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Azoxystrobin (strobilurin fungicide) and imidacloprid (neonicotinoid insecticide) have been detected in surface waters near treated agricultural, urban, and mixed landscapes. The hazards of pestici...

Pesticides can move off-target resulting in contamination of sensitive water bodies and causing adverse effects on inhabiting species. Through best management practices, such as the implementation of vegetative buffer strips, off-target movement of pesticides can be decreased, and compound degradation can be increased via phytoremediation. In this study, blueflag iris (Iris versicolor), broomsedge (Andropogon virginicus) and switchgrass (Panicum virgatum) were planted in soil treated with one of three commonly used pesticides. At 28, 56 and 112 days after treatment (DAT), plants were destructively harvested and analyzed for pesticide residue in soil and above-ground and below-ground vegetation using high-performance liquid chromatography (HPLC). Relative to the amount of pesticide found in planted pots compared to non-planted pots, I. versicolor was found to reduce greater atrazine in soil compared to non-planted pots at 112 DAT by 58.7%. I. versicolor was also the most capable of reducing azoxystrobin, by 86.9% compared to non-planted pots, from the soil at 112 DAT. At the same sampling time, I. versicolor and P. virgatum reduced greater imidacloprid from soil by 62.5% and 64.3% compared to non-planted pots, respectively. This information supports the recommendation for establishment of diverse plant species for optimization of phytoremediation capacities. Novelty statement While research has found that plants can absorb and remediate synthetic chemicals, this practice is only sustainable if used with native plants that require low maintenance and are tolerant to the applied substances. Various previous studies observe plants that are fast-growing, tolerant to environmental conditions, require low-maintenance, and are hardy. However, these plant species are not always suitable for any location and are often considered invasive and/or weed-like. The present research initiates a list of plant species which can be used within the southeastern United States and similar areas to phytoremediate commonly used pesticides atrazine, azoxystrobin, and imidacloprid and prevent off-target movement.

BACKGROUND Unmanned aerial vehicles (UAVs) have been used in agriculture to collect imagery for crop and pest monitoring, and for decision‐making purposes. Spraying‐capable UAVs are now commercially available worldwide for agricultural applications. Combining UAV weed mapping and UAV sprayers into an UAV integrated system (UAV‐IS) can offer a new alternative to implement site‐specific pest management. RESULTS The UAV‐IS was 0.3‐ to 3‐fold more efficient at identifying and treating target weedy areas, while minimizing treatment on non‐weedy areas, than ground‐based broadcast applications. The UAV‐IS treated 20–60% less area than ground‐based broadcast applications, but also missed up to 26% of the target weedy area, while broadcast applications covered almost the entire experimental area and only missed 2–3% of the target weeds. The efficiency of UAV‐IS management practices increased as weed spatial aggregation increased (patchiness). CONCLUSION Integrating UAV imagery for pest mapping and UAV sprayers can provide a new strategy for integrated pest management programs to improve efficiency and efficacy while reducing the amount of pesticide being applied. The UAV‐IS has the potential to improve the detection and control of weed escapes to reduce/delay herbicide resistance evolution. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., The integration of UAVs for weed and pest detection with currently commercially available UAV sprayers can increase the efficiency of pesticide applications and help manage pesticide resistance.

In recent years, unmanned aerial vehicle (UAV) technology has expanded to include UAV sprayers capable of applying pesticides. Very little research has been conducted to optimize application parameters and measure the potential of off-target movement from UAV-based pesticide applications. Field experiments were conducted in Raleigh, NC during spring 2018 to characterize the effect of different application speeds and nozzle types on target area coverage and uniformity of UAV applications. The highest coverage was achieved with an application speed of 1 m s−1 and ranged from 30% to 60%, whereas applications at 7 m s−1 yielded 13% to 22% coverage. Coverage consistently decreased as application speed increased across all nozzles, with extended-range flat-spray nozzles declining at a faster rate than air-induction nozzles, likely due to higher drift. Experiments measuring the drift potential of UAV-applied pesticides using extended-range flat spray, air-induction flat-spray, turbo air–induction flat-spray, and hollow-cone nozzles under 0, 2, 4, 7, and 9 m s−1 perpendicular wind conditions in the immediate 1.75 m above the target were conducted in the absence of natural wind. Off-target movement was observed under all perpendicular wind conditions with all nozzles tested but was nondetectable beyond 5 m away from the target. Coverage from all nozzles exhibited a concave-shaped curve in response to the increasing perpendicular wind speed due to turbulence. The maximum target coverage in drift studies was observed when the perpendicular wind was 0 and 8.94 m s−1, but higher turbulence at the two highest perpendicular wind speeds (6.71 and 8.94 m s−1) increased coverage variability, whereas the lowest variability was observed at 2.24 m s−1 wind speed. Results suggested that air-induction flat-spray and turbo air–induction flat-spray nozzles and an application speed of 3 m s−1 provided an adequate coverage of target areas while minimizing off-target movement risk.

Susceptibility of a system to colonization by a weed is in part a function of environmental resource availability. Doveweed [Murdannia nudiflora(L.) Brenan] can establish in a variety of environments; however, it is found mostly in wet or low-lying areas with reduced interspecies competition. Four studies evaluated the effect of mowing height, interspecies competition, and nitrogen, light, and soil moisture availability onM. nudifloraestablishment and growth. A field study evaluated the effect of mowing height onM. nudifloraestablishment. In comparison with unmowed plots, mowing at 2 and 4 cm reduced spread 46% and 30%, respectively, at 9 wk after planting. Effect of mowing height and nitrogen fertilization on ‘Tifway’ bermudagrass (Cynodon dactylonBurtt-Davy×C. transvaalensisL. Pers.) andM. nudiflorainterspecies competition was evaluated in a greenhouse trial.Murdannia nudifloracoverage was 62% greater in flats maintained at 2.6 cm than flats maintained at 1.3 cm. Supplemental application of 49 kg N ha−1mo−1increasedM. nudifloracoverage 75% in comparison with 24.5 kg N ha−1mo−1. A difference inM. nudifloracoverage could not be detected between flats receiving 0 and 24.5 kg N ha−1mo−1, suggesting moderate nitrogen fertilization does not encourageM. nudifloracolonization. Effect of light availability onM. nudifloragrowth and development was evaluated in a greenhouse study. Growth in a 30%, 50%, or 70% reduced light environment (RLE) did not affect shoot growth on a dry weight basis in comparison with plants grown under full irradiance; however, internode length was 28% longer in a 30% RLE and 39% longer in a 50% and 70% RLE. Effect of soil moisture onM. nudifloragrowth and development was evaluated in a greenhouse study. Plants maintained at 50%, 75%, and 100% field capacity (FC) increased biomass>200% compared with plants maintained at 12.5% or 25% FC.

