Weeding Out Resistance

Pigweed, glyphosate resistanceThe challenge in growing row crops is back. Corn and especially soybeans had almost become a management no-brainer for retailers and their grower-customers, especially with the adoption of glyphosate-resistant crops.

But all that reliance on glyphosate in the majority of U.S. corn and soybean acres has led to resistant and tolerant weeds. The other shoe has dropped, and as these problem weeds — along with the weeds that are resistant or tolerant to other herbicide chemistries — become more widespread, so does the need to keep an eye on them.

How are retailers dealing with this issue? CropLife® magazine talked to some CropLife 100 retailers to get their take on it.

Waterhemp Worries

MFA Inc. services most of Missouri, the state that documented the first case of triple-resistant weeds, so they know a bit about the problem. “We have major resistance issues across the majority of our territory,” says Paul Tracy, MFA’s director of agronomy services. MFA also serves portions of southern Iowa, eastern Kansas, and northern Arkansas, and its growers have encountered weed resistance to glyphosate, ALS (acetolactate synthase), PPO (protoporphyrinogen oxidase), and triazine herbicides. The No. 1 glyphosate-resistant weed in Missouri is waterhemp.

“In the northern part of the state, we’re probably looking at a rough estimate that 75% to 80% of the counties have some glyphosate resistance,” Tracy says. But “probably less than 20%, maybe less than 10%, of the acreage has glyphosate-resistant waterhemp.”

Horseweed, also called marestail, is problematic in southeastern Missouri, while weed resistance is just moving into the southwestern region.

Like many retailers, MFA recommends resistance prevention practices of crop rotation and mode-of-action rotation. “That’s old stuff; we’ve all been preaching it for years and years, but it doesn’t always sink in with growers,” Tracy says.

He surmises that one reason Missouri has more resistance than some other Midwest states is its abundance of continuous soybeans. “In some areas, we have a lot of continuous beans for eight, 10, 12, 15 years in a row,” he says. MFA now tells its growers to rotate to corn for a year or two and use atrazine and/or other corn herbicides to knock out the waterhemp.

MFA chooses to keep the strategy simple for growers, focusing on the use of older and new residual chemistry along with using other herbicide modes of action. “We have always recommended some residuals down with our Roundup Ready corn, and during the last two or three years, we’ve strongly recommended residuals with our Roundup Ready soybeans as well,” Tracy says.

“It is also a way to preserve crop yields if we cannot get across the field in a timely fashion with the first postemergence application of glyphosate,” says Kevin Bradley, University of Missouri Extension weed specialist.

Tracy points out that there are still a lot of fields that glyphosate works very well on. “We’re still going to be promoting glyphosate-tolerant genetics as the base of our weed control program,” he says. “We just have to deal with all these resistant weeds that are coming along.”

Pesky Pigweed

The resistance picture is somewhat different in the South. While mares­tail has been around for a few years, Palmer amaranth-resistant weeds have been building up even more in soybeans and cotton. Also known as pigweed, this resistant population is expected to “explode” this season, according to Ken Smith, University of Arkansas Extension weed specialist. Currently, 19 counties in the state have confirmed glyphosate-resistant Palmer amaranth, and estimates of some level of infestation in Arkansas are in excess of 650,000 acres.

“Farmers have started realizing things are going to have to start being done a little differently,” says Ben Branch, location manager at Ritter Crop Services in Marked Tree, AR. “We have resistant weeds that are popping up in pockets in our area, and we’re having to change our whole plan basically to manage that problem. These weeds didn’t survive thousands of years without being able to change, so they’ve adapted to the glyphosate chemistry.”

Ritter Crop Services’ 12 outlets serve growers in the northeastern quadrant of Arkansas with 10,000 to 15,000 acres of cotton and “tens of thousands of acres of beans,” Branch says. “Just about every farmer here probably has a resistant or tolerant species of pigweed in a field. And if the beans start canopying over a little bit and the herbicide doesn’t just penetrate down to the small pigweed tucked in underneath, just a little bit of Roundup might not kill it. Instead, all it does is just build the resistance up for the next year, for the next population from that plant.”

