Pucker up is taking on a specific meaning across the soybean belt as reports of dicamba injury start to mount in several states.
The slightest whiff of dicamba herbicide causes sensitive soybean leaves to cup and pucker. As of June 12, there had been 41 drift complaints implicating dicamba registered with the Arkansas State Plant Board, according to Adrianne Barnes, communications director for the Arkansas Department of Agriculture.
Tennessee Department of Agriculture officials said three complaints have been received so far — two in Dyer County and one in Shelby County. Weed scientists in Missouri and Mississippi have also been walking fields to inspect potential injury. Across the Midwest, there are urgent pleas for applicators to follow proper protocols and to respect neighboring crops and other sensitive areas as spraying ramps up.
University of Arkansas weed scientist Tom Barber told DTN dicamba injury symptoms are widespread in his state. “We already have more complaints than the 32 total cases in 2016, and we’re a week or more ahead of the first complaint last year,” he said. “That northeast Arkansas crop is still pretty young because of weather and replant — so we’ve got a ways to go on spraying.”
Barber said he suspects most northeast Arkansas soybean fields that weren’t planted to dicamba-resistant seed will be “cupped up.”
The situation is significant because Arkansas, in particular, took the harshest line on dicamba this year. BASF’s Engenia herbicide, a formulation using the BAMPA salt, was the only postemergence product legally available for use in the state. The state also required mandatory applicator training, extended buffer zones around the entire field at application and established a 0.25 mile downwind buffer to sensitive crops. In addition, the state banned the use of any DGA-based dicamba herbicide after April 15, including Monsanto’s XtendiMax and DuPont’s FeXapan that both contain VaporGrip technology.
“The thought during development of these restrictions was an attempt to minimize the amount of injury from off-target movement this season,” Barber said. “Unfortunately, that has not been the case.”
Last year growers planted the soybeans and cotton containing the dicamba trait known as Xtend with no approved dicamba herbicide to use with it. Problems came when they reached illegally for generic, more volatile formulations of dicamba. It also put a spotlight on how sensitive soybeans and other plants are to dicamba and led to very specific application requirements around nozzle selection, tank mixing, ground speed, wind speed and boom height.
University of Missouri weed scientist Kevin Bradley has no desire to return to the problems he saw in his state last summer. Missouri led the way in the number of official complaints in 2016. “As of last week, there were no official complaints turned in to the Missouri Department of Ag,” Bradley said.
However, he issued a terse reminder to applicators this week based on what he sees happening in states to the south. “They are a couple of weeks ahead of us usually, and things that happen down there usually happen up here,” he said. “I’ve fielded some complaints, but so far there’s been nothing official.”
Bradley said there’s no question that 2016 issues left an awareness and a watchfulness for injury. That’s resulted in some defensiveness too since dicamba has been sprayed on corn for decades. “That’s true,” Bradley said. “But we haven’t been spraying dicamba in June and July on soybean. And we haven’t been spraying as much of it as we have the potential to spray right out of the gate on Xtend soybean in its first year of release.”
SIGNS OF INJURY
It can also take one to three weeks for dicamba injury to reveal itself, depending on the growth of the crop. Symptoms only appear on newly emerging vegetation, and current hot, dry conditions have slowed plant growth.
Whether the injury is cosmetic or yield damaging depends on dose and what stage the crop is in when the drift occurs. Late vegetative and early reproductive stages of the soybean, peaking around R-1, are the most sensitive, Barber said.
Herbicide Resistance Info
The combination of Xtend varieties being sprayed in both cotton and soybeans is adding to the situation in Arkansas. Barber said so far there’s no way to know if the drift complaints are coming from growers using generic formulations or the approved lower-volatility formulation of Engenia.
“Of the fields I’ve walked personally, 80% to 90% of the situations were caused by physical drift,” Barber said. “The wind was blowing too high, they didn’t have the correct nozzle set up or configuration, booms were too high or winds were blowing toward a sensitive crop.” He said temperature inversions have also been an issue, particularly when applicators were spraying at night.
“There’s another 10% to 20% that I’m scratching my head and can’t explain. We don’t know if it is volatility or movement on dust particles, but in my mind it is some kind of secondary movement right from the initial application.”
BASF responded to DTN inquiries on the issue by stating that initial reports of drift issues seem to have been caused by improper application and not following label requirements. However, they also stated that many growers are applying Engenia properly with good results.
In a media release to DTN, BASF said: “We are here to support our customers and, if requested, can assist in investigating an off-target allegation in an advisory capacity to provide technical support.” The company has provided free nozzles to growers and has an online digital training module at www.GrowSmartUniversity.com.
Monsanto also told DTN via email that the company is aware of media reports regarding off-target movement of dicamba, but is not willing to draw conclusions on the reports at this time and re-emphasized the importance of following all product labeling and local requirements.
Barnes, with the Arkansas Department of Agriculture, said 2017 case files are being investigated. “We do not have final determinations for products that were used, or even if dicamba was involved.
“Each year, the Arkansas State Plant Board handles a significant number of complaints relating to alleged chemical misuse; the complaints may name a suspected chemical, but until inspectors are able to get on site and diagnose based on symptomology, and collect records, there is no way to make a determination on the chemicals used,” she said.
Barber also noted that, to be fair, other drift complaints have been filed this year and have involved herbicides such as paraquat and Roundup. However, he said those drift events tend to be more localized and damage 100-200 acres.
“Dicamba complaints have been much more widespread and may cover 1,000 acres or more each time,” he noted. “But there is also a much higher acreage planted to Xtend crops and sprayed with dicamba this year compared to last year.” In Phillips County alone, some 20,000 acres are estimated to have some amount of dicamba drift injury. More than 7,000 acres of drift have been reported in Mississippi County — including most of the soybean research plots at the Northeast Arkansas Research and Extension Center at Keiser.
To read Barber’s blog post on the dicamba issue in Arkansas, click here.
For more information on what to do if you suspect herbicide drift, go to Emily Unglesbee’s story: http://bit.ly/…
The University of Illinois article on how to address drift concerns can be found here: http://bit.ly/…
Pamela Smith can be reached at Pamela.firstname.lastname@example.org
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