Breaking Pandora’s Box: Resistant Weed Future Looms Large for US Farmers

“In the next three to seven years, we’ll see the opening of the newest version of Pandora’s Box,” says Jason Bond, a weed scientist at Mississippi State University.
“In the next three to seven years, we’ll see the opening of the newest version of Pandora’s Box,” says Jason Bond, a weed scientist at Mississippi State University.
(Photo by Kenner Patton, Delta Research and Extension Center, MSU)

Roundup Ready was the belle of the ball in the mid-1990s, feted as the eternal guest of honor, until she lost her luster when the clock struck midnight. Despite warnings to the contrary from weed scientists, the presumption, by many both in and out of agriculture, was of permanent herbicide efficacy—a costly fantasy.

When the Roundup Ready revolution blitzed cropland during a stunning group of historically unprecedented crop releases, particularly a chain from 1996-1998 in soybeans, cotton, and corn, weed control suddenly appeared to be relatively simple. And it was for several years—until reality bit back and glyphosate-resistance began surfacing in a handful of weed species across multiple states, notably in Palmer amaranth and waterhemp by 2005, followed by the loss of full efficacy for nearly every chemical concoction in the tank.

Whether the current weed fight is boosted by new innovations of seed destruction, spot spraying, pollen blankets, and electricity, or shotgunned with old-school techniques such as chopping, cover crops, windrow burns, or a return to deep tillage, the status of herbicide-resistant weeds reflects extreme uncertainty or genuine desperation on many farming operations.

Direct from the rows, five weed scientists offer a blunt assessment on present herbicide successes and failures across farm country. Set against a backdrop of increased regulation, label renewals, class-action lawsuits, and plant board litigation, the five is of one accord: The future impact of herbicide-resistant weeds on U.S. farmers is a question within a greater Pandora’s Box.

Tom Barber

Year after year, wading through some of the most notoriously tough Palmer amaranth in U.S. crop fields, Tom Barber, a University of Arkansas weed scientist, has ticked a succession of herbicide-resistant boxes in rapid order, with glyphosate long in the rearview mirror, and glufosinate (Liberty) the latest (confirmed in three pigweed populations; February 2021) to emerge.

 

tb 8 2021
“In the back of their minds, growers think a chemical company is going to ride in and save us once more,” says Tom Barber. “No. The easy-button answer is not there in the future.” (University of Arkansas System Division of Agriculture)

 

Palmer reigns as the bell cow weed enemy of Arkansas soybean and cotton fields, with barnyardgrass as a distant No. 2, at least in terms of sheer acreage affliction. Teaweed, or prickly sida, also presents significant issues: “With Xtend crops gaining popularity, we have been getting more calls on teaweed mostly because dicamba is just not very good on teaweed. Most growers have added either Python or Basagran to the mix to pick up the teaweed in soybean. Yellow nutsedge, and ALS-resistant sedges, particularly annual flatsedge, are also becoming an issue in soybeans and cotton in recent years,” Barber says.

Looking back at a 10-year window to roughly 2010, Barber describes the past decade as a “full circle” journey.  “Roundup Ready was such an easy button answer, and it let growers leave behind residuals in upland crops. Now that pigweed resistance has gotten so bad, we’ve shifted back to some of our old recommendations on residuals. Most successful herbicide programs for pigweed include two-to-three applications of residual herbicide during the growing season”

First used extensively in 2017 with the Xtend system, dicamba-based pigweed programs have been highly effective on Palmer, Barber explains, but the success leads to the old refrain—a one-technology answer. “We already can look across the river to Tennessee and see the dicamba and 2,4-D resistance building. There’s a day coming when dicamba, 2,4-D and glufosinate will no longer control pigweed on large acreage. We’re coming close to finding how hard it was to control weeds back in the early 1980s.”

Across crops in Barber’s geography, even in corn, weed control success starts with two residuals at planting. In soybeans, he recommends a group 15 and metribuzin—two modes of action. Beyond the foundational residuals, he emphasizes a timely post application. “Whether Liberty, Enlist or Xtend, a timely post is crucial, but when you’re dealing with frequent rainfall or numerous windy days, it is very difficult to target pigweed smaller than 6 inches, especially on big acreage.”

