2,4-D is a selective post-emergence broadleaf herbicide that is widely used in numerous agricultural crops, forestry, aquatics, as well as turfgrass systems including athletic fields. While 2,4-D has been routinely applied in numerous commodities worldwide since the 1950's, its use has been questioned for decades due to toxicological concerns. Previous research suggests 2,4-D is not readily dislodged (< 10 % of the applied) from treated turfgrass after application; however, sample collections have typically been conducted in the afternoon when turfgrass foliage is dry. Due to 2,4-D's high water solubility coupled with reports stating < 50 % of applied 2,4-D is sorbed by plants, research was conducted to quantify dislodgeable 2,4-D on a simulated football field over time. Five sample collection times within a day (TWD) (5:00, 7:00, 9:00, 11:00, or 13:00) were evaluated in each of five days after treatment (DAT) (1, 2, 3, 6, or 12). The author's hypothesis was accepted, as dislodgeable 2,4-D decreased as TWD and DAT increased. While dislodgeable 2,4-D decreases over DAT are likely due to a culmination of dissipation processes, data suggest the effect of turfgrass canopy moisture largely impacts dislodgeable 2,4-D over TWD. 2,4-D residues consistently decreased each day from 1 to 3 DAT at both 5:00 and 7:00, while samples collected at 9:00 and 11:00 were higher at 1 DAT than 2 or 3 DAT. Further, no differences were detected across DAT for samples collected at 13:00. When comparing TWD across DAT, data suggest 2,4-D re-suspends on treated turfgrass blades overnight, as 2,4-D dislodged at 13:00 on 1 DAT was 95 % less than samples collected the following morning at 5:00 and 7:00. Further,2,4-D dislodged at 13:00 on 2 DAT was 96 % less than 5:00 at 3 DAT. Correlations between 2,4-D dislodged with relative humidity and the difference between the ambient air temperature and dew point suggest this is due to atmospheric conditions being more favorable for dew formation at earlier TWD sampling times.
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