The growth responses of 10 Rhizoctonia zeae isolates, obtained from turfgrasses in Florida and Ohio, to four temperatures (20, 25, 30, and 35 °C) and seven fungicides at four concentrations (0, 1, 10 and 100 μg·mL-1 a.i.) were compared. Greenhouse pathogenicity tests were conducted using hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy]. Optimal temperature for growth for all isolates was 30 °C. Growth of R. zeae isolates from both geographic locations was severely limited (>75%) at 20 °C. All R. zeae isolates were insensitive to the benzimidazole fungicides, benomyl and thiophanate methyl. Their sensitivities to iprodione, mancozeb, and quinotzene fungicides were similar. The Florida isolates were more sensitive to chlorothalonil, and the Ohio isolates to thiram. All isolates were pathogenic to hybrid bermudagrass. Chemical names used: methyl 1-(butylcarbamoly)-2-benzimidazolecarbamate (benomyl); dimethyl 4,4′-O-phenylene bis(3-thioallophanate) (thiophanate methyl); pentachloronitrobenzene (quintozene); 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidinecarboxamide (iprodione); tetrachloroisophtalonitrile (chlorothalonil); tetramethylthiuram disulfide (thiram); manganese ethylenebisdithiocarbamate (mancozeb).
Many warm-season turfgrass seeds have relatively poor germination percentages. Matriconditioning is a seed enhancement technique with a solid carrier and may be a practical solution to improve the germination characteristics of warm-season turfgrass. The objective of this study was to determine the effectiveness of matriconditioning on three nonaged and aged turfgrass cultivars: ‘Pensacola’ bahiagrass (Paspalum notatum), ‘Princess’ bermudagrass (Cynodon dactylon), and ‘Common’ centipedegrass (Eremochloa ophiuroides). Seeds were matriconditioned with a synthetic calcium silicate (MicroCel E) as a carrier and water at 30 °C for 5 days. Seed, carrier, and water ratio was 1 g, 0.5 g, and 1.5 mL, respectively. Matriconditioning increased final germination to 55% (bahiagrass), 90% (bermudagrass), and 70% (centipedegrass) compared with 92% in nontreated control seeds. Furthermore, matriconditioning decreased mean germination time 20% to 65% in all seeds compared with the nontreated control. Accelerated aging was induced by storing seeds for 0, 7, and 14 days at 42 °C and 95% relative humidity. Germination percentage decreased and mean germination time increased with the aging, especially after 14 days of aging treatment. These results suggest that matriconditioning is an effective technique to improve turfgrass seed performance.
Lambert B. McCarty, Leon T. Lucas, and Joseph M. DiPaola
Spring dead spot (SDS) [Gaeumannomyces graminis (Sacc.) von Arx & D. Olivier var. graminis Walker] is a serious disease of bermudagrass [Cynodon dactylon (L.) Pers.] throughout much of the southern United States and is believed to be at least partially influenced by the previous year's turfgrass management practices. Research was performed to: a) determine the efficacy of selected fungicide control measures; and b) determine the influence of N and K nutrient regimes on the expression of SDS symptoms in Tifway bermudagrass (C. dactylon x C. transvaalensis Burtt-Davy). Averaged over two sites in 2 years, a 72% reduction in SDS followed a fall application of benomyl at 12 kg·ha. Fenarimol applied at three rates (1.5, 2.3, and 3.0 kg·ha) on three fall dates reduced SDS by a combined average of 66%. A single application of propiconazole (2.5 kg·ha) reduced disease by an average of 56%. Application of N (98 kg·ha) in late fall increased SDS 128% in one test location. Application of potassium sulfate (269 kg K/ha) in late fall resulted in an average increase in SDS expression of 89% the following spring over all experiments. Turf managers with severe SDS should minimize heavy late-fall K applications and possibly use benomyl, fenarimol, or propiconazole for disease suppression. Chemical names used: α -(2-chlorophenyl)α -(4-chlorophenyl)-S-pyrimidinemethanol (fenarimol); [methyl 1(butylcarbamoyl)-2-benzimidazolecarbamate] (benomyl); 1-[[2-(2,4-dichlorophenyl)-4propyl-1,3-dioxolan-2-yl]methyl]--1H-1,2,4-triazole (propiconazole).
