As Dicamba Dust Settles, Scientists and Industry Spar

By Tiffany Stecker

Arkansan soybean farmers are wrapping up a summer of harvesting bumper crops alongside the crippling devastation of their neighbors’ fields. The same herbicide is causing both optimism and bitterness in the region, and discussions over its future use is dividing farmers, scientists, and industry.

Dicamba, a weedkiller first registered in 1967, has undergone a makeover to fight weeds immune to most herbicides. BASF Corp., Monsanto Co., and DuPont this year stocked new versions of dicamba, designed for use with Monsanto’s soybeans and cotton that are genetically-engineered to withstand the new herbicides. But the herbicide spread easily to neighboring farms, falling on vulnerable crops.

This summer was one the best growing seasons in years for Arkansans in terms of controlling insidious weeds that creep into fields. It also was a year of unusual harm to nearly a third of the state’s soybean crops, marked by curled leaves, stunted growth, poor yields, and J-shaped pods that have been tied to new formulations of the herbicide.

What was a blockbuster year for many growers cost others millions of dollars, pitting farmer against farmer and scientists against the herbicide’s manufacturers.

State university scientists believe the new formulations can’t be managed to control the damage. They easily evaporate, or “volatilize,” and can spread potentially thousands of feet over a couple of days into a neighbor’s field.

“As a weed scientist, I can’t tell you how to fix this problem,” Jason Norsworthy, an extension scientist with the University of Arkansas told a group of farmers and industry representatives Aug. 17.

The manufacturers are loathe to blame volatility, saying the herbicides were studied extensively before their launch earlier this year. The damage, they say, could be due to errors in applying the herbicide, poorly written instructions, and generally weak control of physical drift—the travel of liquid droplets of dicamba via wind or weather patterns.

To avoid a repeat of the disaster next year, Arkansas’ Plant Board convened a task force of growers and trade association representatives to craft recommendations on the spraying of dicamba.

On Aug. 24, the task force agreed to develop preliminary recommendations for the Plant Board to send to the governor. The panel suggested that the Plant Board impose an April 15 cut-off date for spraying the chemical and thereby prevent spraying in the hot summer months. The cut-off date also effectively would bar use of the herbicide for many farmers, given that most of the soybean planting happens in May.

The task force will incorporate the recommendations in a formal report due in the next three weeks. If implemented by the Arkansas Plant Board, the recommendations will drive hundreds of farmers’ decisions next year. A compromise between those who have gained from the new dicamba and those who have suffered won’t be easy. Farmers in Arkansas have been clamoring for solutions to their weed problems for years, and are feeling the pressure of declining grain prices that can threaten the viability of their farm operations in just one season.

Grasping for Solutions

“It’s something that we desperately need to control the weeds,” Justin Blackburn, a 33-year old, eighth generation soybean and corn grower in Northeastern Arkansas, told Bloomberg BNA. “We’re grasping for anything that works.”

Hundreds of thousands of soybean acres, plus trees, vegetables crops, and flowering plants that feed honeybees, have shriveled this year as the new product for killing weeds came on the market. Soybeans are particularly sensitive to dicamba. The only crops that are safe are Monsanto Xtend seeds that are genetically engineered to withstand the herbicide. About 35 percent of the soybeans planted this year in the state are Xtend crops.

“We’ve got some serious issues we’ve got to address,” Wes Ward, the state’s Agriculture Secretary, told Bloomberg BNA. “We’re hoping that this task force…can try to nail this down a little better.”

In preparing its recommendations, the 19-person panel must consider conflicting information from university researchers and the manufacturers of the new herbicide.

Manufacturers hailed new formulations as a cure for stubborn weeds that suffocate crop yields. The aptly-named pigweed—also called palmer amaranth—began to resist applications of the widely-used weedkiller glyphosate after the turn of the 21st century. Weeds also have developed resistance to another class of herbicides called protoporphyrinogen oxidase (PPO) inhibitors. Resistant weeds can cut yields by up to 91 percent in corn and up to 79 percent in soybean, according to Purdue University Extension.

The new products were made to be less prone to evaporate and spread to neighboring fields than the dicamba of the past. But starting in late May, complaints began to mount. Dozens of calls to the Plant Board turned to hundreds. To date, 950 complaints have been filed.

The State Plant Board voted to ban spraying of dicamba in crops on June 23. As of Aug. 10, an estimated 900,000 acres of Arkansas soybean fields have been allegedly damaged by dicamba, according to state extension scientists, about one-third of the total soybean damage for the nation as a whole.

Ground Zero

Dicamba works by mimicking plant hormones that make weeds grow abnormally and eventually die.

More than 2,200 reports of dicama injury, affecting more than 3 million acres of soybeans, are being investigated nationwide, according to the University of Missouri’s Integrated Pest Management program. Northeastern Arkansas is ground zero for the damage.

