The Changing Face Of Weed Control

Giant ragweed

“What’s good for the goose is good for the gander,” goes an old saying. Besides waterfowl, this adage could also be applied to the world of agriculture, in particular when talking about crops and weeds.

In truth, resistant varieties of weeds have been quite common across many fields of the U.S. for several years now. But most market watchers agree that 2010 was a banner year for herbicide-resistant weeds. The favorable crop growing conditions in 2010 — an early planting window, sunny days and decent rainfall throughout the summer — also appealed to an entire range of weed varieties. In fact, Darrin Dodds, Mississippi Extension cotton specialist, described to CropLife’s® sister magazine Cotton Grower how glyphosate-resistant Palmer amaranth (also known as Palmer pigweed) spread in 2010. “Prior to this year, I had not gotten a call about pigweed control failures with glyphosate south of Highway 82,” said Dodds. “This year, I’ve gotten calls out of Holmes County, out of Humphreys County, and I’ve even gotten some calls off the Mississippi Gulf Coast where we grow cotton. It seems as if it’s just steadily spreading.”

Larry Steckel with the University of Tennessee Extension Service echoed this trend for herbicide-resistant weeds. “It really showed up in middle Tennessee this year, and north Alabama,” Steckel told Cotton Grower. “Palmer pigweed had never been there before — no Palmer pigweed at all, let alone resistant Palmer pigweed. So it’s basically got all of our cotton acres now. Wherever we grow cotton, it’s there to some degree.”

Other Contenders

In addition to Palmer amaranth, several other weed varieties with known resistance are troubling growers. In a recent survey of 800 growers conducted for BASF, common lambsquarters and marestail were chosen as the top weed threats by 45% apiece of respondents. Finishing a close third and fourth on the list were giant ragweed at 43% and waterhemp at 41% (see chart). Among Midwestern-based respondents, waterhemp topped the list of hard-to-control weeds at 60%, followed by lambsquarters at 57% and ragweed at 56%.

Given recent news, these results are not surprising. In July, Kevin Bradley, Extension weed scientist for the Uni­versity of Missouri, did a survey of waterhemp in the state at 144 locations. He found that 58% of this population were resistant to glyphosate. And a survey of giant ragweed from 27 farms within Missouri discovered 12 glyphosate-resistant varieties.

“My concern is not just herbicide resistance, but multiple resistances,” said Bradley of his findings. “What started as resistance to glyphosate, the most widely used herbicide, has become resistance to other herbicides.” In fact, he added, the newly resistant giant ragweed was also found to have at least moderate resistance to ALS herbicides.

More recently, researchers at the University of Illinois confirmed they had discovered a species of waterhemp that had developed resistance to HPPD-inhibiting herbicides. “A fifth example of resistance in one weed species is overwhelming evidence that resistance to virtually any herbicide used extensively on this species is possible,” said Aaron Hager, weed specialist at the University of Illinois. “We are running out of options. This mulitple-herbicide resistance in waterhemp has the potential to become an unmanageable problem with currently available postemergence herbicides used in conventional or glyphosate-resistant soybeans.”

For some growers in the South, un­manageable has already become a reality. According to Dr. Dan Westberg, technical marketing manager for BASF, there were many cotton growers in 2010 that were forced to hire gangs of workers using hoes to control the herbicide-resistant Palmer pigweed in their fields. “Based upon what I heard from these growers, it cost them between $50 and $100 per acre to employ this strategy,” says Westberg. “In addition, no till cotton farming, which has been very beneficial for soil conservation in these areas might end. For many growers, the only way to control herbicide-resistant weeds is to dust off the plow.”

Developing New Strategies

In the end, says Westberg, growers will have to change their approach to weed control. “It was always amazing to me that some growers didn’t think twice about spending $100 per acre on seed and fertilizer, but tried to get by on weed control for less than $20 per acre,” he says. “Those days are probably going away very rapidly.”

University experts recommend that growers follow these steps to manage tough-to-control weeds in their fields:
•  Begin with clean fields and control weeds early with a burndown and/or preemergence application of residual herbicide.
•  Scout your fields regularly, identify weeds and their location in the field and respond quickly to changes in weed populations.
•  Institute an integrated weed management program that employs multiple modes of action.
•  Follow label directions closely to achieve optimal performance and pay close attention to rate and timing information.
•  Use other agronomic practices such as crop rotation, cultivation and cleaning equipment between fields that diversify your weed control options.

