Hybrid Bermudagrass Research Articles

A New Method for Hybrid Bermuda Grass (Cynodon dactylon × C. transvaalensis Burtt.-Davy) Vegetative Propagation

Hybrid Bermuda grasses (Cynodon dactylon × C. transvaalensis Burtt.-Davy) represent one of the greatest contributions to the growing quality of turfgrass in the warm season and transition zone areas of the world. Hybrid Bermuda grass production relies on vegetative propagation from sod or sprigs. In the past, efforts have focused on improving the technique of stolonizing (or sprigging) for establishment in new areas. Such propagation requires bulk harvesting and planting of all rhizomes and stolons. We have developed a novel method of propagation and establishment from a single node harvested from greenhouse grown stolons. Despite a stolon fraction bearing a single node being suitable for effectively propagating a warm-season turfgrass, the technique has been held as economically impractical until now. Our method has been developed to obtain the multiplication of plant material in soilless conditions by harvesting single-node sprigs, propagation of plants from the single nodes, and transplant of single plants in the field. The investigation aimed to identify values for method set-up. Indeed, node and internode size variability with differential between maximum diameters is crucial for discrimination. For Patriot Bermuda grass stolons, nodes exhibited a maximum diameter of 2.43 ± 0.46 mm, while internodes had a maximum diameter of 1.54 ± 0.16 mm. Based on these findings, a 2 mm sieve was selected, achieving an optimal ratio between the node fraction and internode residues. The sieve yielded 87% of node fractions and only 1% of internodes from the initial mix, demonstrating its efficacy. Further results for the transplanting phase indicated that a double release resulted in an average success rate of 98.8%, with only 6.9% blank cells when using a single release. The average was 149 plants per tray over 160 cells, representing a 93.1% success rate. These results underscore the efficiency and acceptability of the overall propagation process in alignment with market references.

Raising Mowing Height Improves Freeze Tolerance of Putting Green–type Bermudagrass

There is a growing trend of cultivating hybrid bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davy] on golf course putting greens in the transition zone because of its excellent quality in the summer months, coupled with less pesticide input than creeping bentgrass (Agrostis stolonifera L.). However, the long-term success of bermudagrass putting greens is hindered by low temperatures in winter months, particularly in the transition zone. To address this issue, in addition to genetic improvement for cold hardiness through the development of new cultivars, effective management approaches are necessary to enhance the winter survival of putting green–type bermudagrass. The objective of this study was to investigate the relative freeze tolerance of four bermudagrasses and the effects of raising mowing height on the freeze tolerance of putting green–type bermudagrasses. In this study, two experimental putting green–type bermudagrasses (11X2 and OKC0805) along with cultivars TifEagle and OKC3920 were tested at two mowing heights (3.2 vs. 6.4 mm) at freeze temperatures that ranged between –4 and –11 °C. The lethal temperature to kill 50% of the population (LT50) as well as regrowth vigor during recovery were evaluated. Variety ‘OKC3920’ demonstrated enhanced freeze tolerance compared with ‘TifEagle’ at both mowing heights. Increasing the mowing height from 3.2 mm to 6.4 mm improved freeze tolerance for most genotypes tested in this study. After exposing the grasses to –8 °C for 1 hour, genotypes such as 11X2 exhibited better regrowth vigor and demonstrated a faster recovery. This study suggests that golf course managers can enhance winter resilience of bermudagrass putting greens by selecting genotypes strategically with superior freeze tolerance and raising mowing heights in the fall acclimation process.

Herbicide effects on dormant and postdormant hybrid bermudagrass putting green turf

AbstractHerbicide resistance coupled with a dearth of selective herbicide options has increased the complexity of annual bluegrass control in hybrid bermudagrass putting greens. Cumyluron, endothall, and methiozolin are herbicides that control annual bluegrass by inhibiting novel sites of action compared with the herbicides currently used for turfgrass management in the United States. However, peer-reviewed literature contains no information on hybrid bermudagrass putting green tolerance to these herbicides. Sixteen field studies were established on eight golf greens in Midlothian, VA, in 2021 and 2022 to evaluate effects of cumyluron, endothall, methiozolin, pronamide, and trifloxysulfuron on bermudagrass spring transition. The 16 studies were split equally between initiation during full dormancy versus mid-spring transition. Methiozolin applied at 500 and 1,000 g ai ha−1 typically increased the heat units (growing degree days with a base temperature of 15 C) required for hybrid bermudagrass to visibly achieve 90% green coverage (T90) when applied to fully dormant hybrid bermudagrass. This delay in green coverage was more pronounced at sites where hybrid bermudagrass vigor was seemingly reduced via abiotic stressors. Endothall was generally more injurious than all other treatments when applied to hybrid bermudagrass during mid-transition. Endothall applied at 840 g ai ha−1 injured hybrid bermudagrass for 0 to 9 d over a threshold of 30% (DOT30), depending on location. In two site-years characterized by increased abiotic stress, methiozolin applied at 1,000 g ai ha−1 caused 44 DOT30. Cumyluron never injured hybrid bermudagrass by more than 30% or delayed T90 regardless of application timing. These results indicate that methiozolin should be applied only within labeled rates to actively growing hybrid bermudagrass putting greens, cumyluron can be safely applied at 6,450 g ai ha−1 to dormant or actively growing bermudagrass greens, and endothall applications should be limited to dormant bermudagrass greens unless transient phytotoxicity is acceptable.

