The active ingredient dicamba (3,6-dichloro-o-anisic acid, C8H6Cl2O3) is an herbicide registered in the United States for selective control of broadleaf weeds that has been used successfully since the 1960’s. As with all herbicides, it is important to understand the potential routes of off-target movement following application. Off-target movement of dicamba can potentially occur via two routes. Physical spray drift can occur when droplets are blown off-target before reaching the target application area. The second route is vapor drift where pesticides are applied on target but later a small fraction of applied (&lt;0.2%) changes state from a liquid to a gas, of which an even smaller portion has the potential to move horizontally off-site during certain meteorological conditions. To evaluate potential dicamba exposure outside of the application area due to volatility, standard air dispersion models were used along with field-measured flux data (rate of volatility) and meteorological data to estimate air concentrations that could exist outside the spray application area. The results of this evaluation are helpful for understanding the fate of dicamba in the atmosphere and to better understand the conditions that influence the magnitude of dicamba air concentrations following applications of dicamba.

Evaluating spatial scale effects of dicamba applications on off-target vapor movement

256th National Meeting (2018)

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