Turfgrass Trends for Changing Times – Poster Session

North Carolina State University’s
Center for Turfgrass Environmental Research and Education
Third Annual Research Symposium


Graduate Student and Post-Doc Poster Competition

Posters will be on display throughout the event. Additionally, authors will be by their posters to answer questions during the reception. The winner of the poster competition will be announced during the closing remarks.

The poster competition is supported by The North Carolina Sod Producers Association. 

  • Distribution of Mefenoxam As Affected By Use of Soil Surfactant

D. Freund1, T.W. Gannon1, J.P. Kerns2

Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695. Department of Entomology & Plant Pathology, North Carolina State University, Raleigh, NC 27695  

Presented by: Daniel Freund, MS student, Dept. of Crop and Soil Sciences

Research to date has shown that use of soil surfactants can enhance vertical soil movement of pesticides. Mefenoxam is a commonly used fungicide for preventative disease suppression of Pythium spp. and its physiochemical properties (K= 26,000 mg/L; KOC = 20 to 790) suggest it may readily distribute through the soil profile. In a laboratory experiment, 14C-mefenoxam was quantified within soil column depths (0.0 to 2.5, 2.5 to 5.0, 5.0 to 7.5, 7.5 to 10, 10.0 to 12.5 and 12.5 to 15.0-cm; 90:10 sand:peat v/v) in an attempt to elucidate vertical distribution when paired with a soil surfactant. The evaluated soil surfactant (Cascade Plus) was applied at 0.25% vol/vol (5.15 mL column-1) to unique soil columns 24 hours prior to 14C-mefenoxam (0.76 kg ai ha-1;  186.4 mL column-1) application, which was applied to the soil surface. Immediately following application, 0.635-cm irrigation was applied to all columns and soil collection occurred at 0, 3, 7, 14 and 21 days after treatment (DAT). Regardless of soil surfactant, the majority of 14C-mefenoxam was detected in the 0 to 2.5-cm depth (85.0 to 100.0% of applied), with less detected in the 2.5 to 5.0-cm depth (1.0 to 11.0%). 14C-mefenoxam was not detected beyond 5.0-cm depth across collection timings. Pooled over collection timings, in the 2.5 to 5.0-cm depth, greater C14-mefenoxam was detected when applied with a surfactant (5.8% of applied), compared to 2.9% with no surfactant. Results from this experiment illustrate the importance of adequate irrigation and the potential use of soil surfactants when targeting soil-borne pathogens.

  • Quantitative Trait Loci for Freeze Tolerance in Two St. Augustinegrass Populations

S.E. Graham1, J.A. Kimball2, X. Yu1, T.D. Tuong3, Y. Zheng4, D.P. Livingston3, S.R. Milla-Lewis1

Crop and Soil Sciences, North Carolina State University, Raleigh, NC. Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN. 3 U.S. Department of Agriculture, Raleigh, NC. 4 College of Forestry, Henan University of Science and Technology

