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Inside agriculture’s hottest controversy: dicamba


A soybean plant grows in the Bond Life Sciences Center’s greenhouse. | Photo by Samantha Kummerer, Bond LSC.

By Samantha Kummerer, Bond Life Sciences Center

Every summer, MU Bond Life scientists Gary and Bing Stacey plant soybeans. In the summer of 2016, they were testing mutant crops’ tolerance to different herbicides. Among the multiple weed killers tested was one called dicamba.

The researchers knew this particular chemical was tricky so they turned to an expert to apply it, MU herbicide researcher Kevin Bradley.

The next morning, a soybean breeder with a neighboring plot discovered his soybeans were damaged.

“These were plots where some of his graduate students experimented so they basically couldn’t use any of their data and we felt terrible, but we explained to them we took every precaution we could possibly take but it was this vaporization that took place,” Gary Stacey explained.

What Gary Stacey didn’t understand at the time was dicamba has an ability to travel even after it is sprayed. The herbicide doesn’t just kill weeds, it kills or damages everything not engineered to be resistant to it.

“So let’s say I spray it in this spot right here. You would think its localized but if the temperature and humidity conditions are right it will vaporize and come up and then go into the air,” Gary Stacey said.

Just how far it can travel and how much damage it can achieve was realized all too well by farmers throughout the country this year.

An estimated 3.5 million acres of soybeans were damaged this summer.

One obvious solution may be to simply stop using the weed killer. But the issue is not that simple.

“This is the hardest issue I can remember because there are good responsible farmers on either side of the issue,” said Missouri Farm Bureau president Blake Hurst.

With so much on the line for all sides, dicamba has tangled farmers, corporations and researchers together in a controversial issue.

Bradley is right in the middle. He’s received calls from farmers who just lost 10 percent of their income for nothing they did wrong.

He’s also received calls from people who are upset by any suggestion that anything about the chemical is wrong. These are the farmers who need dicamba to control weeds that are no longer responding to the traditional weed killer Roundup.

“I’ve had the farmers who planted the traits saying ‘These are my highest yields ever how can you say these things?’ And their neighbor across the road just lost 20 bushels an acre because of your highest yields ever. It’s just a very personal issue for each person involved,” Bradley explained.

One case got so personal that a farmer in Arkansas allegedly shot his neighbor.

“I’ve been here for 14 years and I’ve been doing this kind of work for 20, never seen anything like this is agriculture. Period. Never seen this level of controversy between farmer to farmer and farmer to company or between company and university people. I’ve never seen anything like this,” Bradley said.

Dicamba is not a new formulation, but its use is. Monsanto developed genetically modified soybeans and cotton seeds that are resistant to dicamba. One of the problems farmers are pointing to is that Monsanto released the new seeds while still in the process of developing a better formula of dicamba. The new formula aimed to reduce volatilization, a tendency to vaporize after being sprayed on fields and then drift to neighboring areas. Monsanto claims the new formula reduces volatility by 90 percent, but Bradley said 90 percent is not 100 percent.

Bradley’s work has been consumed by this single herbicide as he tries to find the truth of what aspect of dicamba is causing the damage.

In Bradley’s eyes, there are four factors contributing to the widespread damage: physical drift mistakes (spraying with the wind, nozzle not attached correctly), tank contamination, temperature inversion, and volatility.

These factors are recognized by other researchers and Monsanto. The disagreement is over which factor is most at fault.

“Monsanto has a pretty high number for the farmer fault percentage,” Bradley said explaining the blame game. “ I don’t know when they’ll ever really say, ‘yeah, volatility could be contributing to this problem, too’ and that’s the difference between university weed science.”

This contributes to the confusion among users.

“You don’t know who to believe,” Gary Stacey said.

But Gary Stacey thinks this is where researchers are able to help. By acting as an objective third party, scientists can sort the fact from the fiction.

“We’re just trying to get out the truth and what science says, that’s my job,” Bradley explained. “I don’t care necessarily what amount of money a company has invested in something. Our job is to call it like we see it and show the science.”

With a controversial issue like this, sometimes the truth comes with some risk.

MU has been conducting experiments that test the air for the volatility of the chemical. The research is detecting dicamba in the air up to four days after initial application of the chemical. Bradley explained this is not something the companies want to be made public and there’s been considerable pushback.

In addition to research, Bradley is working with the Missouri Department of Agriculture to create training courses for farmers wanting to use the chemical next season.

Despite millions of damaged acres, dicamba is not going away anytime soon.

Gary and Bing Stacey haven’t used dicamba again, but many farmers making their money off crops have no choice. Bradley said Monsanto is planning on doubling the amount of dicamba-resistant soybeans in 2018 and many of the farmers who have been continuously hit by their neighbors’ chemical plan to plant the new seeds.

Bradley said part of the issue is soybeans are not a crop people directly consume. In general, soybeans yields were considerably high this year, so the damaged acres didn’t make as big of an impact on overall production.

“I think the only thing that is going to make a difference next year is if we have an off-target movement that is hitting more high-value crops, more high-value plant species throughout a wider geography,” Bradley said.

If this same type of damage was affecting produce people directly consume or trees, Bradley thinks dicamba would have been off the market by now.

EPA will reevaluate the use of the herbicide next November. This is one of the first times Bradley can remember that the industry granted only a two-year registration.

“I am absolutely convinced that if we have a summer in 2018 like we had in 2017, it will not be renewed,” Hurst said.

Bradley is not so certain. He said he has heard mixed reviews about how the future of this controversial weed killer could go.

“It is an unique situation for sure, hopefully it ends soon,” Bradley said.

Article originally published on Decoding Science.