John C. Sorochan

Effects of Mesotrione on Perennial Ryegrass (Lolium perenne L.) Carotenoid Concentrations under Varying Environmental Conditions

Mesotrione is a carotenoid biosynthesis inhibiting herbicide, which is being evaluated for use in turfgrass. Carotenoids are important light harvesting and photoprotecting pigments that dissipate and quench excess light energy. The effects of mesotrione on carotenoid concentrations in turf and weed species, such as perennial ryegrass (Lolium perenne L.), are poorly understood. Mesotrione injury to perennial ryegrass has been reported, and symptomology may differ due to postapplication environmental factors such as irradiance and temperature. Research was conducted to investigate the effects of mesotrione on perennial ryegrass under varying irradiance (600, 1100, or 1600 micromol/m (2)/s) at three different temperatures (18, 26, and 34 degrees C). Postapplication irradiance and temperature levels did not affect visual injury symptoms in perennial ryegrass. Bleaching of treated plants was highest 7 days after treatment (DAT; 8%) and recovered to nontreated levels by 21 DAT. Mesotrione applications did not decrease perennial ryegrass foliar biomass accumulations. Carotenoid concentrations of nontreated plants were similar to those reported in creeping bentgrass and many green leafy vegetable crops. However, chlorophyll a and b, beta-carotene, lutein, and violaxanthin concentrations decreased due to mesotrione applications, while phytoene and zeaxanthin, a photoprotecting carotenoid, increased. The photochemical efficiency (F v/ F m) of treated plants was lower than nontreated plants at 3 and 7 DAT; however, treated plants recovered to nontreated levels 21 DAT. Results indicate that postapplication irradiance and temperature levels may not affect mesotrione efficacy in perennial ryegrass. Preferential accumulation of zeaxanthin following mesotrione applications may be a stress-related response, which may reduce light harvesting complex size and directly quench excess light energy.

Efficacy and Safening of Aryloxyphenoxypropionate Herbicides when Tank-Mixed with Triclopyr for Bermudagrass Control in Zoysiagrass Turf

Abstract Aryloxyphenoxypropionate (AOPP) herbicides are used to control bermudagrass contamination in various turfgrasses. Applying AOPP herbicides alone can cause unacceptable injury to zoysiagrass but injury can be reduced when tank-mixed with triclopyr. There are limited data illustrating the extent of bermudagrass control and zoysiagrass cultivar tolerance when these compounds are combined. Research was conducted to determine the efficacy of multiple AOPP herbicides applied alone and tank-mixed with triclopyr for bermudagrass control in zoysiagrass turf. Treatments include three sequential applications of cyhalofop (0.32 kg ai ha−1), fenoxaprop (0.14 kg ha−1), fluazifop (0.11 kg ha−1), or quizalofop (0.09 kg ha−1) applied alone and tank-mixed with triclopyr (1.12 kg ae ha−1) applied to ‘Tifway’ bermudagrass, and ‘Diamond’, ‘Palisades’, and ‘Zenith’ zoysiagrass. Tifway bermudagrass control ranged from 41 to 69% and digital image analysis turf coverage data ranged from 18 to 50% for AOPP herbicides applied alone. The addition of triclopyr to AOPP herbicides increased bermudagrass control (64–79%) and reduced turf coverage (8–29%). Palisades and Zenith zoysiagrass exhibited less injury (1–18%) and greater turf coverage (84–86%) when AOPP herbicides were tank-mixed with triclopyr compared to AOPP herbicides applied alone. Diamond zoysiagrass was not tolerant to any AOPP herbicides applied alone or tank-mixed with triclopyr, except for fluazifop alone (18% injury and 93% turf coverage). Visual ratings and digital image analysis turf coverage data had a strong negative correlation over all tested turfgrasses. In general, AOPP herbicides plus triclopyr will control bermudagrass greater and injure zoysiagrass less compared to AOPP herbicides applied alone; however, these mixtures can cause unacceptable injury to Diamond zoysiagrass. Nomenclature: Cyhalofop; fenoxaprop; fluazifop; triclopyr; quizalofop; bermudagrass, Cynodon spp. Rich.; hybrid bermudagrass, Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davy ‘Tifway’ CYNDA; zoysiagrass species, Zoysia spp. Willd.; zoysiagrass, Zoysia japonica Steud. ‘Palisades’, ‘Zenith’ ZOYJA; zoysiagrass, Zoysia matrella (L.) Merr. ‘Diamond’ ZOYMA.