Presenting: Sydney Graham, MS student, Dept. of Crop and Soil Sciences

St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntz) is a warm season turfgrass commonly used in home lawns. Its popularity in the southern United States is due to its aggressive growth habit and good shade tolerance. However, a lack of freeze tolerance has limited the spread of St. Augustinegrass into the transitional climatic region. ‘Raleigh’, released in the early 1980s is still the industry’s standard in terms of cold tolerance. Despite the identification of freeze tolerant germplasm limited progress has been made in breeding for freeze tolerance in St. Augustinegrass. Breeding efforts to improve freeze tolerance would be aided by the identification of quantitative trait loci (QTL) and associated markers controlling the trait. An SSR-based complete linkage map was developed for St. Augustinegrass and used in conjunction with data on spring green-up and winterkill to identify multiple QTL on linkage groups 1, 3, 6 and 9. An F2 population of cultivar ‘Raleigh’ was developed to be used for validating the previously identified QTL. Laboratory based freeze tests were conducted for the population at both -3⁰C and -4⁰C. Additionally, a linkage map with 120 SSR markers was developed for the population using R/Onemap. Linkage maps for both populations identified nine linkage groups with primarily the same marker groupings. Using MVQTLCIM, composite interval mapping identified QTL for stress after freezing on linkage groups 5, 7, and 8. These correlate with linkage groups 1, 3, and 2 respectively in the ‘Raleigh” x ‘Seville’ map. In both populations QTL associated with freeze tolerance traits were identified on ‘Raleigh’ self LG5/‘Raleigh’ x ‘Seville’ LG1, and LG7/LG3. Preliminary data suggest that some of the validated QTL are integral to freeze response in St. Augustinegrass and may be useful to marker assisted selection. Marker assisted selection (MAS) provides a genomic flag at or near a gene of interest which allows for the genome to be screened for the marker instead of requiring a multi-year field evaluation. For a complex trait such as freeze tolerance a streamlined approach via MAS is particularly valuable. Thus, confirmation of QTL associated with freeze tolerance in St. Augustinegrass will aid breeders in the development of cold tolerant varieties to match demand.

  • Weed Mapping and Management using Unmanned Aerial Vehicles in Turf

J. Hunter, R. Austin, R. Richardson, T. Gannon, J. Neal, and R.G. Leon

Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695

Presenting: Joseph Hunter, MS student, Dept. of Crop and Soil Sciences

The usage of unmanned aerial vehicle (UAV) technologies has increased exponentially for both commercial and recreational purposes.  In recent years, commercial pesticide applying UAVs have been introduced to the marketplace.  Integrating the use of UAVs carrying low cost-high resolution cameras with UAV sprayers creates new management options for the turf industry to increase efficiency for pest management and reduce cost and environmental impact.  High resolution imagery can be collected by UAV systems within minutes and processed within hours to provide real-time data to aid in decision making.  Spot applications with UAV sprayers bring reductions in labor inputs, pesticide inputs, and worker exposure to pesticides.  These new technologies allow reducing herbicide applications in 20 to 66%, depending on weed pressure, while maintaining or increasing weed control. UAV-based herbicide applications can increase application efficiency up to 2.8 fold. 

  • Effect of Post-Application Irrigation and the Usage of Soil Surfactants on Fungicide Movement and Efficacy

W.J. Hutchens1, T.W. Gannon2, H.D. Shew1 and J.P. Kerns1

1 Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, 2 Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC

Presenting: Wendell Hutches, PhD student, Dept. of Entomology and Plant Pathology

Crown and root diseases in turfgrass systems are destructive and limiting to the production of quality turfgrass.  Management of this group of diseases relies heavily on fungicide applications.  The physicochemical properties of fungicides vary greatly but most are not phloem mobile.  Therefore, fungicides do not contact basal and underground structures of turfgrass plants without influence from other factors.  Practices such as post-application irrigation and using soil surfactants offer potential methods for more fungicide to contact the basal portions of the turfgrass plant.  Higher concentrations of fungicide in this region could result in greater crown and root disease suppression.  Two studies were conducted in a laboratory setting to determine the effect of post-application irrigation (0, 0.3, 0.6, 1.3, and 2.5 cm) on the distribution of 14C myclobutanil and 14C tebuconazole in a 90:10% sand:peat moss (v:v) soil medium.  A follow up study was conducted to determine the effect of three different soil surfactants (Aquifer, Fleet, and Revolution) on 14C myclobutanil and water movement in soil.  Furthermore, a growth chamber experiment was conducted to examine the effect of various post-application irrigation amounts on azoxystrobin efficacy against summer patch (Magnaporthiopsis poae) in ‘Penn A-4’ creeping bentgrass (Agrostis stolonifera).  In the 14C post-application irrigation myclobutanil experiment, lysimeters treated with 2.5 cm of post-application irrigation resulted in 3.9% of myclobutanil recovered in the 7.6-10.2 cm sampling depth, which was higher than all other treatments.  Post-application irrigation at 2.5 cm yielded 6.3% of tebuconazole at the 7.6-10.2 cm sampling depth and 2.3% at the 10.2-12.7 cm sampling depth––these recoveries were higher than all other irrigation treatments.  For the soil surfactant study, 14% more of the recovered myclobutanil was detected in the 5-7.6 cm sampling depth and > 4% more in the 7.6-10.2 cm depth with a soil surfactant compared to the fungicide alone.  Each soil surfactant also yielded > 28% more leachate than the fungicide alone.  For the growth chamber experiment, least disease was observed when azoxystrobin received post-application irrigation.  These data indicate that post-application irrigation and soil surfactant inclusion increase fungicide distribution in soil and may enhance suppression of summer patch and potentially other crown and root diseases.