Regardless of present chemical efficacies, Barber insists on the need for innovation beyond a jug, and a mixing of mechanical and cultural practices, tweaked according to farm. “Maybe reduced tillage doesn’t cut it in our area in some places. Maybe we need to bury weed seeds with deep tillage a few inches below ground to reduce emergence the next season—the research data is clear on that. Maybe cover crops are the answer for others. Or something like the Harrington Seed Destructor or Redekop or See & Spray system. We are currently evaluating multiple cultural, mechanical and chemical combinations to determine the best system for future pigweed management”.

Barber punctuates his perspective with plain words: “Our history shows how rapidly we use up chemicals. In the back of their minds, growers think a chemical company is going to ride in and save us once more. No. The easy-button answer is not there in the future. Roundup Ready was a golden moment in time, but it’s likely never going to be that easy again.”

Aaron Hager

In 2008, responding to a juggernaut in the form of glyphosate-resistant waterhemp, weed scientist Aaron Hager and his University of Illinois colleagues hit the turnrows to barnstorm and offer specific recommendations on control, based on a plan of action with five steps of progression.

 

ah 8 2021
“Either rethink your management program or it will cost you even more money, because weeds always win in the end,” says Aaron Hager. (University of Illinois Extension)

 

Hager’s credibility with growers crashed the moment he uttered step No. 1: Use a residual herbicide in soybeans at a full labeled rate. However, fast-forward 13 years and approximately 60-70% of Illinois soybean acres receive a residual. “I was speaking close to blasphemy about residuals in 2008,” Hager recalls. “Guys complained of costs and kept on spraying glyphosate like there was no problem.”

“Change doesn’t happen when weed scientists like myself tell anyone anything,” Hager continues. “Change happens when biology leaves growers with no choice. In other words, either rethink your management program or it will cost you even more money, because weeds always win in the end. That’s right where we are today.”

Waterhemp reigns supreme in Illinois and the Midwest as a weed plague, a position of irony considering the yield-robber was entirely unknown to many growers just 30 years in the past. Hager notes Illinois growers with the most success in fighting waterhemp, or another highly troublesome weed, giant ragweed, are obsessive in asking questions. Translation: face value is not accepted. “Foremost in their decision isn’t cost, but they also don’t just reach for another chemical to throw in the tank,” Hager explains. “The growers with the best results have a big dose of skepticism, do a lot of research, don’t do the same thing every year, and ask tons of questions. It’s so ironic, because those questions are the same ones we asked 40 years ago.”

Control of waterhemp or any resistant weed will never be solved by a herbicide—old or new—Hager stresses. The most economical answer is the addition of custom-fitted extras to a herbicide program: “Maybe it’s harvest weed seed control (HWSC). Maybe some covers. Frankly, the pieces are not yet determined, but they’re all needed in the puzzle, because we all know weeds have been here longer than us, and they will outlast us.”

Stanley Culpepper

Georgia is the original home of herbicide-resistant pigweed—an infamous distinction earned in 2005 when University of Georgia weed scientist Stanley Culpepper found Palmer amaranth in multiple cotton fields capable of fighting off glyphosate. Sixteen years later, Palmer is weed enemy No. 1 in Peach State agriculture. Further, when Culpepper polled 1,737 producers, Palmer ranked as the overwhelming No. 1 agricultural pest (weed, insect, worm, disease) in Georgia, garnering more votes than all the other nine entries added together.

 

cul gr 2021
(Graphic courtesy of Stanley Culpepper)

 

gr scj 8 2021
 (Graphic courtesy of Stanley Culpepper)

 

A decade past, a crop field mowed down due to Palmer infestation was a frequent occurrence, yet today Culpepper describes the resistant weed management situation in Georgia as “monumentally” better. Why? Culpepper says a producer poll speaks best. Ranked in order of importance, 1,062 growers listed key factors in improved Palmer control: timely herbicide applications, residual herbicides, hand weeding, Extension assistance, different herbicide modes, and starting clean.

“The most outstanding growers in weed management understand timeliness, chemistry diversity, crop rotation, tool preservation (implementing non-herbicide control methods), maximizing herbicide activity, and minimizing resistance,” Culpepper says. 