Doveweed is a problematic weed of lawns and sod production, as well as golf course roughs, fairways, and tees. End-user reports of selective POST control options are inconsistent and control is often short-lived. In addition, inconsistent control with non-selective herbicides such as glyphosate is common. The goals of this research were: (1) evaluate selective POST doveweed control options in ‘Tifway’ hybrid bermudagrass turf; (2) compare efficacy of single vs. sequential applications of selective POST herbicides; (3) quantify doveweed tolerance to glyphosate; and (4) quantify recovery of foliar applied glyphosate following treatment with a C14-glyphosate solution. A single application of sulfentrazone metsulfuron; thiencarbazone iodosulfuron dicamba or 2,4-D MCPP dicamba carfentrazone; or thiencarbazone foramsulfuron halosulfuron provided >60% control 2 weeks after initial treatment (WAIT). A second application of these treatments 3 WAIT improved control 6 WAIT. Two applications of 2,4-D MCPP dicamba carfentrazone or thiencarbazone foramsulfuron halosulfuron provided ~80% control 6 WAIT. Doveweed was tolerant to glyphosate application up to 5.68 kg ae ha-1. Absorption of 14C-glyphosate was compared between doveweed with cuticle intact, doveweed with a disturbed cuticle, and smooth crabgrass. 14C-glyphosate recovery from the leaf surface of doveweed plants with an intact cuticle was 93.6%. In comparison, 14C-glyphosate recovery from the leaf surface of doveweed plants with a disrupted cuticle and the leaf surface of crabgrass plants was 79.1 and 70.5%, respectively.Nomenclature: Bromoxynil; carfentrazone; dicamba; foramsulfuron; glyphosate; halosulfuron; iodosulfuron; mecoprop; metsulfuron; MSMA; quinclorac; sulfentrazone; thiencarbazone; 2,4-D; doveweed, Murdannia nudiflora (L.) Brenan; smooth crabgrass, Digitaria ischaemum (Schreb.) Schreb. ex Muhl.; ‘Tifway’ bermudagrass, Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davy.

Turfgrass renovations commonly involve changing cultivars or species that are better suited for a given setting. Common bermudagrass [Cynodon dactylon (L.) Pers.] is a perennial turfgrass that is difficult to eradicate before renovations, and poses contaminant concerns for the subsequent stand. Dazomet is a granular soil fumigant that has activity on various pests, including common bermudagrass. Field research was conducted from 2015 to 2016 in Raleigh, NC and College Station, TX to evaluate dazomet treatments including various combinations of soil incorporation (irrigation- or tillage-incorporated) and sealing (tarp or no tarp) methods, application rates [291, 291 followed by (fb) 291, 468, or 583 kg·ha−1], and fluazifop-P [fluazifop (0.4 kg·ha−1)] + glyphosate (2.8 kg·ha−1 acid equivalent) application(s) for established common bermudagrass control. Overall, treatments required fluazifop + glyphosate before dazomet application for acceptable control (>90% cover reduction) at 42 and 46 weeks after initial treatment (WAIT) in Texas and North Carolina, respectively. Soil-incorporation results varied by location, with dazomet application (583 kg·ha−1) fb tillage resulting in ≥88% cover reduction across locations, while acceptable control from irrigation incorporation was only observed in North Carolina. Tarping did not improve efficacy when tillage incorporation at the maximum label application rate provided acceptable control, suggesting practitioners may eliminate this procedure. Information from this research will aid turfgrass managers in developing cost-effective, ecologically sound common bermudagrass eradication programs before renovations.

Vaseygrass is an invasive, perennial C4-grass commonly found on roadsides in areas with poorly drained soils. Due to its upright growth habit and seedhead production, vaseygrass can impair motorist sightlines and subsequently, require increased management inputs to maintain vegetation at an acceptable height. Two field experiments were conducted from 2012 to 2015 on North Carolina roadsides to evaluate the effect of mowing and mowing timing with respect to applications of various herbicides on vaseygrass control. Both experiments evaluated clethodim (280 g ai ha−1), foramsulfuron halosulfuron thiencarbazone-methyl (44 69 22 g ai ha−1), imazapic (140 g ai ha−1), metsulfuron nicosulfuron (16 59 g ai ha−1), and sulfosulfuron (105 g ai ha−1) with a nonionic surfactant at 0.25% v/v. Experiment one focused on the effect of mowing (routinely mowed or nonmowed) and herbicide application timing (fall-only, fall-plus-spring, or spring-only), while experiment two focused on pre-herbicide application mowing intervals (6, 4, 3, 2, 1, or 0 wk before treatment [WBT]). From experiment one, routine mowing reduced vaseygrass cover in nontreated plots 55% at 52 wk after fall treatment (WAFT), suggesting this cultural practice should be employed where possible. Additionally, routine mowing and herbicide application season affected herbicide efficacy. Treatments providing >70% vaseygrass cover reduction at 52 WAFT included routinely mowed fall-only clethodim and fall-plus-spring imazapic, and fall-plus-spring metsulfuron nicosulfuron across mowing regimens. Within clethodim, mowing vaseygrass 2 or 1 WBT resulted in the lowest cover at 40 (1 to 2%) and 52 (4 to 6%) wk after treatment (WAT) compared to other intervals, which aligns with current label vegetation height at treatment recommendation. Vaseygrass persisted across all treatments evaluated through 52 WAT, suggesting eradication of this species will require inputs over multiple growing seasons.Nomenclature: Clethodim; foramsulfuron; halosulfuron; imazapic; metsulfuron; nicosulfuron; sulfosulfuron; thiencarbazone; vaseygrass, Paspalum urvillei Steud.Paspalum urvillei es una graminea C4 perenne invasiva que se encuentra comunmente a las orillas de caminos y en areas con suelos con poco drenaje. Debido a su habito de crecimiento vertical y produccion de espigas, P. urvillei puede limitar la visibilidad de vehiculos y subsecuentemente incrementar los insumos de manejo para mantener la vegetacion a una altura aceptable. Se realizaron dos experimentos de campo desde 2012 a 2015 en orillas de caminos en North Carolina para evaluar los efectos de la chapia y el momento de chapia con respecto a las aplicaciones de varios herbicidas sobre el control de P. urvillei. Ambos experimentos evaluaron clethodim (280 g ai ha−1), foramsulfuron halosulfuron thiencarbazone-methyl (44 69 22 g ai ha−1), imazapic (140 g ai ha−1), metsulfuron nicosulfuron (16 59 g ai ha−1), y sulfosulfuron (105 g ai ha−1) con un surfactante no ionico a 0,25% v/v. El experimento uno se enfoco en el efecto de la chapia (chapia rutinaria o sin chapia) y el momento de aplicacion de herbicidas (solo otono, otono mas primavera, o solo primavera), mientras que el experimento dos se enfoco en el intervalo entre la chapia y la aplicacion de herbicidas (6, 4, 3, 2, 1, o 0 semanas antes del tratamiento [WBT]). En el experimento uno, la chapia rutinaria redujo 55%la cobertura de P. urvillei en parcelas sin tratamiento con herbicidas a 52 semanas despues del tratamiento de otono (WAFT), sugiriendo que esta practica cultural deberia ser empleada cuando sea posible. Adicionalmente, la chapia rutinaria y la temporada de aplicacion de herbicida afectaron la eficacia del herbicida. Los tratamientos que proveyeron >70% de reduccion en la cobertura de P. urvillei a 52 WAFT incluyeron chapia rutinaria y clethodim solo en el otono e imazapic en el otono mas la primavera, y metsulfuron nicosulfuron en el otono mas la primavera para todos los regimenes de c

Bermudagrass, Cynodon spp. is one of the most commonly grown turfgrass genera in the southern United States having excellent drought tolerance, but poor tolerance to shade. Developing cultivars tolerant to shade would allow bermudagrass to become more prevalent in home lawns or other recreational areas in the southeast, where trees dominate the landscape. In this field study, nine accessions collected from Pretoria, South Africa were evaluated for their ability to grow under shade with varying fertility treatments. These accessions and cultivars ‘Celebration’, ‘TifGrand’, and ‘Tifway’ were evaluated under 0%, 63%, and 80% continuous shade during 2011–12. For both years, significant differences among shade levels, genotypes, and the interaction of the two were observed. As expected, the progression from 0% to 63% to 80% shade reduced normalized difference vegetation index (NDVI), percent turfgrass cover (TC), and turf quality (TQ) readings for all accessions. Some genotypes, however, were able to maintain adequate quality and aggressiveness under 63% shade. ‘Celebration’, WIN10F, and STIL03 performed better than ‘Tifway’ (P ≤ 0.05), the susceptible control. Overall, our results indicate that there are promising genotypes among the bermudagrass materials collected from South Africa. These accessions represent additional sources of shade hardiness to be used in bermudagrass breeding. Furthermore, higher nitrogen fertility provided increased NDVI and TQ in some instances suggesting an added benefit of fertility under low-light conditions. However, the increased economic value attributed to the added inputs associated with these increases is outweighed by the low impacts offered.

