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Why Dicamba-Tolerant Soybean Technology Is in Trouble

Dicamba is Moving Off-Target in Regions Like Missouri’s Bootheel.

A couple weeks ago, Kevin Bradley came to the intersection of U.S. Route 60 and Missouri Route 25 near Dexter in southeastern Missouri.

“I looked off to my left and noticed one volunteer soybean plant,” says the University of Missouri (MU) Extension weed specialist.

Intrigued, Bradley got out to inspect it. The plant exhibited the classic cupping of dicamba damage. Since the closest soybean field was .75 mile from there, the dicamba had to have traveled at least that far to move off-target.

Off-target movement was one of the concerns when Monsanto unveiled its Roundup Ready Xtend System featuring a soybean and cotton trait that tolerates dicamba and glyphosate.

In response, Monsanto, BASF, and DuPont developed dicamba formulations lower in volatility for 2017 that team up with dicamba-tolerant soybeans. Still, that single soybean plant exhibits the soup that Missouri farmers have been in this summer regarding off-target dicamba damage.

“Dicamba appears to be moving miles,” says Bradley.

It’s Different This Year

Federal regulators approved dicamba-tolerant soybeans for use in 2016. However, they did not approve matching dicamba formulations advertised as having low volatility potential to minimize off-target movement. Volatility results when a herbicide converts to a gas. When this happens, the herbicide in a gaseous form can leave the application site and damage plants where it lands.

In 2016, Bradley notes off-target movement of illegal dicamba formulations like Banvel or Clarity on dicamba-tolerant soybeans occurred due to:

  • Physical drift. This occurs when small droplets or droplet fines from herbicide applications move to nontarget vegetation. It’s keyed by factors like wind speed and direction, air temperature, and humidity.
  • Nighttime spraying. This can key herbicide movement through temperature inversions.
  • Tank contamination.
  • Use of generics.
  • Improper spray setup.

These factors have again played a role in this year’s Missouri dicamba dilemma.

Also playing a role, though, has been off-target movement of the legal herbicides pegged as low in volatility potential including:

  • BASF’s Engenia
  • Dupont FeXapan Plus Vapor Grip Technology
  • Monsanto’s Xtendimax with Vapor Grip Technology

Unlike last year, off-site movement has also occurred with daytime spraying and in sprayers that were properly set up, he adds.  

“Most fields I’ve been in have been injured from one end to the other with no discernable difference in soybean symptomology,” says Bradley. “This suggests problems with off-site movement through volatility.”

Damage Tally

So far, the soybean dicamba damage tally in Missouri is 203,045 acres. Total Missouri soybean acreage planted for 2017 is 6 million acres, according to USDA. Other dicamba-damaged crops MDA identified as of late last week include:

  • 6,400 tomato plants
  • 73 acres of watermelons
  • 18 acres of cantaloupes
  • 5 acres of a vineyard
  • 2 acres of pumpkins
  • 24 acres of certified organic vegetables
  • Several residential gardens, trees, and shrubs

Damage from off-target movement led the Missouri Department of Agriculture (MDA) to temporarily suspend sale and application of dicamba last Friday. The order applies to all dicamba formulations, including Xtendimax, FeXapan, and Engenia. Arkansas also has temporarily suspended sale and application of dicamba. This only applies to Engenia, the only formulation that the state approved for over-the-top use this growing season.  

Damage also has emerged in other states. There have been around 55 complaints so far in Mississippi, and around 77 so far in Tennessee. Last Thursday, Aaron Hager, University of Illinois Extension weed specialist, tweeted he had more calls and questions and interviews related to dicamba than he’d had for the past 15 years combined.

What’s New and What Isn’t

Last year, the MDA fielded its first dicamba complaint on June 22, the first of 130 complaints for 2016.

“This year, the first complaint occurred on June 13,” says Paul Bailey, Missouri MDA’s pesticide program manager. “As of July 6, we were closer to 140.”

