The Weed Resistance Problem: A Matter Of Billions

To appreciate just how severe the herbicide-resistant weeds problem has become in the U.S., consider this statistic: According to researchers, approximately half of the country’s growers said that hard-to-kill weeds were a “major problem” in their crop fields during the 2013 growing season. In hard numbers, this translated into more than 70 million acres of land infested with herbicide-resistant weeds, a 17% increase from the previous year. Overall, weed scientists now say there are 200 species of weeds with confirmed resistance to one or more widely used herbicides.

According to Damon Palmer, U.S. commercial leader, Enlist, Dow AgroSciences, this uptick in infested acreage is all the more impressive when you consider that the weather conditions in 2013 didn’t necessarily favor weed growth as in prior years. “As you look across the country, there definitely hasn’t been a decrease in the number of acres being affected by herbicide-resistant weeds,” says Palmer. “With all the cooler and wetter conditions that much of the country experienced during 2013, they should have been a little easier to control than in the hotter weather years we’ve been having. But that wasn’t the case and their numbers still increased.”

The toll these herbicide-resistant weeds can have on growers is staggering. Some varieties can reach 8- to 10-feet in height, with strong stems that can damage farm equipment they encounter. Furthermore, some plants can produce hundreds of thousands of seeds, some of which can remain viable in soil for up to 50 years (as in the case of velvetleaf).

Even worse is the impact these weeds have on the crops themselves. According to a 2009-11 study conducted by the University of Minnesota Extension on corn, when a weed reaches a height of 3 to 4 inches (normally when corn is around the V3 to V4 growth stage), the crop loses approximately 12 to 13 bushels per acre within the first week. During the second week the weed is present, this loss increases to 27 to 29 bushels per acre. By their nature, weeds can exhibit a “luxury consumption” of certain crop inputs such as nitrogen. Furthermore, dense infestations of weeds can lead to allelopathy, a suppression of plant growth due to the release of natural-plant derived substances.

For growers, herbicide-resistant weeds have become a costly problem. At the very least, they are being forced to add additional herbicide applications to protect their investments. At worst, some are going back to hiring crews to hand weed their fields. In both cases, estimates University of Wisconsin researcher Vince Davis, this is adding approximately $2 billion to growers’ annual crop production bills.

And this isn’t the only time billions come up when discussing the impact of herbicide-resistant weeds. “Weed resistance is something we all have to deal with in agriculture,” says David Hollinrake, vice president, agricultural commercial operations marketing for Bayer CropScience. “Today, when you consider the losses in crop yields, weeds around the globe eat the food to feed about one billion people.”

How Resistance Starts

By their nature, many weeds have a natural ability to develop resistance. Recently, a computer model was developed by the University of Arkansas that analyzed the evolution of resistance to herbicides using the Mississippi Delta region of eastern Arkansas as its test case. Looking at 1,000 hypothetical rice fields, this model took into account three stages of growth for the crops and extended it over a 30-year period.

The findings from this computer model were eye-opening, to say the least. Based upon the model, if a certain herbicide is used alone in three annual applications, weed resistance can develop in as little as four years. More interestingly, the model showed that if a grower does not stop using a herbicide soon after resistance takes place, resistance can be accelerated for the next herbicide alternative used, even if it provides a different mode of action.

Waterhemp in soybean stubble
According to the latest data, glyphosate-resistant waterhemp has been confirmed in 12 states.

A similar study was conducted by the University of Missouri on one of the major Midwestern weeds to show resistance, waterhemp. According to the latest data, glyphosate-resistant waterhemp has been confirmed in 12 states. More telling, more than two-thirds of the waterhemp population sampled in the state of Missouri was found to be resistant to the popular herbicide.

For the study, the University of Missouri researchers collected waterhemp seed samples from 144 soybean fields in 54 Missouri counties during 2008 and 2009. Based upon their findings, 94% of the glyphosate-resistant waterhemp populations had three aspects in common:

■ Soybeans were the only crop planted in these fields in consecutive years.

■ Glyphosate was the only herbicide used in these fields for three or more years.

■ The fields contained waterhemp showing signs of having survived the previous herbicide application.

“It isn’t herbicides that create herbicide-resistant weeds,” says Dr. Bryan Young, a professor at Southern Illinois University. “Instead, the culprit is how we use herbicides in an overall weed management strategy. To preserve the effectiveness of herbicides, it is imperative that we become better stewards of their use. Minor changes made today can avoid costly problems in the future.”

Palmer pigweed in soybean stubble
A native to the southwestern U.S., Palmer amaranth first started showing signs of herbicide resistance in the late 1980s.