Saflufenacil, a pyrimidinedione herbicide, is used for contact and residual broadleaf weed control in various crops. Bioactivity of saflufenacil in soil was tested in greenhouse and laboratory studies on 29 soils representing a wide range of soil properties and geographic areas across the United States. A greenhouse bioassay method was developed using various concentrations of saflufenacil applied PPI to each soil. Whole canola plants were harvested 14 d after treatment, and fresh and dry weights were recorded. Nonlinear regression analysis was used to determine the effective saflufenacil doses for 50% (ED50,), 80% (ED80), and 90% (ED90) inhibition of total plant fresh weight. Bioactivity of saflufenacil in soil was strongly correlated to soil organic (R= 0.85) and humic matter (R= 0.81), and less correlated to cation exchange capacity (R= 0.49) and sand content (R= −0.32). Stepwise regression analysis indicated that organic matter was the major soil constituent controlling bioactivity in soil and could be used to predict the bioactivity of saflufenacil. Saflufenacil phytotoxicity was found to be dependent on soil property; therefore, efficacy and crop tolerance from PRE and PPI applications may vary based on soil organic matter content and texture classification.

The synthetic auxin herbicides, aminocyclopyrachlor and clopyralid, control dicotyledonous weeds in turf. Clippings of turfgrass treated with synthetic auxin herbicides have injured off-target plants exposed to herbicide-laden clippings. Labels of aminocyclopyrachlor and clopyralid recommend that clippings of treated turfgrass remain on the turf following a mowing event. Alternative uses for synthetic auxin-treated turfgrass clippings are needed because large quantities of clippings on the turf surface interfere with the functionality and aesthetics of golf courses, athletic fields, and residential turf. A white clover bioassay was conducted to determine the persistence and bioavailability of aminocyclopyrachlor and clopyralid in turfgrass clippings. Aminocyclopyrachlor and clopyralid were each applied at 79 g ae ha−1 to mature tall fescue at 56, 28, 14, 7, 3.5, and 1.75 d before clipping collection (DBCC). Clippings were collected, and the treated clippings were recycled onto adjacent white clover plots to determine herbicidal persistence and potential for additional weed control. Clippings of tall fescue treated with aminocyclopyrachlor produced a nonlinear regression pattern of response on white clover. Calculated values for 50% response (GR50) for visual control, for normalized difference vegetative index (NDVI), and for reduction in harvested biomass were 20.5, 17.3, and 18.7 DBCC, respectively, 8 wk after clippings were applied. Clippings of tall fescue treated with clopyralid did not demonstrate a significant pattern for white clover control, presumably because clopyralid was applied at a less-than-label rate. The persistence and bioavailability of synthetic auxin herbicides in clippings harvested from previously treated turfgrass creates the opportunity to recycle clippings for additional weed control.

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.

Growth chamber experiments were conducted to assess the effects of foliage-only, soil-only, and foliage-plus-soil placements of amicarbazone on annual bluegrass and creeping bentgrass growth. Evaluated herbicide treatments included amicarbazone at 49 or 147 g ai ha−1, as well as bispyribac-sodium at 74 g ai ha−1for comparative purposes. Data from this research agree with previous reports of amicarbazone plant uptake. Amicarbazone is absorbed via above- and belowground pathways; however, plant growth is inhibited more by root uptake. Compared to foliage-only amicarbazone placement, soil-only placement more than doubled reductions in aboveground biomass and root mass 56 d after treatment (DAT), whereas no differences were detected between placements including soil contact. Across all evaluated parameters in this research, amicarbazone (49 g ha−1) impacted creeping bentgrass growth similarly to bispyribac-sodium, whereas annual bluegrass growth was inhibited more by amicarbazone, suggesting it provides a more efficacious chemical option for end-user applications.

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.

Pesticide sorption by soil is among the most sensitive input parameters in many pesticide-leaching models. For many pesticides, organic matter is the most important soil constituent influencing pesticide sorption. Increased fertility, irrigation, and mowing associated with highly maintained turfgrass areas result in constant deposition of organic material, creating a soil system that can change drastically with time. Changes in soil characteristics could affect the environmental fate of pesticides applied to turfgrass systems of varying ages. Sorption characteristics of simazine andS-metolachlor were determined on five soils from bermudagrass systems of increasing ages (1, 4, 10, 21, and 99 yr) and compared to adjacent native pine and bare-ground areas. Surface soil (0 to 5 cm) and subsurface soil (5 to 15 cm) from all sites were air-dried and passed through a 4-mm sieve for separation from plant material. Using a batch-equilibrium method, sorption isotherms were determined for each soil. Data were fit to the Freundlich equation, andKd(soil sorption coefficient) andKoc(organic carbon sorption coefficient) values were determined. Sorption and soil system age were directly related to organic matter content in the soil. Sorption of both herbicides increased with age of the soil system and was greatest on the surface soil from the oldest bermudagrass soil system. Herbicide sorption decreased at greater soil depths with lower organic matter. Greater amount of14C–simazine sorbed to subsurface soil of the oldest turfgrass system compared to14C–S-metolachlor. Results indicate that as bermudagrass systems age and accumulate higher organic matter levels increased herbicide sorption may decrease the leaching potential and bioavailability of simazine andS-metolachlor.

Amicarbazone is a photosystem II–inhibiting herbicide recently registered for annual bluegrass control in established turf systems that include creeping bentgrass. However, research to date reveals potential issues with creeping bentgrass tolerance to amicarbazone. Currently, the plant-growth regulator paclobutrazol is widely adopted by turf managers for chemical annual bluegrass suppression in creeping bentgrass putting greens. Field experiments were conducted throughout North Carolina in the spring of 2010 and 2011 to assess treatment regimens that included amicarbazone (49, 65, or 92 g ai ha−1) and paclobutrazol (70, 140, or 280 g ai ha−1) applied alone, as tank-mixtures, or used in tandem, at varying rates and sequential timings for annual bluegrass control in creeping bentgrass putting greens. In general, regimens including both compounds provided greater annual bluegrass control and acceptable turfgrass tolerance compared with stand-alone applications of amicarbazone at 8 and 12 wk after initial treatment (WAIT). When comparing regimens that included amicarbazone at 49 or 65 g ha−1, creeping bentgrass tolerance was greater for the higher application rate applied less frequently. These results indicate amicarbazone usage on creeping bentgrass greens may be beneficially affected with the incorporation of paclobutrazol to treatment regimens because annual bluegrass control with the combination was equal to or greater than stand-alone amicarbazone applications, and creeping bentgrass tolerance was superior 8 and 12 WAIT.