 

sc 8 2021
“The most outstanding growers in weed management understand timeliness, chemistry diversity, crop rotation, tool preservation, maximizing herbicide activity, and minimizing resistance,” says Stanley Culpepper. (University of Georgia Cooperative Extension)

 

Looking forward, two issues dominate Culpepper’s outlook: resistance and regulation. “Taken together, those two can keep us from economic, sustainable pesticide use, and nobody at any level of agriculture needs to sit back and watch this happen. Instead, everyone from growers to consultants to Extension agents must work with EPA, the states, and WSSA to address the regulatory and resistance management challenges that threaten the practical use of pesticides; sound science is the key to sustainable solutions. Cooperation, cooperation, and more cooperation will be key in making sure growers have the solutions required to provide food, fiber and feed needed by the world.” 

Larry Steckel

The past decade is a tale of two weed realities in Tennessee. Growers have seen “remarkable” improvements in Palmer amaranth control, assisted by dicamba, 2,4-D, and glufosinate, but as a sidecar, herbicide resistance has already appeared in soybean and cotton fields, according to Larry Steckel, University of Tennessee weed scientist. “Most recently we have confirmed dicamba resistant Palmer amaranth where on average we are getting no better than 45% control with the labeled dicamba rate and no better than 60% control with twice the labeled rate. Also, now we have a problem building with grasses that we didn’t have as a problem before. The top issue in corn, soybeans, and cotton is junglerice and goosegrass. We’ve got glyphosate resistance on about 15% of our junglerice population and about 20% in goosegrass.”

 

ls 8 2021
“Any new chemical help is pie in the sky until it actually gets here, and I see nothing close or certain,” says Larry Steckel. (University of Tennessee Extension)

 

Steckel describes a weed version of robbing Peter to pay Paul—dicamba is hindering the efficacy of grass controlling herbicides. “For example, we’re spraying dicamba to kill pigweed with glyphosate over Xtend crops, which makes up so much of our crop total, but it’s antagonizing the control of those herbicides. We end up with a double whammy of, one, resistance to glyphosate, and two, antagonism of the glyphosate by dicamba.”

Steckel advises growers to rely on a high rate of the “bread and butter” of weed control—pre-emerge and residuals. In the moment, he urges growers to spray timely and apply appropriate rates, all done with the realization that no herbicide cavalry is soon to arrive. “A new and old technique of impregnating a herbicide on fertilizer and using it on cotton post emergence when the cotton is 6 to 8 node stage looks to be a good tool for grass and Palmer control.  Also, we’ve got to conserve our herbicides and that can be helped by cover crops and tillage when it’s right. Any new chemical help is pie in the sky until it actually gets here, and I see nothing close or certain.”

Jason Bond

In an ideal year in the Mississippi Delta, the first vehicle with a tire to touch dirt each spring has a planter attached. However, the rainy fall and winter of recent years has thrown off the timing of field prep and contributed to a major proliferation of an already notoriously tough weed—Italian ryegrass, explains Jason Bond, weed scientist with Mississippi State University. “Now we’ve got clethodim resistance in eight counties, and our best recommendation is fall burndown before ryegrass comes out of ground.”

Palmer amaranth and Italian ryegrass rate as the runaway one-two punch concern for Mississippi growers, but with dicamba’s current efficiency against Palmer, ryegrass has climbed several rungs on the grievance ladder.

 

jb 8 2021
“Even if we get a truly new herbicide, why go down the road to run it in the ground which we’ve done over and over?” asks Jason Bond. (Photo by Kenner Patton, Delta Research and Extension Center, MSU)

 

Weed control in the Delta, Bond explains, is often a matter of logistical success. “The common denominator I see for guys who do well with weed management is often the ability to cover ground. These are guys who cover their acres on time, whether that is matching farm size with the right amount of labor and equipment.”

And how does Bond see the future of resistant weeds? “It’s a problem that will continue simmering under the surface. We’ve already seen dicamba resistance up in Tennessee, and that’s just an example of inevitability, but then again I’m not sure many people expected the rapidity of resistance. In the next three to seven years, we’ll see the opening of the newest version of Pandora’s Box.”

As farmers navigate a maddeningly uneven and ever-changing battlefield, and Palmer amaranth, waterhemp, and multiple other weed species across the U.S. continue to pack on genetic muscle, steal precious yield from crop rows, toe-tag every harvest with several billion dollars in overall expense, and attempt to fatten their accounts in the seed bank, Bond offers a hopeful, but sobering perspective on the future of control.