Evaluation of Different Aerification Methods for Ultradwarf Hybrid Bermudagrass Putting Greens

Aerification and topdressing are important cultural management practices that help prevent organic matter accumulation and soil compaction in golf greens. However, these practices result in surface disruption and decreased putting quality during recovery. A 2-year study was conducted on a ‘TifEagle’ hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) putting green to determine the effect of different aerification methods and topdressing materials on soil properties and turfgrass recovery. Plots were aerified four times per year (May to Aug.) using 1/2-inch hollow tines, 1/4-inch hollow needle tines, hollow tines 2X + hollow needle tines 2X, or sand injection, and topdressed with either 90:10 (sand:peat) or green-dyed sand. Visual quality, normalized difference vegetation index, percent green cover, dark green color index (DGCI), surface firmness and volumetric water content were measured before initial aerification and at 7 and 21 days after aerification. Saturated hydraulic conductivity (Ksat) and organic matter (OM) content were measured monthly. Aerification with hollow tines and hollow tines 2X + hollow needle tines 2X resulted in lower firmness and OM and higher Ksat compared with hollow needle tines and sand injection. Sand injection showed the highest percent green cover and similar OM content compared with hollow tines and hollow tines 2X + hollow needle tines 2X. Green-dyed sand showed a higher percent green cover and DGCI compared with 90:10 sand:peat. Using hollow tines only or alternating them with hollow needle tines is the best option to decrease OM content while increasing Ksat in hybrid bermudagrass greens; however, their use could result in slower turfgrass recovery compared with other aerification methods.

Hybrid Bermudagrass Responses to Impaired Water Sources

Low-quality (i.e., impaired) water sources are commonly used to irrigate warm-season turfgrass landscapes as a result of limited supplies of potable water sources. Currently, there is great need to define the impacts of impaired water sources on turfgrass water consumption, growth, and quality. The objectives of this study were to characterize actual evaporation (ETa), clipping production, and quality of three hybrid bermudagrass varieties [‘TifTuf’, ‘Tifway’, and ‘Midiron’; Cynodon dactylon (L.) Pers. × C. traansvalensis Burtt Davy] grown under three water sources [reverse osmosis (RO), local well, and recycled], each supplied at full irrigation levels (1.0 × ETa) over two 8-week study periods. When pooling across water source and date, TifTuf maintained the highest visual quality and normalized difference vegetation index (NDVI) compared with both Midiron and Tifway. This was accompanied by a greater daily ETa rate, clipping production, and water use efficiency (WUE) compared with Midiron in both studies. When pooling across variety and date, daily ETa of turfgrass receiving recycled water was 5% to 10% less than those receiving the local well or RO water. In addition, turfgrasses receiving local well water held the greatest visual quality and NDVI compared with those receiving either RO water in the summer study. Visual quality and NDVI were also less in turfgrasses receiving RO water compared with those receiving local well or recycled water in the fall. Despite turfgrasses having a lower ETa under recycled water in both study periods, these plants had significantly greater clipping production compared with RO water in the summer. Also, clipping production under recycled water did not differ significantly from the other two sources in the fall study. Furthermoe, in both studies, WUE was similar for turfgrasses receiving recycled water compared with those receiving RO or local well water. Results demonstrated that irrigation water quality influences critical factors for hybrid bermudagrass growth and that considerable variability exists among three commercially available varieties for evapotranspiration rates, quality, and clipping production.

Environmental and Edaphic Factors that Influence Spring Dead Spot Epidemics.