Turfgrass weed scientists commonly use visual ratings (VR) to assign a numerical value to a turfgrass or weed response. These ratings lack quantifiable numerical values and are considered subjective. Alternatives to VR, including line intersect analysis (LIA) and digital image analysis (DIA), have been used to varying extents in turfgrass research. Alternatives can be expensive, labor intensive, and can require extensive calibration and increased time for data acquisition. Minimal research has been conducted evaluating rating methods used in turfgrass weed science. Trials were conducted in 2007 and 2008 to evaluate ratings methods used to quantify large crabgrass populations as influenced by tall fescue mowing height (2.5, 5.1, 7.6, and 10.2 cm). Percent large crabgrass cover was assessed utilizing VR, LIA, and DIA to determine if differences existed among evaluation methods. Pairwise comparisons, Pearson's correlation, and linear regression were performed to compare evaluations. All rating methods were significantly correlated to one another. Differences of large crabgrass cover estimates existed between LIA and DIA data at all mowing heights and between VR and DIA data at the 7.6 and 10.2 cm mowing heights in 2007. Authors believe that shadows produced by the turf canopy at higher (≥ 7.6 cm) mowing heights increased DIA estimates of large crabgrass cover. At trial initiation in 2007, researchers did not capture calibration images because the methodology to eliminate a shadow influence using a standard digital image had not been published. Additional DIA calibration in 2008 corrected for canopy shadows, and no differences were observed in large crabgrass cover between all evaluation methods indicated by nonsignificance pairwise comparisons and estimated regression parameters. These data indicate VR are no different than LIA or DIA in estimating large crabgrass cover as affected by tall fescue mowing height.

Aminocyclopyrachlor (AMCP) is a newly developed synthetic auxin herbicide for broadleaf weed control in turfgrass systems. AMCP has been observed to undergo rapid photodecomposition in shallow water when exposed to sunlight. Most herbicide applications on golf courses occur during the morning when dew is still present on the turfgrass canopy. These conditions could result in efficacy loss if photolysis occurred while AMCP is suspended in dew droplets. Research was conducted to determine the effect of ambient moisture on AMCP efficacy. AMCP (79 and 105 g ae ha−1), aminopyralid (280 g ae ha−1), and two AMCP granular formulations (84 g ha−1) were applied to dew-covered (WET) and dew-excluded (DRY) ‘Tifway' bermudagrass plots. Herbicide treatments applied to WET plots had greater visually rated bermudagrass injury than respective treatments applied to DRY plots at 7 and 21 d after treatment (DAT), with the exception of aminopyralid at 21 DAT. Normalized difference vegetative index on turfgrass quality complemented visual ratings, indicating greater turfgrass quality reductions when applied to WET vs. DRY plots. These results indicate that AMCP applications made to dew-covered turfgrass can increase herbicidal efficacy, and no significant losses due to photodegradation were observed.

Research has shown that pesticide residue in clippings from previously treated turfgrass may become bioavailable as grass decomposes, adversely affecting off-target organisms. We conducted a field study to quantify 2,4-D (2,4-dichlorophenoxyacetic acid) and azoxystrobin (methyl(E)-2-{2[6-(2-cyanophenoxy)pyrmidin-4-yloxy]phenyl}-3-methoxyacrylate) residues in turfgrass clippings collected from hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt–Davy], tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire], and zoysiagrass (Zoysia japonica Steud.). A subsequent greenhouse experiment was conducted to measure pesticide release from clippings into water. 2,4-D (1.6 kg a.i. ha⁻¹) and azoxystrobin (0.6 kg a.i. ha⁻¹) were applied to field plots at 32, 16, 8, 4, 2, 1, or 0 d before collection of the clippings. Clippings were collected from each experimental unit to quantify pesticide release from clippings into water. Both 2,4-D and azoxystrobin were detected when turfgrass was treated over the 32-d experimental period, suggesting that clipping management should be implemented for an extended period of time after application. Pesticide residue was detected in all water samples collected, confirming 2,4-D and azoxystrobin release from turfgrass clippings; however, pesticide release varied between compounds. Two days after clippings were incorporated in water, 39 and 10% of 2,4-D and azoxystrobin were released from clippings, respectively. Our research supports the currently recommended practice of returning clippings to the turfgrass stand when mowing because removal of 2,4-D and azoxystrobin in clippings may reduce pest control and cause adverse off-target impacts.

Greenhouse experiments were conducted to evaluate the effect of selective herbicide placement on sedge shoot number, shoot weight, and root weight. Sulfentrazone, sulfosulfuron, and trifloxysulfuron were applied to soil only, foliage only, or soil plus foliage. Sulfentrazone provided greater yellow nutsedge and false green kyllinga growth reduction compared to purple nutsedge. Sulfosulfuron provided greater purple nutsedge and false green kyllinga growth reduction compared to yellow nutsedge; these species responded similarly to trifloxysulfuron. Soil and soil plus foliar applications provided the highest level of growth suppression, indicating herbicide–soil contact is required for optimum sedge control with these three herbicides. Future research should evaluate techniques that optimize herbicide–soil contact to improve herbicide efficacy. Nomenclature: Sulfentrazone; sulfosulfuron; trifloxysulfuron; false green kyllinga, Kyllinga gracillima Miq.; purple nutsedge, Cyperus rotundus L.; yellow nu...

Experiments were conducted during 2007 and 2008 to evaluate various herbicide treatment regimes for POST purple nutsedge and false-green kyllinga control. Evaluated herbicides included halosulfuron, sulfentrazone, sulfosulfuron, and trifloxysulfuron. Evaluated treatments did not cause objectionable bermudagrass injury at any time. Results were variable across years, likely due to reduced rainfall in 2007 causing reduced purple nutsedge and false-green kyllinga growth. In 2007, averaged across herbicide rate and number of applications, sulfosulfuron provided greater purple nutsedge control than trifloxysulfuron. Sulfosulfuron and trifloxysulfuron provided similar levels of control in 2008, although both were less effective than in 2007. In 2007, sulfosulfuron and trifloxysulfuron provided excellent (> 90%) false-green kyllinga control, and trifloxysulfuron provided greater control (80%) compared to sulfosulfuron (61%) in 2008. Sulfentrazone provided < 30 and 60% purple nutsedge and false-green kyllinga control, respectively. A sequential application applied 6 wk after initial treatment provided the highest level of purple nutsedge and false-green kyllinga control with evaluated herbicides. Tank-mix partners to enhance purple nutsedge control with sulfentrazone provided inconsistent results. Sulfosulfuron and trifloxysulfuron offer acceptable POST perennial sedge control in tolerant warm-season turfgrasses.

Flue-cured tobacco is sensitive to foliar and soil residues of off-target synthetic auxin drift. Aminocyclopyrachlor is a newly developed synthetic auxin herbicide that may be used in right-of-way applications for broadleaf weed and brush control. Aminocyclopyrachlor is considered a reduced-risk alternative in rights-of-way compared with similar compounds because of its low application rate and volatility risk. However, no research is available on the response of field-grown, flue-cured tobacco to aminocyclopyrachlor drift exposure. Research was conducted in 2009 and 2010 at the Border Belt Tobacco Research Station in Whiteville, NC, to determine the response of ‘NC 71’ flue-cured tobacco to five simulated drift rates of aminocyclopyrachlor (0.31, 1.6, 3.1, 15.7, and 31.4 g ae ha−1) and one aminopyralid (6.1 g ae ha−1) simulated drift rates applied pretransplant incorporated, pretransplant unincorporated, 3 wk after transplant, and 6 wk after transplant. All herbicide rates and application timings caused significant visual tobacco injury, ranging from slight to severe with increasing herbicide drift rates. Tobacco plant heights and fresh weights were reduced at all application timings receiving ≥ 15.7 g ha−1aminocyclopyrachlor and the comparative aminopyralid rate.