“In my opinion, it’s a combination of an agronomic innovation and herbicide technology,” he concludes. “Even if we get a truly new herbicide, why go down the road to run it in the ground which we’ve done over and over? People may not want to hear this, but the technological key to resistant weed control may be the innovation we haven’t stumbled on—yet.”

 

For questions or to read more stories from Chris Bennett (cbennett@farmjournal.com), see:

While America Slept, China Stole the Farm

Where's the Beef: Con Artist Turns Texas Cattle Industry Into $100M Playground

The Arrowhead whisperer: Stunning Indian Artifact Collection Found on Farmland

Fleecing the Farm: How a Fake Crop Fueled a Bizarre $25 Million Ag Scam

Truth, Lies, and Wild Pigs: Missouri Hunter Prosecuted on Presumption of Guilt?

US Farming Loses the King of Combines

Ghost in the House: A Forgotten American Farming Tragedy

Rat Hunting with the Dogs of War, Farming's Greatest Show on Legs

Misfit Tractors a Money Saver for Arkansas Farmer

Predator Tractor Unleashed on Farmland by Ag's True Maverick

Government Cameras Hidden on Private Property? Welcome to Open Fields

Farmland Detective Finds Youngest Civil War Soldier’s Grave?

Descent Into Hell: Farmer Escapes Corn Tomb Death

Evil Grain: The Wild Tale of History’s Biggest Crop Insurance Scam

Grizzly Hell: USDA Worker Survives Epic Bear Attack

A Skeptical Farmer's Monster Message on Profitability

Farmer Refuses to Roll, Rips Lid Off IRS Behavior

Killing Hogzilla: Hunting a Monster Wild Pig  

Shattered Taboo: Death of a Farm and Resurrection of a Farmer     

Frozen Dinosaur: Farmer Finds Huge Alligator Snapping Turtle Under Ice

Breaking Bad: Chasing the Wildest Con Artist in Farming History

In the Blood: Hunting Deer Antlers with a Legendary Shed Whisperer

Corn Maverick: Cracking the Mystery of 60-Inch Rows

Against All Odds: Farmer Survives Epic Ordeal

Agriculture's Darkest Fraud Hidden Under Dirt and Lies

 

Latest News

From Farm to Fire: First Soybased Fire Suppressant Hits the Market
From Farm to Fire: First Soybased Fire Suppressant Hits the Market

Since the 1950s, fire departments across the country have used products containing dangerous PFAS to put out fires. But the United Soybean Board has announced a greener alternative made from soybean meal.

Smartwyre Launches New Data Insight Tool
Smartwyre Launches New Data Insight Tool

Grower Compass is a web interface that uses past data to help retailers better understand their customers and business opportunities.

Ferrie: In Dry Soils, Is It Better to Use Anhydrous and Strip-Till or a Zone Builder?
Ferrie: In Dry Soils, Is It Better to Use Anhydrous and Strip-Till or a Zone Builder?

Based on fieldwork he's done so far, the farmer asks, “Am I drying out the soil early in what looks to be a dry year? Or, am I making the soil more fit so roots can go down as they should?”

Telus Explains Proagrica Acquisition, The Future of Digital Ag Platforms
Telus Explains Proagrica Acquisition, The Future of Digital Ag Platforms

As Chris Terris, VP and Global Head, Animal Agriculture & M&A Growth at Telus Agriculture & Consumer Goods, explains, this acquisition’s complexity led to how the integration unfolded. 

Skills Survey Reveals U.S. Agriculture & Food Industry Workforce Needs and Gaps
Skills Survey Reveals U.S. Agriculture & Food Industry Workforce Needs and Gaps

U.S. employers report challenges in finding suitable job candidates with work-ready skills to fill open roles in ag. The AgCareers.com U.S. Skills Survey offers insights, data and trends to address skill development.

Port of Baltimore Shuttered: What Does It Mean for Farm Equipment?
Port of Baltimore Shuttered: What Does It Mean for Farm Equipment?

A 95,000 gross ton container ship crashed into a pylon supporting the Francis Scott Key Bridge near the Port of Baltimore early Tuesday morning. The port is a main access point for automobile and farm equipment imports.