Spring dead spot (SDS) (Ophiosphaerella spp.) is a soilborne disease of warm-season turfgrasses grown where winter dormancy occurs. The edaphic factors that influence where SDS epidemics occur are not well defined. A study was conducted during the spring of 2020 and repeated in the spring of 2021 on four 'TifSport' hybrid bermudagrass (Cynodon dactylon × transvaalensis) golf course fairways expressing SDS symptoms in Cape Charles, VA, U.S.A. SDS within each fairway was mapped from aerial imagery collected in the spring of 2019 with a 20 MP CMOS 4k true color sensor mounted on a DJI Phantom 4 Pro drone. Three disease intensity zones were designated from the maps (low, moderate, high) based on the density of SDS patches in an area. Disease incidence and severity, soil samples, surface firmness, thatch depth, and organic matter measurements were taken from 10 plots within each disease intensity zone from each of the four fairways (n = 120). Multivariate pairwise correlation analyses (P < 0.1) and best subset stepwise regression analyses were conducted to determine which edaphic factors most influenced the SDS epidemic within each fairway and each year. Edaphic factors that correlated with an increase in SDS or were selected for the best fitting model varied across holes and years. However, in certain cases, soil pH and thatch depth were predictors for an increase in SDS. No factors were consistently associated with SDS occurrence, but results from this foundational study of SDS epidemics can guide future research to relate edaphic factors to SDS disease development.

Evaluating St. Augustinegrass [Stenotaphrum Secundatum (Waltz.) Kuntze] Cultivar Morphological Differences

Current trends toward energy conservation in home landscaping present problems in warm-season turfgrass selection since all species grow best in full sunlight. Previous research has identified several St. Augustinegrass [Stenotaphrum secundatum (Waltz.) Kuntze] selections with excellent shade and cold tolerance. To determine if germplasm samples are truly different than established cultivars, morphological traits were evaluated. The objective of this study was to determine if experimental St. Augustinegrass germplasm samples possessed different morphological differences compared to industry standards, ‘Raleigh’ and ‘Palmetto’. Turf height measurements, visual seedhead density counts and morphological measurements were taken to quantify leaf width, leaf length, and internode distance. Measurements were taken at the third internode of each stolon. Internode distance was measured between the third and fourth internode. Significant differences between leaf width, leaf length, and internode distance occurred as did differences between turf height and seedhead density when compared to the industry standards, ‘Raleigh’ and ‘Palmetto’ St. Augustinegrasses. Findings suggest these germplasm samples have sufficient different morphological characteristics to indicate they are probably different cultivars. Differences in morphological characteristics is one tool used to determine differences between cultivars. Additional verification is justifiable if technology advances allow genetic sequencing to be definitive enough to determine if these grasses are truly different. As homeowners trend towards greater energy efficiency, demands for better performing, more shade tolerant turfgrasses also increase. Current trends toward energy conservation in home landscaping present problems in warm-season (C4) turfgrass selection since all species grow best in full sunlight. As the use of shade for cooling homes and buildings has increased, the need for a shade and cold tolerant turfgrass by homeowners and landscapers has arrived [1-3]. To determine if germplasm samples are truly different cultivars than established ones, morphological traits are typically evaluated to justify further research such as genetic sequencing. In addition, turf height and seedhead production differences would be valuable information for those turf managers interested in cultivars not requiring as frequent mowing as others. Genotypic sequencing, however, isn’t always able to delineate between cultivars. In hybrid bermudagrasses (Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy), genotyping-by-sequencing was unable to consistently distinguish triploid standard cultivars from one another [4]. Researchers also were not able to distinguish these selections from their parents due to similar origin and clonal propagation but could distinguish triploids from diploid and tetraploid samples. To the author’s knowledge, molecular genotyping of St. Augustinegrasses has yet been published. Busey [5] classified 94 gentotypes based on 26 characters into five groups and developed a key based on their geography, chromosome number, and adaptation characteristics. The objective of this study was to determine if experimental St. Augustinegrass germplasm samples possessed different morphological differences compared to industry standards ‘Raleigh’ and ‘Palmetto’

Ditylenchus dactylonae n. sp. (Tylenchomorpha: Anguinidae), an associate of Cynodon dactylon (L.) Pers. in the USA

