The Next Steps In Weed Control

Many Midwestern fields now sport herbicide-resistant waterhemp, and the problem is getting worse.
Many Midwestern fields now sport herbicide-resistant waterhemp, and the problem is getting worse.

For anyone who pays attention to the news, the spread of herbicide-resistant weeds in agricultural fields is quickly becoming a pandemic of sorts. To appreciate this fact, consider just a few of the numbers to come out at the recent 53rd meeting of the Weed Science Society of America (WSSA/67th meeting of the Northeastern Weed Science Society (NWSS):

In America during 2012, it is estimated by researchers that more than 60 million acres of farmland were invested with herbicide-resistant weeds. “I’ve been through the Mid-South and it is not uncommon to see whole cotton fields filled with Palmer amaranth,” said Jason Norsworthy, associate professor, department of crop, soil and environmental sciences, the University of Arkansas, at the meeting.

Of those weeds that have a single form of herbicide resistance, 30% usually develop multiple resistance. For weeds with glyphosate resistance, this figure grows to 62%.

Globally, herbicide resistance has evolved for all modes of action in 208 weed species represented by 382 weed biotypes ­— and this figure keeps growing on an almost daily basis.

In 2013, herbicide-resistant Palmer amaranth could cost Tennessee soybean growers more than $200 million in herbicide/application costs and crop yield loss.

A single herbicide-resistant weed can have a significant impact on crop yields. For example, research has shown that just one giant ragweed plant per square meter can reduce crop yields between 45% and 77%. “More food is lost due to weeds than all other pest complexes combined,” said Dr. Michael Owen, Extension weed specialist and professor of agronomy, Iowa State University.

With these numbers in mind, perhaps Mark Peterson, global biology leader for Enlist at Dow AgroSciences, said it best at the meeting: “Resistant weeds represent a significant challenge to global agricultural production at a time of unprecedented demand.”

How We Got Here

Some in the agricultural industry might be wondering how today’s widespread infestation of resistant weeds came about, but according to Jodie Holt, professor of plant physiology at the University of California-Riverside, resistance is universal. “The evolution of weed resistance will occur no matter what control methods are being used,” said Holt.

Furthermore, according to Harold Coble, agronomist for USDA, it is unfair for critics to blame the herbicides themselves for creating resistant weeds. “Many people in agriculture want to blame the technology, but it is not the technology’s fault,” said Coble. “If anything, maybe it was too good when using it. Up until now, the main focus has been on killing weeds with the weed control being chemically-based. Herbicide-tolerant crops allowed growers to grow more acres and spend less time on weed control.”

Still, there were some at the meeting that did see the widespread use of glyphosate-resistant crops as at least part of the reason for today’s host of herbicide-resistant weeds. For instance, back in the 1970s, it wasn’t usually for growers to have to use four or five different herbicides to control weeds in their fields. Then along came glyphosate. Now, instead of applying multiple products per season, a single application of glyphosate could provide widespread weed control. As Bryan Young, professor, department of plant, soil and agricultural systems, Southern Illinois University (SIU), put it: “What happened with Roundup Ready crops is that they made everyone an excellent applicator.”

However, as glyphosate use expanded, conditions were ripe for quickly adaptive weeds to begin appearing. “There were 154 million acres of genetically-modified crops planted in 2012,” said Dr. David Mortensen, researcher at Penn State University. “Nothing is rare across that many acres when it comes to weeds.”

In addition, said SIU’s Young, this situation has been further complicated by efforts to address spray drift. “The desire to reduce glyphosate drift has probably led to more resistance because applicators aren’t using the product at its prescribed rates,” he said. “This has given survivor weeds the opportunity to adapt more quickly.”

Instead, many at the meeting placed the blame at the grower’s feet. “I have a grower friend who asked me recently ‘how did you let us get into this mess?’, referring to the resistant weed problem,” said USDA’s Coble. “I quoted back to him that famous Pogo cartoon strip: ‘We have met the enemy, and he is us.’”

According to Coble, many growers have tended to focus on their weed issues “one year at a time.” In these instances, having marginal weed control “will help pay the bills for that season,” without considering how missed weeds might evolve into resistant ones during the next crop season.

In other instances, growers tend to have an attitude that herbicide-resistant weeds “could not be avoided,” so they do nothing to address them in the long-term.

“Maybe resistance is unavoidable, but growers could have managed it better,” said Coble. “Weed control is not rocket science — it’s harder because it isn’t based solely on numbers and keeps changing all the time.”

Making this problem even worse, said Amy Asmus, co-owner of Asmus Farm Supply, Rake, IA, is what could be called “The Neighbor Effect.” In essence, growers who have neighbors with resistant weeds problems tend to view any control methods on their parts as futile. “In a survey I conducted of growers, only 40% of them said they implemented weed resistance best management practices when resistant weeds showed up in their fields,” said Asmus.