“We are working with our distributors and retailers to comply with the order issued by the Missouri Department of Agriculture,” says Laura Svec, U.S. communications lead, DuPont Crop Protection. “As with all our chemistries, DuPont is committed to the stewardship of DuPont FeXapan Plus VaporGrip Technology. We intend to work with the department to help identify a solution to enable FeXapan to be used this growing season to help growers in Missouri manage weeds.”

Monsanto issued a response following the Arkansas temporary ban that included the following:

 “We sympathize with any farmers experiencing crop injury, but the decision to ban dicamba in Arkansas was premature since the causes of any crop injury have not been fully investigated. While we do not sell dicamba products in Arkansas, we are concerned this abrupt decision in the middle of a growing season will negatively impact many farmers in Arkansas. We strongly encourage farmers using dicamba in other states to make their voices heard. Share how important this tool is to your farm and how you are using it responsibly. We have heard those stories. To ensure your continued access to dicamba products, make sure your elected officials and relevant agencies hear those stories, too. In the many states where we do sell dicamba, we will continue our efforts to help farmers use dicamba successfully.”

Frustrated by Industry Response  

Bradley, though, has picked up on other industry responses this summer that dismiss complaints as “unsubstantiated.”

“To act like this is not a problem, I cannot understand that mind-set,” says Bradley.

Part of the problem is the mind-set that the resulting injuries are growing pains, similar to those that occurred when the Roundup Ready or Liberty Link technology was introduced. Given the scope of the damage, it’s more than that, says Bradley.

The magnitude of injury in hard-hit spots like the Bootheel part of southeastern Missouri — where Bradley estimates around 22% of that areas’s soybeans have been damaged — make it difficult for the dicamba technology to co-exist with non-Xtend soybeans like Liberty Link, Roundup Ready, or conventional ones.

“In that area where there is that much dicamba being sprayed, I don’t see where that will work (with current label stipulations),” he says. “The vast majority of Liberty Link soybeans in the Missouri Bootheel, about 80% to 85%, have injury. It will take a combination of amendments for this technology to survive in the marketplace.”

He also takes issue with a tweet that Robb Fraley, Monsanto chief technology officer, sent out on June 30 saying “Investigate, don't speculate. Leaf cupping being observed in soybean fields never exposed to dicamba.”

“I know what dicamba damage looks like,” says Bradley.

“We’ve heard it’s the oil in the Liberty sprays, it’s metolachlor (Dual Magnum’s active ingredient), it’s anything but dicamba,” adds Steve Smith, who chairs the Save Our Crops Coalition and is also the director of agriculture for Red Gold Tomatoes in Elwood, Indiana.

Nor is the industry claim that injury is cosmetic and will not cause yield loss accurate, says Bradley.

“We have done as much work on it as anyone,” says Bradley. “And I can’t walk out in a field of V3 soybeans that have been injured and say it won’t have yield loss. In many cases, we cannot give them (farmers) an answer,” he says.

Bootheel Dilemma

So far, dicamba damage has been a split decision in Missouri. Outside the Bootheel, complaints regarding dicamba cover just 5,000 to 6,000 acres of soybeans.

Of the Missouri’s Bootheel’s 875,000 soybean acres, though, 65% are Xtend soybeans. Almost all are sprayed with dicamba, Bradley says.

Meanwhile, there are 306,000 acres of soybeans that are non-Xtend. Of these, Bradley says there are 195,000 acres estimated to be injured. That tallies up at 64% of total non-Xtend soybeans, or 22% of all soybeans grown in the Bootheel.

Damage in the mid-South states like Tennessee and Arkansas is akin to Bootheel dicamba damage.

“Part of the difference (between the Bootheel-Mid-South region and the rest of Missouri) is due to the volume sprayed,” says Bradley. Roundup Ready Xtend technology is also used in about 80% of the region’s 300,000 acres of cotton. Like Roundup Ready Xtend soybeans, most cotton is sprayed with dicamba, says Bradley.

“It is warmer there, so that may play a role,” he adds.

“Their average daily temperature is so much different than Iowa or Minnesota. So those are things that we can make progress on if we get more data.”

Temperature Inversions

As in 2016, temperature inversions are likely a reason for off-target movement this year.

