The use of insecticides and cultural control for the management of soil-borne pests during plantation establishment
- Authors: Siwela, Evidence Miyelani
- Date: 2019
- Subjects: Insecticides , Plant diseases Pests -- Control Pesticides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43446 , vital:36882
- Description: Over the past decades, the productivity of South African forestry plantations has been negatively impacted by abiotic (fire, hail, wind, frost, drought etc.) and biotic factors (pests and diseases). The biotic component of insect pests and pathogens cause significant loss to the forestry industry and this affects the productivity, financial viability and long-term sustainability of plantations. Common establishment insect pests and diseases in South Africa include the pine bark beetle (Hylastes angustatus), cutworms (Agrotis spp), white grubs (Scarabaeidae larvae), rhizina root rot (Rhizina undulata), fusarium pitch canker (Fusarium circinatum), and pine dieback (Diplodia pinea). Soil-borne pests, mainly white grubs and cutworms can contribute to high seedling mortality following the re-establishment of eucalypts and wattle. Synthetic insecticides used for their control include alpha-cypermethrin, deltamethrin, and imidacloprid. However, all these insecticides are considered highly hazardous to the environment and/or human health and can no longer be considered for use in South African plantations. A need has therefore arisen to find and screen alternative products (synthetic and/or natural), that are not only environmentally safe for use, but also effective for the control of soil-borne pests during plantation establishment. In addition, these products can then be combined with other control mechanisms (such as cultural and biological control) to form an integrated pest management strategy. To address the above, a series of research trials were implemented with the outcomes discussed below. Two trials were implemented in KwaZulu-Natal (Demagtenberg) and Mpumalanga (Klipkraal) to determine if seedling size in combination with, or without an insecticide would result in improved survival of Pinus Patula. The main factors tested were Root Plug Volume (36 cm3 versus 103 cm3), Seedling Age (Standard [smaller] versus Older [larger]), and Pesticide application (untreated versus treated). Seedling quality was assessed in terms of Shoot:Root ratio, optimum Height (Ht in cm), and root collar diameter (Rcd in mm) before planting, with tree growth variates measured at planting, and then at regular intervals. The final measurements were taken at 7 years and 2 months for Demagtenberg and 5 years and 1 month for Klipkraal. For both trials, the Root Growth Potential (RGP) and total Plant Quality Index (PQI) indicated that Root Plug Volume 36 cm3 and Seedling Age (SA)_Standard (smaller) had a better Sturdiness ratio and Shoot:Root ratio compared to that of Root Plug Volume 103 cm3 and Seedling Age (SA)_Older (larger), with these benefits translated into improved field performance. The diameter at breast height (Dbh), Basal area (BA), Stocking and Volume indicated that SA_Standard and Root Plug Volume 36 cm3 resulted in better survival and growth than that of SA_Older (larger) seedlings and Root Plug Volume 103 cm3. The application of a Pesticide resulted in improved survival and growth at Klipkraal, but not at Demagtenberg. This indicated the presence of soil-borne pests at this site. In addition, the interaction between Pesticide application and SA_Standard resulted in a significantly larger BA than all other treatments only at Klipkraal, which indicates that both improved seedling quality and pesticides contributed to improved performance. One trial was established to Eucalyptus dunnii William Dunn at Umvoti North to investigate the effectiveness of the synthetic insecticides (deltamethrin, clothianidin, imidacloprid, imidacloprid + fertilizer, imidacloprid + clothianidin + fertilizer) and two natural products (azadirachtin and potassium silicate) for the control of soil-borne pests following planting. Groundline diameter (Gld), Height (Ht) and survival were assessed over a six-month period. Despite the selection of a site known to have a high incidence of soil-borne pests, few soil-borne pest were detected on the site for the trial duration, with no treatment differences observed for any of the tree growth variates. Significant differences were observed for foliar discolouration (possible phytotoxicity), however, these results were inconclusive as majority of the affected treatments (those that survived) showed full recovery. Three-month results from 12 eucalypt trials in KwaZulu-Natal, South Africa were compared to determine the benefits (including costs) of insecticides for the control of soil-borne pests. The 12 trials were selected to represent different physiographic regions, mainly within the warm temperate regions where white grubs and cutworms are likely to occur. Data for the trials were obtained from previous management research (published documents) and included six where mortality was the only variate assessed, with the Ht and Gld also assessed in the remaining six trials. There was a ≥ 2.5% increase in survival in seven of the 12 trials through the use of insecticides relative to the control, although only four of these seven were statistically significant. Of the 12 trials, the use of insecticides resulted in > 90% survival compared to the control at Mistley (93 versus 83%), Bloemendal (96 versus 62%) and Enon (burn) (96 versus 89%). At Garfield, Vulindlela, and Baynesfield, survival in both the treated and untreated treatments was below 90%, whereas both the treated and untreated treatments were above 90% at Rustig, Greenhill, Enon (slash), Umvoti, Dargle and Umvoti North. This data indicates that where soil-borne pests are present, the application of an insecticide is beneficial. Due to the costs associated with insecticide application, the challenge will be to determine which are high-risk sites that require treatment with an insecticide. Results from these trials indicate that on sites where soil-borne pests are present (and active), the application of insecticides is beneficial. However, even if present, the level of impact is less obvious, and possibly influenced by life cycle stage, site management and climate. The testing of alternative and less highly hazardous insecticides indicated the potential future use of insecticides in terms of limited seedling phytotoxicity (some of the products tested). To understand more fully the extent of their efficacy, these products would need to be re-tested again on sites where soil-borne pests are active. Optimum establishment practices, together with the planting of quality seedlings and application of an approved insecticide, will all contribute to improved survival and growth. Perhaps the biggest challenge will be the determination of soil pest activity, such that the application of pesticides can be limited to those sites where control is necessary..