New Practices Needed

When it comes to these best management practices for weed control, virtually everyone at the meeting agreed that the days of simply controlling fully-developed weeds and sprouts “are at an end.” Instead, agriculture needs to adopt a “zero tolerance” approach to weed control and target the entire weed life cycle. “We are losing herbicides in agriculture at an alarming rate,” said the University of Arkansas’ Norsworthy.

According to Norsworthy, there are 11 best management practices that should be followed to keep the herbicide-resistant problem from spreading faster than it already is. These include:

  • Understanding the biology of the weeds already present in the field.
  • Using a diversified approach to weed management that focuses on preventing seed production and reducing the seed bank already in the soil.
  • Using an effective burndown strategy for growers who are planting in weed-free fields.
  • Planting weed-free crop seed.
  • Scouting fields regularly during the season to keep an eye out for weeds that might have survived early-season application work.
  • Using multiple modes of action herbicides that are effective against the most troublesome weeds.
  • Applying herbicides at the recommended label rates and for the recommended weed sizes.
  • Using mechanical weed control methods along with biological ones when it is appropriate to do so.
  • Prevent field-to-field movement of weed seed by cleaning equipment before it moves out of a particular patch of land.
  • Manage weed seed spread at harvest time.
  • Prevent an influx of weed seed by monitoring field borders (where potential resistant weeds might have been missed during any in-season application work).

“These best management practices will vary by crop, region and the types of weeds involved,” said Norsworthy. “However, if these are followed, they should provide an effective way to prevent the spread of resistant weeds.”

As USDA’s Coble noted, many of these best management practices seem common sense and involve simply paying attention. And, he added, that may be exactly what’s needed to keep resistant weeds from spreading.

“If we can get growers to do a better job of monitoring their fields for weeds, we could curb some of these problems,” said Coble.

What’s Ahead

Besides these best management practices, there are a few other new weapons ready to enter the fight against herbicide-resistant weeds. For example, in the next year or so, crops with tolerances for dicamba and 2,4-D should be entering the marketplace. One such product line is the Enlist system from Dow AgroSciences. According to the company’s Peterson, research has shown that using Enlist Duo herbicide with Colex-D technology can provide 95% control of several key weed species with glyphosate-resistance.

“Herbicides have been shown to be a key part of efficient, sustainable weed management systems that maximize production while preserving soil and water resources,” said Peterson. “It is important to note that herbicide-tolerant crops have enabled great advances in soil conservation and carbon sequestration — having growers go back to widespread tillage to control weeds will negate those environmental advantages. New technologies such as Enlist will enable more modes of action, increasing weed management diversity and sustainability.”

Also in the pipeline is BioDirect technology from The Monsanto Co. According to Dr. John Soteres, scientific affairs, weed resistance management lead for the company, BioDirect is based upon interfering with the RNA of a weed, which can ultimately kill it. “BioDirect can be applied via spray equipment and be used in conjunction with glyphosate and other herbicides for weed control,” said Soteres. “This method was introduced in April 2012 and is now in its Phase II testing.”

Despite these new products/systems coming down the line, a few speakers at the WSSA/NWSS meeting were less than enthusiastic about their introductions. “These new systems will neither help nor hinder the spread of resistant weeds,” said Stephen Duke, researcher for USDA. “These are more tools that will be available to growers to fight weeds, but they will have to have the will to use them. These won’t be widespread answers to the question of herbicide-resistant weeds, but they will offer some new options for growers to consider.”

To achieve this kind of widespread answer to the question of weed resistance, perhaps ag retailer Asmus offered the best advice. “Those that advise growers on how to control their weed problems need to be knowledgeable about all the ways to do this, not just repeat the same marketing programs we’ve used in the past,” she said. “As an industry, we need to stop trying to change the way growers have traditionally managed their weeds and offer them short-term solutions to gain control of the situation. Then, we need to provide them with a more long-term solution to maintain that control.”

Topics:

Leave a Reply

2 comments on “The Next Steps In Weed Control

  1. It's interesting how an "easy" weed control program can quickly create resistance and then create a lot of problems and pain. I studied weed science in college and left the crop protection business in the late 90's. I could see the writing on the wall that knowledge of how and when to use different chemistries on different weed species was not as valuable. Now some of that knowledge is now needed again, and hopefully it will create more sustainable weed management programs. Our current situation is unfortunate, in nearly every case with tillage, multiple modes of action and scouting the resistance issues can be prevented. It is not easy for no-till growers who need to think about the long term impacts of their weed management programs.