“If you read almost all pesticide labels, there is a line that says don’t apply during temperature inversions,” says Mandy Bish, MU senior research specialist.

During the daytime, warm air rises when sunlight hits the ground. Meanwhile, cool air comes down, hitting the warm air. When this happens, wind results, which keys air circulation.

As nighttime beckons, air patterns flip-flop, with cool air at the bottom and warm air on the top. This creates a stable environment that traps any pesticide particles in a suspended air mass.

When this air mass encounters a horizontal wind, those particles move someplace, says Bish. At its worst, the trapped pesticide can land in the middle of a multithousand-dollar-per-acre field of fruits or vegetables.

Inversions are common, occurring anywhere sun hits the surface of the soil, Bish adds. This summer, MU researchers have found inversions setting up at 5 p.m. or 6 p.m., a time when many applicators are still spraying.

Bish says factors associated with inversions are:

  • Clear night skies.
  • No wind. “That is indicator of an inversion, but if you spray the night before you see the fog, it is not the best indicator,” she says.
  • Dew or frost present in the morning.
  • Low-lying fog.

Although not foolproof, smoke bombs are one way to detect temperature inversions. Smoke bombs set off at 4 p.m. by MU scientists showed fairly rapid dispersal. Ones set off at 7:30 p.m. lingered around 50 seconds, which indicated inversion presence, she says.

Dicamba’s Future

The registration for dicamba use in dicamba-tolerant soybeans will expire on November 9, 2018. Environmental Protection Agency (EPA) documents indicate the registration will automatically expire “…unless the EPA determines before that date that off-site incidents are not occurring at unacceptable frequencies or levels.” 

Translation: The continued availability to use dicamba in dicamba-resistant soybeans highly depends on those who now use it.

If EPA does not renew the three products for another conditional registration period or give it full Section 3 registration, there could be dicamba-tolerant seed products on the market with no dicamba herbicides to accompany it.

It’s also possible that states may prohibit the use of products after a certain date, says Bailey. In the Missouri Bootheel, for example, one option may be to restrict applications after April 15. In essence, this would limit dicamba use to a burndown herbicide.

States may also customize use, perhaps permitting spraying to occur between just 9 a.m and 3 p.m. says Bradley. “We know inversions will set in due to evening hours and last all night,” he says.  

For now, applicators in states where they can still apply dicamba need to use all steps required to minimize off-target movement, says Bradley.

“Trust me, if you don’t have all of those things checked off, such as having the right tips, the right boom height, the right wind speed, and everything else, you will see a problem with dicamba moving off target,” he says.

A farmer who files a dicamba damage complaint also has to have his or her house in order, says MDA’s Bailey.

“When they file a complaint, we cannot ignore what they have applied to their own crop,” says Bailey.

If farmer-applicators don’t have a spray rig dedicated to dicamba — few do — MDA investigators will check steps farmer-applicators have taken if they have applied dicamba on their own farms. These include properly cleaning out their out their spray tank and spray lines when switching to other herbicides.

“We cannot accept a complaint (by them) just by pointing a finger at their neighbor,” says Bailey.

Insurance also is a concern. “We know that insurance companies will begin to be highly involved in considerations of policies in coming years, as they are destined to take a tremendous liability hit,” says Smith.

Bradley encourages dicamba companies to share data like complaint numbers, the amount of products sold and sprayed, and the number of acres planted.

“Think about the greater good,” he asks.

On the farmer side, Bradley advises them to communicate with neighbors about their spraying applications. This isn’t always occurring.

“In the past week driving (between) injury complaints, I have seen on two different occasions farmers leaving their field on a four-wheeler or in a pickup taking their ‘Flag the Technology’ flags out of the field," he says. (Flag the Technology is a coding strategy matching herbicide applied with a specific colored flag.) "Why? I suspect they didn’t want to get blamed for something (like off-target movement)."

“All this is hurting neighbor relationships,” says Bradley. “One reason I am passionate about this is I have no desire to live through this again after last year. This cannot be dismissed as a nonissue.”  

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