  • A Comparison of Pollinator Communities in Managed Turfgrass Systems in the Piedmont and Sandhills of North Carolina

L. Kilpatrick and D. Seth-Carley

Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695

Presenting: Lauren Kilpatrick, MS student, Dept. of Horticultural Science

With increasing land development and recognizing that the importance of suitable habitat for pollinators is key to their survival and ecological role, it is imperative to evaluate the potential for managed urban greenspaces to recreate pollinator habitat. The objective of this research is to understand how turfgrass systems under different management techniques effect pollinator communities by exploring the potential of utilizing rough areas/no play zones on golf courses, as well as homeowner lawns in North Carolina. Twelve managed green spaces, golf courses and home lawns, were selected based on location, site suitability for establishment, and management intensity. Initial insect sampling was conducted beginning in the summer of 2018 in order to record a baseline of the current pollinators found at each site. In October 2018, sites were seeded with a pollinator-friendly wildflower seed mix.  Formal sampling for pollinators and floral resources will begin in Spring 2019. We anticipate that our findings will support the hypothesis that pollinator communities found in association with managed turfgrass systems are abundant and biodiverse. 

  • Characterization of Reactive Nitrogen Emissions from Turfgrass”

A. Nahas1, J.T. Walker2, F. Yelverton3, and V.P. Aneja1

1Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695. 2Office of Research and Development, U.S. Environmental Protection Agency, RTP Campus, NC 27711. 3Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695.

Presenting: Alberth Nahas, PhD student, Dept. of Marine, Earth and Atmospheric Sciences

Turfgrass management is a multibillion-dollar industry that has been regarded as an important part of urban and suburban landscape practices. A rapid growth of this industry is projected due to strong demand for its use in residential and commercial properties, and in golf courses. However, intensive use of irrigation, fertilizers, and pesticides for maintaining the aesthetic value of turfgrass is often viewed as an environmental impact, particularly with respect to its role in carbon and nitrogen biogeochemical cycles. This study, conducted at the Lake Wheeler Turfgrass Field Laboratory in Raleigh, NC, is aimed at characterizing seasonal emissions of three reactive nitrogen species, i.e., ammonia (NH3), nitric oxide (NO), and nitrous oxide (N2O), from turfgrass over the course of a year. These species are produced in the soil via nitrification and denitrification and are known for their roles in atmospheric processes including the formation of inorganic particulate matter (NH4+ and NO3) and other secondary pollutants (e.g., NO2 and O3) as well as radiative forcing (N2O). Soil emissions are measured using the dynamic chamber approach following a randomized complete block design with 10 replicates of three N-fertilizer (2.3% ammoniacal N, 22.7% urea N) levels (0, 36.5, and 73 kg N ha-1 yr-1). NH3 and NO emissions are measured continuously using a chemiluminescence analyzer following conversion of NH3 to NO by heated (825°C) catalyst, while discrete air samples are collected for N2O analysis using the GC-ECD method. Emission measurements during 2018 spring and summer intensives indicate a wide range of emissions for NH3 (21.8-1384.6 ng N m-2 s-1); NO (15.5-307.7 ng N m-2 s-1); and N2O (186.5-635.8 ng N m-2 s-1). Results show that the seasonal effect of warmer soil temperature contributes to the variation and magnitude of the emissions. Highest NH3 and NO emissions were observed from the highest N treatment, while the pattern of N2O emissions was less consistent across treatments. The role of external physicochemical factors, such as local meteorology, soil properties, and microbial activity, will be further analyzed. Field measurements will be coupled with a process-based biogeochemical model to produce a temporal and spatial analysis of reactive nitrogen emissions from turfgrass on a larger scale.

