• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 3
  • 1
  • Tagged with
  • 8
  • 8
  • 8
  • 4
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The effects of nitrogen and potassium on the uptake of calcium and magnesium by Kentucky bluegrass (Poa pratensis L.) :: as related to infection by Helminthosporium vagans /

Griffin, John J. 01 January 1978 (has links)
No description available.
2

Chemical and environmental factors affecting pesticide volatilization from turfgrass

Conway, Michael S. 18 December 2002 (has links)
Volatile loss rates of pesticides from turfgrass were measured using the Backward-Time Lagrangian Stochastic Dispersion model (Flesch et al., 1995). Solar radiation, ambient temperature, surface temperature, relative humidity, wind direction, and wind speed were monitored continuously. Growth regulator was applied to the turf plot several days before pesticide application to maintain a constant grass height and aerodynamic roughness length during the experiment. No irrigation occurred following application. Pesticides were applied as mixtures to allow direct comparison of evaporative loss. Mixtures studied were chlorpyrifos + triadimefon + ethofumesate and triclopyr (acetic acid) + propiconazole + cyfluthurin. Airborne flux estimates correlated with temperature, solar radiation, wind speed, time, and vapor pressure of the active ingredient. A log vapor pressure vs. 1/Temperature (K) relationship was observed between flux and surface temperature over a single day for most pesticides. An exponential attenuation of flux was observed over a period of several days and correlated with attenuation of dislodgeable surface residues for two of the pesticides. A fugacity-based model for predicting initial evaporative loss rates from turf grass is presented. Input parameters include pesticide vapor pressure, molecular diffusion coefficient, surface temperature, wind speed profile, atmospheric stability, surface roughness, and average upwind fetch. The GC retention method (Jensen, 1966) was used to estimate pesticide vapor pressures over an environmentally relevant temperature range. The model predicts fluxes that are an order of magnitude greater than measured values. This bias may be due, in part, to deviation from the assumption of pesticide saturated vapor density at the foliar surface. In addition, sensitivity analysis suggests improved estimates of leaf surface temperature and pesticide vapor pressures have the greatest potential to improve model performance. / Graduation date: 2003
3

Postemergence activity of isoxaflutole on cool-season turfgrass and weed species in turfgrass environments /

Drohen, James Andrew 01 January 1999 (has links)
No description available.
4

Testing susceptibility of some turf grasses to certain known pathogens

Price, Reggie Monroe, 1932- January 1959 (has links)
No description available.
5

Evaluation of the potential use of antagonistic microbes on grass species, turf and pasture, for disease control and growth stimulation.

