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

Young corn plants in soil
HerbicidesBest Management Practices To Control PPO-Resistant Weeds
March 14, 2017
Weeds resistant to the class of herbicides called protoporphyrinogen oxidase (PPO) inhibitors are spreading at a faster rate than weed Read More
Soybean Plant closeup
HerbicidesRegional Listening Sessions Give Farmers A Voice In The Battle Against Herbicide Resistance
February 27, 2017
Both scientists and regulators have had a lot to say about the growing problem of herbicide resistance and how weed Read More
Palmer amaranth
HerbicidesSeed Industry Introduces New Palmer Amaranth Test
January 31, 2017
Weed seed can be spread in a variety of ways-including by air, animals, rain, soil and mechanical means. In a Read More
Giant Ragweed
HerbicidesHerbicide Resistance Goes Viral On Twitter
January 26, 2017
“Think differently. Behave differently. Diversify however you can. Not every practice fits on every acre.” That was the message from Read More
Trending Articles
AdjuvantsA New Weed-Control Era Begins: But First, One Last Obstacle
March 4, 2017
There is trepidation, there is reluctance, and there is excitement. Ag retailers feel it all about the new dicamba and Read More
LIFT Academy video screenshot
Crop InputsLIFT Agriculture Academy: A Q&A With West Central Distribution’s Dean Hendrickson
March 1, 2017
West Central Distribution recently launched its LIFT Agriculture Academy, a new, premiere training and professional development resource for West Central’s ag Read More
Farmer and aptop
Matt Hopkins10 Warning Signs Your Website Is Grossly Outdated
February 8, 2017
Your Website is often a visitor’s first impression of your ag retail business. A positive first impression can set the Read More
AgriSync
Matt Hopkins17 Agriculture Apps That Will Help You Farm Smarter In 2017
December 9, 2016
Ag professionals are working smarter, not harder, than ever before. Smart farming technologies have enabled them to reduce costs, maximize Read More
R4023 Sprayer, John Deere
CropLife 100Ag Retail Equipment Report: The Green Party Continues
December 7, 2016
In the annual race for sales in the ag retail equipment marketplace, the color schemes for participants are a little Read More
Mike Stern
Precision AgClimate Corp. CEO Talks Retailer Support For Digital Ag
December 1, 2016
CropLife Magazine’s sister publication, AgriBusiness Global, recently sat down with Mike Stern, CEO of The Climate Corp., following the Monsanto subsidiary’s Read More
Latest News
UncategorizedPrecision Ag, Iowa Water, and GM Corn Updates
March 24, 2017
Editors Paul Schrimpf and Eric Sfiligoj look at the state of precision agriculture, the dismissal of the Des Moines Water Read More
Pam Marrone
Crop InputsMarrone Bio Innovations Enters Biostimulants Market Wit…
March 23, 2017
Marrone Bio Innovations, Inc. is expanding beyond biopesticides and crop protection and into the biostimulant market by commercially launching Haven Read More
Nutrients for Life Foundation Teacher
FertilizerNutrients For Life Foundation Celebrates 10 Years Teach…
March 23, 2017
Those in agriculture know fertilizer is a vital ingredient to grow strong, productive crops. In fact, fertilizer is responsible for Read More
ManagementThink You Know Water? Take WinField United’s R…
March 22, 2017
Water is among our most precious resources, and arguably the hardest working, with just one percent available for human use, Read More
Corn Field
LegislationTFI Hopes Court Dismissal Is ‘Final Chapter’…
March 20, 2017
The Fertilizer Institute (TFI) released the following statement from President, Chris Jahn on the March 17, 2017, federal court dismissal Read More
Wheat Growers
Industry NewsWheat Growers CEO Dale Locken To Retire
March 20, 2017
CEO Dale Locken has announced that he plans to retire from Wheat Growers. Locken has served almost 15 years as Read More
Bayer Monsanto
Eric SfiligojBayer-Monsanto: Life, LibertyLink, And The Pursuit Of R…
March 20, 2017
As the calendar officially turns to spring, life is in full renewal mode. Flowers are blooming, birds are singing, and Read More
Corn Field
Crop InputsUltra Yield Micronutrients Acquires Kronos Micronutrien…
March 16, 2017
Ultra Yield Micronutrients, Inc. ”Ultra”, an affiliate of Cameron Chemicals, Inc., is pleased to announce that it has acquired the Read More
ManagementSnowstorms, Asset Sales, and Soybeans Prices
March 16, 2017
Editors Paul Schrimpf and Eric Sfiligoj discuss the weather, precision ag, crop protection company mergers, and commodity prices in this Read More
Soybean Field
Seed/BiotechBayer Invests $8.1 million In Soybean Advancement In Th…
March 16, 2017
Growers in Illinois and across the Midwest now have the added benefit of a state-of-the-art soybean research facility, increasing accessibility Read More
CHS
CropLife 100CHS Acquires Western Co-op Transport Association
March 16, 2017
CHS Inc., North America’s leading farmer-owned cooperative and a global energy, grains and foods company, has purchased Western Co-op Transport Read More
Young corn plants in soil
HerbicidesBest Management Practices To Control PPO-Resistant Weed…
March 14, 2017
Weeds resistant to the class of herbicides called protoporphyrinogen oxidase (PPO) inhibitors are spreading at a faster rate than weed Read More
Photo credit: The United Soybean Board/The Soybean Checkoff.
Eric SfiligojFungicide Resistance On The Horizon
March 13, 2017
For many years now, the agricultural market has struggled to keep ahead of an ever-growing number of herbicide-resistant weeds. According Read More
Management2017 Commodity Classic Review
March 10, 2017
Editors Paul Schrimpf and Eric Sfiligoj discuss what happened at the recent Commodity Classic in San Antonio. Read More
Farmer using AgriSync
ManagementMajor AgriSync Update Aims To Extend Ag Experts’ Power …
March 10, 2017
AgriSync announced a major update to its leading collaboration and service management tool for professional ag advisors and their farmer Read More
Agrible Pocket Spray Smart App
EquipmentNew Agrible Pocket Spray Smart App Alleviates Spraying …
March 10, 2017
There’s a new app to help farmers decide when to spray their fields. Pocket Spray Smart is a free iOS Read More
BPIA logo
Crop InputsBiological Products Trade Association Changes Name, Exp…
March 9, 2017
The Biological Products Industry Alliance (BPIA), formerly the BioPesticide Industry Alliance, is the new name of the rapidly growing U.S.-based Read More
BBI MagnaSpread Salford BBI
Equipment14 Fertilizer Spreaders For 2017
March 9, 2017
Application equipment manufacturers stressed flexibility and accuracy with this year’s crop of fertilizer spreaders. From AGCO’s TerraGator TG9300B and Case IH’s 810 Read More