Patrick E. McCullough, Haibo Liu, Lambert B. McCarty, and Ted Whitwell
Research was conducted in two studies at the Clemson University Greenhouse Complex, Clemson, S.C., with the objective of evaluating `TifEagle' bermudagrass (Cynodon dactylon × C. transvaalensis) response to paclobutrazol. TifEagle bermudagrass plugs were placed in 40 cm polyvinylchloride containers, with 20.3-cm-diameters and built to U.S. Golf Association specifications with 85 sand: 15 peatmoss (by volume) rootzone mix. Paclobutrazol was applied to separate containers at 0, 0.14, 0.28, and 0.42 kg·ha-1 (a.i.) per 6 weeks. Minor phytotoxicity occurred with 0.14 kg·ha-1 applications, but turf quality was unaffected. Severe bermudagrass phytotoxicity occurred from paclobutrazol at 0.28 and 0.42 kg·ha-1. Total clipping yield from 12 sampling dates was reduced 65%, 84%, and 92% from 0.14, 0.28, and 0.42 kg·ha-1, respectively. Root mass after 12 weeks was reduced 28%, 45%, and 61% for turf treated 0.14, 0.28, and 0.42 kg·ha-1, respectively. Paclobutrazol reduced root length 13%, 19%, and 19% by 0.14, 0.28, and 0.42 kg·ha-1, respectively. Turf discoloration and negative rooting responses advocate caution when using paclobutrazol on `TifEagle' bermudagrass. Chemical names used: (+/-)-(R*,R*)-ß-[(4-chlorophenyl) methyl]-alpha-(1, 1-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol).
Y.L. Qian and M.C. Engelke
Determining the appropriate level of irrigation for turfgrasses is vital to the health of the turfgrass and the conservation of water. The linear gradient irrigation system (LGIS) allows long-term assessment of turf performance under continuous irrigation gradients from excess to no irrigation. The objectives of this study were to: 1) evaluate the minimum irrigation requirements and relative drought resistance of `Rebel II' tall fescue (Festuca arundinacea Schreb.), `Meyer' zoysiagrass (Zoysia japonica Steud.), `Tifway' bermudagrass [Cynodon dactylon (L.) Pers.], `Prairie' buffalograss [Buchloe dactyloides (Nutt.) Engelm], and `Nortam' St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze]; and 2) evaluate the long-term effects of irrigation levels on turf persistence, weed invasion, and disease incidence for the five selected turfgrasses under field conditions. Turf was sodded under LGIS with an irrigation gradient ranging from 120% Class A pan evaporation (Ep) to natural precipitation, along a 20-m turf area. Evaluation during the summers of 1993–96 indicated that grasses differed in drought resistance and persistence under variable irrigation regimes. Irrigation (Ep) required to maintain acceptable turf quality for respective grasses was `Rebel II' (67%), `Meyer' (68%), `Nortam' (44%), `Tifway' (35%), and `Prairie' (26%). Higher dollar spot (Sclerotinia homoeocarpa Bennett) infection was observed at 115% Ep irrigation regime in `Tifway' bermudagrass, whereas gray leaf spot [Pyricularia grisea (Hebert) Barr] was observed only at 10% Ep irrigation regime in St. Augustinegrass plots. An outbreak of brown patch (Rhizoctonia solani Kuehn.) occurred in Sept. 1996 in St. Augustinegrass plots receiving irrigation at >80% Ep.
Michael S. Harrell and Grady L. Miller
The benefits of composted yard waste applied as a mulch were demonstrated in a field study at two locations and supporting greenhouse research. Compost was applied to eroded roadside slopes of about 12° and 27° to determine the influence on soil displacement and establishment and/or enhancement of permanent roadside vegetation. Treatments consisted of compost rates of 5 cm and planted with asiastic jasmine (Trachelopermum asiaticum), 5 and 10 cm, seeded with 110 or 220 kg·ha–1 80:20 bahiagrass (Paspalum notatum Flugge): bermudagrass (Cynodon dactylon L.) seed mix by weight, straw erosion control mats, and bahiagrass sod. Compost treatments effectively controlled soil displacement regardless of compost rate or seeding with turfgrass at both locations. Effects on roadside vegetation and visual quality varied with location. Asiatic jasmine did not establish at either site. Compost mulch applications increased total vegetation, turfgrass density, and quality at the site with 27° slope and 4% initial soil organic matter content, but resulted in a decline in cover at the site with a 12° slope and <1% organic matter content. Compost mulch can effectively prevent soil displacement from roadside slopes, but may not promote establishment or enhancement of permanent vegetative cover.