- Full Text:
- Date Issued: 2019
Development of polymer templates for ZnO nanorods
- Authors: Dobson, Stephen Robert
- Date: 2014
- Subjects: Polymers , Semiconductor industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10556 , http://hdl.handle.net/10948/d1020805
- Description: One of the biggest challenges for the semiconductor industry is the development of nanofabrication techniques that allow for the fabrication of structures on a scale tens of nanometers in size. This provides greater potential functionality at reduced costs. Established conventional techniques, such as photolithography, are unable to achieve features below 30 nm due to the inherent limitations of the wavelength of light sources currently available. For this reason block copolymers received considerable attention in order to overcome these challenges in lithographic technology. Block copolymers have an inherent processing advantage of self assembling into various nanoscopic structures such as spheres, cylinders and lamellae amongst others on a scale below 50 nm. The dimensions and structures are readily tuneable based on molecular weights (Mw) and compositions of the copolymers. However, to be usable within industry a great deal more research still needs to be conducted on the use and nature of block copolymers. In this study the block copolymer of poly(styrene-block-methylmethacrylate) (PS-b-PMMA) was investigated as a potential nano-mask for semiconductor growth. Research was conducted on thin films of PS-b-PMMA by altering the parameters influencing the kinetics and thermodynamic effects on the thin films, in order to produce a structure of cylinders of PMMA perpendicular to the substrate within a PS matrix on a silicon (Si) substrate. It is shown that thermally annealing the PS-b-PMMA thin films under conditions where there is no preferential interaction of the substrate or open surface with either components of the block copolymer (i.e. PS or PMMA with Si or ambient) and at an appropriate thin film thickness, perpendicular cylinders of PMMA within a PS matrix form in the thin films. The determined ideal thin film thickness is 32 nm, with non-preferential interaction attained between block and substrate by coating a poly(styrene-random-methylmethacrylate) (PS-r-PMMA) on the Si substrate and annealing within a vacuum. Additionally, acetic acid, as a known selective solvent of PMMA, is used to further process the thin film of PS-b-PMMA. Thus a final PS nano-mask containing pores with a diameter tens of nanometers in size is produced. The pores are shown to have an average diameter of 13.5 nm. Measurements were taken throughout the investigation using a scanning probe microscope (SPM) to determine surface topography and phase morphology of the PS-b-PMMA thin films. X-ray reflectometry (XRR) is used to measure film thickness. The research in this study shows that thin films of PS containing hexagonally arranged pores can be produced and could find potential use as a nano-mask for semiconductor growth.
- Full Text:
- Date Issued: 2014
A study of the use of value based management (VBM) by multinational entities in the Eastern Cape motor industry cluster (ECMIC)
- Authors: Blouw, Mbuyiselo Edwin
- Date: 2005
- Subjects: Corporations -- Valuation , Automobile industry and trade -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8550 , http://hdl.handle.net/10948/421 , Corporations -- Valuation , Automobile industry and trade -- South Africa
- Description: Management’s response to shareholders’ return on investment as a priority occurs in an increasingly dynamic environment. Accompanying these activities is the need to realign responsibilities and to allocate scarce resources effectively. This is done in order to ensure that companies achieve global competitiveness and increase shareholders’ return on investment. Against this backdrop, local industry needs to find new methods or strategies in order to achieve world-class competitiveness, and to be able to access foreign investment. One way to achieve these goals is through Value Based Management (VBM). The objective of this study is to evaluate the strategic intent of Multinational Entities in applying VBM to increase shareholders’ return on investment. Based on the study, certain factors are critical to ensure the success of VBM. A postal survey to managers in the motor manufacturing and component manufacturing companies was conducted to check the managers’ familiarity with VBM, and their scope, and usage of VBM; and, based on the finding, to evaluate the impact of VBM on companies’ results. The empirical finding was compared with a literature review, and the following findings were made: There is a strong understanding and application of the VBM principle on the part of local entities with Foreign Direct Investment (FDI); Departmental performance is critical to an entity’s overall performance; Based on the study, 23 per cent of the respondents use Economic Value Added (EVA) as an internal reporting measure, and an average of 19 per cent use other metrics; A total of 89 per cent of respondents indicated that they strongly agree with the use of incentives for motivation. The above-mentioned points were covered by means of 4-M framework ― that is: Measurement, Management, Motivation, and Mindset.
- Full Text:
- Date Issued: 2005