Effect of Surfactant on Dislodgeable 2,4-D Residues from Athletic Field Turf.

2,4-D is a post-emergence auxin herbicide used in turfgrass that previous research has shown can readily dislodge from treated vegetation. Practitioners commonly spray 2,4-D as a tank-mix with various commercially available surfactants to enhance efficacy. Research was completed to assess the effect of surfactant use and time within a day on 2,4-D dislodgeable foliar residues (DFR) from treated perennial ryegrass (Lolium perenne L. ‘Carly’). Field research was initiated May 24, 2015 in Raleigh, NC to measure DFR following 2,4-D application (2.1 kg ai ha^-1) either alone, or in combination with a nonionic surfactant (0.5% v/v). Sample collection occurred 1, 2, 3, 6, 12 or 24 d after treatment (DAT) at 7:00:00 (canopy moisture present) and 14:00:00 (canopy moisture absent) Eastern Standard Time. Dislodgeable 2,4-D residues increased at 7:00:00 and decreased at 14:00:00 for each DAT through 6 DAT, at which time 2,4-D was not detected. Sampling at 7:00:00 resulted in 25.3, 20.2, 11.9% more of the applied dislodged compared to 14:00:00 at 1, 2 and 3 DAT, respectively, suggesting 2,4-D re-suspended on treated turfgrass vegetation overnight following canopy moisture development. 2,4-D applied with a surfactant reduced DFR 3.3% 1 DAT; however, no differences were detected in subsequent DAT. In conclusion, although DFR differences were minimal, surfactant inclusion consistently resulted in less dislodge than 2,4-D applied alone. Furthermore, surfactants can improve efficacy, which may result in overall reduced herbicide inputs. This research will improve turfgrass management practices for athletic field schedulers to reduce potential human exposure.