Abstract
2,4-dimethylamine salt (2,4-D) is an herbicide commonly applied on athletic fields for broadleaf weed control that can dislodge from treated turfgrass. Dislodge potential is affected by numerous factors, including turfgrass canopy conditions. Building on previous research confirming herbicide-turfgrass dynamics can vary widely between species, field research was initiated in 2014 and 2015 in Raleigh, NC, USA to quantify dislodgeable 2,4-D residues from dormant hybrid bermudagrass (Cynodon dactylon L. x C. transvaalensis) and hybrid bermudagrass overseeded with perennial ryegrass (Lolium perenne L.), which are common athletic field playing surfaces in subtropical climates. Additionally, dislodgeable 2,4-D was compared at AM (7:00 eastern standard time) and PM (14:00) sample timings within a day. Samples collected from perennial ryegrass consistently resulted in greater 2,4-D dislodgment immediately after application (9.4 to 9.9% of applied) compared to dormant hybrid bermudagrass (2.3 to 2.9%), as well as at all AM compared to PM timings from 1 to 3 d after treatment (DAT; 0.4 to 6.3% compared to 0.1 to 0.8%). Dislodgeable 2,4-D did not differ across turfgrass species at PM sample collections, with ≤ 0.1% of the 2,4-D applied dislodged from 1 to 6 DAT, and 2,4-D detection did not occur at 12 and 24 DAT. In conclusion, dislodgeable 2,4-D from treated turfgrass can vary between species and over short time-scales within a day. This information should be taken into account in human exposure risk assessments, as well as by turfgrass managers and athletic field event coordinators to minimize 2,4-D exposure.
Highlights
Turfgrasses are used for a variety of societal purposes, including activities on athletic fields
Samples collected from perennial ryegrass consistently resulted in greater 2,4-D dislodgment immediately after application (9.4 to 9.9% of applied) compared to dormant hybrid bermudagrass (2.3 to 2.9%), as well as at all AM compared to PM timings from 1 to 3 d after treatment (DAT; 0.4 to 6.3% compared to 0.1 to 0.8%)
Across species in 2014, greater 2,4-D dislodgment occurred at 1 DAT in AM (0.6 to 3.7% of applied) compared to PM (0.1%) sample collections, while this was only true for perennial ryegrass in 2015 (6.3 and 0.1% of applied in AM and PM, respectively)
Summary
Turfgrasses are used for a variety of societal purposes, including activities on athletic fields. The National Turfgrass Research Initiative reported in 2003 there were > 700,000 managed athletic fields in the US [1]. Warm-season turfgrass species such as bermudagrass (Cynodon spp.) are often overseeded during dormancy periods with a cool-season turfgrass to improve athletic field surface aesthetics and functionality [4]. Regardless of the turfgrass species present on athletic fields, conditions can unfold that degrade playing surface quality and compromise playing surface safety via weed encroachment. Athletic field managers employ multiple weed control practices to alleviate this issue, including synthetic herbicide applications. One such herbicide athletic field managers utilize for selective broadleaf control is 2,4-dimethylamine salt (2,4-D), which is registered for use on cool- and warm-season turfgrasses [6]. Research to date is inconclusive on human-carcinogenic effects from 2,4-D, it is a confirmed toxin to blood, kidney, and liver, as well as an eye irritant [6,7,8,9,10]
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