Summary A new species of the genus Ditylenchus was recovered from rhizosphere soil of a ‘TifEagle’ hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis (Burtt-Davy)) putting green located at the Pee Dee Research &amp; Education Center, Clemson University, Florence, SC, USA. It is described herein as Ditylenchus dactylonae n. sp. and is characterised by possessing the combined characters of a medium body size (682-815 μm in females; 618-718 μm in males), six incisures at the lateral fields, a delicate stylet (7.6-8.0 μm) with rounded knobs, a bottle-shaped basal pharyngeal bulb (BPB), an excretory pore (EP) near anterior end of BPB, a posteriorly located vulva (V = 78-83%), a reflexed ovary, a uterus with crustaformeria anteriorly and nearly spherical structure posteriorly, a post-vulval uterine sac (30-50% of the vulva-anus distance), an elongate conoid and ventrally bent tail, a tylenchoid spicule (17-18 μm), and a leptoderan bursa. Ditylenchus dactylonae n. sp. was differentiated from other sequenced species by the partial small subunit (SSU) rRNA gene, D2-D3 expansion segments of the large subunit (LSU) rRNA gene and internal transcribed spacer (ITS) rRNA. Phylogenetic analysis revealed that D. dactylonae n. sp. belongs to the D. dipsaci-group, and is sister to D. medicaginis and/or D. ferepolitor based on SSU 18S, LSU D2-D3 and ITS sequences.

Stress coefficients for hybrid bermudagrass in the transition zone

AbstractThe use of drought tolerant turfgrass cultivars is desirable due to greater water use efficiency and sustained acceptable turfgrass quality during times of drought stress. Crop coefficients (Kc) have traditionally been utilized to assist in reducing irrigation by comparing reference evapotranspiration (ETo) to actual evapotranspiration (ETa) of specific crops. However, Kc values are most relevant during times of nonlimiting conditions and do not quantify the amount turfgrasses restrict evapotranspiration (ET) under moderate drought stress. Stress coefficients (Ks) estimate water needs while maintaining minimally acceptable turfgrass quality. The objective of this study was to derive Ks values for four bermudagrass (Cynodon spp.) cultivars managed in the transition zone. Direct measurements of actual evapotranspiration were made through weighing lysimetry during a 2‐year field study. Experimental units were allowed to naturally dry down near wilting point and maintained at a steady level of soil moisture to calculate Ks for each cultivar. A lower Ks value indicates increased turfgrass tolerance to water stress; whereas a Ks value ≥1 suggests higher soil moisture levels are required to sustain turfgrass quality. ‘TifTuf’, ‘Latitude 36’ and ‘Tifway’ were the best performing cultivars with mean Ks values of 0.747, 0.766, and 0.796, respectively. ‘Celebration’ had the highest Ks value of 0.944. The results indicate certain bermudagrass cultivars can maintain quality with less soil water, and the reduced water requirements may be used to schedule efficient irrigation applications.

Predicting Munsell color for turfgrass leaves

AbstractLinking turfgrass color to hue, value, chroma (H V/C) in the Munsell Plant Tissue Color Book is a visual comparison process for specifying and communicating plant color. If subjectivity of visual comparison can be mitigated, then the accuracy of color matching may be improved. Research was conducted to develop an algorithm predicting H V/C from CIE‐xyY color (xyY) in digital images of leaves of four turfgrasses. First, value‐chroma (V/C) arrays for Munsell hue groups 5Y, 2.5GY, 5GY, 7.5GY, 10GY, and 2.5G were converted to xyY. Next, chromaticity (xy) plots from each array were fitted with 95% prediction bands. Then, xy points for leaves (N = 60) for each turfgrass were plotted versus prediction bands. The prediction interval containing the most leaf xy points specified leaf H. Pairing each V from each hue group (N = 98) with its corresponding Y regressing log10V on log10Y predicted leaf V from leaf Y (log10V = 0.0715 + 0.5303logY – 0.0332logY2). Pairing each C (N = 98) with its corresponding xy predicted leaf C from leaf xy (C = −11.6021 − 11.2908x + 48.0880y). Predicted H V/C for “Champion” and “TifEagle” hybrid bermudagrass [Cynodon dactylon (L.) Pers. var. dactylon × Cynodon transvaalensis Burtt‐Davy] was 10GY 8/4 and 7.5GY 8/4 mirroring H V/C predicted from xyY using open‐source algorithms in R and Python. The experimental algorithm predicted H V/C accurately, and objectively advancing the way turfgrass color is specified and communicated. Specifying turfgrass color in situ could be possible by interfacing the algorithm with smartphone technology.

Distribution and Prevalence of Plant-Parasitic Nematodes of Turfgrass at Golf Courses in China.

