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Volatility From New Formulations Drives Some Dicamba Damage, Say University Weed Scientists

They say volatility is a factor that causes low-volatile dicamba formulations to damage soybeans and other crops.

Kevin Bradley was puzzled.

The University of Missouri (MU) Extension weed scientist could not determine why parties involved in this summer’s off-target dicamba dilemma differed in opinions regarding dicamba-tolerant technology. 

To better understand it, Bradley told those attending the North Central Weed Science Society (NCWSS) meeting held earlier this month in St. Louis that he started reading behavioral science journal articles. One such article examined radiologists who scan lung tissue slides for cancer. Unknown to the radiologists, an attention researcher at Harvard Medical School superimposed a gorilla shaking its fist on a slide. Surprisingly, 83% of the radiologists in the study missed the angry ape that was in plain sight

This phenomenon, called inattentional blindness, explains why people miss the obvious because they focus solely on one matter. In this case, radiologists who intensely searched for cancer nodules missed seeing the gorilla.

The Gorilla in the Soybean Patch 

Bradley says inattentional blindness is occurring in debate about dicamba when it comes to volatility. 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.

Monsanto, BASF, and DuPont sold new dicamba formulations in 2017 marketed as low in volatility. They include: 

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

Monsanto says testing for volatility on its XtendiMax product included testing in over 1,200 GLP (Good Laboratory Practices) studies over 25 geographies. (The Environmental Protection Agency’s Good Laboratory Practice Standards (GLPS) compliance monitoring program ensures the quality and integrity of test data submitted to the EPA.) Monsanto officials say these studies showed consistent findings supporting low-volatility claims of Xtendimax between controlled environments and field studies in various geographies.

University and Extension weed scientists disagree, noting it’s akin to missing the gorilla in the lung tissue slides. 

Even with the new formulations, the potential for volatility still exists, says Aaron Hager, University of Illinois (U of I) Extension weed specialist. He cites a statement made in a 1967 Illinois Customer Spray Operators Training School proceeding: 

“Unfortunately, Banvel-D (a dicamba formulation) produces a more severe reaction in soybeans than 2,4-D does, and there is a possibility that volatility may be a serious threat.”

“So what did we learn in 2017 about soybeans and dicamba that hasn’t been known for 50 years?” Hager asks. “Herbicide volatility can occur when the spray solution settles on-site, and then changes to a vapor and is then carried off-site by wind. It doesn’t matter if new formulations have lower volatility than older ones. When I see a product that’s labeled as low in volatility, that tells me everything I need to know about the volatility of products. We know it can happen. The only unknown is the scale in which it will happen.”

He’s frustrated by the dicamba manufacturers who say volatility didn’t occur in fields where new dicamba formulations were applied in 2017. 

“To my knowledge, manufacturers did not install any air sampling equipment in treated fields (to detect movement via volatility),” he says. “If you don’t measure for it, you aren’t going to find it.”

Hager cites a 2017 Illinois Fertilizer and Chemical Association survey sent to Illinois member retail applicators. “These are the individuals either selling the product or making the applications themselves,” says Hager.

The survey asked 28 questions regarding 2017 dicamba applications. 

One question was striking to Hager: “If you saw symptoms in a non-dicamba-tolerant soybean field, what were the factors that caused it?” 

“Some said physical drift occurred, while others said it was due to (spraying in) an inversion,” he says. “Some said it was due to applicator error, while others said it was due to not cleaning out the sprayer.”  

The top factor singled out by applicators, though, was volatility. The fact that applicators also listed other factors indicated the validity of the study, says Hager. 

“That tells me the applicators were honest (in their responses),” he says.
Hager doesn’t believe new EPA restrictions including factors like wind speed and spraying next to adjacent sensitive crops will improve matters in 2018.

The new label requirements do nothing to address volatility, says Hager. “In fact, they raise confusion about how to define adjacent sensitive crops downwind. I don’t know what adjacent means. (The new federal restriction on sensitive crop adjacency gives no metric for distance.) If distance is not given, how will anyone know how to legally apply those products?”

What companies say

BASF officials say its field reps investigated 787 soybean symptomology claims during the 2017 season, most of which had no impact on yield. However, in a few isolated cases, BASF officials say yield may have been affected where the terminal growth was inhibited. Main causes include:

  • Incorrect nozzle and/or boom height 
  • Wind speed or direction
  • Insufficient buffer 
  • Spray system contamination 
  • Use of unregistered product 
  • Inversion present 
  • Spray tank contamination

“We are confident that volatility (from new dicamba formulations) is not a driving factor with off-target movement,” says Gary Schmitz, BASF Midwest technical service regional manager. “We brought Engenia in the marketplace as low volatile, 90% less volatile than dicamba with DGA salt (Clarity).”