In Mississippi County, a sprawling horizon of soybean and cotton fields one hour northwest of Memphis, Tenn., 240 dicamba misuse complaints were filed this year—one quarter of all of the complaints in the state.

David Wildy, a task force member who pushed for an April 15 cutoff date for spraying the chemical, is one of the most vocal critics of the new formulations. A silver-haired grower of soybeans, corn, and other crops from Manila, in the northeastern part of Arkansas, he’s earned awards for his high production, management style, and outreach to the agricultural community.

Earlier this season, Wildy estimated his loss from soybean damage to be a little shy of $1 million, injury that is not covered by federal crop insurance or private insurance unless a neighbor admits to spraying dicamba and agrees to cover the loss with liability insurance.

“This technology is driving a wedge between farmers,” he told Bloomberg BNA.

Arkansas was the only state of 34 not to approve XtendiMax for use, despite allowing farmers to plant Extend seeds that can withstand applications of dicamba. The Plant Board denied XtendiMax’s approval because university scientists were not able to do independent tests, particularly under local conditions, Arkansas Agriculture Department spokeswoman Adriane Barnes told Bloomberg BNA in an email. This dampened their confidence in the product.

In A Pickle

Monsanto’s vice president of global strategy Scott Partridge said the refusal to approve the use of Xtendimax drove farmers to use older versions of dicamba not suitable for use with the company’s genetically-modified seeds. It’s no surprise that Arkansas has fared the worst in the dicamba crisis, Partridge told Bloomberg BNA.

“I can understand why Arkansas is scrambling,” he said. “I think they got themselves into a bit of a pickle.”

Some states that have seen little to no problems with dicamba, a pattern BASF attributes to more in-person training. Arkansas Agriculture Secretary Ward told Bloomberg BNA that his state relied on the protocol for Mississippi, which did not require face-to-face training.

On a press call Aug. 17, BASF pointed to the in-person training in states like Alabama, North Carolina, and Georgia as a likely reason for fewer complaints in those states.

“We do recognize differences in agriculture around the country, but we shouldn’t be quick to discount the value of in-person and face-to-face training,” Scott Kay, vice president of U.S. Crops forBASF, said. “We do believe that’s an important contributor to their reduced numbers of alleged complaints coming from those states.”

But Norsworthy said those differences could be attributed to different agricultural systems, like smaller fields and forests interspersed with farmland.

In that county, a farmer was shot and killed after a dispute with a dicamba-spraying neighbor last year. At the time, Xtend seeds were legal, but the Environmental Protection Agency had not yet approved the new versions of dicamba, leading to widespread “off-label” use. It is illegal to use older versions of dicamba on the genetically-engineered plants.

This year was supposed to be different. The EPA approved the new formulations last November, more than a year after the Agriculture Department allowed for Monsanto’s Xtend seeds to go on the market. But this year’s calls to the Arkansas Plant Board have far outpaced last year’s 33 complaints, 23 of which were confirmed to be dicamba injury.

Record Soybean Crop

The crisis won’t lead to a national soybean shortage. On the contrary, the U.S. is set to break its soybean record this year, and Arkansas is expected to produce 400,000 more acres than in 2016, with a slight increase in yields per acre, according to USDA. Monsanto Chief Technology Officer Robb Fraley said Aug. 29 that the company is planning to supply enough Xtend seeds for up to half of the U.S. soybean acreage for next year’s growing season.

But that gain comes at a significant cost, Wildy said. Sycamore trees are wilting. Tomato plants are wiped out. Wildy needs and wants the technology. But if this is the price of progress, he says, it’s not worth it. Non-agricultural plants—from ornamental trees to flowers that feed honeybees—have been affected too.

“When the general public gets involved, to me that’s very serious,” he said, referring to the broader number of groups affected.

Wildy planted about 300 of his 3,300 soybean acres with Xtend seeds this year. He said he will plant more next year as a protective measure if the state Plant Board allows continued use. Farmers pay about $8 more per acre for dicamba-resistant beans than for LibertyLink seeds, Bayer AG’s technology that matches glufosinate-tolerant crops to a new version of the herbicide glufosinate—another result of farmers’ clamor for tools to beat weeds.

Arkansas farmer Blackburn tends to 1,700 acres with his brother in Greene County. Last year, he was hit with a wave of dicamba that damaged his soybeans. This year, he went on the defense. The brothers planted every acre of their soybeans to be dicamba-resistant. It was an extra expense, he said, but worth it. It worked wonderfully until late June, when the state imposed its ban.

That bothers Blackburn. This new technology has brought benefits to farmers, and smearing the formulations with a broad brush means a step backwards.

“We followed all of the regulations, all of the guidelines,” he said. “They’re sort of making it out to be that everybody who sprays this stuff is an outlaw, is a criminal.”

Still, Blackburn thinks the product is “flawed” because it’s been so easy for farmers to misuse.