Simple SummaryPlant-parasitic nematodes (PPNs) are one of the most important pests to cause infectious diseases on turfgrass. Numerous studies have been conducted on PPNs associated with turfgrass worldwide. However, little published research is available on PPNs associated with turfgrass in China. Information on the occurrence, distribution, diversity, and dominant species of PPNs associated with turfgrass in different regions of China is limited, making it challenging to design suitable management practices for control. In this study, we assessed morphological characteristics and utilized molecular methods to identify PPNs from turfgrass soil samples. The purpose of this study was to determine the species, distribution, incidence, and diversity of PPNs associated with turfgrass at golf courses in North, East, and South China (NC, EC, and SC, respectively). The results provide valuable information for the management of PPNs on turfgrass in China.We sampled 127 turfgrass soil samples from 33 golf courses in NC, EC, and SC for plant-parasitic nematodes (PPNs). PPNs were extracted from soil samples using the shallow dish method and were identified at the genus or species levels with a combination of morphological and molecular methods. The results revealed 41 species of nematode belonging to 20 genera and 10 families. Nine genera are new records of PPNs associated with turfgrass in China. The PPNs show strong geographical distributions. Of the 20 genera, Helicotylenchus, Paratrichodorus, Hoplolaimus, Meloidogyne, Hemicriconemoides, and Mesocriconema showed higher infestation and frequency, and most of these genera had numbers in soil samples above established damage thresholds. Four golf courses had soil samples with PPNs > 30%, indicating the potential for nematode damage. The biodiversity indices H’, SR, J’, λ, and H2 showed significant differences among different regions and turfgrass species; H’, SR, J’, and H2 were significantly higher in EC than in NC and SC, while λ was lowest in EC. Creeping bentgrass had the highest H’, SR, J’, and H2 and the lowest λ in comparison with seashore paspalum and hybrid bermudagrass. These findings provide baseline information on the occurrence of turfgrass-associated PPNs in China, and have important implications for the effective management of PPNs causing damage on turfgrass.

First Report of Take-All Root Rot Caused by Gaeumannomyces graminis on Hybrid Bermudagrass in China.

Take-all root rot caused by Gaeumannomyces graminis (Sacc.) Arx & Olivier is a destructive disease of hybrid bermudagrass (Cynodon dactylon × C. transvaalensis Burtt-Davy) (Elliott 1991; Stephens et al. 2020). In April 2018, multiple circular to irregular patches (10 to 200 cm in diameter) were evident on 'Tifway419' bermudagrass fairway of Wohu golf course (Huangshan city, Anhui province). Patches were found at five of the 18 fairways and showed a decrease in stand density. Individual plants in patches exhibited off-color to white foliage, dark and necrotic lesions were frequently observed on roots and associated stolons. Ectotrophic runner hyphae and lobed hyphopodia are ubiquitous on the surface of necrotic roots. Two diseased samples were collected from each patch by a soil corer (10 cm in diameter), and a total of ten patches were sampled across the five symptomatic fairways. Symptomatic roots or stolons were cut into 2 to 3 cm length and surface disinfested for 3 min in 0.6% sodium hypochlorite solution. The sterilized tissues were rinsed, air dried on sterile filter paper for 5 min and placed on potato dextrose agar (PDA) amended with 50 mg L-1 each of ampicillin, streptomycin sulfate and tetracycline. Plates were incubated in the dark at 20°C for 5 days, and similar colonies were consistently recovered from 85% of the symptomatic tissues. After hyphae purification, a total of 20 fungal isolates were obtained with morphology similar to G. graminis (Hernández-Restrepo et al. 2016). DNA was extracted and amplified with primers ITS5/ITS4 (White et al. 1990). PCR products were sequenced (deposited as MZ889119 and MZ889120 in GenBank), and showed 99.43 to 99.81% homology when compared with a known G. graminis isolate (accession no. KX306505). To complete Koch's postulates, healthy Tifway419 hybrid bermudagrass was grown in 5 × 20 cm Cone-Tainers containing a sand and Pindstrup substrate (Pindstrup Mosebrug, Pindstrup, Denmark) mixture (1:1, V/V) nine weeks after transplanting from the experimental field of the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences. Five sterile oat seeds infested with G. graminis were inserted 5 cm below the soil surface in the root zone of Tifway419. Cone-Tainers inoculated with five noninfested sterile oat seeds served as controls, and each treatment was replicate 3 times. All Cone-Tainers were transferred into a growth chamber with a 12-h day/night cycle at 25/20°C and 95% relative humidity. They were covered with plastic bags for the first week, and watered once daily to encourage disease development. Hybrid bermudagrass inoculated with G. graminis decreased in plant density and turfgrass quality, black and necrotic roots covered with lobed hyphopodia were observed eight weeks after inoculation, no symptoms were present on the roots and above-ground of noninfested control plants. G. graminis was consistently reisolated from symptomatic roots and stolons, and confirmed by sequencing the ITS region as mentioned above. To our knowledge, this is the first report of G. graminis causing take-all root rot of hybrid bermudagrass in China, which may influence the management of this important root disease.

