Aryloxyphenoxypropionate (AOPP) herbicides are used to control bermudagrass contamination in various turfgrasses. Applying AOPP herbicides alone can cause unacceptable injury to zoysiagrass but injury can be reduced when tank-mixed with triclopyr. There are limited data illustrating the extent of bermudagrass control and zoysiagrass cultivar tolerance when these compounds are combined. Research was conducted to determine the efficacy of multiple AOPP herbicides applied alone and tank-mixed with triclopyr for bermudagrass control in zoysiagrass turf. Treatments include three sequential applications of cyhalofop (0.32 kg ai ha−1), fenoxaprop (0.14 kg ha−1), fluazifop (0.11 kg ha−1), or quizalofop (0.09 kg ha−1) applied alone and tank-mixed with triclopyr (1.12 kg ae ha−1) applied to ‘Tifway’ bermudagrass, and ‘Diamond’, ‘Palisades’, and ‘Zenith’ zoysiagrass. Tifway bermudagrass control ranged from 41 to 69% and digital image analysis turf coverage data ranged from 18 to 50% for AOPP herbicides applied alone. The addition of triclopyr to AOPP herbicides increased bermudagrass control (64–79%) and reduced turf coverage (8–29%). Palisades and Zenith zoysiagrass exhibited less injury (1–18%) and greater turf coverage (84–86%) when AOPP herbicides were tank-mixed with triclopyr compared to AOPP herbicides applied alone. Diamond zoysiagrass was not tolerant to any AOPP herbicides applied alone or tank-mixed with triclopyr, except for fluazifop alone (18% injury and 93% turf coverage). Visual ratings and digital image analysis turf coverage data had a strong negative correlation over all tested turfgrasses. In general, AOPP herbicides plus triclopyr will control bermudagrass greater and injure zoysiagrass less compared to AOPP herbicides applied alone; however, these mixtures can cause unacceptable injury to Diamond zoysiagrass.

Monosodium methyl arsenate (MSMA) is a commonly used herbicide for weed control in turfgrass systems. There is concern that arsenic from applied MSMA could leach to groundwater or run off into surface water, thereby threatening human and ecosystem health. The USEPA has proposed a phase-out of the herbicide but is seeking additional research about the toxicity and environmental impacts of MSMA before establishing a final ruling. Little research has systematically investigated MSMA in field-based settings; instead, risks have been inferred from isolated field measurements or model-system studies. Accordingly, the overall goal of this study was to quantify the fate of arsenic after MSMA application to a managed turfgrass system. After MSMA application to turfgrass-covered and bareground lysimeters, the majority of arsenic was retained in turfgrass foliage and soils throughout year-long experiments, with 50 to 101% of the applied arsenic recovered in turfgrass systems and 55 to 66% recovered in bareground systems. Dissolved arsenic concentrations from 76.2-cm-depth pore water in the MSMA-treated soils were consistently <2 μg L, indistinguishable from background concentrations. As measured by adsorption isotherm experiments, MSMA retention by the sandy soil from our field site was markedly less than retention by a washed sand and a clay loam. Collectively, these results suggest that under aerobic conditions, minimal arsenic leaching to groundwater would occur after a typical application of MSMA to turfgrass. However, repeated MSMA application may pose environmental risks. Additional work is needed to examine arsenic cycling near the soil surface and to define arsenic speciation changes under different soil conditions.

Synthetic auxin herbicides are commonly used in forage, pasture, range, and turfgrass settings for dicotyledonous weed control. Aminocyclopyrachlor (AMCP) is a newly developed pyrimidine carboxylic acid with a chemical structure and mode of action similar to the pyridine carboxylic acids—aminopyralid, clopyralid, and picloram. Injury to sensitive dicotyledonous plants has been observed following exposure to monocotyledonous plant material previously treated with pyridine compounds. The absorption, translocation, and metabolism of AMCP has been documented in susceptible broadleaf weeds; however, no information is available, to our knowledge, regarding AMCP fate in tolerant Poaceae, which may serve as the vector for off-target plant injury. Based on this premise, research was conducted to characterize absorption, translocation, and metabolism of AMCP in tall fescue.14C-AMCP was applied to single tiller tall fescue plant foliage under controlled laboratory conditions at North Carolina State University (Raleigh, NC). Radiation was quantified in leaf wash, treated leaf, foliage, crown, roots, and root exudates at 3, 12, 24, 48, 96, and 192 h after treatment (HAT).14C-AMCP was rapidly absorbed by tall fescue, reaching 38 and 68% at 3 and 48 HAT, respectively. Translocation of14C-AMCP was limited to the foliage, which reached maximum translocation (34%) at 96 HAT. Most of the recovered14C-AMCP remained in the leaf wash, treated leaf, or foliage, whereas minimal radiation was detected in the crown, roots, or root exudates throughout the 192-h period. No AMCP metabolism was observed in tall fescue through the 192 HAT. These data suggest AMCP applied to tall fescue can remain bioavailable, and mishandling treated plant material could result in off-target injury.

Bushkiller (Cayratia japonica) is a herbaceous, perennial vine that reproduces from seed and vegetative root structures within its native range. However, this species is considered invasive in the United States due to prolific shoot production, which can overtop surrounding vegetation. Cultural control practices, such as mulching, have been observed to further the spread of this species through regeneration of root fragments. Research was conducted to determine the regenerative capacity of bushkiller root fragments (1 to 7 cm; 2.5 to 18 inches) buried at various depths (0 to 40 cm). Root length and planting depth affected leaf number, shoot number, plant height, and shoot biomass. Bushkiller leaf density, shoot density, plant height, and dry weight increased as root fragment length increased from 1 to 7 cm; conversely, these variables decreased as planting depth increased from 0 to 40 cm. Results indicate bushkiller regeneration capacity from root fragments is extremely high and control practices that fragment roots should be avoided to reduce further spread.

Synthetic auxin herbicides are widely utilized in golf course settings for selective broadleaf weed control. Aminocyclopyrachlor (AMCP) is a newly registered pyrimidine carboxylic acid with similar chemical mode-of-action and structure to triclopyr (TRIC) and clopyralid (CLPY). Off-target injury on terrestrial plants has been documented following exposure to turfgrass clippings previously treated with TRIC and CLPY. Management practices on golf courses can distribute turfgrass clippings into water bodies; however, research has not evaluated the bioavailability of synthetic auxin residues from turfgrass clippings to aquatic and riparian plants within these environments. A bioassay study was conducted to determine the response of alligatorweed and parrotfeather to tall fescue clippings previously treated with synthetic auxin herbicides. Previously treated AMCP and TRIC + CLPY clippings were placed into growth containers mimicking a lentic system containing both alligatorweed and parrotfeather. Results indicated all herbicide treated clippings induced significant growth responses to alligatorweed and parrotfeather growth compared to a nontreated mulch and nontreated control. Alligatorweed control was greater from AMCP clippings treated 14, 7, 3, and 1 DBCC (49, 60, 90, and 80%, respectively) than comparative TRIC + CLPY clippings (33, 25, 37, and 64%, respectively) at 10 weeks after treatment (WAT). Parrotfeather control was greater from AMCP clippings (57 to 87%) than TRIC + CLPY clippings (9 to 63%) collected from all days before clipping collection (DBCC) timings when evaluated 6 WAT. At 10 WAT, greater parrotfeather control and shoot reduction was observed from AMCP than TRIC + CLPY clippings when treated 14, 7, and 3 DBCC. Based on these data, synthetic auxin residues can become bioavailable to aquatic and riparian plants within aqueous environments.