Dicamba Details - 1

Decision Time for Dicamba

Spray applicators face a long list of restrictions if they plan to spray dicamba herbicide this spring. (DTN photo by Pamela Smith)

DECATUR, Illinois (DTN) -- There is no easy button for dicamba applications.

Not only was training made mandatory for use of new dicamba formulations in 2018, but the Environmental Protection Agency (EPA) also severely tightened spray requirements in an attempt to avoid the off-target movement experienced last spray season.

While controversy has swirled around whether these label requirements are adequate, or even logistically possible, some fundamental facts exist:

-- Farmers will have access to in-season use of dicamba in soybeans and cotton. Some states have set specific calendar and/or temperature cutoffs.

-- The future use of these products rests in the success or failure of the 2018 spray season. EPA registrations for Engenia, FeXapan and XtendiMax expire this fall.

That means the pressure is on for spray applicators to do everything they learned during training when they finally reach the field. As a refresher, DTN has compiled a series of articles that will run over the next few days called "Dicamba Details."


In February, Grant Rowland, with EPA's Registration Division, told those attending the Weed Science Society of America (WSSA) annual meeting, that the agency edited existing label recommendations after identifying five major ways dicamba movement led to injury symptoms in 2017. With this series of articles, we dig into the details behind those categories, which include:

-- Physical drift -- the physical movement of relatively small spray particles during spray application.

-- Tank contamination -- pesticide residue left in sprayer components or not rinsed properly following previous loads.

-- Misuse -- use of illegal high volatility formulations or mistakes such as adding the wrong additive to the tank.

-- Temperature inversions -- when a cool air mass becomes trapped near the ground and suspends herbicide particles until the air warms and disperses.

-- Volatility -- the movement of a herbicide as a gas or vapor after a spray application hits its target. It results from molecules of the chemical vaporizing from the surface of the plants or soil into the air.

Managing the details behind each of these categories is no small effort. Larry Steckel, University of Tennessee extension weed specialist, came up with a list of more than 20 steps spray applicators must carry out to make a correct post-emergence application of dicamba in soybean and cotton in his state this year.

"I think everyone can now safely stop comparing the Xtend technology to anything else we have previously experienced," said Steckel. "We've never had a label like this to follow."


Farmers are also being urged to put aside petty differences over whether the symptoms experienced in 2017 resulted in actual yield damage.

"I'm not sure we know the extent over overlapping dicamba injury yet and every year is going to be different. We are going to have more acres of Xtend crops in Tennessee this year," Steckel said. "What I do know is that everyone is now watching and every curled up, puckered up plant is going to likely be blamed on dicamba -- right or wrong.

"This is not a wholly agricultural issue at this point," he added.

"I assure you, concerned groups are watching us," Illinois Fertilizer and Chemical Association director Jean Payne has said repeatedly.

"If dicamba on soybean is not carefully managed in 2018 to reduce off-target movement, there is a high probability that USEPA will cancel these labels," Payne said.

"Furthermore, there's a strong possibility that in subsequent years, the potential misuse of other dicamba products on soybean could threaten the use of dicamba in all crops."

Pesticide use in the U.S. hinges upon the premise that the pesticide label will be followed by the applicator. The failure to do so not only threatens a valuable agriculture herbicide, but it could also open up all pesticide use policies for review.

The devil is in the dicamba details. Review your training received this winter before you sit in the sprayer. Do your diligence. It's this simple:

If you aren't willing to follow the label, don't use the product.

Continue to check for up-to-the-minute label changes on the three dicamba herbicides on the following websites:





Editor's Note: A number of suppliers and herbicide companies are offering weather-monitoring apps or software to help growers plan ahead for days least likely to have off-target movement. DTN subscribers can access the DTN Spray Outlook app from the Weather area of MyDTN or, if they are a weather network participant, from their weather dashboard.

Pamela Smith can be reached at Pamela.smith@dtn.com

Follow her on Twitter @PamSmithDTN