Experiments were initiated during 2003 and 2004 to evaluate application placement equipment for plant growth regulator (PGR) applications along bahiagrass roadsides. Recently designed equipment combine low-volume application and pesticide placement technology. Application placement equipment conceal the image of a traditional spray application. Evaluated application placement equipment included a wet-blade mower (Burch Wet Blade) and rotary-wick applicator (Weedbug™) compared with a traditional broadcast spray. Wet-blade mowers are designed to mow and simultaneously apply a pesticide solution to a cut stem or leaf in a single pass, whereas rotary-wick applicators are designed to wick a solution onto foliage. Evaluated PGRs included imazapic (9, 35, or 53 g ha−1) and sulfometuron-methyl (26 g ha−1). Bahiagrass injury varied with application placement equipment and was greater with rotary-wick applications in 2003, compared with foliar broadcast applications and the wet-blade mower. Bahiagrass seedhead suppression ranged from 31 to 60% with application placement equipment in July 2003 compared with 93% for a broadcast spray. In 2004, rotary wick- or broadcast-applied PGRs provided excellent (> 90%) seedhead suppression. Although application placement equipment may have advantages to broadcast-spray applications, evaluated equipment did not enhance bahiagrass suppression along roadsides in North Carolina compared with a foliar broadcast spray. Additional research is needed to determine if this type of application may provide consistent results with other species and compounds.

Anthraquinone (AQ)-based repellents have been shown to reduce Canada goose (Branta canadensis) use of turfgrass; however, impacts of frequent mowing on efficacy of AQ have not been studied. Our objective was to determine efficacy and longevity of a rain- fast AQ-based avian repellent, FlightControlH PLUS (FCP), as a deterrent of free-ranging resident Canada geese under 2 mowing frequencies. We conducted the study at 8 sites in the Triangle region (Raleigh, Durham, and Chapel Hill) of North Carolina, USA. We arranged our experiment in a randomized complete block design, with each of 8 sites containing 4 0.1-ha treatment combinations: 1) treated with FCP and mowed every 4 days (T4), 2) treated with FCP and mowed every 8 days (T8), 3) untreated and mowed every 4 days, and 4) untreated and mowed every 8 days. We conducted 4 37-day field sessions (Jun-Jul 2007, Sep-Oct 2007, Jun-Jul 2008, and Sep-Oct 2008), representing the summer molting phase and the full-plumage phase. Resident goose use (measured by daily no. of droppings) was 41-70% lower on treated plots than on untreated plots, but use was similar between T4 and T8. Average FCP coverage on grass blades decreased in coverage from approximately 95% to 10% over the 30-day posttreatment phase. Results indicate that resident Canada goose use of FCP-treated turfgrass areas was lower than untreated areas even when chemical coverage on grass was 10%. Further, mowing frequency did not have a clear impact on the efficacy of FCP as a Canada goose repellent.

High populations of Canada geese (Branta canadensis L.) can lead to feces accumulation in areas adjacent to surface waters, creating concern about aquatic eutrophication. Further, turf managers and livestock farmers work to keep their facilities free of noxious or toxic weeds that geese potentially disperse. We investigated the prevalence of viable seeds and nitrogen and phosphorus content in resident Canada goose droppings. During spring, summer, and fall of 2008, we collected 127 fresh individual droppings which were placed in seedling trays within an irrigated greenhouse and allowed 30 days for weed seed to germinate. Trays were cold stratified for 30 days and returned to the greenhouse for an additional 30 days. Also, during summer and fall of 2007 and 2008, we tested 304 fecal samples from 8 sites for total Kjeldahl nitrogen (TKN) and total phosphorus (TP). Out of 127 droppings planted, 4 plants germinated (3.1%): Pennsylvania smartweed (Polygonum pennsylvanicum L.), annual bluegrass (Poa annua L.), and 2 Kyllinga spp. The average amounts of TKN and TP in fecal samples were 24.2 mg/g (range = 12.6 to 55.7) and 3.6 mg/g (range = 1.4 to 8.3) of dry matter, respectively. The results indicate that Canada geese in suburban and urban areas are not frequent vectors of viable seeds, but do have potential to contribute nutrients to adjacent surface waters.

Concern about pesticide losses from maintained turfgrass areas led us to examine the fate of the triazine herbicide simazine in turfgrass systems and, specifically, interactions between simazine binding to soil organic matter and biodegradation. Soil samples were removed from turfgrass systems of different ages, placed in microcosms, conditioned as sterile or nonsterile, and exposed to 14 C-simazine. At seven sampling intervals, the soil was extracted and 14 C was separated into three pools; bound, extractable, and CO 2 . With sterilized surface soil (0-5 cm), 52, 70, and 71% of applied 14 C-simazine was bound to soil from the 4-, 21-, and 99-yr-old turfgrass systems, respectively, after 16 wk. With nonsterile conditions, biodegradation became dominant, as 60 to 80% of the 14 C was recovered in the CO 2 fraction and binding was held at -20%. Among all soils evaluated, bound 14 C and 14 CO 2 production was lower in subsurface soil (5-15 cm) from the 4- and 21-yr-old turfgrass systems. 14 C-simazine disappearance time (DT 50 ) values under nonsterile conditions ranged from 0.9 to 5.8 wk. Results indicate that turfgrass systems have a relatively low amount of simazine available for leaching as the systems age due to a large capacity for biodegradation and binding to organic matter.

Anecdotal evidence suggests that dallisgrass (Paspalum dilatatum Poir.) and bahiagrass (Paspalum notatum Fluegge), two of the most troublesome weed species in managed turfgrass, are both drought and flood tolerant. Water table depth gradient tanks were employed to identify habitat specialization and competitive differences between dallisgrass and bahiagrass. Shoot and rhizome final biomass and survival were used as metrics for plants grown in monoculture or competition with hybrid bermudagrass (Cynodon transvaalensis Burtt Davy x C. dactylon (L.) Pers. 'Tifway 419') in sand or sandy loam soil. Shoot and rhizome growth of dallisgrass was greatest at the levels of highest soil moisture within each gradient tank regardless of soil type or competition. Percent survival of dallisgrass decreased to a low of 50% as depth to water table increased when grown as a monoculture and 12.5% when grown in competition with hybrid bermudagrass. Percent survival of bahiagrass was 100% regardless of water table depth, soil type, or competition. Shoot and rhizome growth of bahiagrass was greatest as depth to water table increased when grown in sandy loam soil. The opposite trend was observed when grown in sandy soil. Results suggest that dallisgrass may be more competitive with hybrid bermudagrass when volumetric soil moisture is high, while bahiagrass may be more competitive when volumetric soil moisture is low.

Dallisgrass (Paspalum dilatatum Poir.) and bahiagrass (Paspalum notatum Fluegge) are two of the most troublesome weed species in managed turfgrass. These rhizomatous, perennial grass species affect appearance, texture, and playability of turf in home lawns, golf courses, and athletic fields. The severity and prevalence of these problem species as well as the difficulty of achieving control with herbicide management alone invite the examination of their realized niches for clues to improved management tactics. The distribution of these species was evaluated in both fairways and roughs of three holes on each of two golf courses in North Carolina. Golf courses were selected based on the presence of both weed species. Individual plants were mapped using a high-precision global positioning system unit. This unit was also used to delineate between the rough and fairway height of cut as well as obtain elevation characteristics of each hole. Soil moisture and soil compaction estimates were obtained by sampling on a 9-m grid. Environmental characteristics used for χ2 analysis consisted of mowing height, soil compaction, soil moisture, and elevation. Data were subjected to χ2 analysis to determine if the existing distribution of Paspalum spp. differed from an expected random distribution across all environmental factors. Bahiagrass growth and distribution was more affected by mowing height than dallisgrass. Bahiagrass was predominantly distributed in the rough, whereas dallisgrass occurred at both mowing heights. Similar responses were observed for both species with regard to soil compaction. Higher plant density for both species was observed in moderately compacted soil (40 to 60 N·m−2). Bahiagrass distribution was unaffected by soil moisture. Dallisgrass density was lower in areas with low volumetric soil water content (less than 27%). Although different from an expected uniform distribution on all six holes, the elevation with the highest Paspalum spp. density varied across holes. Results suggest that it may be possible to disadvantage Paspalum spp. in competitive interactions with desirable species through the alteration of landscape attributes. Substrate selection during construction, aeration, and mowing height may help create a landscape that discourages Paspalum spp. infestation.

