Research Update from VT

Titles and Abstracts of all Projects

By Ava Veith, Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg, VA

• ITC Annual Meeting in Japan 2025

o Title: Improving Blue Grama Seedling Establishment As a Low Input Residential Lawn Grass Using Pre- and PostEmergent Herbicides

o Abstract: Blue grama (Bouteloua gracilis) is a low-input residential lawn alternative that is native to North America. Research indicates weed competition can be a detriment to successful establishment, inspiring this study. Our objective is to evaluate the growth attributes during establishment of ‘Birds Eye’ blue grama using pre- and post-emergence herbicides. Pre- and post-emergence herbicides were applied at three different seedling maturation ages. Plant response to herbicides was quantified by leaf height, leaf count, tiller count, root and shoot weight, and visually estimated injury over three weeks after application. Post-emergence herbicides were less injurious when applied three to five weeks after germination. Among post-emergence herbicides tested, carfentrazone-ethyl (Quicksilver, FMC GSS) and metsulfuron-methyl (Manor, NuFarm US) negatively impacted seedling establishment the least, regardless of maturity at application. Data collection of pre-emergence herbicides is underway.

• ASA Annual Meeting in St. Louis November 2023

o Title: Distribution of Winter Injury on Bermudagrass Athletic Fields Relative to Athlete Movement

o Abstract: Cold-related injury (winterkill) commonly impacts hybrid bermudagrass (Cynodon dactylon) athletic fields within the transitional zone during spring green-up. Winterkill can cause poor field conditions, potentially leading to more injuries among athletes using the fields recreationally. Widespread prevalence of winterkill across the Mid-Atlantic in 2023 led sports field managers to question the factors that contribute to this issue. One hypothesis is that areas with high soil compaction are more likely to experience winterkill. This study is designed to explore the relationship between the distribution of cold-related injury of bermudagrass athletic fields and estimated soil compaction. Georeferenced soil compaction across athletic fields was estimated using the IDW function in ArcGIS Pro with ground-truth surface firmness data collected using a Clegg Impact Tester. Aerial imagery was collected from a Mavic 2 Enterprise Advanced drone and ortho mosaicked using Pix4Dmapper, with the turfgrass classified as winterkill or not using the binary Raster Calculator function in ArcGIS Pro. The frequency of winterkill occurring within estimated areas of compacted soils was assessed using 10,000 random points. Estimated surface firmness was 23% higher across all locations in areas that experienced winterkill than areas of green, actively growing bermudagrass (p<.0001). Estimated surface firmness varied by testing location, but areas within fields consistently overlapped areas of higher surface firmness regardless of location. Our data suggest that winterkill is most likely to occur within compacted soil surfaces.

o Title: Improving Blue Grama Seedling Establishment As a Low Input Residential Lawn Grass Using Post-Emergent Herbicides

o Abstract: Blue grama (Bouteloua gracilis) is a low-input residential lawn alternative that is native to much of North America, from the Mexican Plateau to Canada and throughout much of the Great Plains. Previous research indicates weed competition can be a detriment to successful establishment of blue grama, which inspires the following investigation. Our objective is to evaluate the growth attributes during establishment of ‘Birds Eye’ blue grama as a residential lawn grass using post-emergence herbicides. Six commercially available post-emergence herbicides with single or multiple active ingredients were applied to blue grama at three different seedling maturation ages. Plant response to herbicides was quantified by leaf height, leaf count, tiller count, root and shoot weight, and visually estimated injury over three weeks after application. Our data suggest that all herbicides were less injurious to blue grama when applied three to five weeks after germination, with many products causing unacceptable injury one week after germination. Among post-emergence herbicides tested, carfentrazone-ethyl (Quicksilver, FMC GSS) and metsulfuron methyl (Manor, NuFarm US) negatively impacted blue grama seedling establishment the least, regardless of plant maturity at application. These two products can successfully be applied one week after germination to aid in establishment, with limited injury compared with all other herbicides tested.

o Title: Spring Dead Spot and Winter Injury Impacts on Athletic Field Playability and Safety

o Abstract: Spring dead spot (SDS) is the most destructive disease of hybrid bermudagrass (Cynodon dactylon x transvaalensis) in the transition zone. Sunken patches create a non-uniform playing surface on recreational fields that may impact surface playability and increase athlete injury potential. Cold-related injury (winterkill) also impacts hybrid bermudagrasses and often leaves much of the playing surface with minimal living turfgrass canopy. Both SDS and winterkill caused significant injury on athletic fields throughout much of the Mid-Atlantic US in 2023, leaving field managers concerned for athlete safety. Little research has been done to investigate the impact of SDS and winter injury on athletes. Our objective is to quantify the effects of SDS and cold-related injury on field performance and player safety, as measured using the Clegg Impact Tester, soil moisture sensor, shear vane, ball rebound device, and a FLEX testing device that simulates player acceleration and deceleration. Further, our study examined how an increase in surface moisture on SDS impacts these metrics. Data were collected from twenty matched pairs of SDS-symptomatic and asymptomatic bermudagrass on four athletic fields during peak symptom expression in May. Ten pairs were irrigated at each testing location immediately before data collection. To assess the impact of winterkill on field performance, data were collected from twenty matched pairs of symptomatic and asymptomatic bermudagrass on three athletic fields in May, however without irrigation. Our data suggest that winterkill has an impact on field playability. Bermudagrass winterkill impacts overall field playability based on increased surface hardness levels, less rotational resistance, and greater ball rebound values. SDS areas were shown to have less structural strength, have a higher ball rebound, and greater energy restitution than healthy areas. Additionally, our data suggests that SDS had a greater impact on athlete safety and field playability immediately after simulated rainfall.

• ASA Annual Meeting in Baltimore November 2022

o Title: Spring Dead Spot Impact on Athlete Safety and Performance

o Abstract: Spring dead spot (SDS) of bermudagrass presents a major concern on athletic fields due to the non-uniform surface created. However, the impact of SDS on athlete safety and performance has not been evaluated. The primary objective of this study was to define the influence of SDS on key metrics associated with field performance and athlete safety, including surface hardness and shock absorption, moisture levels, ball rebound, shear strength, force reduction, vertical deformation, energy restitution, and force impact. Additional metrics to define the impact of SDS on field uniformity were also collected. Data was collected from three hybrid bermudagrass baseball field fields in Richmond, VA in late May when SDS symptoms were most visible. Twenty matched pairs of SDS symptomatic and asymptomatic bermudagrass served as replications for each data collection. Data was analyzed using ANOVA by comparing the percentage difference between SDS and healthy averages for each measurement. Our data suggests that SDS impacts surface depression, ball rebound, soil moisture, firmness of surface, and shear strength. When the field has an increased moisture content, vertical deformation, energy restitution, and impact values are also affected. We conclude that SDS impacts hybrid bermudagrass athletic field playing surfaces by creating a significant surface void that is firmer than the surrounding turf grass and absorbs more force from the athlete, therefore returning less energy to the player. Additionally, athletes’ cleat grip will be impacted by a weaker shear strength in SDS patches, suggesting an increased likelihood of slipping. Ball rebound is impacted by SDS, altering player perception of ball travel. Finally, our data suggests that SDS impacts field performance and player safety more on wet fields, though more data is needed to validate.