Fomesafen, saflufenacil, and sulfentrazone had similar parameters for their mass spectrometry analysis, all being analyzed in negative mode with similar ionization energies. Flumioxazin was analyzed in positive mode using different ionization temperatures and voltage energies, and a larger injection volume (10 �l vs 2-5 �l) due to lower detector response.  Quantitative limits of detection in soil were < 5 ppbw for all herbicides.  The field study was conducted three times (2010, 2011, 2012) with four blocks of each treatment each year. Herbicide concentrations over time were based on field samples that were later extracted and quantified using the described LC MS procedures. Data were examined using simple first-order (SFO) equation with each year by herbicide treatment combination regressed using SigmaPlot version 12.5 to determine regression parameters. The SFO rate constant was used to determine a DT 50 (in days) for each curve. All data were analyzed using a GLMMix ANOVA procedure using SAS version 9.3 and contrast statements were used to directly compare each herbicide comparison. Slopes for each herbicide use the SFO curve were estimated using SAS.  The order from shortest to longest DT 50 was flumioxazin (21.1 d) = saflufenacil (21.4 d) <  fomesafen (45.6 d) < sulfentrazone (70.8 d).  These results concur with the labeled recrop recommendations after application for flumioxazin and saflufenacil which have shorter cotton plant-back restrictions compared to sulfentrazone and fomesafen.  In these studies, none of the herbicides were highly persistent (all half-lives < 100 d), so none would be expected to be persistent pollutants in the environment, although further research is needed in this area.

Fomesafen, saflufenacil, sulfentrazone, and flumioxazin dissipation from a Tennessee field soil

248th National Meeting (2014)

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