The retailer’s resolution is to put down residuals, even overlapping residuals and changing the herbicide mode of action as much as possible. “It’s kind of hard to do in cotton and beans, but crop rotation’s a big help,” Branch says. “You can go to milo or corn and use a different form of chemistry on your problem fields.”

They recommend one of Syngenta‘s Dual products — an older chemistry — and Syngenta’s Reflex and Valent U.S.A. Corp.‘s Valor, which are newer. This application would be followed by Roundup as needed.

“The first shot in the crop, we’re definitely talking about putting out some type of Dual product (an S-metolachlor from Syngenta), or some type of meto­lachlor, just to have a double whammy because once you get the weeds up, it’s hard to kill them,” Branch says.

Smith adds that his office recommends using a residual like Valor or Syngenta’s Prefix as a preemergence or preplant application, scout closely for escapes, and treat while small. Or rotate to a LibertyLink soybean program. “We have some very good recommendations for control of pigweed in LibertyLink soybeans,” he says. Including atrazine in the corn program is still providing excellent pigweed control in the state.

Ritter Crop Service’s staff has been sitting down with growers to talk about the process. “Some of them have already grasped the whole process, and they see that’s what they’re going to have to do,” explains Branch. The extra step of spraying weeds when they’re small is much like conventional soybean management, a practice many haven’t used since switching to Roundup Ready crops.

“It’s going to require a little more management,” Branch adds.

Lessons Learned

MFA’s growers have learned to deal with triazine resistance, which preceeded glyphosate resistance. “We still use atrazine on a large percentage of our corn acres,” says Tracy. “Just because we have resistance to a certain chemistry doesn’t mean we’re going to lose that chemistry, it’s just not as effective as it used to be.

“I always use atrazine as an example when people get really, really fearful of resistance with glyphosate,” he adds. “I use that as an example of something that we have resistance to and we’ve learned to deal with. After we hit field after field year after year with ALS chemistries, we got resistance that’s still out there. But some of those ALS products are coming back around as tools to fight glyphosate resistance.”

Some of MFA’s growers will be planting the recently approved Li­bertyLink soybeans, available on a limited basis for 2009. “That does give them another bullet in their gun to fight resistance,” Tracy says. “But the bottom line on this is unless we change modes of actions on herbicides or management practices one way or another, we’ll get resistance no matter what we throw at these weeds; we know that.”

Topics:

Leave a Reply

Herbicides Stories

Crop InputsEU Glyphosate Controversy Heating Up Yet Again
August 17, 2016
The battle over glyphosate rages on in Europe, creating a lot of question marks over whether the herbicide will continue Read More
Winter Wheat
HerbicidesNew Wheat Herbicide Helps Growers Manage Resistant Weeds
August 2, 2016
Quelex herbicide from Dow AgroSciences is now registered by the U.S. EPA, providing wheat growers a new solution for advanced Read More
Palmer pigweed seedhead in cotton
HerbicidesStudy: Fall Weed Controls Can Make Significant Impact On Glyphosate-Resistant Palmer Amaranth
July 28, 2016
An article published in the latest issue of the journal Weed Science shows that adopting harvest-time and post-harvest weed controls Read More
Palmer pigweed in soybean stubble
HerbicidesSpecial Issue Of Weed Science Explores Human Aspects Of Herbicide Resistance
July 27, 2016
Weeds that evolve resistance to herbicides are a serious threat to global agricultural production. In this Special Issue of Weed Science, Read More
Trending Articles
Key Cooperative Marcus Construction Steel Building
Retail FacilitiesMarcus Construction Builds High-Speed Agronomy Center For Key Cooperative
July 7, 2016
Key Cooperative in Grinnell, IA, wanted a state-of-the-art Agronomy Center to better serve its customers. Marcus Construction delivered exactly that. Read More
Heritage Cooperative
Retail FacilitiesKahler Automation Designs State-Of-The-Art Facility For Heritage Cooperative
July 4, 2016
Heritage Cooperative in Marysville, OH, needed an efficient liquid, dry and grain facility to serve the many needs of their Read More
The Andersons Waterloo
ManagementFirst Indiana Facility Certified Under 4R Nutrient Stewardship Certification Program
June 27, 2016
The 4R Nutrient Stewardship Certification Program has announced that The Andersons, Inc.’s Waterloo, IN, facility has been added to its Read More
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
Latest News
Crop InputsDuPont Pioneer: Corn Belt P and K Levels Lagging
August 24, 2016
A new DuPont Pioneer study conducted across 12 Corn Belt states demonstrates that growers may be leaving profit potential in Read More
Monsanto sign
Crop InputsCould a Monsanto-Bayer Union Be 2 Weeks from Fruition?
August 24, 2016
Via STLToday.com (The St. Louis Post-Dispatch): Merger talks between Monsanto Co. and Bayer AG are advancing after a series of Read More
EquipmentCase IH Debuts Nutri-Tiller 955 Strip-Till Applicator
August 24, 2016
With strip-till continuing to expand across new acres, Case IH designed the new Nutri-Tiller 955 strip-till applicator to help producers Read More
EquipmentCase Launches Aim Command FLEX, 25th Anniversary Patrio…
August 24, 2016
Case IH announces new AIM Command FLEX advanced spray technology for greater application accuracy, as well as special 25th Anniversary Read More
ASMARK 2016 Retailers Live! Tour - CPS
CropLife 100CPS Acquires Texas Retail Operation
August 23, 2016
Crop Production Services (CPS) has acquired the assets of Larry’s Chemical and Spray, Inc., for an undisclosed amount in an Read More
PrecisionAg Video Conference
Precision AgVideo: PrecisionAg Vision Conference
August 22, 2016
A Strategic Conference Focused on the Future of Farm Digitization and Precision Agriculture Visit precisionagvision.com and register today! Read More
Young Corn Plants
Industry NewsOABA Welcomes Nicole Wallace As Communication & Adm…
August 22, 2016
The Ohio AgriBusiness Association has hired Nicole Wallace as its communication and administrative coordinator. Wallace will help provide comprehensive communication Read More
Syngenta Sign
Crop InputsChemChina, Syngenta Receive Clearance From CFIUS
August 22, 2016
China National Chemical Corp. (ChemChina) and Syngenta have announced that the companies have received clearance on their proposed transaction from the Read More
ManagementAg Industry Shows and Rumors
August 18, 2016
Editors Paul Schrimpf and Eric Sfiligoj talk about the upcoming trade show schedule, crop protection merger updates, and content for Read More
MAGIE 2015
EquipmentMAGIE Takes The Pulse Of The Ag Retail Industry
August 18, 2016
Every year, one of the major highlights of my career as an ag journalist is attending the Midwest AG Industries Read More
MAGIE 2015 Overview
EquipmentPride In Professionalism On Display At MAGIE
August 18, 2016
The Illinois Fertilizer & Chemical Association (IFCA) is proud to partner with CropLife IRON and continue the tradition of bringing Read More
SprayersJenner Ag To Debut 25th Anniversary Edition Case IH Pat…
August 18, 2016
Visitors at the 2016 Midwest Ag Industries Exhibition (MAGIE) in Bloomington, IL, will have a unique photo opportunity, as Jenner Read More
Crop InputsEU Glyphosate Controversy Heating Up Yet Again
August 17, 2016
The battle over glyphosate rages on in Europe, creating a lot of question marks over whether the herbicide will continue Read More
Industry NewsNew Partnership Provides Improved Representation At Ohi…
August 16, 2016
The Ohio AgriBusiness Association (OABA) has retained Belinda Jones of Capitol Consulting Group, Inc. (CCG) for government relations work in Read More
Tissue testing
FertilizerMosaic: 6 Tips For Better Crop Nutrition In Corn
August 16, 2016
Late in the crop season is a good time to assess visual nutrient deficiencies and ensure early- and mid-season deficiencies Read More
WebinarsWebinar Schedule
August 14, 2016
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
Dow DuPont
Crop InputsDowDuPont Update: EU Takes Closer Look at Merger
August 12, 2016
Dow Chemical Co. and DuPont Co. face months of haggling with European Union antitrust regulators who opened an in-depth probe Read More
ManagementNews from InfoAg 2016 and Weed Wands
August 11, 2016
Editors Paul Schrimpf and Eric Sfiligoj review what happened at last week’s big Precision Ag event and a possible solution Read More