Dicamba Deja Vu

State Regulators Brace for Another Year of Dicamba Injury

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
Connect with Emily:
EPA promises that soybean injury won't be the only type of dicamba damage on the radar of the agency this summer, as state regulators brace for a third year of off-target movement. (Photo courtesy of Aaron Hager)

ALEXANDRIA, Va. (DTN) -- State pesticide regulators are responsible for overseeing a lot of chemicals, but some expect to police only one this year -- dicamba.

"So many resources are dedicated to dicamba that it has made my program a one-issue program," said Tim Creger, a pesticide regulator with the Nebraska Department of Agriculture. As his agency has spent the past two years investigating roughly 200 complaints of off-target dicamba injury, they have had to delay or abandon routine pesticide inspections, Creger told regulators, scientists and agrichemical companies gathered for the annual meeting of the Association of American Pesticide Control Officers in Virginia this week.

"We have a lot of other [pesticide regulation] problems -- I've had to push those off for two years," Creger said. "Other issues that don't have the priority this product has are not getting the service they deserve. And that's what it looks to me again coming up in 2019 -- it's deja vu."

The meeting organizers devoted nearly a quarter of the annual conference to discussing the causes and effects of off-target movement of the dicamba formulations Engenia, XtendiMax and FeXapan the past two years, as well as expectations for 2019.


With 60 million acres of dicamba-tolerant Xtend crops expected this spring, many soybeans and cotton fields will be protected from damage from dicamba drift and volatility, noted Dan Kenny, herbicide branch chief for EPA's Office of Pesticide Programs. "We don't want that to create a false positive," he said. "We want to focus not just on [soybean] acres this year, but also other crops that might be sensitive ... and also focus on effects on perennial crops. Vineyards, orchards, things like that."

Several state pesticide officials assured Kenny they expect the federal agency to get plenty of data on dicamba injury this year. "We don't have an apparent end in sight," Creger said of off-target dicamba movement. "And I'm not alone in this -- it just seems like there is no end in sight to the problems this will generate for us."

Leo Reed, pesticide licensing manager for the Office of Indiana State Chemist, agreed. For two years in a row, Indiana has fielded record numbers of dicamba injury complaints. The OISC spent $1.2 million in 2018 alone investigating dicamba injury claims. The agency's laboratory is still processing injury claims from 2018 and is braced for more. "How long we can sustain that is anybody's guess," Reed said. "This devalues our agencies in as much as it's literally all we've done for the last two years. Routine inspections have plummeted."


Kenny said EPA believes the new labels the agency released in October 2018 will help address some of the ways dicamba formulations move off target. His point was undercut by state regulators and academics, who criticized the labels' language and enforceability.

"It's extremely difficult to make a legal application," said Bryan Young, a Purdue University weed scientist, who presented his dicamba research at the annual meeting. Even many researchers and pesticide manufacturers found it nearly impossible to conduct on-label applications last year for their field trials, Young noted.

"I tried three times and I failed three times," Young said of his large-scale field trials on dicamba volatility last year, which -- like many dicamba research trials -- came in under the labeled wind speed minimum of 3 mph. Purdue University researchers estimated that Indiana applicators only had a handful of days to spray dicamba legally in June of 2017 and 2018.

Now, even as applicators face more acres of dicamba-tolerant crops to spray than ever before, those spray windows will tighten even more this year, thanks to new restrictions on the re-registered dicamba formulations.

Those new restrictions can be confusing, added Reed. "This is the most scrutinized label in the history of the agency, other than maybe fumigants," he said. "And yet we're still finding amazingly poorly written label language."

For example, research indicating certain tank mix ingredients, in particular glyphosate, lower the pH of a dicamba spray solution and increase volatility led EPA to add a label clarification. But that section of the label merely tells applicators to consult experts, such as agricultural consultants or Extension agents, for recommendations to increase pH in their spray mixtures.

These people do not have answers for growers, Young said. "My weed science community doesn't know what to recommend to alter the pH," he said. "Right now, I can't educate you on how you can adjust the pH up and still kill weeds."


The dicamba sessions at AAPCO did have some bright spots. Ping Wan, a laboratory supervisor at OISC, presented research on how she and her team are learning to analyze a wide range of dicamba residues with increasing accuracy. One of her primary findings has been that testing for additional tank mix partners, such as glyphosate, improves a laboratory's ability to pinpoint the time of a dicamba application and source of the injury.

Moreover, Dan Kenny of EPA said the agency is learning from its challenging rollout of dicamba-tolerant technology. The agency is currently requiring registrants to conduct field trials on how various environmental conditions affect the volatility of new formulations of dicamba this year -- and those tests will be required of any future dicamba products, Kenny said.

"We're learning from what we've got today, and we're making this a must-do requirement for anybody else," Kenny told DTN. "For example, we've had other dicamba premixes that have come in years ago, that are pounding on the door to get registrations. Everything that we've learned here, we're adding to what we need for those [to be registered]."

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

Follow her on Twitter @Emily_Unglesbee


Emily Unglesbee