August 1, 2017
As of late Friday, July 28, the Minnesota Department of Agriculture confirmed it has received 67 complaints of alleged dicamba drift.
Possible dicamba drift and volatility have been reported in soybean-growing states across the U.S. as farmers see evidence of plant injury. Soybeans are sensitive to dicamba unless they contain the herbicide-tolerant trait for it. Field reports indicate that very small amounts of dicamba as drift or contamination from spray tanks or booms can produce symptoms such as leaf cupping. Dicamba injury does not show up until new leaves appear.
Since the MDA investigations are active, data are classified as not public, so no one at the department is able to speak about specific complaints at this time, says Allen Sommerfeld, MDA senior communications officer.
In southwest Minnesota, independent crop consultant Stephan Melson with United Ag Tech in Trimont reports that dicamba drift and volatilization have been a big issue in the region over the last few weeks. Melson says farmers and consultants are seeing new leaf growth cupping and wonder if it was caused by dicamba.
“So far, we have documented 1,700 acres affected,” he says. However, he expects more acreage is affected outside his service area. “Many other soybeans are affected that we don't work with, so the true number of acres is hard to identify,” he adds. “We expect that number to increase.”
FIELD IMPACT: Damage has been reported in a number of fields in southwest Minnesota that may have been impacted by dicamba applications. (Stephan Melson)
Melson thinks some of the alleged dicamba injury is the result of physical drift of the chemical.
“However, it is my opinion that some of the dicamba injury is the result of volatilization of the dicamba chemical,” he says. “Volatilization is when the chemical turns to a gaseous state and can easily move with temperature inversions or wind after it was applied. Volatilization is completely out of the farmer's control.”
He adds that manufacturers of the new formulations of dicamba claimed that the new chemical formulations would not volatilize.
The main questions that farmers have are how soybean yields will be affected and if yield losses will covered — and by whom.
“Yield loss should be minimal, from 0% to 10%,” Melson says. “However, it is often impossible to measure a yield loss because entire fields are affected, leaving no unaffected areas to compare injury against.”
Regarding coverage for yield loss — that remains to be seen, if dicamba is shown to have caused it.
“Physical drift is the applicator's fault and they are liable, but what about volatilization?” Melson says. “Will the manufacturers cover this? The insurance issue has yet to be resolved.”
MDA’s Sommerfeld says the department investigated three alleged dicamba drift complaints in 2016. They were:
• 12.5 acres of soybeans from Diflexx (trade name) herbicide. No dicamba was detected in vegetation samples analyzed.
• 1 acre of alfalfa from Strut (trade name) herbicide. No dicamba was detected in vegetation samples analyzed.
• 1 acre of grass/alfalfa mix from Sterling Blue (trade name) herbicide. No dicamba was detected in vegetation samples analyzed.
Researchers weigh in
University of Minnesota Extension shared an article from the University of Illinois entitled "The Dicamba Dilemma: Facts and speculations," noting that similar observations were made in Minnesota. The article also contained pertinent information about soybean injury symptoms, possible routes of exposure and potential yield effects.
Interesting points from the U of I article include:
• Soybean’s sensitivity to dicamba has occurred since the herbicide’s commercialization nearly 50 years ago. U of I researchers back then described symptoms of soybean exposure to dicamba nearly identical to those observed today.
• With more dicamba currently being applied, it’s not surprising the instances of soybean exposure have increased, whether applied in corn or dicamba-resistant soybean.
• There appears to be some confusion about symptoms of exposure to dicamba, compared with leaf symptoms caused by non-dicamba factors. Researchers back then described the effects of dicamba on soybean leaves as cupped and crinkled. These terms are still used today. Other symptoms consistent with dicamba injury are prominent parallel leaf veins and stunted plants.
• Symptoms do not develop immediately after exposure to dicamba. U of I researchers noted instances where 21 days elapsed between exposure and symptom development.
• Symptoms are different on soybeans directly sprayed with dicamba (often dead plants), compared with soybeans exposed to a very low concentration (leaf cupping, etc.) farther from the source. Exposure from physical drift has been observed in Illinois this year. However, it does not appear to account for the majority of off-target exposure instances to date.
• Volatility tends to increase as soil moisture and temperature increase. All commercially available formulations of dicamba have the potential to volatilize.
• Labels of dicamba-containing products approved for in-crop application to dicamba-resistant soybean restrict applications during temperature inversions. Some have speculated applications made at night (when inversions occur) have been responsible for off-target damage. However, no actual data are available on how many acres are treated when headlights are needed on the applicators.
• It is too early in the season to predict whether or not yield will be impacted by dicamba. Research has shown it depends on soybean growth stage at the time of exposure, dosage of exposure and growing conditions for the remainder of the growing season. There are no data available that describe yield effects on soybean exposed to dicamba more than once.
• Dicamba investigations must be completed before drawing conclusions. Some industry professionals term reported losses as “negligible,” causing concern among farmers and researchers.
• Some say applications of older, non-approved dicamba formulations are causing volatility. No data or investigative reports support this claim.
• Newer formulations reportedly have lower volatility formulations, yet only one university has evaluated volatility of only one commercial formulation.
• Low volatility is not the same as no volatility.
Monsanto officials and agronomists are in the process of talking with farmers and conducting investigations. Read a blog post about what Monsanto is doing.
U-M Extension weed scientist Jeff Gunsolus also posted a at blog on dicamba.
If you suspect chemical drift in your field, U-M Extension offers a thorough discussion of what to do and how to prevent it.
U-M Extension also provides a list of hotlines available for reporting:
• MDA Complaint Line: 651-201-6333 (Monday to Friday, 8 a.m. to 4 p.m.) or the Minnesota duty officer, 800-422-0798 (day or night, seven days a week). Or report it online at bit.ly/1ytti9b. Contacting MDA provides documentation of issues. It is up to you what you want to do from there. Contacting MDA also helps to determine the scope of the problem across the state.
• Monsanto (XtendiMax), 844-RRXTEND
• BASF (Engenia), non-performance.basf.us
• DuPont (FeXapan), 888-6-DUPONT
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