Research suggests glyphosate lowers pH of dicamba spray mixtures below acceptable levels
(PHYSorg.com Biology)

A University of Tennessee Institute of Agriculture study published in the Journal of Weed Technology found that mixing glyphosate with formulations of dicamba consistently lowered the pH of the spray solution below 5.0-a critical value according to the latest dicamba application labels. These labels recommend maintaining a spray solution pH above 5.0 to reduce potential for dicamba volatility.