  • Sand Topdressing Influences Fraise Mowing Recovery of Bermudagrass

G.D. Pinnix, G.L. Miller, and R. McCauley

 Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695

Presenting: Drew Pinnix, PhD candidate, Dept. of Crop and Soil Sciences

Fraise mowing is an effective cultural practice for bermudagrass thatch management. However, prolonged bermudagrass recovery times ensue, and any practices to hasten bermudagrass recovery should be explored. The objective of this study was to evaluate the effects of sand topdressing depth and timing on bermudagrass recovery following fraise mowing. Trials were conducted in Raleigh, NC during the summers of 2017 and 2018 on ‘Celebration’ and ‘Tifway’ bermudagrass. All plots were fraise mowed in mid-June and subsequently received one independent topdressing application at 0, 7, or 14 days after fraise mowing to a depth of 0 (control), 0.3 cm (light), 0.6 cm (medium), or 1.3 cm (heavy) (0, 0.125, 0.25, or 0.5 in, respectively). In 2017 acceptable turf quality and cover were achieved in both cultivars with control, light, and medium topdressing rates at 28 days after fraise mowing (DAF), regardless of application date. Heavy topdressing rates delayed bermudagrass recovery by ≥7 days, regardless of application date in 2017. However in 2018 all depths applied immediately after fraise mowing on Tifway had acceptable turf quality by 21 DAF. Control and shallow topdressing depths on Tifway had acceptable turf quality by 21 DAF regardless of application date.  Both years, turf quality of heavy topdressing rates applied 7 or 14 DAF remained unacceptable throughout the studies.  Both years light sand topdressing rates did not delay bermudagrass recovery. However, all sand topdressing  depths did not accelerate bermudagrass recovery following fraise mowing.

  • I like to Move it, Move it: Fungicide Fate Following Various Mowing and Irrigation Treatments

C. Stephens1, T.W. Gannon2, J.P Kerns1

Department of Entomology & Plant Pathology, North Carolina State University, Raleigh, NC 27695.Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695. 

Presenting: Cameron Stephens, PhD student, Dept. of Entomology and Plant Pathology

The turfgrass industry is an estimated $40 billion industry with approximately $175 million spent on fungicide applications annually. Recent research demonstrated 24 to 34% of the liquid formulation of azoxystrobin could be removed in turfgrass clippings following a single mowing event one day after application in high cut turfgrass. Irrigation is typically applied immediately following fungicide applications when targeting soil-borne pathogens. However, there is little published research elucidating the effect of post-application mowing and irrigation timings on the environmental fate of fungicides targeting soil-borne pathogens on golf course putting greens. Therefore, the objective of this study was to determine the influence of post-application mowing and irrigation timing on fungicide movement and distribution in turfgrass clippings and the soil profile. Independent fungicide applications of pyraclostrobin and triademefon were administered and experimental units received either .635 cm post-application irrigation immediately following the fungicide application or .635 cm post-application 6 hours after the fungicide application. Turfgrass clippings were harvested immediately following respective irrigation treatments, 1 day after fungicide treatment (DAFT), or 3 DAFT. Cores were harvested using a 10.80-cm diameter cup cutter at 0, 1, 3, 7, and 14 DAFT. Each core was sectioned into four subsamples including remaining above ground vegetation (RAV), 0 to 2.54-cm, 2.54 to 5.08-cm, and 5.08 to 7.62-cm depths. Turfgrass clippings, RAV, and soil subsamples were homogenized and subjected to residue analysis using liquid chromatography mass spectrophotometry. Less pyraclostrobin and triadimefon was removed in turfgrass clippings in plots receiving immediate post-application irrigation and more fungicide was recovered in the RAV and deeper soil depth following this treatment. Similarly, delaying mowing events post-fungicide application resulted in less fungicide removed in turfgrass clippings. Irrigating immediately and skipping at least one mowing event can limit fungicide removal in clippings and increase fungicide movement into the RAV and soil profile. Results from this study provide practical fungicide management strategies that could help turfgrass managers target soil-borne pathogens more efficiently and limit the potential for off target movement.

