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Stacy A. Bonos, William A. Meyer, and James A. Murphy

The apomictic breeding behavior of Poa pratensis L. provides an opportunity to study many unique genotypes that can vary dramatically in characteristics such as disease resistance, stress tolerance and growth habit. The classification of Kentucky bluegrass into types is based on common growth and stress performance characteristics gathered from field turf trials. These classification types include the Compact, Bellevue, Mid-Atlantic, BVMG (`Baron, `Victa', `Merit', and `Gnome'), Common, and Aggressive types. A spaced-plant nursery trial was established in May 1996 to quantify morphological and growth characteristics of 45 cultivars and selections representing the major types of Kentucky bluegrass. Plant height, panicle height, flag leaf height and length, subtending leaf length and width, rhizome spread, and longest extending rhizome were measured 10 days after anthesis. Compact type cultivars had a lower, more prostrate growth habit than the Common, Mid-Atlantic, and Bellevue types. Mid-Atlantic type cultivars had a wider rhizome spread than Compact type cultivars. Principal component analysis of morphological measurements made on spaced-plants supports the classification types of the Common, Compact, Bellevue, Mid-Atlantic, and BVMG, but not necessarily the Aggressive type.

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Pedro Perdomo, James A. Murphy, and Gerald A. Berkowitz

Understanding the factors influencing the performance of Kentucky bluegrass (Poa pratensis L.) cultivars under summer stress is necessary for developing criteria for identifying resistant germplasm. The objectives of this study were to evaluate two Kentucky bluegrass cultivars for leaf water (ψl) and osmotic potential (ψπ), stomatal resistance (Rs), leaf: air temperature differential (ΔT) and determine the relationship of these parameters to drought and heat tolerance. Stress-resistant (`Midnight') and susceptible (`Nugget') cultivars were evaluated in a field study during 1993 and 1994 under moisture-limiting conditions. Leaf water potential for `Nugget' was higher than for `Midnight' in 1993 and similar in 1994. `Midnight' had lower ψπ than `Nugget' during the evaluation period in 1994. `Midnight' maintained more open stomata (lower Rs) and lower ΔT than `Nugget' at the end of the dry down period when `Nugget' was showing visual signs of stress. `Midnight' and `Nugget' had similar root weight at the 0- to 45-cm depth zone in 1994. Lower basal osmotic potential (i.e., higher solute concentration) may be the physiological mechanism allowing larger stomatal aperture in `Midnight'. Greater transpirational cooling in `Midnight' relative to `Nugget' was correlated with higher turf quality for `Midnight'.

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Gerald M. Henry, Stephen E. Hart, and James A. Murphy

Field trials were conducted in 2000 and 2001 to determine the potential of converting pure stands of annual bluegrass [Poa annua L. spp. reptans (Hauskins) Timm.], maintained at a 3.2-mm height, to bentgrass (Agrostis spp.). Parameters evaluated included three overseeding dates and four cultivars from two bentgrass species. Overseeding dates were 1 July, 18 Aug., and 18 Sept. 2000 and 27 June, 17 Aug., and 17 Sept. 2001. Three creeping bentgrass (A. stolonifera L.) cultivars (`Penncross', `L-93', and `Penn A-4') and one velvet bentgrass (A. canina L.) cultivar (`SR7200') were evaluated. Initial bentgrass establishment was evident across all seeding dates and cultivars in October of the year of overseeding. However, the 1 July 2000 and 27 June 2001 overseeding dates had the highest levels of bentgrass coverage 12 months after overseeding across all cultivars except `Penncross'. Coverage of `Penn A-4' and `L-93' increased to 72% in the 1 July 2000 overseeding date, 24 months after the initial overseeding. When overseeded in early summer, velvet bentgrass `SR7200' showed the greatest potential for establishment with annual bluegrass. `SR7200' and creeping bentgrass cultivars `Penn A-4' and `L-93' exhibited the greatest potential for long-term competitiveness with annual bluegrass, while `Penncross' exhibited the lowest potential.

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Matthew T. Elmore, James A. Murphy, and Bradley S. Park

Creeping bentgrass (CBG; Agrostis stolonifera L.) is a problematic weed of cool-season turfgrass. The herbicide mesotrione is often used for selective control, but CBG often recovers from sequential applications. Research evaluated the efficacy of mesotrione-based sequential application regimens for CBG control in kentucky bluegrass (Poa pratensis L.) over a 2-year period. In two separate experiments, identical herbicide regimens were initiated in Oct. 2014 or May 2015 and then reapplied to the same plots in Oct. 2015 or May 2016, respectively. Regimens consisted of various sequential application regimens of mesotrione alone (totaling 560 g·ha–1 annually), three sequential applications of mesotrione (175 g·ha–1) tank-mixed with either triclopyr ester (560 or 1120 g·ha–1) or amicarbazone (50 or 100 g·ha–1), and topramezone (32 or 37 g·ha–1) tank-mixed with triclopyr ester (1120 g·ha–1). At the end of each 2-year experiment, the most effective treatments did not eliminate CBG completely. Among treatment regimens initiated in the fall, the most effective treatments reduced CBG cover 49% to 73% at the conclusion of the experiment in Oct. 2016. At the conclusion of the spring experiment in May 2017, the most effective treatments reduced CBG cover 66% to 94%. Topramezone + triclopyr tank mixtures were less effective than mesotrione-containing treatments on most dates. Mesotrione + amicarbazone tank mixtures reduced CBG more effectively than mesotrione alone, but these tank mixtures also caused severe kentucky bluegrass injury. CBG cover reductions from mesotrione + triclopyr tank mixtures and mesotrione alone were generally similar. Among mesotrione-only regimens, there were no consistent differences in CBG cover reduction. This research indicates that turf managers using a selective herbicide regimen to control CBG in kentucky bluegrass should apply mesotrione at the maximum annual use rate (560 g·ha–1) in two to four sequential applications at 2- to 3-week intervals.