EFFECTS OF DIFFERENT NITROGEN SOURCES ON TURF QUALITY AND PLANTS GROWTH OF SOME WARM-SEASON TURFGRASSES

This research was conducted to determine the effects of different nitrogen sources and rates on some warm-season turfgrasses under Mediterranean-type climate conditions in 2017-2018. The experimental design was a split-split plot with design with three replicates; turfgrass species as the main plot, nitrogen sources as the subplots, and nitrogen doses as the sub subplots. The main plots consist of four nitrogen sources: two slow-release fertilizers, one organomineral fertilizer, and one sewage sludge. Subplots consist of three warm-season turfgrass species; zoysiagrass (Zoysia japonica Steud.), hybrid Bermudagrass (Cynodon transvaalensis x Cynodon dactylon), seashore paspalum (Paspalum vaginatum Sw.), and one cool-season turfgrass species, tall fescue (Festuca arundinacea Schreb.). The nitrogen doses were as follows; 0.0, 2.0, 3.0 and 4.0 g m-2. Turf color and quality were evaluated visually monthly. Also, clipping weight is determined. According to the result, slow-release and organomineral fertilizers can be assessable as N sources that will meet the nutritional needs of the turfgrasses. Zoysiagrass and seashore paspalum showed almost equivalent scores and gave sufficiently dark turf color and quality. Turfgrass should be fertilized at least with 3.0 g m−2 N to provide acceptable turf color and quality.

Monitoring fall CO2 efflux of dallisgrass and hybrid bermudagrass: Implications for nonselective weed control

AbstractChemical control options for dallisgrass (Paspalum dilatatum Poir.) are limited, inconsistent, and damaging to desirable species. Dallisgrass and hybrid bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy] may enter dormancy at different times, allowing for safe, efficacious use of nonselective herbicides for dallisgrass control. Field experiments evaluated dallisgrass and hybrid bermudagrass dormancy by measuring plant respiration in fall and subjecting the carbon efflux data to a nonlinear exponential decay regression model fitted against cooling degree‐days (CDDs). Total plant respiration differed between the species at trial initiation. Dallisgrass exhibited higher net respiration, indicating that each species proceeded into dormancy at different rates. A postemergence dallisgrass control trial was initiated at 5 to 125 CDD22C to evaluate potential rates of quinclorac (1.5, 2.3, and 3.0 kg acid equivalent ha–1), monosodium methanearsonate (6.1, 9.1, and 12.1 kg a.i. ha–1), glyphosate (5, 7.6, and 10.1 kg a.i. ha–1), and thiencarbazone + foramsulfuron + halosulfuron (0.14, 0.18, and 0.22 .kg a.i. ha–1). Dallisgrass control 36 wk after the initial treatment was greatest with glyphosate (≥97%). Minimal bermudagrass survival was observed next spring in response to fall glyphosate. Total plant respiration per sample area differed between species at trial initiation. However, dallisgrass exhibited greater net respiration, indicating differences in behavior concerning the initiation and procession of dormancy between dallisgrass and bermudagrass. Microclimates such as shaded or low‐lying areas may yield different results. Further research should determine the significance of this phenomenon to use nonselective herbicides to control dallisgrass in bermudagrass.

Evaluation of irrigation scheduling approaches within sand‐capped turfgrass systems

AbstractIn an effort to improve performance of turfgrass irrigated with poor‐quality water, the practice of sand capping is increasing. Given current strains on water supplies, evaluation of various methods of irrigation scheduling approaches for these systems is needed. The objectives of this 2‐yr field study were to evaluate turfgrass performance, temporal and spatial soil moisture and salinity dynamics, and comparative water use among four irrigation scheduling approaches including (a) wireless soil moisture sensor (SMS), (b) on‐site reference evapotranspiration (ETo), (c) National Oceanic and Atmospheric Administration forecasted reference evapotranspiration, and (d) visual‐wilt‐based treatment. The turfgrass used was ‘Latitude 36’ hybrid bermudagrass [Cynodon dactylon (L.) Pers. ×C. transvaalensis Burtt‐Davy] planted atop a 17.8‐cm medium‐coarse textured sand cap. Results demonstrated that all approaches produced similar levels of acceptable turfgrass quality and percentage green cover with no apparent differences in root development. Forecasted reference evapotranspiration was found to be a good predictor of on‐site ETo (R2 = .97) when comparing daily values across two growing seasons. Under wilt‐based irrigation, the volumetric water content (7.6 cm sand‐cap depth) at which wilt occurred was highest mid‐summer (4.1–4.7%) but declined during early and late summer months (1.8–2.2%), suggesting different thresholds may be needed throughout the season when using SMS‐based scheduling. Finally, seasonal water use was 23% lower for the on‐site ETo–based approach compared with SMS‐based scheduling, although this did not result in elevated electrical conductivity within the sand cap. The results provide important information to guide adoption of data‐driven approaches to irrigation scheduling.