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
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

Trending Articles

Equipment2014 Product Of The Year Voting
September 19, 2014
Many new products were introduced to the ag retail marketplace this year. From this group, CropLife IRON and its consulting partners have selected five finalists for the Product of the Year award. Please cast your vote today to help us determine the winner. Read More
FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
CropLife 100CHS To Build $3 Billion Fertilizer Plant In North Dakota
September 5, 2014
The fertilizer plant in Spiritwood will be the single largest investment in CHS history, as well as the single largest private investment project ever undertaken in North Dakota. Read More
EquipmentNew Holland Acquires Miller-St. Nazianz
September 3, 2014
The assets of Miller acquired as part of the transaction will become part of New Holland Agriculture, a CNH Industrial brand, building on a successful four-year partnership between the two companies. Read More
CropLife 100Pinnacle Acquires East Kansas Chemical
September 2, 2014
Ranked 82nd on the CropLife 100, East Kansas Chemical will operate as part of Pinnacle's Performance Agriculture brand. Read More
MAGIE 2014 ShowStopper
EquipmentJohn Deere Again Wins MAGIE ShowStopper Award
August 25, 2014
For the second consecutive year, John Deere was honored at the Midwest AG Industries Exposition (MAGIE) for its new R4045 sprayer. Read More

Latest News

Syngenta
Seed/BiotechSyngenta Faces Second Lawsuit Over Agrisure Viptera Cor…
September 23, 2014
A second company has sued Syngenta AG over sales of genetically modified corn seed not approved by China. Read More
StewardshipCover Crops Field Guide For Farmers Expanded
September 23, 2014
Farmers interested in planting cover crops to improve soil health now have an updated and expanded resource in the second edition of the Midwest Cover Crops Field Guide. Read More
HerbicidesArysta LifeScience Launches Contest For Wheat Growers
September 23, 2014
The Flush after Flush Photo Finish contest encourages farmers across the U.S. to participate through Instagram or Twitter using the hashtag #FlushAfterFlush. Read More
FertilizerCF Industries Confirms Merger Of Equals Discussions Wit…
September 23, 2014
CF Industries Holdings, Inc. has confirmed that it is in preliminary discussions with Yara International regarding a potential merger of equals transaction. Read More
StewardshipProgram To Examine Ag-Related Practices, Policies To Pr…
September 22, 2014
A panel discussion on October 14 will include a significant discussion on key issues and solutions related to all aspects of harmful algal blooms. Read More
Eric SfiligojIt’s Product Of The Year Voting Season
September 22, 2014
Readers of CropLife IRON will choose 2014’s best new product over the next month. Read More
Palmer pigweed in soybean stubble
HerbicidesValent To Discontinue Gangster Herbicide
September 22, 2014
Valent will discontinue Gangster Herbicide after the 2015 growing season as growers can now deploy Fierce XLT herbicide in soybeans. Read More
Equipment2014 Product Of The Year Voting
September 19, 2014
Many new products were introduced to the ag retail marketplace this year. From this group, CropLife IRON and its consulting partners have selected five finalists for the Product of the Year award. Please cast your vote today to help us determine the winner. Read More
Equipment2014 Farm Science Review Crowd Tops 2013 Show
September 19, 2014
The 52nd annual Ohio State University Farm Science Review welcomed more than 130,000 farmers, industry professionals, FFA students and agricultural enthusiasts during the three-day event. Read More
Seed/BiotechUSDA Approves Enlist Following Rigorous Review
September 18, 2014
Dow AgroSciences now awaits EPA registration of Enlist Duo herbicide, the companion herbicide to the Enlist traits, which is expected in the near future. Read More
BlendersYargus Appoints New Plant Manager
September 18, 2014
Steve Shaffer will direct and coordinate daily operations at the company’s Marshall, IL, manufacturing plant, where the Layco line of material handling equipment is produced. Read More
CropLife 100Pinnacle Acquires Kansas-Based Cedar Ridge Supply
September 16, 2014
Cedar Ridge Supply will operate as part of Pinnacle's Performance Agriculture brand. Read More
StewardshipSecretary Vilsack Highlights Innovative Conservation Ef…
September 15, 2014
Nearly $16 million in Conservation Innovation Grants (CIGs) will be awarded to 47 organizations to help develop cutting-edge ideas to accelerate innovation in private lands conservation. Read More
Seed/BiotechSyngenta Responds To Cargill Lawsuit
September 15, 2014
Syngenta believes that the lawsuit is without merit and strongly upholds the right of growers to have access to approved new technologies. Read More
Equipment2014 Farm Science Review Launches Mobile App
September 15, 2014
Smartphone and tablet users planning on attending the 2014 Farm Science Review can now download this year’s customized mobile application. Read More
CropLife 100Southern States Coop Grower Sets Georgia Soybean Yield …
September 15, 2014
Georgia farmer Randy Dowdy's soybeans yielded an astonishing 110.66 bushels per acre, crushing the previous record of 82 bushels-per-acre. Read More
NIMITZ Treated vs Untreated pepper plant
InsecticidesNIMITZ Nematicide Approved By EPA
September 12, 2014
NIMITZ is a novel, non-fumigant nematicide with simplified application features, user safety and an active ingredient with a unique mode of action. Read More
InsecticidesMarrone Bio Innovations Receives Patent For Chromobacte…
September 11, 2014
The patent is the first step for MBI in developing a commercially viable product to inhibit infestations of corn rootworm larvae across America and other regions. Read More