Pesticides applied to bermudagrass (Cynodon dactylon L.) can be captured by the canopy, absorbed by the roots, or bound in the thatch layer, which reduces the amount available to leach compared with a fallow soil system where pesticides may be applied directly to soil. 14 C-Simazine was applied to dormant bermudagrass and fallow soil in lysimeters in a cold growth chamber (5°C) (cold-fallow soil) and to actively growing bermudagrass and fallow soil in lysimeters in a greenhouse (25°C) (warm-fallow soil) in April. Following clipping collection, lysimeters were irrigated with 5 cm of water every 3-4 d, and leachate was collected. After 25 d, lysimeters were divided into 2-cm increments from 0 to 10 cm, then 5-cm increments from 10 to 30 cm. Because of evapotranspiration, actively growing bermudagrass and warm-fallow soil yielded significantly less leachate than dormant bermudagrass and cold-fallow soil indicating less moisture is available for downward movement during summer. After the addition of 31 cm of irrigation, the greatest quantities of 14 C-simazine were in the 0- to 2-cm increment for all treatments and decreased with depth. Although the greatest quantities of 14 C-simazine in leachate occurred in dormant bermudagrass, the reached factor was greatest for cold-fallow soil (0.20), followed by dormant bermudagrass (0.17), warm-fallow soil (0.16), and actively growing bermudagrass (0.14). Therefore, simazine is least mobile in bermudagrass during summer and most mobile in fallow soil in winter.

Several field studies have observed increased foramsulfuron efficacy for the control of dallisgrass when foramsulfuron is applied after MSMA. Therefore, laboratory studies were conducted with mature dallisgrass to study the absorption and translocation of 14C-foramsulfuron, and then examine the impact of preliminary applications (preapplications) of MSMA or foramsulfuron on herbicide absorption and movement. Herbicide absorption increased rapidly through 4 h, and by 8 h, differences in absorption between pretreated and control plants were evident. After 48 h, foramsulfuron absorption in non-pretreated plants was 55%, whereas plants that received either pretreatment absorbed 70% of the herbicide. Translocation above (younger tissue) and below (older tissue) the treated leaf was 0.65 and 0.62% for non-pretreated plants, respectively. Pretreatment with foramsulfuron resulted in the translocation of 2.12 and 1.55% of applied radioactivity above and below the treated leaf, respectively. Pretreatment w...

The effect of mowing regime on lateral spread and rhizome growth of dallisgrass and bahiagrass was determined in field studies conducted in 2003 and 2004 in North Carolina over 5 mo. Treatments were selected to simulate mowing regimes common to intensively managed common bermudagrass turfgrass and include 1.3-, 5.2-, and 7.6-cm heights at frequencies of three, two, and two times per week, respectively. A nonmowed check was included for comparison. Lateral spread of dallisgrass was reduced 38 to 47% regardless of mowing regime when compared with the nonmowed check. Rhizome fresh weight of dallisgrass was reduced 49% in 2003 and 30% in 2004 when mowed at the 7.6-cm regime after 5 mo, whereas the 5.2-cm mowing regime caused a reduction of 31%. Rhizome fresh weight of dallisgrass was most negatively affected by the 1.3-cm regime, which caused reductions of 57% in 2003 and 37% in 2004. Lateral spread of bahiagrass was more strongly affected by mowing height and frequency than dallisgrass, with reductions of 21 to 27%, 40%, and 44 to 62% when mowed at 7.6, 5.2, and 1.3-cm regimes, respectively. Rhizome fresh weight of bahiagrass was reduced 24 to 33%, 55%, and 70 to 73% when mowed at 7.6, 5.2, and 1.3 cm, respectively. Based upon these results, areas mowed at a golf course rough height (≥ 5.2 cm) may be more conducive to bahiagrass spread, whereas dallisgrass may tolerate areas mowed at a fairway height (1.3 cm). Mowing at the shorter heights examined in this study clearly reduced the potential ofPaspalumspp. vegetative spread and may help to explain observed distributions ofPaspalumspp. infestations in bermudagrass turfgrass.

Field research was conducted to evaluate plant growth-regulator efficacy for tall fescue growth and seedhead suppression applied using application placement equipment. Specially designed equipment outfitted with fluid application systems applies low-volume plant growth regulator directly on plant foliage, reducing opportunity for drift and visible application. Wet-blade mowers are equipped to apply plant growth regulators and mow in a single pass, whereas rotary-wick applicators simply wipe chemicals directly on uncut vegetation. Therefore, a wet-blade, rotary-wick, and broadcast sprayer system were chosen to apply imazapic at three rates (9, 35, and 53 g ai/ha), and a mefluidide + chlorsulfuron tank mix at 7 + 140 g ai/ha to tall fescue roadsides for vegetative growth and seedhead suppression. Experiments were conducted during the spring and summer of 2004 in central and western North Carolina. Tall fescue was slightly injured and discolored by all treatments but fully recovered by 2 mo after treatment. ...

Dallisgrass response to various MSMA and foramsulfuron herbicide combinations was evaluated from 2004 through 2006 in North Carolina. Dallisgrass control declined with herbicide rates; therefore, only the highest rates (foramsulfuron, 0.15 kg ai/ha; MSMA, 2.5 kg ai/ha) are discussed. Foramsulfuron followed by (fb) foramsulfuron 1 wk after initial treatment (WAIT) provided 60% control of dallisgrass 1 mo after initial treatment (MAIT), but control declined to 40% 3 MAIT. MSMA (2.5 kg ai/ha) applied three times provided 89% dallisgrass control 1 MAIT, but control declined to 71% 3 MAIT. Among 22 MSMA and foramsulfuron sequential application programs, MSMA fb foramsulfuron 2 WAIT fb MSMA 3 WAIT provided the highest control (94%) of dallisgrass 1 MAIT, and control levels remained high (93%) 3 MAIT. This herbicide program provided 85% control 1 yr after initial treatment (YAIT), whereas no other treatment provided greater than 37% control 1 YAIT. Timing of foramsulfuron application following the initial MSMA a...

Understanding herbicide mobility in soils is necessary to prevent ground water contamination. We studied the mass balance distribution of three 14 C-labeled herbicides (atrazine, metolachlor, and primisulfuron-methyl) in three soils (Blanton, Norfolk, and Rains) 128 days after treatment (DAT) to fallow soil column field lysimeters. Analyses were made of surface soil, subsoil, and leachate samples. Volatilization losses were calculated by difference. Our objectives were to examine, measure, and correlate the leaching patterns of the chemicals and correlate their leaching characteristics with physicochemical and biological properties of the herbicides and the physicochemical properties of the soils. Metolachlor was the most mobile herbicide, as indicated by the retardation factor ( R f ) ( R f =0.48 in 1992 and 0.19 in 1993), followed by primisulfuron-methyl ( R f =0.41 in 1992 and 0.12 in 1993), and atrazine ( R f =0.38 in 1992 and 0.15 in 1993), where mobility was greatly affected by water input (637 mm in 1992 and 509 mm in 1993). Herbicide mobility ( R f ) was related to 14 C-parent compound in leachate (0.02–6.9% of 14 C applied), 14 C in the subsoil (9–24%), and the pesticide leaching potential (PLP) index of each herbicide, as computed using a simple decision-aid model. The herbicides were most mobile through Blanton, followed by Norfolk and Rains soils and mobility ( R f ) was inversely related to mean % organic matter (OM) content of the soil profiles and directly related to soil pH and soil leaching potential (SLP) indices of the soils. Physicochemical and biological properties of the herbicides and soils were related to many of the measured herbicide distribution parameters.