The Effects of Different Irrigation Levels and Nitrogen Doses on Growth, Quality and Physiological Parameters of Warm-Season Turfgrasses

This research was conducted to determine to effects of different irrigation levels and nitrogen doses on the various warm-season turfgrasses at DELETED by JAS for two years in a row. The experimental design was the randomized blocks in a split-split plot design with three replications. The main plot was irrigation levels (I1=25%, I2=50%, I3=75%, and I4=100% of pan evaporation), subplots were turfgrass species [hybrid Bermudagrass (Cynodon transvaalensis x Cynodon dactylon) cv. Tifdwarf, seashore paspalum (Paspalum vaginatum Sw.) cv. Seaspray, zoysiagrass (Zoysia japonica Steud.) cv. Zenit], and sub subplots were nitrogen doses (monthly 0.0, 1.25, 2.5, and 5.0 g N m-²). Visual turfgrass color and quality, clipping yield, leaf relative water content, loss of turgidity, chlorophyll content, and electrolyte leakage were measured. According to the results, significant differences were determined among irrigation levels, turfgrass species, and nitrogen doses for color, quality, clipping yield and physiological parameters. Turfgrass visual color, quality and clipping yield were shown to decrease significantly with decreases in irrigation water and N fertilizer. The study findings demonstrated that under a non-limiting water supply, irrigation could be decreased by adjusting N fertilizer rates with I3N3 treatments can maintain acceptable turfgrass visual color and quality under Mediterranean climatic conditions. In addition, at 25%(I1) deficit irrigation level, leaf relative water content, chlorophyll content decreased significantly, while an increase was determined in loss of turgidity. This research indicated that under 75%(I3) deficit irrigation and N3 nitrogen dose, acceptable quality can be maintained with ‘Seaspray’ seashore paspalum under Mediterranean climate performed.

Registration of ‘MSB‐264’ and ‘MSB‐285’ bermudagrasses

Abstract‘MSB‐264’ (Reg. no. CV‐47, PI 699313) and ‘MSB‐285’ (Reg. no. CV‐48, PI 699314) are fine‐textured, high‐quality interspecific bermudagrasses (Cynodon dactylon × Cynodon transvaalensis) developed at Mississippi State University. These two grasses were released on 25 Aug. 2021 from the Mississippi Agricultural and Forestry Experiment Station. Compared with Tifgreen‐derived bermudagrass cultivars, MSB‐264 and MSB‐285 were bred from a much different genetic background. Through the 2013 National Turfgrass Evaluation Program warm‐season putting green test, data were collected for 4 yr across 11 locations in the United States. Compared with the commercial cultivars (‘Sunday’, ‘TifEagle’, ‘Tifdwarf’, and ‘Mini‐Verde’) and other experimental lines, both MSB‐264 and MSB‐285 exhibited superior turf quality, leaf texture, density, genetic color, fall and winter color retention, spring green‐up speed, and percent ground living cover. MSB‐264 and MSB‐285 also have a more upright leaf orientation than traditional bermudagrass putting green cultivars. Although MSB‐264 and MSB‐285 had higher seedhead production compared with the commercial cultivars and other experimental lines, regular mowing could effectively remove seedheads. MSB‐264 and MSB‐285 have demonstrated positive performance data and are the first hybrid bermudagrass cultivars used for golf greens that are not related to Tifgreen.

