Dicamba drift problems continue in farm states

Fewer instances of dicamba drift onto non-target crops are being reported this year in the United States, but it continues to divide agriculture community

Aaron Hager has seen many changes in American agriculture in his 25 years at the University of Illinois. As an extension specialist and weed scientist, he saw the introduction and controversy around genetically modified crops and the emergence of herbicide resistant weeds.

But nothing compares to the battle and nastiness over the last 12 months in rural Illinois, all because of the dicamba herbicide.

Why it matters: The evolution of the introduction of dicamba resistant crops will provide lessons for the introduction of future herbicide-resistant crops.

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“It’s done things to agriculture that I’ve never seen done before,” said Hager from his office in Urbana, Illinois.

“It’s created divisiveness in the farming community in this state like I’ve never seen in the (years) that I’ve been here.”

In Ontario, by comparison, there have been some, but many fewer dicamba drift issues, due to a strong local campaign to encourage farmers only to use dicamba pre-plant.

Last year was a chaotic growing season for soybean growers across the United States, but particularly in Illinois, Missouri and Arkansas.

In 2017, American farmers planted about 25 million acres of Xtend soybeans, a Monsanto technology in which beans are tolerant of glyphosate and dicamba herbicides.

On a portion of those acres, farmers sprayed older versions of dicamba or new formulations that were supposed to be less volatile. Herbicide volatility is when the herbicide converts to a gas and moves from the application site to another field.

University of Missouri estimates suggest that 3.6 million acres of soybeans suffered off-target damage from the use of dicamba, and there were 2,700 complaints of damage across the U.S.

Drift of dicamba and volatility injured soybean fields that didn’t have the Xtend trait. The off-target damage also affected horticultural growers in the U.S., injuring fruit crops, vegetables and nursery trees.

Dicamba can cause severe damage to soybean crops.
photo: PBouman/iStock/Getty Images

In response to the problems of 2017, the U.S. Environmental Protection Agency introduced several label changes to dicamba:

  • Spraying is permitted only when wind speeds are below 16 km-h.
  • Dicamba-specific training is required for all certified applicators.
  • Dicamba can be applied only during daytime hours to avoid temperature inversions.

On top of that, a number of states created calendar deadlines for dicamba use and some said it can only be used when air temperatures are below 30 C.

Arkansas, for example, prohibited dicamba use after April 15.

Despite the label changes and restrictions, dicamba still caused off-target damage this year.

“We’re estimating … somewhere around 400,000 acres of soybeans that had damage in the northeast portion of the state,” said Jason Norsworthy, a University of Arkansas weed scientist.

The amount of damage is similar in Illinois. Hager estimated that 500,000 acres of soybeans have been damaged by dicamba drift and volatility.

Monsanto didn’t comment on the acreage estimates, but did say the number of complaints is down significantly from 2017.

“Our latest report, we’ve had a 156 (inquiries) as of the end of June, having some type of symptomology that we’re following up with,” said Ryan Rubischko, Monsanto’s dicamba portfolio lead.

That’s compared to around 1,500 cases that Monsanto looked into last year. That means complaints to Monsanto have declined even though acres of dicamba-tolerant beans doubled in 2018.

That tells Rubischko that the label changes and dicamba training are working because in 2017 more than 90 per cent of incidents could be explained by applicators not following the label.

“I think it underscores, from a symptomology perspective, like all pesticides … the importance of following the label and understanding what your local conditions are,” he said.

“And making the decision not to spray on a particular day.”

As for volatility, Rubischko said that hasn’t been a problem in 2018.

“Through all of the evaluations we’ve been on this season … the 156 here in the U.S. market, thus far, we’ve not seen any symptomology that has been attributed to XtendiMax volatility.

“We also … feel confident that these new, low-volatility formulations, when following the label and having appropriate tank mixes, are not leading to that volatility risk that may be of concern with some farmers.”

Monsanto may be getting positive feedback from growers, but Hager sees it differently. He’s heard stories of Illinois farmers pressuring their neighbours to grow Xtend beans so all soybeans fields are protected from dicamba drift and volatility.

“We’ve got large farmers calling small farmers, threatening them, telling them that they need to plant these varieties,” Hager said.

“That’s not the Illinois agriculture that I grew up in.”

Hager compared it to someone calling their neighbour and telling them they have to drive a Chevy truck, or else.

Norsworthy said the dicamba issue has become exhausting and many producers are sick of it.

“The issue, nationally, is probably as big in 2018 as it what it was in 2017,” he said.

“Some states have more complaints with the department of ag than last year. Some have less (but) folks are just tired of talking about it.”

Hager is also tired of talking about dicamba because that’s all he’s done for the last 12 months. Still, he emphasized this is bigger than farmers getting mad at other farmers about off-target damage.

“This is not just a farming issue…. This is a public relations potential disaster.”

An urban family, driving on an interstate highway, isn’t going to notice that soybean fields have damaged plants, Hager said, but they will notice damage to trees and other vegetation in rural Illinois.

“(If) they pull in the campground and all of a sudden there are trees there that have dropped all their leaves, you don’t miss that.”

A version of this article was originally published on The Western Producer.

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