  • Mapping the Soil Microbial Community from the Perspective of Soil Texture

Q. Xia, T. Rufty, and W. Shi

Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695

Presenting: Qing Xia, PhD student, Dept. of Crop and Soil Sciences

Soil texture is known to affect soil pore size distribution, water network connectivity, and nutrient availability, and yet few have studied its impacts on the soil microbial community. We aimed to examine how soil texture shaped the diversity, composition, and function of the soil microbial community. Soil cores (5 cm in diameter and 10 cm depth) taken from 12 bermudagrass golf courses across North Carolina. The soil textures covered by the sites included loamy sand, sandy loam, loam, sandy clay loam, sandy clay, clay loam, and clay. For interpretation purpose, soils were separated into three groups according to sand percentage: clayey (30-53%), loamy (54-71%), and sandy group (71.3-83%). After incubation of soil cores at different moisture contents (control, air-dried, and saturated), we had both bacteria 16S rRNA genes and fungal ITS sequenced and soil edaphic properties measured. Our data showed that soil texture did affect the soil microbial community composition, but the effect was moderate. Both bacterial and fungal community composition tended to cluster within texture groups. Influences of soil properties on microbial communities varied with texture groups. Soil organic C and N accounting for <10%, 12%, and 27% of total variation in bacterial communities in sandy, loamy, and clayey groups respectively, indicating an increasing importance of soil organic matter in shaping microbial communities in clayey soils. Genetic diagnose for N cycling showed that texture also affected soil N processes, where a higher sand percentage resulted in increasing potential in denitrification and N fixation. This work may provide better guidance in texture-based bacterial and fungal mapping and soil management.

  • Elucidating the Genetic Control of Drought Tolerance in St. Augustinegrass

X. Yu and S.R. Milla-Lewis

Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695

Presenting: Xingwang Yu, Post-doctoral researcher, Dept. of Crop and Soil Sciences

St. Augustinegrass (Stenotaphrum secundatum) is a warm-season grass species commonly utilized as turf in the southeastern US. Improvement in the drought tolerance of the St. Augustinegrass has significant value within the turfgrass industry. Understanding quantitative trait loci (QTL) in genomic regions associated with drought tolerance will allow for advancement of breeding strategies to identify St. Augustinegrass germplasm with improved performance for this trait. A multi-year and multi-environment study was performed to identify QTL in a ‘Raleigh’ x ‘Seville’ mapping population segregating for phenotypic traits associated with drought tolerance. Phenotypic data was collected from a field trial and a two-year greenhouse study, which included relative water content (RWC), chlorophyII content (CHC), leaf firing (LF), leaf wilting (LW), green cover percent (GCP) and normalized difference vegetative index (NDVI). QTL were detected for all traits and distributed on seven of nine linkage groups. Several hotspot regions were found where QTL overlapped for multiple traits. Sequence analysis revealed several drought response genes within these regions. The QTL identified in this study have potential to be used in the future to identify genes associated with drought tolerance and for use in marker-assisted breeding.