Correlations among Soil, Leaf Morphology, and Physiological Factors with Wear Tolerance of Four Warm-season Turfgrass Species

Traffic resistance of turfgrasses is an essential indicator of urban recreational and sports turf quality (TQ). In our study, four turfgrass species were investigated for their wear resistance. A self-made traffic simulator was used to determine the wear resistance of the study turf area in a 2-year field trial (2019–20). The experimental plots were established using a randomized block design with three replicates. The morphological characteristics, soil physical properties, and physiological indices of the grasses were analyzed. Using the acquired quantitative data, we set the turf cover index (TCI), the turf quality index (TQI), and the shoot density index (SDI) as the wear tolerance index, and assessed the correlations among these morphological characteristics, soil physical properties, physiological indices, and wear tolerance. ‘Lanyin III’ zoysiagrass and ‘Tifgreen’ hybrid bermudagrass provided relatively greater wear tolerance, followed by ‘Qingdao’ zoysiagrass and common bermudagrass after 12 weeks of traffic exposure in 2019 and 2020. Traffic changes the soil physical properties and affects the physiological metabolism of turfgrasses. Leaf morphology characteristics and the mechanical strength of these grasses were related significantly to TCI, TQI, and SDI, and most physiological responses and soil properties correlated significantly with TCI and TQI. Our findings of the correlations among physiological responses, soil properties, leaf morphology, and wear tolerance will allow grass breeders to evaluate their breeding procedures more efficiently.

Residues and Routes of Exposure of Insecticides in Turfgrass for Control of Fall Armyworm Larvae (Lepidoptera: Noctuidae)

Fall armyworm, Spodoptera frugiperda (J.E. Smith), is a generalist pest of food crops and turfgrasses. Insecticides such as diamides provide longer residual control of some grass-feeding caterpillars relative to pyrethroids. The objective was to compare the responses of fall armyworm larvae to residues of commonly used insecticides on hybrid bermudagrass (Cynodon dactylon (L.) × C. transvaalensis Burtt-Davy). A field experiment determined mortality of free-ranging fall armyworms exposed for 1–3 h on turfgrass at 1, 7, 14, 28, and 42 d after a foliar application. A laboratory experiment determined the mortality of larvae fed grass clippings harvested from treated plots at 1, 3, 7, 14, 28, and 42 d after application. Larvae crawled similar or greater distances across bermudagrass treated with bifenthrin and permethrin relative to nontreated grasses. After crawling on bermudagrass treated with chlorantraniliprole or cyantraniliprole 14 d after application, larval mortality was ≥77%. Mortality of larvae fed pyrethroid-treated clippings was ≤40% and no different from control larvae regardless of residue age. Larvae fed bermudagrass with 1 to 7 d old residues of cyantraniliprole or indoxacarb resulted in significantly greater mortality than larvae fed nontreated clippings. No residues of cyantraniliprole or indoxacarb older than 7 d resulted in mortality significantly greater than larvae fed nontreated clippings. Larvae fed chlorantraniliprole-treated clippings of all residue ages produced larval mortality greater than larvae fed nontreated clippings. These experiments support previous reports of extended residual control from chlorantraniliprole against other grass-feeding caterpillar species. The diamides protect turfgrass from larvae better than pyrethroids.

Influence of post-application irrigation and soil surfactants on tebuconazole efficacy against spring dead spot

Spring dead spot (SDS) (Ophiosphaerella spp.) causes damage to hybrid bermudagrass (Cynodon dactylon (L.) Pers. x transvaalensis Burtt Davy) grown in areas where winter dormancy occurs. The pathogen infects the stolons, rhizomes, and roots of warm-season grasses. Symptoms appear as circular, necrotic patches at spring greenup that reduce the playability and aesthetics of bermudagrass. Historically, fungicide efficacy against SDS has been inconsistent. There may be opportunities to improve application and post-application practices to mitigate the inconsistency. A study was conducted from 2019 to 2021 to examine the influence of post-application irrigation and soil surfactant on tebuconazole efficacy against SDS. The study was conducted at three locations: Virginia Tech Turfgrass Research Center (TRC), Blacksburg, VA; Independence Golf Club (IGC), Midlothian, VA; Nutters Crossing Golf Club (NCGC), Salisbury, MD. Tebuconazole was applied in the fall either once at 1.5 kg ai ha−1 or twice at 1.5 kg ai ha−1 two to four weeks apart when soil temperatures were between 10.7 and 21.8 °C. Treatments were applied with or without a soil surfactant and with or without 0.6 cm of post-application irrigation. Bermudagrass was assessed the following spring two or three times for patch number and percent SDS. Data were analyzed by assessment date, subjected to analysis of variance, and means were separated using Tukey's Honest Significant Difference test (P = 0.05). There were no treatment differences at IGC or NCGC in 2020 or 2021. At the TRC in both 2020 and 2021, results were inconsistent with tebuconazole generally suppressing SDS compared to the nontreated control. However, differences between tebuconazole-treated plots were variable. Our study suggests that including a soil surfactant with tebuconazole applications and/or irrigating post-application does not consistently increase SDS suppression.