Annual Bluegrass (Poa Annua) Control in Creeping Bentgrass (Agrostis Stolonifera) Putting Greens with Bispyribac-sodium

Annual bluegrass is one of the most difficult-to-control weeds in creeping bentgrass putting greens. Field trials were conducted in 2003 and 2005 to evaluate bispyribac-sodium for annual bluegrass management in creeping bentgrass greens maintained at a 3 mm mowing height. Bispyribac-sodium applied weekly at 12 or 24 g ai/ha controlled annual bluegrass 86% 12 wk after initial treatment (WAIT). In 2003, bispyribac-sodium applied at 12 and 24 g/ha/wk injured creeping bentgrass approximately 15 and 50% by 4 WAIT, respectively. However, injury was transient and was not evident by 12 WAIT. In 2005, the 12 and 24 g/ha/wk injured creeping bentgrass 15 and 85% by 8 WAIT, respectively, and was still evident throughout the trial. Putting green quality was reduced when compared to nontreated creeping bentgrass by the same treatments. The removal of annual bluegrass caused soil exposure until creeping bentgrass grew over the bare areas, contributing to decreased quality evaluations. Management of annual bluegrass in creeping bentgrass putting greens is possible with bispyribac-sodium. However, these results indicate bispyribac-sodium can cause excessive injury when applied to creeping bentgrass mowed at 3 mm. Nomenclature: Bispyribac-sodium; annual bluegrass, Poa annua L. POANN; creeping bentgrass, Agrostis stolonifera L. AGSST, ‘Penncross’.

Efficacy of Flazasulfuron for Control of Annual Bluegrass (Poa annua) and Perennial Ryegrass (Lolium perenne) as Influenced by Nitrogen

Abstract Certain sulfonylurea (SU) herbicides are used to remove overseeded cool-season species from bermudagrass. The effects of nitrogen (N) on the efficacy of a new SU herbicide, flazasulfuron, have not been determined. Field and laboratory studies were conducted in 2008 and 2009 evaluating the efficacy of flazasulfuron for control of overseeded perennial ryegrass contaminated with annual bluegrass. Flazasulfuron was applied at rates of 4.4, 8.8, and 17.5 g ha−1 alone, and in between sequential applications of N fertilizer at 73 kg N ha−1. N was granularly applied immediately prior to herbicide treatment and 4 wk later. In both years, the level of annual bluegrass control with flazasulfuron and two applications of N at 73 kg N ha−1 was significantly greater than following treatment with flazasulfuron alone. This response was observed for all application rates of flazasulfuron on every rating date. The level of annual bluegrass control with flazasulfuron at 4.4 g ha−1 and two applications of N at 73 kg ha−1 was greater than flazasulfuron at 17.5 g ha−1 alone each year. No significant differences in perennial ryegrass control were observed for flazasulfuron with and without N fertility. In laboratory studies with annual bluegrass, treatment with N fertilizer at 73 kg N ha−1 increased translocation of 14C flazasulfuron (and any potential metabolites) from treated annual bluegrass leaves to other shoot tissues by 18% at 1 h after treatment and 22% at 4 h after treatment compared to plants not treated with N fertilizer. This increase in translocation may explain the increased level of annual bluegrass control observed in the field. Nomenclature: Flazasulfuron; annual bluegrass, Poa annua L. POAN; bermudagrass, Cynodon dactylon (L.) Pers. CYNDA; perennial ryegrass, Lolium perenne L. LOLPE.

