Update on Dicamba Application to Soybean
It is now common knowledge that the US-EPA granted a new five-year registration for the dicamba herbicides Engenia, XtendiMax, and Tavium to be applied to Xtend soybeans. This new registration contains some additional label directions for the application of these herbicides. One of the updated label elements is the required addition of an approved volatility reducing agent (VRA) that is to be tank-mixed with a dicamba application. The VRA in this case is actually a pH buffering agent that is added to the spray solution to maintain the pH of the solution near a desired value when another component is added.
The below excerpts from the Engenia and XtendiMax labels confirm this requirement.
• On p. 15 of the Engenia label, there is the statement “Mandatory Use of an approved pH buffering adjuvant product and minimum use rate, such as Sentris™ Buffering Technology, is required”.
• On p. 2 of the XtendiMax® with VaporGrip® Technology label, there is the statement “For every application of XtendiMax with VaporGrip Technology, an approved Volatility Reduction Adjuvant (VRA) must be included in the spray solution. An approved Drift Reduction Adjuvant (DRA) must also be included in the spray solution....”
In a UTcrops.com article titled “New Dicamba Labels Mandate Adding Volatility Reducing Agent”, Dr. Larry Steckel, UT Extension Weed Specialist, presents results from recent research that was conducted by Dr. Tom Mueller, UT Professor of Weed Science. The research involved evaluating Sentris, a buffering agent from BASF that is to be used as a VRA in a tank-mixture with Engenia, BASF’s dicamba herbicide. Sentris is the only VRA product that was made available for testing in this research.
This research is important because a spray solution pH below 5.0 is considered a strong contributor to dicamba volatilization occurrence shortly after its application. Tank-mixing glyphosate with dicamba herbicides (an oft-used tank mixture) will likely result in the spray tank solution pH falling below 5.0.
• The results presented in the above article show that this particular VRA did effectively reduce the volatility of Engenia dicamba herbicide when it was applied in a tank mix with glyphosate. In fact, Dr. Steckel states that “...of all the new label changes on Engenia, adding Sentris to every dicamba application–based on the results of this research–could be the most impactful on keeping the herbicide in the target field.”
• The addition of Sentris to the spray solution raised the solution pH above 5.0, even at locations where the water used for mixing had a pH that started near 3.0.
The following points about this product are in the BASF Sentris Fact Sheet.
• When added to Engenia herbicide spray mixtures, Sentris Buffering Technology will further reduce the potential for off-target movement by stabilizing pH of the spray solution.
• Use of a pH buffering adjuvant is important with tank mixtures because mixtures of Engenia with herbicides such as glyphosate can lower the pH of a spray mixture and increase the risk of potential volatility.
• With an alkaline pH, this buffering technology–i.e. Sentris–is designed to increase and stabilize spray mixture pH, which helps reduce the volatility potential that is related to spray solution pH.
• Every application of Engenia dicamba herbicide requires the use of a qualified pH buffering adjuvant such as Sentris (see above statement from Engenia label).
The above presentation is not intended to endorse Sentris as a VRA agent to the exclusion of other like products. In fact, it is assumed that other manufacturers have or will offer approved VRA’s (e.g. Bayer’s Vaporgrip Xtra Agent, (see label for Cornbelt Vapor-Shield, a VaporGrip Xtra Agent) to be used with the dicamba herbicides. However, the results from the above-cited research with Sentris as a VRA certainly indicate that its addition to Engenia dicamba herbicide will be a significant contributor to keeping the herbicide in the target area.
Caveat: Producers must be aware that there may be a specificity about which VRA’s can be added to tank mixtures of individual dicamba herbicide products–i.e., not all VRA’s can be added to all dicamba herbicide products. As with all pesticides, simply follow the label when adding a VRA to any of the dicamba herbicide products.
Composed by Larry G. Heatherly, Dec. 2020, larryheatherly@bellsouth.net