In particular, says Westberg, using a herbicide with good residual characteristics such as Kixor will become even more important moving forward. “This can help provide broadspectrum control of broadleaf weeds including ALS-, triazine- and glyphosate-resistant biotypes,” he says. “This provides burndown and soil activity across a wide range of crops.”

Jeff Carpenter, corn portfolio manager for DuPont Crop Protection, agrees that different modes of action and good residual characteristics are now needed to provide effective weed control. “Agriculture needs sound science-based approaches and new ways of controlling resistance weeds,” says Carpenter. “This is what virtually every crop protection supplier in the market is working on right now. We all lived through ALS resistance when it first appeared. This is no different.”

A More Complicated Future

In this new reality for weed control, industry insiders agree that the practice of applying a single mode of action herbicide such as glyphosate is quickly being replaced by one of applying multiple herbicides to achieve control and reduce the chance for future resistance evolution. “That’s not to say that glyphosate will completely disappear as an important weed control tool for agriculture to use,” says Susan Macy, soybean portfolio manager for DuPont Crop Protection. “But I doubt it will even again be the only herbicide growers use to control weeds.”

And the prospects for any new single product being the “magic bullet” for all weed varieties also appear dim. As DuPont’s Carpenter points out, the last new mode of action herbicides (HPPD-inhibitors) were introduced back in the early 2000s. Even with plenty of activity in the development pipeline, he doesn’t foresee another “magic bullet” in the industry’s gun barrel.

Going into 2011, BASF’s Westberg reports that several weed varieties bear watching. In particular, marestail — which was first confirmed showing glyphosate-resistance in the early 2000s in Delaware — is continuing to spread, now found in some 20 states. The latest to report a glyphosate-resistant marestail is Oklahoma, earlier this year.

Two other weeds that are showing some signs of resistance include morningglory and burcucumber. “Morningglory always has shown some hints of resistance to certain herbicides,” says Westberg. “As for burcucumber, it tends to germinate over a long period of time and is an aggressive grower. These are the same kind of characteristics other resistant weeds tend to possess.”

Topics:

Leave a Reply

Herbicides Stories
HerbicidesScouting Key To Next Season’s Soybean Herbicide Program
August 12, 2014
When growing soybeans, growers need to think ahead to stay one step ahead of weeds. That means examining weed threats and evaluating which herbicides work best. Read More
Winter Wheat
HerbicidesArysta Touts Burndown Herbicide For Brome Management In Wheat
June 4, 2014
Arysta LifeScience North America recommends PRE-PARE Burndown Herbicide for effective brome management in winter wheat. Read More
HerbicidesFall Herbicide Applications More Effectively Manage Resistant Italian Ryegrass
May 14, 2014
Field studies show that a fall application of certain herbicides before weed emergence, leads to more successful crop planting and weed control in spring. Read More
Waterhemp in soybean stubble
HerbicidesThe Weed Resistance Problem: A Matter Of Billions
April 1, 2014
Not only is the amount of money being spent to control these yield robbers high, but the toll it has taken on the human population is growing lager by the day. Read More
Top 100 Articles
Milan Kucerak, president/CEO, West Central
CropLife 100West Central Cooperative And Its New President Are A Match Made In Deviation
June 29, 2015
To appreciate just how unique West Central Cooperative is in the world of ag retail, an observer need only consider Read More
Winter Wheat
CropLife 100South Dakota Co-op Member Owners Vote No On Unification
June 26, 2015
The Boards of Directors for North Central Farmers Elevator (NCFE) and Wheat Growers (WG) have announced that member-owners have voted Read More
CropLife 100The Andersons Acquires South Dakota Plant Nutrient Manufacturer Kay-Flo
May 20, 2015
The Andersons, Inc., ranked No. 22 on the CropLife 100, has purchased Kay Flo Industries of North Sioux City, SD. “This Read More
CropLife 100AgGateway’s Barcoding Initiative Progressing Nicely
May 8, 2015
According to legend (or Wikipedia), the first step towards modern bar codes came back in 1948, when Bernard Silver, a Read More
CropLife 100Pinnacle Agriculture Acquires Minnesota Retailer
April 14, 2015
Pinnacle Agriculture Holdings, LLC, ranked No. 6 on the CropLife 100,  has successfully acquired Liebl Ag, LLC in Ada, MN.  Read More
CropLife 100CHS, Aurora Cooperative Complete Fertilizer Storage, Grain Shuttle Loading Facility
April 13, 2015
CHS Inc., the nation’s leading cooperative and ranked No. 5 on the CropLife 100, and Aurora Cooperative (ranked No. 21) Read More
Latest News
Topcon AGI-4 on MF Planter
EquipmentAutosteer: Compatibility, Accuracy Remain Top Of Mind
July 3, 2015
The world of automatic steering solutions in agriculture has evolved rapidly in the last few years. From after-market add-ons that Read More
ManagementUnited Suppliers/Land ‘O Lakes Merger & Crop Update
July 2, 2015
CropLife’s Paul Schrimpf and Eric Sfiligoj talk about the reasons behind the United Suppliers/Land ‘O Lakes merger and USDA’s recent Read More
Industry NewsBioSafe Adds To Sales Force
July 2, 2015
BioSafe Systems has announced the hire of two new members for its service team. David Britt recently joined the team Read More
Chesapeake Bay
ManagementChesapeake Bay Clean-Up Gets Renewed Attention
July 2, 2015
The Chesapeake Bay has been called one of the most biologically productive ecosystems in the world. It’s also one of Read More
Measuring Bulk Tanks
ManagementBulk Pesticide Compliance: Top 10 Areas Of Improvement …
July 1, 2015
  In honor of the 33-year run of David Letterman’s Late Show, the American Agronomic Stewardship Alliance (AASA) is happy Read More
Industry NewsArysta North America Hires Midwest Sales Manager
July 1, 2015
Arysta LifeScience North America recently announced the hiring of Brian Battles as the Senior Technical Sales Manager for the Midwest Read More
Farmer on tablet
Eric SfiligojThe Never-Ending Battle Against Modern Agriculture
July 1, 2015
In the world of comic books, the character of Superman often refers to the fight to save the world as Read More
Retail FacilitiesBuilding Up Ag Retail
July 1, 2015
In the oftentimes unpredictable world we live in, it’s nice to know some things can be reliably countered on to Read More
Retail FacilitiesMaple River Grain And Agronomy Phases In Site Developme…
July 1, 2015
Marcus Construction helped Maple River Grain and Agronomy in Casselton, ND, with the design-build of its dry fertilizer, liquid chemical/seed Read More
Retail FacilitiesA&B Welding Builds A New Liquid Terminal Hub For Br…
July 1, 2015
To build its new hub facility, Briggs Crop Nutrients enlisted the help of A&B Welding. The result, an efficient facility Read More
Edon Farmers Co-op
Retail FacilitiesNew Marcus Facility At Edon Farmers Co-op Provides More…
July 1, 2015
Edon Farmers Co-Op in Edon, OH, needed a new facility to consolidate outdated locations. Marcus Construction was able to design Read More
Retail FacilitiesKinder Morgan Expands Its Storage With A New Dome Barre…
July 1, 2015
Kinder Morgan wanted additional covered storage at its Dakota Bulk Terminal on the Mississippi River in St. Paul, MN. With Read More
Retail FacilitiesHeartland Tank Protects Fertilizer From Extreme Cold At…
July 1, 2015
The Arthur Companies in Harvey, ND, enlisted the help of Heartland Tank Companies to develop a new liquid fertilizer facility Read More
The McGregor Co. fertilizer loadout
Retail FacilitiesThe McGregor Co. Partners With Kahler Automation To Cre…
June 30, 2015
Kahler Automation helped The McGregor Co. expand its Clarkston, WA, operation with unstaffed loadout technology that enables customers to pick Read More
Dry and Liquid Plant
Retail FacilitiesKahler Automation Helps CHS Dakota Ag Cooperative Build…
June 30, 2015
CHS Dakota Ag Cooperative in Mooreton, ND, wanted a liquid/dry blender system that could meet the needs of its customers Read More
Crop InputsLand O’Lakes, United Suppliers To Merge Crop Inpu…
June 29, 2015
Land O’Lakes, Inc. and United Suppliers, Inc. of Ames, IA, today announced their intent to merge their crop inputs businesses. Read More
FungicidesHelena To Distribute Unique Summit Agro Fungicide
June 29, 2015
RANMAN 400 SC fungicide, the only fungicide with a FRAC group 21 designation, is now part of the innovative Summit Read More
Eric SfiligojIARC Targets 2,4-D In Latest Report
June 29, 2015
The International Agency for Research on Cancer (IARC) has struck again. Earlier this year in March, this agency of the Read More