DECATUR, Ill. (DTN) -- Add tank additives to the list of requirements necessary when spraying dicamba in Xtend-tolerant crops this year. EPA labels now require the use of an approved volatility reduction agent, often called a VRA, for applications of Engenia, Tavium and XtendiMax.
"This is not an optional inclusion," said BASF Technical Marketing Manager Tracy Rowlandson. "Every application must now include the addition of an approved pH buffering adjuvant."
There's also a recordkeeping component to the new rules. The name of the VRA used and the use rate must be entered into spray application records.
A separate drift reduction agent (DRA) may also be required if an applicator wants to tank mix other active ingredients, such as herbicides or biologicals, with XtendiMax, Engenia or Tavium.
This is the fourth in a DTN series of articles examining the most recent label changes for these three dicamba herbicides. EPA revised the labels in 2020 with an eye toward reducing dicamba volatility after consecutive years of off-target movement in an array of sensitive crops and plants.
While pouring an adjuvant into the tank sounds simple enough, there are a few wrinkles to consider this year.
ONLY TWO APPROVED VRAS
The new rule allows the use of "specific" VRA tank additives only. At press time, there were two types of pH buffering agents or VRA formulations approved for the task, noted Larry Steckel, University of Tennessee extension weed specialist.
Sentris has been developed by BASF and is being marketed as a BASF product and is available at local retail and distribution locations. Sentris is made from potassium carbonate and comes with an 8-ounce/acre minimum use rate, Rowlandson told DTN.
VaporGrip Xtra Agent developed by Bayer is being marketed under a variety of retail names by various manufacturers and distributors. For 2021, each of those products should contain the same buffering component, potassium hydroxide/ethanoic acid (potassium acetate), regardless of brand name, noted Jeff Herrmann, Bayer Crop Protection Engagement Manager. At press time, there were 26 different brand names containing VaporGrip Xtra Agent listed as approved on the XtendiMax website.
VaporGrip Xtra Agent is also the exact same active ingredient as the VaporGrip Technology already included in XtendiMax and Tavium, Herrmann confirmed.
So why not just include the VRA in the formulation? Part of reasoning, at least for VaporGrip Xtra Agent, is that it is labeled for a 20 ounce/acre minimum use rate. Bayer spokesperson Kyel Richard told DTN this large use rate made it too unwieldy to simply add to the XtendiMax jug.
MIX AND MATCH
By spray season, both types of VRA should be approved for use with all three herbicides. VaporGrip Xtra Agent is already listed as approved for XtendiMax, Engenia and Tavium.
However, at press time, Sentris was listed as approved for Engenia and XtendiMax, but not Tavium.
"Syngenta is currently testing Sentris in tank mix combination with Tavium, and we expect Sentris to be added to the approved Tavium tank mix webpage in the coming weeks," said Paul Minehart, Syngenta Head of Crop Protection Communications, North America.
DON'T BE SO VOLATILE
The concept behind these VRA products is to increase and/or maintain the spray solution pH, Steckel said.
In making its decision to reregister these herbicides, EPA stated "that there was evidence to show that as the pH of a solution containing the dicamba salt, in the products for use in DT (dicamba tolerant) crops, is lowered, dicamba forms a more volatile dicamba acid." By adding a pH buffering adjuvant, the spray solution can be kept closer to a neutral pH, and therefore, the dicamba will remain in a less volatile form, according to EPA documents.
"Previous labels for Engenia, Tavium and XtendiMax included some wording on the importance of keeping the spray tank pH above 5.0 to reduce the likelihood of dicamba acid forming and volatilizing into a gas after application. Now it is no longer voluntary," Steckel said.
Steckel added that low pH can be a common problem, particularly if glyphosate is mixed in the tank. "Our research with Engenia and XtendiMax has suggested that spray tank pH will nearly always fall below 5.0 when glyphosate is added, for example," he said.
The lower the pH falls, the more likely the herbicide is to move off as a gas, he noted.
Steckel has only tested the Sentris buffering agent so far. But in his studies, the VRA brought a tank mix of 3.0 pH water, Engenia and PowerMax back above 5.0.
"We're still learning things about these labels and these products," he said. "But the simple fact is that adding them (adjuvants) is no longer an option if you want to stay on label.
"In our state, regulators have already stated they will be doing spot checks in the field. Applicators will need to be able to document from the sprayer cab that they purchased an approved VRA and be able to list the product and rate at which it is being used," Steckel added.
Remember to keep ammonium sulfate (AMS) out of these tank mixtures too. "And you can't use just any glyphosate," Steckel added. "It needs to be one that contains a potassium (K) salt, such as Roundup PowerMax.
"A K-salt glyphosate will drop the tank pH two units every time -- that's on a log scale, so that's 100-fold," he observed. "Other forms of glyphosate typically have ammonia in them, which does not affect pH much more than a K-salt, but nevertheless can increase the volatility even more."
DRIFT REDUCTION MEASURES
The pH buffering adjuvants may reduce volatility, but they do not reduce offsite particulate drift (spray drift). Again, applicators need to carefully check the various manufacturer websites (listed at the end of this article) to see what drift reduction adjuvants (DRA) may be required as ingredients are added to the mix.
There's a wide selection of products available in this DRA category, Herrmann said. He also noted that the XtendiMax website offers a tankmix tool to help applicators identify whether a DRA is required in addition to the mandatory VRA.
"Testing has shown us that adding Roundup PowerMax, PowerMax II and PowerMax 3 to XtendiMax, for example, influences droplet size enough that it will always require a DRA," he said. Select Max or the clethodim-type products are other examples that require a DRA, Herrmann said.
EPA documents show that registrants BASF and Bayer estimated that a buffering agent could cost growers an additional $1 to $2 per application per acre. A drift reduction agent may cost between $1 and $4 per acre. Both adjuvants together would cost $2 to $6 per application per acre or $4 to $12 per acre for two dicamba passes. See EPA document page 24:
Other VRA compounds are being developed from a variety of sectors. Herrmann hopes that combination VRA and DRA products might be possible in the future.
"I think growers would appreciate not having to handle several different jugs and rates. Several retail partners are looking at going to combination products, but there's still a lot of testing to be done and I don't expect to see those available this year," he said.
CHECK TO CONFIRM
Retail partners might promote a particular VRA or DRA, but again, the caution is to keep checking herbicide websites to make sure you are using products that have been approved for use with the Xtend system, Rowlandson urged.
Put simply, Herrmann added, "You have to check the websites to see IF a DRA is required, but this year, a VRA is ALWAYS required. That's the same, regardless of whether you are using XtendiMax, Engenia or Tavium."
How well will these additional VRA products control volatility this season? Steckel said he's hopeful, but also a bit frustrated.
"We're going to be testing everything again this summer. If they work, great ... but if they do, part of me will wonder why haven't we been using these for the past five years?
"If they don't work, then I guess I'll be going on drift calls all summer.
"One thing is for certain, they won't work if we don't put them in the tank and that responsibility has been put on the shoulders of the applicator," Steckel said.
Find more on University of Tennessee's studies on pH and VRA use: https://news.utcrops.com/…
For more information on VaporGrip Xtra Agent:
For more information on BASF Sentris: https://agriculture.basf.us/…
Application requirement websites from registrants are constantly updated. Here's the links to find VRA lists:
If you missed the other Dicamba Rules Update series stories, go here:
Dicamba Rules Update - 1
Dicamba Rules Update - 2
Dicamba Rules Update - 3
Pamela Smith can be reached at firstname.lastname@example.org
Follow her on Twitter @PamSmithDTN
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