Digging Into Dicamba Rules

Here's What We Know About the New Dicamba Rules So Far

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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The new dicamba regulations will limit over-the-top dicamba applications on soybean fields to 45 days post-plant. (Photo courtesy of TeeJet)

ROCKVILLE, Md. (DTN) -- EPA has extended the registration of three dicamba herbicides, XtendiMax, FeXapan and Engenia, for use over-the-top of soybeans and cotton through the 2020 growing season.

EPA has not yet released the dicamba labels, but the agency published a press release that shed some light on changes in the use of these restricted use pesticides, from applicator certifications to spray cutoffs and new buffer requirements.

We dig into those new rules here, starting with the question of whether states will actually be able to add more restrictions to these dicamba labels in 2019.


Weed scientists from Iowa, Missouri, Tennessee and Indiana expressed disappointment in the new federal restrictions on spraying dicamba, and many said additional state restrictions would be necessary to reduce off-target damage in 2019.

In the past, states have used section 24(c) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), to pass more-restrictive state rules on federal pesticide labels. However, this practice is coming under some scrutiny by EPA, because the actual FIFRA language may not support it, state regulators told DTN.

"What we've heard is that the purpose of Section 24(c) is to allow additional uses of a federal pesticide, as opposed to restrict uses," said Leo Reed, AAPCO board director from Indiana. "And states have been using it to restrict federal labels, and EPA is leery of continuing that process."

Without 24(c) as an option for restricting federal pesticides, states would have to turn to their own internal rulemaking process to alter the use of these dicamba herbicides, Reed explained.

Unless a state has an emergency authority to pass a new rule quickly, this process can be extremely time-consuming. In Indiana, for example, passing a rule to restrict dicamba use beyond the federal label would take at least a year. No changes would be in place for the 2019 season, Reed noted.

In an emailed statement, EPA said told DTN that it wants to work with states, using 24(c) if necessary. "If a state wishes to modify the over-the-top labels for dicamba in order to better meet their state's circumstances, EPA will work with them to support their goals," the agency said.

See a full DTN story on the 24(c) topic here: https://www.dtnpf.com/….


The new federal dicamba labels will limit spraying the herbicides from one hour after sunrise to two hours before sunset -- a provision aimed at limiting applications during temperature inversions.

This is similar to the time-of-day restrictions passed in some states last year, such as Missouri's 7:30 a.m.-to-5:30 p.m. spray limit. While it may cut down on inversion-related off-target movement, it will also whittle away at the number of legal spray hours available to applicators, noted Bill Johnson, a Purdue University weed scientist.

The new labels will also ban over-the-top dicamba applications 45 days after planting in the case of soybeans, and 60 days after planting for cotton. These restrictions are an effort to "stay out of the heat of the summer when the volatilization is most likely to occur," EPA Region 7 Administrator Jim Gulliford told DTN.

But, in Iowa, where on average 51% of soybean planting is done by May 20, that would allow dicamba applications well into the month of July, Hartzler noted. "In 2017, 90% of dicamba misuse complaints to [Iowa's Department of Agriculture and Land Stewardship] were associated with applications made after June 15," he said.

Double-cropped soybeans planted in June or July would also make the 45-day restriction unlikely to limit late-summer spraying, said University of Missouri weed researcher Kevin Bradley.

The cutoff dates will likely be hard to enforce, added Purdue's Johnson. "People can just lie about planting date to escape that one," he said.

The rules also limit Xtend cotton growers to two over-the-top dicamba applications, down from four in 2018. This could cut dicamba use slightly, said University of Tennessee weed scientist Larry Steckel. He estimates cotton growers in the state sprayed two to three times on average in 2018.


For 2019 and 2020, only individuals who have been certified by their state to use restricted use pesticides (RUP) will be able to spray, mix or load dicamba.

"The [previous dicamba label] allowed for individuals to make RUP applications if they're not credentialed, as long as they were operating under the supervision of fully certified applicators," Reed explained. "What they've done with this now is require that you must be fully certified to make the application."

Both Iowa's Hartzler and Tennessee's Steckel expressed doubt that sprayer certification would make much of a difference in off-target movement. In 2018, Tennessee Department of Agriculture spot checks found that most applicators in Tennessee were operating while properly certified and on label, Steckel noted. "But we still had problems," he said of the state's 50-plus dicamba injury complaints.

"In 2017, the breakdown of applicators responsible for misuse complaints in Iowa from dicamba on Xtend soybean was 22%, 40%, and 38% for certified commercial, certified private, and uncertified private applicators, respectively," Hartzler added in his blog. "... These numbers don't suggest the classification of applicator has a big influence on the likelihood of off-target movement."

EPA also promised to make training requirements consistent among the three different herbicide products.


All postemergence applications of dicamba herbicides in 2019 will require a 110-foot downwind buffer. In counties "where endangered species may exist," applicators will also have to abide by a new 57-foot buffer around the other sides of the field.

Missouri's Bradley said he was already compiling lists of the counties in the state that had endangered species listed, but the EPA's phrasing has muddied the process.

"I've already started looking at endangered species in Missouri, but I don't know how to figure out if an endangered species 'may exist' in a county," he said. Johnson expressed concern that these buffers will be just as hard to enforce as original buffers were in 2018.

"How do you prove they did it wrong?" he said. "They will overburden regulatory agencies with that one."


This summer, AAPCO sent EPA some recommended changes, few of which are reflected in the newly published dicamba rules. Specifically, the group asked for a one-year registration, an "early-season" cutoff date, financial assistance for overwhelmed state regulators and more enforceable labels.

None of these changes are reflected in EPA's most recent dicamba rules, except perhaps the last one. The agency stated that the new dicamba registrations will feature "label clean up and consistency to improve compliance and enforceability."

"That's huge -- we really want to see what that means and what changes have been made," AAPCO's Reed said. Other mysteries include an EPA reference to "an enhanced label to improve applicator awareness on the impact of low pH's on the potential volatility of dicamba."

That could refer to tank mix instructions, Bradley and Steckel noted. "It's becoming established fact that spray tank pH influences volatility," Bradley said.

For now, state regulators are in wait-and-see mode, Reed added. "The bottom line is, without being able to dive into the labels and determine what's been changed, it's almost impossible to form a solid opinion on whether we're pleased, displeased or neutral on these changes," he said.

See the EPA dicamba registration announcement here: https://www.epa.gov/… and its rules on dicamba training here: https://www.epa.gov/….

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

Follow her on Twitter @Emily_Unglesbee


Emily Unglesbee