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

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
Palmer amaranth in soybean stubble
HerbicidesWSSA: Billions In Potential Economic Losses From Uncontrolled Weeds
May 4, 2016
What losses would corn and soybean growers experience if they were forced to eliminate herbicides and other control techniques from Read More
Trending Articles
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
Aerial Drone
Precision AgA Deeper Dive Into The Future Of Precision Ag
May 9, 2016
For about two decades now, through the good and the bad times, the ups and the downs inherent in agriculture, Read More
Latest News
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
Crop InputsFields of the Future: WinField Doubles Down with Agri-E…
June 16, 2016
Land O’Lakes, Inc., joined by Agriculture Secretary Tom Vilsack, today will host Fields of the Future, a live broadcast about Read More
Bayer sign
Crop InputsMonsanto Turns Back Bayer Again
June 14, 2016
Bayer AG’s bid to buy Monsanto Co. for more than $60 billion has hit an impasse that could pose a Read More
Young Corn Field
Crop NutritionNext Generation Of Nitrogen Efficiency Technology Conve…
June 13, 2016
Commodity price projections indicate farmers will continue to face tight margins again this year. Delivering higher yields and more bushels Read More
Industry NewsLa Crosse Seed Acquires Cover Crop Solutions Brand
June 10, 2016
La Crosse Seed announces that it is the new and exclusive owner of the entire family of brands of Cover Read More
ManagementTravel Plans and EU Rejection of Glyphosate, Biotech Cr…
June 9, 2016
Editors Paul Schrimpf and Eric Sfiligoj talk about upcoming trips and the latest in the European Union’s moves against glyphosate Read More
Aspire with Boron
Crop InputsStudy: Aspire with Boron Ups Alfalfa Yields
June 8, 2016
Alfalfa growers are successfully improving yields through the cutting season by applying an important micronutrient. In a recent study, The Read More
Industry NewsAGCO Announces Tragic Death of Longtime Employee
June 8, 2016
It is with deepest regret that we announce the passing of our dear friend, colleague and customer advocate-in-chief Kevin W. Read More
Wheat Field North Dakota
Industry NewsBASF Inks Northern Seed for Clearfield Wheat R&D Li…
June 6, 2016
BASF has licensed Northern Seed LLC to perform research and development of BASF’s proprietary and patented Clearfield technology in wheat. Read More
ManagementBayer/Monsanto, EU/Glyphosate, Corn/Soybeans
June 2, 2016
Editors Paul Schrimpf and Eric Sfiligoj discuss the latest regarding industry mergers, the glyphosate debate in Europe, and an update Read More
Growers looking at soybeans
Industry NewsKoch Licenses 2 Marrone Products For North American Dis…
June 2, 2016
Koch Agronomic Services (Koch), with support from its affiliate, Koch Biological Solutions, has secured exclusive rights to sell REGALIA Rx Read More
Gypsum
Industry NewsBeneficial Reuse Management Launches GYPSOIL BLENDABLE
June 2, 2016
Beneficial Reuse Management (BRM) has introduced GYPSOIL BLENDABLE, a new high-quality pelleted gypsum fertilizer that supplies 17% sulfate sulfur and Read More
StewardshipAgrible Joins Field To Market To Pursue Sustainable Sou…
June 1, 2016
Agrible, Inc. has joined Field to Market: The Alliance for Sustainable Agriculture as an associate member. As a leading multi-stakeholder Read More