Patrick E. McCullough, Haibo Liu, Lambert B. McCarty, and Joe E. Toler
Dwarf-type bermudagrass (Cynodon dactylon Pers. × C. transvaalensis Burtt-Davy) putting greens tolerate long-term mowing heights of 3.2 mm but require heavy nitrogen (N) fertilizations that increase ball roll resistance. Applying a plant growth regulator, such as trinexapac-ethyl (TE), could reduce uneven shoot growth from high N fertility and improve putting green ball roll distances. Field experiments were conducted from April to August 2003 and 2004 in Clemson, SC to investigate effects of ammonium nitrate applied at 6, 12, 18, or 24 kg N/ha per week with TE applied at 0 or 0.05 kg a.i. per ha every 3 weeks on `TifEagle' bermudagrass ball roll distances (BRD). BRD were measured weekly with a 38-cm stimpmeter in the morning (900 to 1100 hr) and evening (>1700 hr) beginning 1 wk after initial TE treatments. Interactions were not detected among N, TE, or time of day. TE increased BRD about 15% from non-TE treated. BRD was reduced with increased N rate and from am to pm; however, bermudagrass treated with TE averaged 10% longer PM BRD than am distances of non-TE treated. Overall, increased N fertility and diurnal shoot growth may reduce BRD but TE will be an effective tool for mitigating these effects on bermudagrass putting greens. Chemical name used: [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (trinexapac-ethyl).
Patricia Sweeney, Robert Golembiewski, and Karl Danneberger
Random amplified polymorphic DNA (RAPD) markers from leaf tissue extractions are effective for discrimination of turfgrass varieties. The usefulness of RAPD markers for turfgrass variety identification can be enhanced by use of seed rather than leaf tissue for DNA extraction. To determine whether DNA extracted from turfgrass seed was suitable for amplification, DNA was extracted from bulk samples and individual seeds of bermudagrass [Cynodon dactylon (L.) Pers.], chewings fescue (Festuca rubra var. commutata Gaud.), Poa annua L., Poa supina Schrad., creeping bentgrass [Agrostis stolonifera L. var. palustrus (Huds.) Farw.], Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.). All samples were successfully amplified using an arbitrary primer. Amplification intensity varied among species. With an almost infinite number of arbitrary primers available, it is likely that suitable primers can be found to amplify DNA from most turfgrass species. Amplification of turfgrass seed DNA, whether bulk or individual seed, is possible and should prove more useful than amplification of leaf tissue DNA for discrimination of turfgrass varieties.
Grady L. Miller
The effects of several soil amendments, following a single filling of core aerification holes, on growth and transpiration of `Tifdwarf' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] were examined during drought stress. Soil amendments had variable effects on turf quality. In general, turf grown in ZeoPro®- and Profile®-amended sand had the highest quality. Data indicated that the evaluated soil amendments have the potential to influence soil water content, ultimately influencing transpirational response to drought stress. Amended sand contained 1% to 16% more transpirable water compared with non-amended sand. Turfgrass grown in Axis®- and Isolite®-amended sand required 0.4 to 1.4 days longer to reach the endpoint (transpiration rate of drought stressed plants <12% of well-watered plants) during a period of rapid water depletion. Data from this study suggest that the total volume these amendments occupied in the root zone, following a single filling of core aerification holes in sand, may positively influence soil moisture status, resulting in an increase in drought avoidance.
Marco Fontanelli, Michel Pirchio, Christian Frasconi, Luisa Martelloni, Michele Raffaelli, Andrea Peruzzi, Nicola Grossi, Lisa Caturegli, Simone Magni, Monica Gaetani, and Marco Volterrani
Turfgrass species can be classified into two main groups: cool-season and warm-season species. Warm-season species are more suited to a Mediterranean climate. Transplanting is a possible method to convert a cool-season to a warm-season turfgrass in untilled soil. It generally requires the chemical desiccation of the cool-season turfgrass. However, alternative physical methods, like flaming and steaming, are also available. This paper compares flaming, steaming, and herbicide application to desiccate cool-season turfgrass, for conversion to hybrid bermudagrass (Cynodon dactylon x C. transvaalensis) in untilled soil, using transplanting. Two prototype machines were used, a self-propelled steaming machine and a tractor-mounted liquefied petroleum gas flaming machine. Treatments compared in this work were two flaming treatments and two steaming treatments performed at four different doses together with two chemical treatments with glufosinate-ammonium herbicide applications. The cool-season turfgrass species were tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne). The desiccation effect of the various treatments on cool-season turf was assessed by photographic survey 15 days after treatment. The percentage cover of hybrid bermudagrass was visually assessed at 43 weeks after planting. Steaming and flaming effects on both parameters were described by logistic curves. The highest doses of steaming and flaming almost completely desiccated cool-season turf, and similar hybrid bermudagrass cover was established by both the methods as the chemical application (50% to 60%). Thus both flaming and steaming may be considered as valid alternatives to herbicides aimed at turf conversion.