Dicamba drift complaints up sharply this season

dicamba injury
Suspected dicamba drift onto soybeans—photo courtesy University of Arkansas

Dicamba drift complaints are up sharply this year compared to 2016 in Arkansas, with 117 having already been logged with the Arkansas State Plant Board as of June 19.

Jason Bond, a weed Extension specialist at Mississippi State University, also is seeing his share of dicamba drift onto soybeans in that state, according to photos he has tweeted.

The Arkansas Plant Board plans to take up the subject at a specially called meeting 1:30 p.m., June 20, in Little Rock. If passed, Gov. Asa Hutchinson would have to approve the measure. On June 16, the board’s Pesticide Committee recommended an emergency regulation to stop all in-season dicamba sales and applications.

The Arkansas complaints came from 15 counties, with all but one of the counties in the eastern part of the state.

Among the damaged fields in Arkansas are about 100 acres of soybeans in University of Arkansas research plots at the Northeast Research and Extension Center at Keiser, according to a university news release.

Ironically, those plots were part of research by Division of Agriculture weed scientist Jason Norsworthy on dicamba drift and volatility.

The dicamba drift and volatility trials, for herbicides from Monsanto and Syngenta, are needed before the products can be registered for use in Arkansas, Norsworthy says. The damage from unexpected dicamba drift interrupted the trials, making Norsworthy’s data useless in most of the plots unless he replants and starts over.

Nearly 100 acres of the plots will be replanted. Forty acres of Xtend soybeans — varieties from Monsanto genetically engineered to tolerate dicamba — were undamaged by the drift.

Soybean varieties that don’t contain the Xtend genetic trait are highly sensitive to dicamba.

“As we have seen in our research, a very low rate of dicamba can cause soybean leaves to cup,” University of Arkansas weed scientist Tom Barber said in the release. “There will not be any yield loss at this low of a rate, but you will see the symptoms on the beans.”

More information on Barber’s research on dicamba drift and its potential effects on soybean yield can be found at http://www.arkansas-crops.com.

Additional safeguards

Because of the herbicide’s potential for drift, the Arkansas Plant Board last year implemented additional safeguards. Only Engenia, a BAPMA dicamba formulation from BASF, can be applied inseason over the top of Xtend soybeans and XtendFlex cotton. Even then, applicators or anyone spraying dicamba must first undergo training and successfully pass an applicators’ exam.

The state banned the use of DGA-based dicamba, which includes Monsanto’s XtendiMax and DuPont’s FeXapan, after April 15. Both contain proprietary VaporGrip technology, designed to reduce volatility.

In addition, the plant board also restricted application to certain weather conditions. According to an Arkansas state label, Engenia can only be applied when winds are less than 10 mph, a reduction of 5 mph from the federal label.

The plant board requires a 100-foot buffer around any field where dicamba is applied and a 0.25-mile buffer between the field and sensitive crops located downwind.

Barber says the increased drift complaints are partly because more farmers are using Xtend soybeans and cotton with dicamba this year to combat glyphosate-resistant pigweed.

“Nearly all cotton and a significant percentage of soybeans in Arkansas are Xtend varieties this year,” Barber says.

Extension soybean agronomist Jeremy Ross said he doesn’t have hard numbers but would estimate about 40 percent of Arkansas soybean fields are planted with Xtend beans.

The highest percentage of those Xtend soybeans likely are in northeast Arkansas, where many growers are dealing with glyphosate- and PPO-resistant pigweed.

Barber says that area is also where most of the dicamba drift complaints are originating.

Beyond northeast Arkansas, Ross says, there are pockets of growers using Xtend technology, mostly in cotton growing areas.

“The farmers want to use one technology,” Ross said. “If a farmer has Xtend cotton, he’s more likely to use Xtend soybeans so that he doesn’t have to worry about switching herbicides.”

Barber says a number of other factors also are contributing to increased dicamba drift complaints.

The weather may have had something to do with at least some improper applications, he says.

“Bad weather makes it very difficult to get in the fields and make proper applications,” Barber says. “A lot of farmers or applicators may have sprayed in conditions that were not ideal for spraying, but were ideal for drift, but we rely on the Plant Board to make these final determinations.”

Because of high winds during the day, Barber says he had heard that some chose to spray at night when winds stopped. But temperature inversions are common when there’s no wind at night, holding the volatile spray above the canopy. Drift can then occur when wind returns in the morning.

“I believe that physical drift accounts for at least 80-90 percent of all the dicamba injured fields that I have walked and observed patterns of injury,” Barber says.

Although improper application may account for much of the reported dicamba drift, Barber says most farmers and applicators are following the regulations and applying dicamba properly.

Even so, he says 10-20 percent of the injury has occurred even when everything appears to have been done correctly.

“These are the fields that have me scratching my head wondering how on earth the dicamba symptoms appeared a quarter mile upwind from the reported application.”

What to do if you suspect drift

“The first thing you should do if you suspect dicamba injury from off-target movement is call the Arkansas State Plant Board,” Barber says. “This will provide an official record of the complaint.”

There is nothing that can be done or sprayed on the soybeans once the injury has occurred to help reduce potential yield losses, he says. It can take up to three weeks before full symptoms of dicamba drift are seen.

Norsworthy says damage done early in the plant’s growth cycle will have little effect on yields.

“But when you get dicamba on them around flowering, our research shows some damage to yields, depending on growth stage,” he says.

The Arkansas Agriculture Department has a webpage devoted to dicamba updates on affected areas, news, situation updates and frequently asked questions: http://www.aad.arkansas.gov.

 

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