Fred H. Yelverton

Canada Goose Weed Dispersal and Nutrient Loading in Turfgrass Systems

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.

Effects of Mowing on Anthraquinone for Deterrence of Canada Geese

Abstract 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, FlightControl® 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.

Soil Properties Influence Saflufenacil Phytotoxicity

Abstract 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 u200a=u200a 0.85) and humic matter (R u200a=u200a 0.81), and less correlated to cation exchange capacity (R u200a=u200a 0.49) and sand content (R u200a=u200a −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. Nomenclature: Saflufenacil; canola, Brassica napus L.

Persistence and Bioavailability of Aminocyclopyrachlor and Clopyralid in Turfgrass Clippings: Recycling Clippings for Additional Weed Control

Abstract 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. Nomenclature: Aminocyclopyrachlor; clopyralid; tall fescue, Lolium arundinaceum (Schreb.) S.J. Darbyshire; white clover, Trifolium repens L. ‘Dutch’.

Effect of Selective Amicarbazone Placement on Annual Bluegrass (Poa annua) and Creeping Bentgrass Growth

Abstract 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−1 for 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. Nomenclature: Amicarbazone; bispyribac-sodium; annual bluegrass; Poa annua L. var. annua; creeping bentgrass; Agrostis stolonifera L. ‘Penn A1’. Resumen Se realizaron experimentos en cámaras de crecimiento para evaluar los efectos de aplicar amicarbazone solamente en el follaje, solamente en el suelo y en el follaje más el suelo, sobre el crecimiento de Poa annua y Agrostis stolonifera. Los tratamientos de herbicidas evaluados incluyeron amicarbazone a 49 ó 147 g ai ha−1, y bispyribac-sodium a 74 g ai ha−1 para fines de comparación. Los datos de esta investigación concordaron con reportes previos sobre la absorción de amicarbazone, porque este compuesto es absorbido por vías por encima y debajo del suelo. Sin embargo, el crecimiento vegetal es inhibido más cuando la absorción se da por la raíz. Al compararse con la localización foliar del amicarbazone, la localización solamente en el suelo redujo la biomasa aérea y de raíz en más del doble a 56 días después del tratamiento (DAT), mientras que no se detectaron diferencias entre tratamientos que incluyeron contacto con el suelo. A lo largo de todos los parámetros evaluados en esta investigación, amicarbazone (49 g ha−1) impactó el crecimiento de A. stolonifera en forma similar a bispyribac-sodium, mientras que el crecimiento de P. annua fue inhibido más por amicarbazone, lo que sugiere que este herbicida provee una opción química eficaz de control para los usuarios.

Herbicide Inputs and Mowing Affect Vaseygrass (Paspalum urvillei) Control

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 gramínea C4 perenne invasiva que se encuentra comúnmente a las orillas de caminos y en áreas con suelos con poco drenaje. Debido a su hábito de crecimiento vertical y producción de espigas, P. urvillei puede limitar la visibilidad de vehículos y subsecuentemente incrementar los insumos de manejo para mantener la vegetación 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 iónico a 0,25% v/v. El experimento uno se enfocó en el efecto de la chapia (chapia rutinaria o sin chapia) y el momento de aplicación de herbicidas (sólo otoño, otoño más primavera, o sólo primavera), mientras que el experimento dos se enfocó en el intervalo entre la chapia y la aplicación de herbicidas (6, 4, 3, 2, 1, ó 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 después del tratamiento de otoño (WAFT), sugiriendo que esta práctica cultural debería ser empleada cuando sea posible. Adicionalmente, la chapia rutinaria y la temporada de aplicación de herbicida afectaron la eficacia del herbicida. Los tratamientos que proveyeron >70% de reducción en la cobertura de P. urvillei a 52 WAFT incluyeron chapia rutinaria y clethodim sólo en el otoño e imazapic en el otoño más la primavera, y metsulfuron+nicosulfuron en el otoño más la primavera para todos los regímenes de chapia. Dentro de los tratamientos con clethodim, la chapia 2 ó 1 WBT resultó en la menor cobertura a 40 (1 a 2%) y 52 (4 a 6%) semanas después del tratamiento (WAT) al compararse con otros intervalos, lo que se alinea con la actual recomendación de la etiqueta de tratamiento según la altura de la vegetación. P. urvillei persistió en todos los tratamientos evaluados hasta 52 WAT, lo que sugiere que la erradicación de esta especie requerirá insumos a lo largo de múltiples temporadas de crecimiento.

Postemergence Control and Glyphosate Tolerance of Doveweed (Murdannia nudiflora)

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.

Herbicide Applications and Incorporation Methods Affect Dazomet Efficacy on Bermudagrass

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 (irrigationor tillage-incorporated) and sealing (tarp or no tarp) methods, application rates [291, 291 followed by (fb) 291, 468, or 583 kg ha], and fluazifop-P [fluazifop (0.4 kg ha)] D glyphosate (2.8 kg ha acid equivalent) application(s) for established common bermudagrass control. Overall, treatments required fluazifopD 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) 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.

Persistence in and Release of 2,4-D and Azoxystrobin from Turfgrass Clippings.

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 [ (L.) Pers. × Burtt-Davy], tall fescue [ (Schreb.) S.J. Darbyshire], and zoysiagrass ( Steud.). A subsequent greenhouse experiment was conducted to measure pesticide release from clippings into water. 2,4-D (1.6 kg a.i. ha) and azoxystrobin (0.6 kg a.i. ha) 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.