In a greenhouse experiment, fipronil was applied at 0.014 kg ai/ha to bermudagrass, Cynodon dactylon L., in plastic 5-liter containers 120, 90, 60, 30, and 0 days before adding one tawny mole cricket nymph, Scapteriscus vicinus Scudder to the container. After the exposure period, soil in the containers was divided into depth increments of 0-4, 4-8, and 8-18 cm, and cricket status was recorded as dead, absent, or alive by thoroughly examining soil. Soil in the 0-4 cm-increment was analyzed for fipronil and four fipronil metabolite residues. Fipronil residue concentrations decreased with time (C = 0.00002x2 - 0.0053x + 0.3675, R2 = 0.9998 where C = fipronil concentration (μg/g of soil) and x = days after treatment). Concentrations of two metabolites, fipronil sulfone and fipronil sulfide, increased as fipronil residues decreased. Each treatment’s affect on late instar mole crickets was significantly different from the non-treated; however, there were no significant differences in nymph status among...

Laboratory and greenhouse experiments were conducted to determine the allelopathic potential of centipedegrass. Germination and growth of indicator species were evaluated in soil leachates, leaf debris, and aqueous leaf extracts of centipedegrass. Centipedegrass soil leachates did not inhibit annual bluegrass, goosegrass, henbit, large crabgrass, or perennial ryegrass germination compared with the nonfertilized control. Incorporated centipedegrass leaf debris did not reduce lettuce germination, shoot weight, or root weight compared with the control. However, shoot and root dry weights of radish were reduced with increasing rates of centipedegrass leaf debris. Six and 9 mg debris g−1 soil reduced radish shoot weight by 49 and 64%, respectively, compared with the control. Aqueous leaf extracts of centipedegrass reduced lettuce germination; however, radicle and hypocotyl length were similar to the control. These data do not conclusively suggest centipedegrass has widespread allelopathic activity; ho...

Knowledge of the influence of environmental factors on weed populations is important in developing sustainable turfgrass management practices. Studies were conducted to evaluate the relationship of green and false-green kyllinga population densities with elevation and edaphic factors in turfgrass systems. Studies were conducted on five different golf courses in North Carolina, three affected by green kyllinga, and two affected by false-green kyllinga. According to Spearman correlation coefficients, both green and false-green kyllinga were correlated with increasing soil volumetric water content, whereas correlation of other edaphic variables varied among sites and species. Stepwise logistic regression confirmed the correlation of volumetric water with green kyllinga presence, but model components varied among sites for false-green kyllinga. Increasing green kyllinga populations correlated with increasing soil sodium; however, sodium did not reach a level believed to be detrimental to turfgrass growth. No other variables correlated with green or false-green kyllinga across all sites. We hypothesized that the lack of significant correlations was due to the overall influence of relative elevation on edaphic variables. According to principal components analysis (PCA), relative elevation had a profound impact on the measured edaphic variables at all sites. However, results of PCA at one site differed sharply from other sites. Results from that site demonstrate the potentially strong effects of management practices to alter edaphic trends normally observed with topography.

Herbicides and herbicide prepackaged mixtures registered for use on established bermudagrass turf may cause significant injury to recently seeded bermudagrass cultivars, delaying full establishment. Research was conducted to evaluate the use of 12 herbicide treatments applied at onset of uniform stolon development (4 to 8 wk after seeding) to recently seeded ‘Princess 77,’ ‘Riviera,’ ‘Savannah,’ and ‘Yukon’ bermudagrass cultivars. In general, Yukon was more susceptible to herbicide injury than other cultivars. Atrazine at 1.1 kg ai/ha injured all cultivars 55 to 59% 14 d after initial treatment (DAIT), which lead to reduced bermudagrass cover 21 DAIT. Triclopyr + clopyralid at 0.63 + 0.21 kg ae/ha, respectively, injured Savannah and Yukon greater than other broadleaf weed herbicides (2,4-D + mecoprop + dicamba or 2,4-D + clopyralid + dicamba). Foramsulfuron did not injure or reduce bermudagrass cover of any cultivar evaluated at any rating date. The only adverse effect of trifloxysulfuron was a reduction ...

Herbicides commonly used to control Cyperus spp. are not completely effective against Kyllinga spp. Field trials were conducted on North Carolina golf courses to evaluate green and false-green kyllinga control at fairway and rough golf course mowing heights. Treatments included single and sequential applications of bentazon (1.12 kg ai/ha), halosulfuron (0.07 kg/ha), MSMA (2.24 kg/ ha), and trifloxysulfuron (0.03 kg/ha); imazaquin (0.56 kg/ha) with and without MSMA; and two rates of sulfentrazone (0.42 and 0.56 kg/ha). Green or false-green kyllinga control was equivalent at fairway and rough mowing heights. Halosulfuron applied sequentially, imazaquin with and without MSMA, and trifloxysulfuron applied singly or sequentially, controlled green and false-green kyllinga 89 to 99% 10 wk after initial treatment (WAIT). However, Kyllinga spp. control decreased over the course of the study regardless of herbicide treatment. By one year after treatment (YAIT), bentazon or MSMA alone controlled green or false-gree...

Studies were conducted in the summer and fall of 2001 in North Brunswick, NJ, and Marion County, Oregon, to evaluate the response of glyphosate-resistant and glyphosate-susceptible creeping bentgrass hybrids, colonial bentgrass, redtop, and dryland bentgrass grown as individual plants to postemergence (POST) herbicides. Glyphosate at 1.7 kg ae/ha, glufosinate at 1.7 kg ai/ha, fluazifop-P at 0.3 and 0.4 kg ai/ha, clethodim at 0.3 kg ai/ha, sethoxydim at 0.5 kg ai/ha, and a combination of glyphosate and fluazifop-P were applied 6 wk after planting. Glyphosate provided almost complete control of all susceptible bentgrass species at 4 weeks after treatment (WAT). Glufosinate provided 95% or greater control of all bentgrass species at 4 WAT, but regrowth was observed on all species in the summer experiment in Oregon. Fluazifop-P, clethodim, and sethoxydim provided slower control of bentgrass species, which ranged from 38 to 94% at 4 WAT, depending on species, herbicide, and experimental location. By 8 WAT, fluazifop-P at 0.4 kg/ha applied alone or in combination with glyphosate showed the highest levels of control (>90%) across all bentgrass species. Studies were also conducted in 2002 in the spring and summer in North Carolina to evaluate the response of a mature stand of glyphosate-susceptible ‘Penncross’ creeping bentgrass to POST herbicides. Two applications of glyphosate at 1.7 kg/ha were required to achieve 98% bentgrass control at 8 WAT. Fluazifop-P at 0.4 kg/ha, clethodim at 0.3 kg/ha, and sethoxydim at 0.4 kg/ha exhibited herbicidal activity, but two applications were required to reach (>82%) control of bentgrass at 8 WAT. Two sequential applications of clethodim or the combination of glyphosate and fluazifop-P provided 98% control of bentgrass at 8 WAT. Of the other herbicide treatments evaluated, only atrazine and sulfosulfuron provided (>80%) control at 8 WAT. The results of these studies demonstrate that fluazifop-P, clethodim, and sethoxydim have substantial herbicide activity on bentgrass species and may be viable alternatives to glyphosate for control of glyphosate-resistant creeping bentgrass and related bentgrass species in areas where they are not wanted. Glufosinate, atrazine, and sulfosulfuron also exhibited substantial herbicidal activity on bentgrass, and further research with these herbicides is warranted.