Genetic analysis of fungicide-resistant Sclerotinia homoeocarpa isolates from Tennessee and northern Mississippi

Sclerotinia homoeocarpa is the causal agent of dollar spot disease that reduces the uniformity and aesthetic value of golf putting greens. Fungicide-resistant isolates of S. homoeocarpa were collected from putting greens at 10 locations across Tennessee and northern Mississippi. Genetic diversity among the 60 isolates was investigated using vegetative compatibility, conserved gene sequences, and amplified fragment length polymorphism (AFLP). Six tester strains were paired with Tennessee and northern Mississippi isolates on potato dextrose agar. Some of the 60 isolates were delineated into vegetative compatibility groups, but fungicide resistance could not be associated with a particular vegetative compatibility group. Genetic similarities of isolates at the vegetative compatibility level could be attributed to founder effects. Sequencing the regions of CAD, EF1-α, β-tubulin, and internal transcribed spacers revealed 100% homology among isolates. Capillary gel electrophoresis and analysis of AFLP fragments indicated 86 to 100% similarity between the isolates. Vegetative compatibility and molecular data indicate that the populations of the pathogen are clonal. Isolates did not cluster according to fungicide resistance during unweighted pair group with arithmetic means analysis, but did appear to cluster according to vegetative compatibility group and location. Although associations could not be made between molecular markers and fungicide resistance, links between vegetative compatibility and AFLP markers may provide a foundation from which other studies could be performed.

Hybrid Kentucky Bluegrass Tolerance to Preemergence and Postemergence Herbicides

Field studies were conducted near Knoxville, TN, from 2003 to 2005 to evaluate the response of ‘Thermal Blue’, a new interspecific hybrid Kentucky bluegrass to commonly applied PRE and POST herbicides for weed management. Dithiopyr, oryzalin, oxadiazon, pendimethalin, prodiamine, quinclorac, and trifluralin applied at seeding injured hybrid bluegrass greater than 81% and reduced hybrid bluegrass cover greater than 57%. In a second study, established hybrid bluegrass was treated POST with acetolactate synthase–inhibiting herbicides including bispyribac-sodium, chlorosulfuron, foramsulfuron, halosulfuron, imazapic, imazaquin, metsulfuron, rimsulfuron, sulfosulfuron, and trifloxysulfuron at low and high rates (one and two times the suggested use rates in Kentucky bluegrass or other turfgrasses). By 5 wk after treatment (WAT), foramsulfuron at 88 g ai/ha and trifloxysulfuron at 35 g ai/ha injured hybrid bluegrass greater than 26% and reduced visually estimated quality and chlorophyll meter indices. However, hybrid bluegrass injury was no longer evident at 10 WAT. In a third study, established hybrid bluegrass was treated with clethodim, diclofop-methyl, fluazifop-p-butyl, and sethoxydim applied at low, medium, and high rates (0.5, 1, and 2 times the registered Kentucky bluegrass or other turfgrass use rates). Clethodim applied at 280 and 560 g ai/ha, fluazifop at 420 g ai/ha, and sethoxydim at 630 g ai/ha injured hybrid bluegrass 5 WAT. These treatments also reduced quality (to less than 5 on a scale of 1 to 9) and chlorophyll meter indices (24 to 37%) when compared to the untreated control. By 10 WAT, only clethodim at 560 g ai/ha caused injury (14%). By 10 WAT, hybrid bluegrass had recovered and injury was only observed in plots treated with clethodim at 560 g ai/ha. No differences in chlorophyll indices or quality were observed at 10 WAT for any POST graminicides. Nomenclature: Bispyribac-sodium, chlorosulfuron, clethodim, diclofop-methyl, dithiopyr, fluazifop-p-butyl, foramsulfuron, halosulfuron, imazapic, imazaquin, metsulfuron, oryzalin, oxadiazon, pendimethalin, prodiamine, quinclorac, rimsulfuron, sethoxydim, sulfosulfuron, trifloxysulfuron, trifluralin, Kentucky bluegrass, Poa arachnifera Torr. × P. pratensis L. ‘Thermal Blue’

Using Ground-Penetrating Radar to Evaluate Soil Compaction of Athletic Turfgrass Fields

Repairing a compacted turfgrass athletic field is a laborious activity, requiring significant expense. The objective of this project is to develop a rapid survey method for mapping soil compaction that occurs from player trafficking. Once mapped, field managers can target compacted regions of their fields for site-specific remediation; thereby, reducing their labor and expenses.

