Asked February 15, 2020, 11:54 AM EST

What is the process by which 2,4D and Dicamba volatize to damage some trees and shrubs

Montgomery County Pennsylvania

1 Response

Volatilzation is simply a chemical evaporating from where it is located. The potential for volatilization is dependent on the vapor pressure of a chemical, which is a measure of the potential of the chemical's likelihood to convert from a solid or liquid phase to a gas. Both 2,4-D and dicamba have relatively high vapor pressures, so concentrations capable of injuring plants may leave treated areas. On the other hand, Roundup (glyphosate) has a low vapor pressure and won't evaporate from the surface it lands on. Several factors influence the potential for volatilization: 1) temperatures - as the temp increases, more herbicide will evaporate. 85 degrees is often used as the temp where problems can occur. 2) Many herbicides are available in different formulations, and this may affect the risk of volatilization. Amine formulations of 2,4-D have very little risk of vapor loss, whereas there is risk with ester formulations. New formulations of dicamba were introduced to be used on dicamba resistant crops, but they are not low volatile enough to prevent problems. 3)The surface a herbicide is sprayed influences vapor loss. If a lawn is sprayed with 2,4-D and the spray lands on a sidewalk or driveway, a lot more chemical will evaporate from the concrete than if it lands on the turf. Hope this is helpful.