read More
ManagementMerger Mania
September 16, 2016
Editors Paul Schrimpf and Eric Sfiligoj discuss this week’s mega-ag mergers of Bayer and Monsanto and Potash and Agrium. Read More
Monsanto sign
Crop InputsMonsanto Ends Up Being A Bargain For Bayer
September 16, 2016
History will say Bayer got a bargain in its $66 billion purchase of Monsanto, writes David Nicklaus, St. Louis Post-Dispatch. The Read More
Greg Musson, Gar Tootelian
CropLife 100California Ag Retailer Steps Up To Feed Families Affect…
September 16, 2016
GAR Tootelian, Inc. (GAR) in Reedley, CA, is challenging the Central Valley to help raise enough money and provide 525,000 meals Read More
Crop InputsBayer, Monsanto CEOs Discuss Merger
September 15, 2016
Werner Baumann, Bayer CEO, and Hugh Grant, Monsanto CEO, discuss why they decided to merge their companies. Read More
Corn close up
Crop InputsNY Times: Bayer-Monsanto a Bad Deal for Farmers
September 15, 2016
Via NY Times: Don Halcomb, a 63-year-old farmer in Adairville, KY, is expecting his profit to vanish this year, largely Read More
Werner Baumann, Bayer AG, and Hugh Grant, Monsanto
Crop InputsBayer-Monsanto Merger Creates New Global Ag Giant
September 14, 2016
During the whole of 2016, many of the companies that do business in the agricultural industry have concluded the best Read More
Bayer Monsanto
Crop InputsBayer-Monsanto Mega-Merger: 6 Things You Need To Know
September 14, 2016
Mega mergers have become almost routine in the agricultural industry. Right on the heels of Monday’s news that fertilizer giants Potash Read More