An April 15 cutoff wouldn’t work for Blackburn, who spends that month planting corn and begins sowing soybeans in May.

‘This Is A Product That Is Broken’

The task force meetings on Aug. 17 and Aug. 24 were held at the Winthrop Rockefeller Institute, atop the fog-covered Petit Jean Mountain north of Little Rock. Named after the state’s Republican governor who pushed for civil rights and prison reform in his state, the resort-like stone lodge serves as a neutral outpost to discuss the region’s most pressing matters, from rural healthcare to agricultural trade with Cuba.

The dicamba matter may be the most contentious issue addressed there yet. Norsworthy gave an hour-long presentation to the audience of about 50 at the Aug. 17 meeting, summarizing a number of his field studies on the new dicamba formulations.

In one experiment that was replicated by scientists at the University of Tennessee, Norsworthy covered certain soybeans with buckets in a field where he sprayed XtendiMax (Monsanto’s dicamba herbicide) and Engenia (BASF’s new formulation). He removed the buckets 30 minutes after spraying, and soon after, the plants exhibited the telltale signs of dicamba damage. Had it been drift, the weedkiller would have moved away from the areas in minutes, Norsworthy said.

In another trial, Norsworthy sprayed two 3.5 acre plots with Engenia and XtendiMax each, with wind traveling 2.9 miles per hour. Though applied well below the label instruction limit of 15 miles per hour, the herbicide traveled more than 300 feet. With field sizes in the thousands of acres, a real life situation could see dicamba travel well beyond the state’s quarter-mile buffer zone, he said.

His conclusion: When it comes to volatility, there’s no buffer big enough, no nozzle spray fine enough, no wait period long enough, to control the movement. Drift can be controlled by the type of nozzle, by the boom height, and by refraining from spraying at times of high wind speed and at certain times of the day.

The distinction between drift and volatility is important. Regulations and label instructions on its use can control physical drift. Volatility is uncontrollable, Norsworthy said.

“This is a product that is broken,” he told the task force Aug. 17.

Those findings bristled the handful of manufacturer representatives present, who had just a few minutes to defend their new herbicides. The presentation, they said, would taint farmers’ opinions of the product and bring on hasty recommendations to restrict a necessary tool for clearing weeds.

“I wasn’t happy with the process,” Dan Westburg, a BASF technical services manager with a doctorate in weed science, told Bloomberg BNA at the meeting.

Companies worked hard to suppress this in their new formulations. Monsanto’s proprietary VaporGrip technology was developed specifically to reduce volatility by preventing the formation of dicamba acid in a solution.

Perry Galloway, a farmer in Northeastern Arkansas and proponent of the technology, agreed that a presentation from only the extension scientists was “biased.”

‘Dicamba Is Heavier Than Air’

The companies brought their concerns to the Arkansas Plant Board. A week later at the second task force meeting, Monsanto deployed three scientists to defend their data. BASF had one presentation.

Monsanto has conducted extensive volatility studies since 2009, company scientists said at the Aug. 24 meeting. Those studies, mostly done in closed enclosures called humidomes, show that dicamba concentration in the air drops dramatically in the first day, meaning it can’t volatilize and travel far.

“Volatility does occur, it absolutely occurs, but the amount that occurs will happen very quickly in 24 hours,” Ty Witten, North America Crop Protection Systems Lead for Monsanto, told the participants. “Dicamba is heavier than air, it’s going to fall over time.”

Can dicamba drift? Yes, said Witten, maybe by 40 or 100 feet. But not by half a mile or ten miles, as some have suggested.

Tom Mueller, a professor of weed science at the University of Tennessee Institute of Agriculture, challenges this 24-hour claim from Witten in recent trials. He found that dicamba concentrations in the air can shoot back up the day following an application after dipping overnight.

Mueller has repeated this trial several times. “It always follows the same pattern,” he told Bloomberg BNA.

Mueller attributes the increase in concentrations to higher temperatures the following day rather than in the evening. Heat drives volatility, and researchers link the dicamba problems to a relatively new phenomenon in its use. Older formulations were applied only on corn in the cooler temperatures of early spring, he said, whereas the new versions are being sprayed in 90-degree June weather.

The EPA ultimately will decide the herbicide’s future. The agency gave companies a provisional two-year registration for the herbicides in 2016 and it is investigating the complaints and meeting weekly with Arkansas and other states affected via teleconference.

The underlying causes of the various cases of damage are not yet clear, EPA spokesman Robert Daguillard said, “but EPA is reviewing the available information carefully.”

If the EPA revokes the registration, or imposes greater restrictions, on use of the herbicides, they would not go into effect until the 2019 growing season. That leaves another year of rising tensions in the Heartland.

To contact the reporter on this story: Tiffany Stecker in Washington at

To contact the editor responsible for this story: Rachael Daigle at

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