Further south, the problem child of herbicide-resistant weeds is Palmer amaranth (or pigweed, as it sometimes known). A native to the southwestern U.S., Palmer amaranth first started showing signs of herbicide resistance in the late 1980s. According to researchers, the weed showed confirmed resistance to glyphosate in 2006 in Macon County Georgia. Since then, glyphosate-resistant Palmer amaranth — which can produce more than 600,000 seeds per female plant — has spread across 13 states, including Texas, Virginia and Indiana.

Due to its rapid proliferation ability, the cost to control Palmer amaranth for growers has grown considerably over the past few years. In fact, for the cotton industry, herbicide costs for Palmer amaranth control have increased from $23 per acre in 2004 to $100 per acre in 2012.

“The current model simply isn’t sustainable,” says Dr. Stanley Culpepper, a professor in crop and soil science at the University of Georgia. “Growers have gone to war, and they are making progress from a weed management perspective, but not from an economic or environmental perspective. We need to figure out a way to get the same results far more cost-effectively and in a way that better protects our natural resources.”

The Race For Alternatives

Naturally, crop protection product suppliers have been working on the problem of herbicide-resistant weeds for years and several have potential solutions either just ready to enter the marketplace or coming out in time for the 2015 planting season.

For 2014, the options include Cobra from Valent U.S.A. Containing the active ingredient lactofen, Cobra can be used on such problem weeds as Palmer amaranth and waterhemp in soybeans.

Meanwhile, SePRO Corp. and Nichino America have partnered to launch Brake F2 for Palmer amaranth control in cotton. Containing the active ingredients fluridone and fomesafen, Brake 2F has been granted a Section 18 emergency exemption for 2014 in approved counties in Georgia, South Carolina, North Carolina and Tennessee. According to Dr. Tyler Koschnick, vice president of research and regulatory for SePRO, fomesafen requires low moisture for activation, but provides shorter residual control. Meanwhile, fluridone requires more moisture for activation, but has longer residual control. “The combination of the two complementary active ingredients has shown a tremendous advantage with crop safety with growers reporting extended control of up to six to 10 weeks or longer, depending upon soil type and conditions,” says Koschnick.

Then there’s Engenia, described as a “technologically advanced” dicamba formulation by developer BASF. Expected to have its commercial launch for soybeans in 2014, Engenia has demonstrated “effective control of key broadleaf weeds, including glyphosate-resistant Palmer amaranth, waterhemp, marestail and common/giant ragweed,” says Luke Bozeman, technical market manager, BASF.

In 2015, Dow AgroSciences expects to receive approval for its Enlist Weed Control system. A version of 2,4-D using the company’s Colex-D technology, Enlist has achieved greater than 95% control of several glyphosate-resistant weed types, according to Mike Peterson, global biology leader for the Enlist system at Dow. “Herbicides have been shown to be a key part of efficient, sustainable weed management systems that maximize production while preserving soil and water resources,” says Peterson. “It is important to note that herbicide-tolerant crops have enabled great advances in soil conservation and carbon sequestration. Having farmers go back to widespread tillage to control weeds will negate those environmental advances.”

Also expected to hit the market in 2015 is Acuron from Syngenta Crop Protection. Containing four active ingredients including bicyclopyrene, Acuron employs three modes of action to tackle more than 70 broadleaf weeds including Palmer amaranth and waterhemp, says Dr. Gordon Vail, technical product lead for herbicides at the company.

No matter what options are available in the future for combating herbicide-resistant weeds, the Univer­sity of Wisconsin’s Davis says the more, the better. “Di­versification is the most important thing farmers can do to manage these weeds,” he says. “This includes diversification of effective herbicide modes of action, diversified weed management practices and also utilizing non-herbicide control options such as judicious tillage, cleaning equipment of weed seed and diversified crop rotations. Weeds develop resistance more quickly when production systems remain static.”