Hybrid Bluegrass Tolerance to Postemergence Applications of Mesotrione and Quinclorac

New hybrid bluegrass cultivars have been bred for increased heat and drought tolerance compared with traditional Kentucky bluegrass cultivars. Research was conducted to evaluate hybrid bluegrass tolerance and smooth crabgrass and goosegrass control with mesotrione and quinclorac during seeded establishment. Mesotrione applied as a single application 14, 28, or 42 d after emergence (DAE) injured hybrid bluegrass acceptably from 1 to 11% 7 d after treatment (DAT). A sequential mesotrione application at 0.14 kg/ha 28 DAE did not injure hybrid bluegrass greater than the initial 14 DAE application; however, a sequential application at 0.28 kg/ha 28 DAE injured hybrid bluegrass greater than the initial 14 DAE application. Three sequential mesotrione applications did not reduce hybrid bluegrass ground cover 63 DAE. Quinclorac applied singly at 1.68 kg/ha 14 DAE and sequentially at 0.84 kg/ha 14 and 28 DAE injured hybrid bluegrass that continued throughout the rating period resulting in decreased ground cover at 63 DAE. Quinclorac at 0.84 kg/ha plus mesotrione at 0.28 kg/ha injured hybrid bluegrass < 20% throughout the rating period but reduced ground cover 63 DAE. All quinclorac-containing treatments controlled smooth crabgrass ≥ 92%. All mesotrione sequential-application treatments controlled smooth crabgrass and goosegrass ≥ 87%. These data indicate that sequential mesotrione applications can be used for smooth crabgrass and goosegrass control during seeded hybrid bluegrass establishment. Quinclorac should be applied according to label recommendations at 0.84 kg/ha no earlier than 28 DAE. Nomenclature: Mesotrione, quinclorac, goosegrass, Eleusine indica (L.) Gaertn. ELEIN, smooth crabgrass, Digitaria ischaemum (Schreb.) Schreb. ex Muhl. DIGIS, hybrid bluegrass, Poa pratensis L. × Poa arachnifera Torr. ‘Solar Green’, ‘Durablue’, and ‘Thermal Blue’, Kentucky bluegrass, Poa pratensis L. POAPR

Effects of two football stud configurations on biomechanical characteristics of single-leg landing and cutting movements on infilled synthetic turf

Multiple playing surfaces and footwear used in American football warrant a better understanding of relationship between different combinations of turf and footwear. The purpose of this study was to examine effects of shoe and stud types on ground reaction force (GRF) and ankle and knee kinematics of a 180° cut and a single-leg 90° land-cut on synthetic turf. Fourteen recreational football players performed five trials of the 180° cut and 90° land-cut in three shoe conditions: non-studded running shoe, and football shoe with natural and synthetic turf studs. Variables were analyzed with a 3 × 2 (shoe × movement) repeated measures analysis of variance (p < 0.05). Peak vertical GRF (p < 0.001) and loading rate (p < 0.001) were greater during 90° land-cut than 180° cut. For 180° cut, natural turf studs produced smaller peak medial GRFs compared to synthetic turf studs and non-studded shoe (p = 0.012). For land-cut, peak eversion velocity was reduced in running shoes compared to natural (p = 0.016) and synthetic (p = 0.002) turf studs. The 90° land-cut movement resulted in greater peak vertical GRF and loading rate compared to the 180° cut. Overall, increased GRFs in the 90° land-cut movement may increase the chance of injury.

Profiling USGA Putting Greens Using GPR—An As-built Surveying Method

Putting greens that are constructed to United State Golf Association (USGA) standards must adhere to strict installation specifications to maintain proper subsurface drainage. Because the infrastructure is buried, it can be difficult to ascertain if these structures were properly installed. Insufficient drainage affects agronomics, compromising the playability of the putting surface. Repairs are expensive and laborious. This study introduces a nonintrusive survey protocol that combines ground-penetrating radar (GPR) and real-time kinematic (RTK) positioning. A case study was used to examine a putting green designed using the USGA specifications. The protocol created ‘‘as-built’’ subsurface maps. The protocol non-intrusively identified the tile slope and spacing. It also determined the depth and thickness of the root-zone mixture and gravel. The green adhered to the tile spacing specification, but failed to meet specifications as to tile slope and root-zone mixture depth. These findings suggest that this protocol provides a relatively inexpensive method to determine adherence to USGA greens standards. Generated maps highlighted conformity (or lack thereof ) to the design specifications.