Nav: Home

Researchers explore the many factors impacting the pH of dicamba spray mixtures

September 11, 2019

WESTMINSTER, Colorado - September 11, 2019 - The EPA now requires new dicamba formulations registered for dicamba-resistant crops to have a pH of 5.0 or higher because of volatility and off-target damage concerns. When it comes to applying spray mixtures under field conditions, though, how do you ensure that pH remains sufficiently high?

In an article written for the journal Weed Technology, researchers summarize studies to determine the pH effect of various commercial products used in dicamba-based spray mixtures - including dicamba formulations, glyphosate, drift retardant, ammonium sulfate and several pH modifiers. In each instance, the products were added to water with an initial pH of 4.6 to 8.4.
  • Factors Increasing pH. The team found that the BAPMA salt formulation of dicamba (Engenia) increased spray solution pH. In addition, all the pH modifiers they tested raised pH above 5.0 - the critical value on the latest dicamba application labels.

  • Factors Decreasing pH. Adding potassium salt of glyphosate to dicamba spray mixtures decreased pH by 1 to 2.1 units, which could have a profound effect on dicamba volatility. Isopropylamine salts of glyphosate produced similar results. Ammonium sulfate, which is commonly used to increase the activity of glyphosate, also decreased pH - but typically by less than 0.5 pH units.
  • Factors Producing Mixed Results. In contrast to BAPMA, diglycolamine formulations of dicamba plus the pH modifier VaporGrip™ produced a mixed response.
  • Factors with Little to No Impact. The drift retardant Intact had no effect on pH. Spray carrier volume and the mixing order of various pH modifiers had only limited influence.
"Though no direct efficacy or volatility measurements are made in our report, it is clear that having an accurate understanding of what is happening to spray mixture pH is foundational to the sustainable and environmentally responsible use of dicamba products," says Tom Mueller, Ph.D., lead author of the paper and a professor at the University of Tennessee.
Full text of the article "Spray mixture pH as affected by dicamba, glyphosate, and spray additives" is now available in Weed Technology Vol. 33, Issue 4.

About Weed Technology

Weed Technology is a journal of the Weed Science Society of America, a nonprofit scientific society focused on weeds and their impact on the environment. The publication presents original research and special articles about weeds, crops and new technologies used for more effective weed management. To learn more, visit

Cambridge University Press

Related Glyphosate Articles:

Study reveals how pesticide use and climate affect monarch butterflies
An analysis of data in Illinois has found a link between higher county-level use of an herbicide called glyphosate and reduced abundance of adult monarch butterflies, especially in areas with concentrated agriculture.
Looking beyond the breeding grounds
Monarch butterfly populations are shrinking. New research at Michigan State University, published in the current issue of the journal Ecography, makes a strong case that the reasons for this decline go far beyond what's happening on the wintering grounds and addresses a current controversy about the primary causes of the specie's decline.
Tillage farming damaging earthworm populations, say scientists
The digging, stirring and overturning of soil by conventional ploughing in tillage farming is severely damaging earthworm populations around the world, say scientists.
US streams carry surprisingly extensive mixture of pollutants
Many US waterways carry a variety of pollutants, but not much is known about the composition or health effects of these chemical combinations.
Weedkiller chemical (glyphosate) safety standards need urgent review
Emerging evidence suggests that the safety standards for glyphosate -- a chemical widely used in common weed-killers -- may be failing to protect public and environmental health, suggest experts
More Glyphosate News and Glyphosate Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...