Dixie Dicamba Dilemma

Off-Target and Off-Label Herbicide Issues Arise

Pam Smith
By  Pam Smith , Crops Technology Editor
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Cupped soybeans are the first clue that soybeans have experienced injury from off-target movement of dicamba. (Photo courtesy of Aaron Hager, University of Illinois)

DECATUR, Ill. (DTN) -- Soybeans are very sensitive to dicamba and this summer is showing it. Damage complaints have been filed in several Southern states because of what appears to be off-target movement of dicamba herbicide onto sensitive crops.

The damage is also being connected with applications made in herbicide-tolerant crops that do not yet have a federally approved dicamba herbicide labeled for in-crop use. The situation could hold legal implications for errant applicators and bring additional regulatory scrutiny to a technology many farmers have been asking the Environmental Protection Agency (EPA) to sanction.

Seed companies repeatedly issued warnings that there would be no approved dicamba product available for use on the trait this growing season after EPA failed to label the product in May. However, dicamba herbicides are readily available in the marketplace. Growers that applied those herbicides are not only in violation of federal and state law, but the herbicide formulations currently available tend to be volatile and more likely to move off-target under summer conditions, according to university weed Extension specialists contacted by DTN.

"It looks like a bomb went off in some parts of the South," said Ford Baldwin, an independent weed consultant based in Arkansas. "Some growers returned dicamba soybeans when they learned the beans did not yet have clearance in the European Union (EU) and dicamba applications would not be legal. It's a good thing, otherwise we might have been facing Armageddon."

The EPA told DTN it "is aware of reports of illegal use of dicamba having caused damage to neighboring crops. We are working with state and other federal agencies to investigate these incidents."

Monsanto, DuPont Pioneer and various other seed companies sold dicamba-tolerant soybean and cotton varieties engineered to tolerate the herbicide after receiving U.S. approvals for the trait. However, EPA has yet to approve a dicamba-based herbicide to use in the Roundup Ready Xtend Crop System.

Tom Barber, a University of Arkansas weed scientist, issued a news release Thursday that estimated several thousand acres have been affected by either drift, volatility, temperature inversions or tank contamination from dicamba herbicide applications across the Midsouth.

The Arkansas Plant Board has received complaints, according to Susie Nichols, assistant director of the pesticide division. "Investigations are still ongoing, so I cannot confirm that dicamba was the cause of the symptoms yet," Nichols told DTN. Dicamba is labeled for application in crops such as corn and sorghum, and some sources told DTN they preferred to wait until investigations are complete before linking the damage specifically to Xtend crops.

In Tennessee, there are currently 19 complaint cases pending, said Corinne Gould, assistant commissioner for public affairs with the Tennessee Department of Agriculture. "All are in west Tennessee, in seven different counties. All relate to apparent drift of a pesticide onto soybean crops. We are currently preparing samples for analysis to determine what product(s) the soybeans may have been exposed to.

"If chemicals are found, we will follow up with the farmers who experienced crop damage and try to determine who applied the spray," she added. "That person or those persons would potentially face civil penalties and/or have their application permit modified, suspended or revoked." Fines vary from state to state. Representatives from Illinois and Georgia told DTN they have had no reports of damage filed.

University of Tennessee weed Extension specialist Larry Steckel confirmed he has received damage calls. "It has been often difficult to determine where the source of the damage is coming from," Steckel said.

Barber's release noted that this has been one of the worst years for Palmer amaranth in recent memory. Growers that planted Xtend soybeans were left with the equivalent of a Roundup Ready 2 Yield soybean. Glyphosate resistance coupled with the onset of PPO-resistant Palmer pigweed in these regions left growers in a bind, he noted. "Many growers I am sure felt they did not have a choice -- either spray dicamba or lose the crop," Barber said. He added that it appeared many fields of cotton and soybean containing Xtend technology were sprayed with an off-label application of dicamba either preemergence or postemergence or both.

"In addition, the improved formulations of dicamba that reduce volatility are not available, so any dicamba formulations that have been sprayed to these fields are ones that tend to be more volatile, which increases the potential for off-target movement. The result of these applications is damage on neighboring susceptible soybean and cotton fields that are not Xtend or tolerant to dicamba herbicide. Over the last two weeks, we have received more phone calls than we can count wondering what to do and what to expect once this injury occurs," Barber wrote.

Steckel noted in his recent newsletter that dicamba formulations available today can move off intended target areas under warm air temperatures. The herbicide turns into a gaseous state and moves into the air up to 24 hours after application. "Clarity and Banvel are designed and indeed labeled to be applied in March and April for burndown or to small corn," Steckel said. "The air temperatures during that time of the year are almost never warm enough to be conducive for volatility. They are not designed for use in June and July in Tennessee as 80- to 90-degree temperatures greatly increase the probability that these herbicides will move off the target and with a small breeze move on to a sensitive crop," he said.

Steckel added that soybeans in the vegetative stages that receive a small amount of drift have more time to recover and often will see little yield loss if good growing conditions occur the remainder of the season. Soybeans in the reproductive stages have a higher chance of seeing significant yield loss.

Monsanto and DuPont Pioneer would not speculate on current field situations, but both companies provided statements to DTN that emphasized that, until approved by the EPA, it is against the law to use any dicamba herbicide in-crop with Roundup Ready 2 Xtend Soybeans and Bollgard II XtendFlex Cotton. "Over the past several years we have implemented a robust communication plan with multiple touch-points to remind licensing partners, growers, dealers and members of the industry that no dicamba products are currently approved for in-crop use with Roundup Ready 2 Xtend Soybeans or Bollgard II XtendFlex Cotton," said Kyel Richard, Monsanto product communications lead.

Baldwin said the big question now is what happens to this technology from here. "It's too bad. Agriculture needs tools and we're under a microscope by regulatory authorities and the public to do this right," he said.

Read Larry Steckel's post on dicamba injury to soybean here: http://bit.ly/…

Read Tom Barber's post on dicamba drift and potential effects on soybean yield here: http://bit.ly/…

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

Follow her on Twitter @PamSmithDTN

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Pam Smith