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
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

EquipmentAdvance Your Technology IQ At MAGIE
August 13, 2014
The Midwest AG Industries Exposition (August 20-21) is the place you need to be to see, study and evaluate how new advances in the equipment, operations, crop protection and fertility sectors can help your business prosper. Read More
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
StewardshipMichigan Agriculture Leaders On Toledo Water Ban: We Want To Be Part Of The Conversation
August 8, 2014
Leaders of Michigan agricultural organizations said Thursday that the government should not have a “knee-jerk reaction” based on last weekend’s water ban in Toledo due to fertilizer run-off in Lake Erie. Read More
CropLife 100BRANDT Acquires Lemon Ag Services
August 4, 2014
The acquisition of Lemon Ag fits BRANDT’s aggressive corporate strategy of providing superior agronomic advice and services for customers in central Illinois. Read More
Eric SfiligojThe Resurgence Of Crop Protection
August 4, 2014
Plenty of new offerings over the next few years should see a rebirth for the crop protection products category in terms of market share. Read More
LegislationUSDA Implements Key Farm Bill Crop Insurance Provision
July 30, 2014
The new Supplemental Coverage Option, available through the federal crop insurance program and set to begin with the 2015 crop year, is designed to help protect producers from yield and market volatility. Read More

Latest News

CropLife 100GROWMARK CEO To Retire
August 22, 2014
GROWMARK chief executive officer Jeff Solberg has announced his retirement effective September 15, 2014. Read More
InsecticidesDuPont’s Prevathon Approved For Dry Beans
August 22, 2014
DuPont Prevathon insect control powered by Rynaxypyr has received EPA registration for foliar use on dry bean crops, including dried shelled peas and beans. Read More
ManagementNCGA DuPont New Leaders Program Enters Sophmore Season
August 20, 2014
The National Corn Growers Association and DuPont are pleased to announce the second year of the NCGA DuPont New Leaders Program. Read More
FungicidesVerdesian Links Up With Mitsui, Hokusan
August 20, 2014
Mitsui Chemicals Agro, Inc., and Hokusan Co., announced the signing of an exclusive licensing agreement allowing Verdesian Life Sciences global access to its patented technology for suppressing mycotoxin contamination in wheat and barley. Read More
SprayersUniversity Of Illinois Introduces New Spray App
August 18, 2014
University of Illinois Extension has released a new smartphone app for making sprayer-related calculations. Pesticide Spray Calculator, or Spray Calc, Read More
Crop InputsSyngenta Names New Manager Of Federal Government Relati…
August 18, 2014
Laura Wood Peterson has joined Syngenta as manager of federal government relations, based in Washington, DC. Read More
ManagementExpert To Discuss Farmland Value, Rent At Farm Science …
August 18, 2014
While cropland values in Ohio increased in the past two years, they have remained flat in 2014, declining in some cases, according to an Ohio State University agricultural economist. Read More
EquipmentDeere Announces Factory Layoffs
August 18, 2014
Deere & Co. has announced it will reduce the size of its manufacturing workforce at some agricultural equipment factories in response to current market demand for its products. Read More
HerbicidesNew DuPont Afforia Herbicide Gives Crops A Clean Start
August 18, 2014
DuPont Afforia is a preplant herbicide for soybeans and other field crops that provides excellent burndown and residual control of many challenging weeds, such as marestail and waterhemp. Read More
Equipment21 Products Showcased At MAGIE 2014
August 18, 2014
The annual Midwest AG Industries Exposition is upon us. Here is CropLife IRON's look at some of the products visitors can expect to see at this week's event. Read More
EquipmentAGCO Seeks Nominations For 2014 Operator Of The Year
August 15, 2014
Ag retailers throughout the U.S. and Canada are encouraged to nominate their best applicators. Read More
EquipmentAdvance Your Technology IQ At MAGIE
August 13, 2014
The Midwest AG Industries Exposition (August 20-21) is the place you need to be to see, study and evaluate how new advances in the equipment, operations, crop protection and fertility sectors can help your business prosper. Read More
ManagementCropLife’s Buyers’ Guide Issue Now Availabl…
August 13, 2014
One of our most read issues of the year — the August Buyers' Guide — is ready to download on the iPad. This popular issue features equipment for "In The Field," "At The Plant" and "In The Office." Read More
WebinarsWebinars On Demand
August 13, 2014
Register for one of our upcoming Webinars or access our archive of past Webinars to view recordings of presentations that may be of interest to you. Read More
HerbicidesBASF: Fall Burndown Benefits Go Beyond Weed Control
August 12, 2014
While unpredictable weather may delay application timing of spring herbicides, more growers are adding a burndown application in the fall Read More
HerbicidesScouting Key To Next Season’s Soybean Herbicide P…
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
StewardshipNitrogen Efficiency Supports Environmental Stewardship
August 12, 2014
As growers prepare for another harvest, it’s important to consider how nitrogen stabilization not only supports healthy plant growth but also fosters environmental stewardship. Read More
Seed/BiotechMycogen Seeds Introduces 19 New Corn Hybrids For 2015
August 12, 2014
Many of the new hybrids feature Mycogen's SmartStax Refuge Advanced technology for maximum protection of the genetic potential and planting convenience. Read More