Experiments were conducted to evaluate safety and effectiveness of herbicides during establishment of seeded centipedegrass. Centipedegrass tolerance to herbicides was evaluated at seeding and early postemergence. Imazapic at 105 g ai/ha, sulfometuron at 53 g ai/ha, or metsulfuron at 21 or 42 g ai/ha applied at seeding reduced centipedegrass ground cover compared with the nontreated. Imazapic at 18 or 35 g/ha or applications of atrazine or simazine at seeding did not reduce centipedegrass ground cover compared with the nontreated. Applications of chlorsulfuron plus mefluidide (7 + 140 g ai/ha) or metsulfuron at 21 or 42 g/ha applied 6 wk after seeding (WAS) centipedegrass (one-leaf to one-tiller growth stage) caused 20, 16, and 83% phytotoxicity, respectively, 56 d after treatment (DAT). Imazapic, sulfometuron, atrazine, or simazine applied 6 WAS caused

Field experiments were conducted to evaluate chemicals for silvery-thread moss control and bentgrass turfgrass quality. Treatments included iron (Fe)-containing products, nitrogen fertilizers, Ultra Dawn dishwashing detergent (UD) at 3% (v/v), and oxadiazon. In general, greater silvery-thread moss control was achieved with Fe-containing products. Ferrous sulfate at 40 kg Fe/ha plus ammonium sulfate at 30 kg N/ha, a combined product of ferrous oxide, ferrous sulfate, and iron humates (FEOSH) at 125 kg Fe/ha, and a combined product of iron disulfide and ferrous sulfate (FEDS) at 112 kg Fe/ha reduced silvery-thread moss populations 87, 81, and 69%, respectively, 6 wk after initial treatment (WAIT). UD reduced silvery-thread moss populations 57% 6 WAIT. The addition of oxadiazon to Fe-containing treatments did not improve silvery-thread moss population reduction. Other experiments evaluated two formulations of chlorothalonil, each applied at two rates, chlorothalonil with zinc at 9.5 and 17.4 kg ai/ha and chlorothalonil without zinc at 9.1 and 18.2 kg/ ha, and two spray volumes (2,038 and 4,076 L/ha). Greater silvery-thread moss population reduction was observed at Jefferson Landing in 1999 compared with Elk River in 1999 and 2000. Rainfall events at Elk River in 1999 and 2000 within 24 h after application and no rain at Jefferson Landing may account for variation in performance of products between sites. However, no difference in chlorothalonil formulation, rate, or spray volume was observed in any location or year. These data indicate that Fe-containing fertilizers or chlorothalonil can be used to reduce silvery-thread moss populations in creeping bentgrass putting greens.

Experiments were conducted in environmental chambers to the evaluate effects of photoperiod and temperature on Florida betony growth and development. Plants were exposed to two photoperiods, short day (9 h) and long day (9 + 3 h night interruption), and three day/night temperature regimes, 18/14, 22/18, and 26/22 C. After 10 wk of growth, shoot length and weight were 3.4 and 3.5 times greater, respectively, in the long-day photoperiod and with the 26 and 22 than with the 22 and 18 C day and night temperature regime, respectively. Shoot number, however, was greatest in the short-day photoperiod and at a lower temperature of 22/18 C. Shoot number in long day 22/18 C and 26/22 C environments increased asymptotically. No difference in root weight was observed between long- and short-day environments, but root weight increased with increasing temperature. Flowering and tuber production only occurred in long-day environments, with greater production of both at higher temperatures. Results provide a general framework for understanding Florida betony growth and development characteristics in the field and provide insights that should be considered in developing control strategies.

Nutrient movement from turfgrass systems into surface and ground water is a public concern. Data indicate that actively growing turf rapidly immobilizes applied N, thus restricting nutrient movement. It is possible, however, that growth suppression with plant growth regulators (PGRs) could reduce N demand and thus N uptake, resulting in greater leaching losses. An experiment was conducted with column lysimeters to investigate the effects of trinexapac-ethyl (TE) on nitrate leaching and N-use efficiency in Tifway bermudagrass (Cynodon dactylon × C. transvaalensis). The experiment was conducted in a growth chamber with day/night temperature set at 29/24°C and a 12-h photoperiod. Trinexapac-ethyl was applied twice at 4-wk intervals at 0.11 kg a.i. ha -1 . Ammonium nitrate (AN) was applied at 50 kg N ha -1 2 wk after each TE application, and again 6 wk after the second TE application. Separate sets of columns received 15 N-labeled AN for the first two applications. Irrigation was scheduled to provide a leaching fraction of 50%; leachate was collected after each irrigation and analyzed for nitrate and ammonium. Cumulative nitrate leaching was unaffected by TE after the first two N applications, but was reduced =60% by TE following the third N application. Trinexapac-ethyl reduced 15 N allocation to clippings by 25% and increased 15 N allocation to roots and rhizomes; total recovery of applied N in tissues was 65%. Results demonstrate chemical growth suppression with TE does not reduce N uptake or increase nitrate leaching from bermudagrass.

Greenhouse studies were conducted to evaluate shoot number, shoot weight, rhizome weight, and root weight reduction of green and false-green kyllinga at three placement levels (soil applied, foliar applied, and soil + foliar applied) and five herbicide treatments (CGA-362622, halosulfuron, imazaquin, MSMA, and imazaquin + MSMA). Averaged over herbicide and placement level, false-green kyllinga shoot number 30 d after treatment (DAT) and rhizome weight 60 DAT were reduced more than those of green kyllinga. Furthermore, imazaquin, MSMA, and imazaquin + MSMA, averaged across placement levels, as well as CGA-362622 and halosulfuron, both foliar and soil applied, reduced false-green kyllinga shoot number greater than that of green kyllinga 60 DAT. Halosulfuron reduced false-green kyllinga shoot weight greater than that of green kyllinga 60 DAT; however, MSMA reduced green kyllinga greater. In general, foliar- and soil + foliar–applied treatments reduced shoot number (30 DAT), rhizome weight, and root weight of...

Greenhouse studies were conducted to evaluate shoot number, shoot weight, and root weight reduction of yellow and purple nutsedge to three placement levels (soil, foliar, and soil + foliar applied) and four herbicide treatments (CGA-362622, imazaquin, MSMA, and imazaquin + MSMA). Soil-applied CGA-362622 reduced shoot number, shoot weight, and root weight greater than foliar-applied CGA-362622. Foliar-applied imazaquin and soil-applied MSMA achieved little reduction in measured variables compared with the nontreated control. Foliar-applied imazaquin and soil-applied MSMA reduced shoot number, shoot weight, and root weight less than imazaquin + MSMA applied in a similar manner. Averaged over placement levels, imazaquin reduced shoot weight of yellow nutsedge greater than purple nutsedge. Averaged over herbicide treatments, soil-applied treatments were more effective in reducing purple nutsedge shoot number, whereas foliar-applied treatments were more effective in reducing yellow nutsedge shoot number. Nomen...

Preemergence (PRE) herbicides may affect the ability to reestablish warm-season turfgrasses in winter-injured areas. Experiments were conducted in 1996 and 1997 to evaluate the effects of fall or spring applications of six PRE herbicides on the vegetative establishment of Tifway bermudagrass, and Meyer and El Toro zoysiagrass. PRE herbicides were applied at the recommended rates during the fall of 1995 and 1996 and at recommended or reduced rates during the spring of 1996 and 1997. Oxadiazon, benefin plus trifluralin, or oryzalin did not inhibit Tifway bermudagrass or zoysiagrass sprig establishment. Fall applications of prodiamine and dithiopyr at full rates suppressed Tifway bermudagrass establishment as much as 25%, but recovery was evident by the end of the growing season. Reduced spring rates of prodiamine diminished its suppressive effects on Tifway establishment. Zoysiagrass establishment was suppressed as much as 20% by full or reduced rates of prodiamine but was less affected by dithiopyr. Pendim...