Open access

Ruying Wang, James W. Hempfling, Bruce B. Clarke, and James A. Murphy

Sand size can affect the ability to incorporate topdressing into the turf canopy and thatch on golf course putting greens; unincorporated sand interferes with mowing and play. This 3-year field trial was initiated to determine the effects of sand size on sand incorporation, surface wetness, and anthracnose (caused by Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman) of annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama] maintained as a putting green. The experimental design was a randomized complete block with four replications; treatments included a non-topdressed control and three topdressing sands (medium-coarse, medium, or medium-fine) applied every 2 weeks at 0.15 L·m−2 during the summer. Topdressing with medium-coarse sand was more difficult to incorporate than the medium and medium-fine sands, resulting in a greater quantity of sand collected with mower clippings. Analyzing the particle distribution of sand removed by mowing confirmed that coarser sand particles were more likely to be removed in mower clippings. Surface wetness measured as volumetric water content (VWC) at the 0- to 38-mm depth zone was greater in non-topdressed plots than topdressed plots on 35% of observations. Few differences in VWC were found among sand size treatments. Turf responses to topdressing were not immediate; however, as sand accumulated in the turf canopy, topdressed plots typically had lower anthracnose severity than non-topdressed turf after the first year. Additionally, topdressing with medium and medium-fine sands produced similar or occasionally lower disease severity than topdressing with medium-coarse sand. The lack of negative effects of medium and medium-fine sands combined with better incorporation after topdressing and less disruption to the putting surface should allow golf course superintendents to apply topdressing at frequencies and/or quantities needed during the summer to maintain high-quality turf and playing conditions.

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Arlie A. Powell, James Witt, William Dozier Jr., Scott Goodrick, Ed Tunnell, and Richard Murphy

Lack of winter chilling periodically becomes a serious problem for commercial peach producers in the Southeast, especially along and near the Gulf Coast areas. Studies were conducted over 3 years (1989-1991) to evaluate the effects of hydrogen cyanamide (Dormex - SKW) on replacing lack of winter chilling in 7 varieties of peaches.

Initial findings using whole tree sprays to point of runoff indicated a problem with efficacy and phytotoxicity. A combination of hydrogen cyanamide rates (0, .5, 1, 2 and 4% V/V) and timings (0, 25, 50 and 75% of chilling level) were evaluated in 1991. Rates above 2% were phytotoxic. Rates of 0.5 to 1.0% were safe and effective when applied at 75% chilling.

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Arlie A. Powell, Scott Goodrick, James Witt, William Dozier Jr., and Richard Murphy

Lack of winter chilling can be a serious problem for commercial peach producers in the Southeast. Studies were conducted over 3 years (1989-91) to evaluate the effects of hydrogen cyanamide (Dormex-SKW) on replacing lack of winter chilling on 7 varieties of peaches. This study specifically reports on the effects of hydrogen cyanamide on 'Ruston Red' peach, a 850-hour variety.

Results from 1990 studies using whole tree sprays to the point of runoff indicated a problem with the efficacy and phytotoxicity. In 1991, a combination of hydrogen cyanamide (49%) rates (0, 0.5, 1, 2, and 4% V/V) and timings (0, 25, 50 and 75% of chilling level) were evaluated using 7-year-old 'Ruston Red' peach trees. Only 590 hours of chilling at 7.3°C and lower were accumulated at this site. Rates of 0.5 75% (actually only 70%) chilling level induced full cropping while control trees produced practically no crop.

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Chengyan Yue, Jingjing Wang, Eric Watkins, Stacy A. Bonos, Kristen C. Nelson, James A. Murphy, William A. Meyer, and Brian P. Horgan

The development and evaluation of new turfgrass cultivars require considerable resources. A systematic understanding of the breeders’ and distributors’ trait selection behavior can provide a basis for making adjustments and improvements based on industry needs and thus accelerate the breeding process and make it more efficient. The objective of this study is to investigate the selection priorities for turfgrass traits and identify the most influential factors affecting turfgrass breeders’ and distributors’ likelihood of selecting turfgrass traits. Results show that the most important trait clusters for both breeders and distributors were abiotic stress resistance and growth characteristics. Breeders were more likely than distributors to select appearance traits when setting trait priorities. Program characteristics such as program size, education level, and being a male respondent had positive effects on the reported likelihood of selecting studied turfgrass traits, and these effects varied for different trait clusters.

Full access

Chengyan Yue, Jingjing Wang, Eric Watkins, Stacy A. Bonos, Kristen C. Nelson, James A. Murphy, William A. Meyer, and Brian P. Horgan

An online survey was conducted to investigate the current practices of and challenges for turfgrass breeders and turfgrass seed distributors (or sales staff) in the United States. We found that turfgrass seed breeders rated producers/growers and consumers as more important parties compared with other interested parties. However, variations in ratings were found for breeders/distributors according to different program characteristics. The volume of seed sales of the species was the most highly rated technical consideration for both breeders and distributors. Compared with distributors, breeders considered the following technical factors more important than others: funding, labor, field trial performance, diversity in working priorities, availability of germplasms, scheduling, and staff training. Costs, followed by resource allocation and resource availability, were rated as the most challenging factors when breeders were implementing priorities. Our findings provide important insight regarding breeding and distribution practices and management in the turfgrass industry.