Cunningham, Debra M. January 2003 (has links)
Public tendency, of late, is to reduce liberal use of harmful synthesized chemicals for promoting plant health. Today, biological control is becoming a commonly cited disease control option. Biological control agents (BCAs) not only control disease , but also promote plant growth. Application of biological control is based largely on knowledge of control mechanisms employed by antagonists, as well as the means of application that will ensure that an antagonistic population is established. Knowing the advantages is not the only factor that should be considered before application commences as, the disadvantages must be clearly outlined and explored further before a constructive decision as on implementation of biological control. A literature review was undertaken to provide the necessary technical information about biological control, its potential uses, methods of application, mechanisms of action employed, advantages and disadvantages associated with biological control application, public perceptions and the potential future of biological control. Diseases encountered within the KwaZulu-Natal Midlands on pasture and turf grasses were determined by a once-off survey conducted over 1999/2000. The aim of the survey was to determine broadly the management practices of farmers and groundsmen in KwaZulu-Natal and the potential impact of these on the occurrence of weeds, insects and diseases. The survey also addressed the level of existing knowledge about biological control and willingness to apply such measures. In the pasture survey, farmers were questioned about: soil type, grass species common used, irrigation , fertilization and liming, grazing programs and weed, insect and disease occurrences and control measures implemented. The same aspects were addressed in a survey to a representative sample of groundsmen (turfgrass production) , including also: topdressing, greens base used, drainage systems, mowing practices and decompaction principles. The survey showed correlation between pest incidence and management practices implemented. In terms of pest control, both farmers and groundsmen indicated a stronger preference to the use of herbicides , insecticides and fungicides. Use of fungicides for disease control by farmers is considered an often unfeasible expense, rather more emphasis was placed on implementing cultural control methods. At present farmers do not apply biological control strategies, but they did indicate much interest in the topic. Alternatives to current, or lack of current, disease management strategies are important considerations, with two new diseases identified in the KwaZulu-Natal Midlands just within the period of this thesis. Biological control strategies are implemented by 8% of the groundsmen surveyed, with emphasis being placed on augmenting the already present natural predators rather than the introduction of microbial antagonists. Although often mis-diagnosed by farmers Helminthosporium leaf spot is a common disease in the KwaZulu-Natal Midlands on Pennisetum clandestinum (kikuyu), This disease reduces pasture quality and detracts from the aesthetic appearance and wearability of turfgrasses. Helminthosporium leaf spot is incited by a complex of causal agents , Bipolaris was confirmed as the casual agent of Helminthosporium leaf spot on kikuyu at Cedara. Disease control by two BCAs, Bacillus (B. subtilis Ehrenberg & Cohn.) and Trichoderma (T. harzianum Rifai), as commercial formulations was tested against the fungicide, PUNCH EXTRA®. In vitro, Trichoderma was shown to be aggressive in controlling Bipolaris sp. In vivo, disease control achieved with Trichoderma kd was comparative with PUNCH XTRA® but not statistically different (P>=0.05). Trichoderma and Bacillus provided better disease control in comparison to an untreated control. Improved growth of Lolium sp. was determined in vitro, with Trichoderma kd and Bacillus B69 treatments. The microbe-based treatments accounted for growth stimulation, with significant (P<=O.05) growth differences noted. A microbial activator, MICROBOOST®was added to the treatments to improve microbial efficiency. Improved plant growth with MICROBOOST® applications was shown. Improved growth associated with microbial treatments, Trichoderma harzianum kd; Bacillus subtilis B69 and Gliocladium virens Miller, Gibens, Foster and con Arx. ,was also determined in vivo at Cedara, on L.perenne L., Festuca rubra L. and Agrostis stolonifera L. Establishment of a suppressive soil with antagonistic microbes resulted in significant (P<=O.05) effects on final grass coverage (except G. virens), as well increased root and shoot lengths (P<=O.05). Increased germination rates, as expressed in vitro, were not shown in vivo. Microbial activity with the application of MICROBOOST® showed little effect on germination but increased root and shoot lengths significantly (P<=O.05). Increased weed growth associated with the treatments (except G. virens) was considered a drawback of the microbial-treatments. Microbial treatments were also applied to pasture grasses. An in vitro grazing trial was established at Cedara, using L. multiflorum L. to evaluate the microbe-based treatments Trichoderma kd, Bacillus B69 and G. virens for improved pasture establishment and for increased grazing preference by Dohne Merino sheep. Trichoderma kd was associated with increased dry and wet biomass , but lower dry matter yields in comparison to the control. Only G. virens accounted for a higher dry matter percentage than the control. However, differences between the control and the microbial treatments was very small and not significant (P>=0.05). Of the three grazing observations made, sheep showed no grazing preference to plots with or without microbial treatments In general, the body of this research has shown that microbial treatments have the potential for increased disease control and growth stimulation of grasses. However, lack of significant differences between microbial treatments and controls has raised the question as to effect of external factors on microbial activity and survival, especially in vivo. This raises the question as to the validity of the use of microbial treatments where growth conditions cannot be controlled , remembering that the cost of establishment must be covered by the economic returns from utilization. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.
6

Aspect of the biology of sod webworms (Lepidoptera: Pyralidae: Crambinae) and turfgrass inhabiting insects of Virginia

Tolley, Mike P. January 1982 (has links)
Turfgrass is subject to attack by a variety of insect pests. However, there has been no research on the sod webworm pests associated with turfgrass in Virginia and little research on habitat preferences of other insect pests of turf. The purpose of this research was to contribute to the basic knowledge of the biology of sod webworm species in Virginia. There are at least 16 sod webworm species found to occur in Virginia; all can be identified to species level by forewing color patterns. The species complex is distributed nearly evenly throughout Virginia with some species adapted to higher elevations (700m). The species complex is present from spring to late fall. The number of generations and peak flight periods differ depending on the species. Most species were sampled in low numbers except Parapediasia teterrella (Zincken). Accumulated degree-days can predict an additional years worth of occurrence of Microcrambus elegans (Clemens), Crambus lagueatellus Clemens, Pediasia trisecta (Walker) , and Agriphila ruricolella (Zeller), in the Appalachian region of Virginia. Behavior patterns of P. teterrella. M. elegans, and A. ruricolella adults indicate the utilization of shrubs instead of turfgrass as resting sites during the day. In addition, 10 species of 7 families of insects were found to inhabit tall fescue, ryegrass, and bluegrass in Virginia. / Master of Science
7

Relative susceptibility of endophytic and non-endophytic turfgrasses to parasitic nematodes /

Lafaille, Norman R. 01 January 1998 (has links)
No description available.
8

Development, phonotaxis and management of Gryllotalpa africana Palisot de Beauvois (Orthoptera: Gryllotalpidae) on turfgrass

De Graaf, Johan 08 September 2005 (has links)
Please read the abstract in the section 00front of this document / Dissertation (MSc (Entomology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted

Page generated in 0.0956 seconds