He adds that following label directions is critical for success in using Engenia. 

“For applicators unwilling or unable to follow application requirements specified on the label, we recommend that he or she not use Engenia herbicide,” says Schmitz. “Dicamba is just one tool out of many available for managing weeds. It doesn’t need to be applied on every acre.

Monsanto officials say that as of October 26, it had fielded 1,467 applicator inquiries regarding potential dicamba damage and made 1,418 site visits. Of that, 1,222 applicators supplied data for review and climatological evaluation. In 91% of those cases, applicators had self-reported errors from one or more label requirements that could have contributed to off-target movement. These include factors like:

  • Insufficient buffers
  • Wrong nozzle type
  • Boom height set too high
  • Improper tank mixes
  • Wrong spray pressure

“We have not seen off-label movement (from new dicamba formulations) due to volatility,” says Scott Partridge, Monsanto vice president of global strategy. “The errors we did find are easily addressable through the enhanced education we continue to do.”

For 2018, Monsanto officials say they will be:

  • Evolving and tailoring trainings based on 2017 learnings.
  • Distributing free spray nozzles that comply with product labels.
  • Establishing a technical support call center to help applicators access information on best practices and application requirements.
  • Developing spray app for applicators to help avoid problematic weather conditions to achieve on-target application.
  • Offering free flags to mark Roundup Ready Xtend Crop System fields.
  • Engaging retailers on best management practices
  • Offering discounts on Redball Hooded Sprayers with a qualifying Xtendimax purchase.

This month, Monsanto announced it will be offering a cash incentive to farmers who apply Xtendimax to dicamba-tolerant soybeans as part of its Roundup Ready Plus program and incentives. This could shave the price of Xtendimax over 50% in 2018. 

Volatility Acknowledgement Needed

Even so, many university weed scientists fear education and training won’t be enough. Larry Steckel, University of Tennessee Extension weed specialist, says his program has done just that since the dicamba-tolerant technology was launched. They include 

  • 5,523 applicators who took 30-minute stewardship module exam
  • 13 blog posts on stewardshipand management that were accessed 3,600 times
  • 16 in-season YouTube videos on stewardship and management that had 13,500 views

This was accompanied by numerous stewardship training sessions that Monsanto and BASF conducted, Steckel says. Even so, an estimated 400,000 soybeans acres out of 1,720,000 acres planted in Tennessee in 2017 exhibited off-target dicamba damage. Specialty crops like grapes also incurred damage from off-target dicamba. 

“We hear from the Captains at Monsanto that we can easily fix this (off-target dicamba movement) with increased training,” says Steckel. “I don’t think we can. I will do my best, but I think we are fighting a losing battle.”

A University of Missouri evaluation of soybean plant injury for volatility following application of labeled and unlabeled dicamba formulations shows volatility is reduced with newer formulations. However, gaps between the two are narrower than what Bob Hartzler, Iowa State University (ISU) Extension weed scientist, would like to see.

In the 24- to 72-hour window, for example, 22% of plants treated with Banvel showed visual injury 21 days after application. Soybeans with injury from Xtendimax, though, weren’t far behind with 18% injury. Engenia had the lowest rate of injury at 11%. 

“There was just a 20% (damage) reduction with Xtendimax compared with Banvel,” says Hartzler. “I say that is not enough.”

“Even today, we get no acknowledgement that we have any volatility occurring (with new dicamba formulations) from manufacturers,” says Bradley. “We need a higher degree of transparency, impartiality, and integrity by all company representatives, from the lowliest sales person at the field level to the highest CFO, CEO, CTO, or whatever when it comes to diagnosing off-target movement of dicamba.”

Disheartening to Bradley are visits he made last summer to meet with farmers after company representatives stated dicamba volatility didn’t cause crop damage. 

“That part eats away at me more than anything else,” he says. “Some of those people are trained here at the University of Missouri, and they go away from the field and say there is no possibility of volatility from these products. Why? Because someone in the R and D (research and development) of the company says so? I can’t get behind that. Everything mentioned (by companies regarding dicamba damage) is a possibility, but volatility is also one of those possibilities.”


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