Field evaluation of the use of select entomopathogenic fungal isolates as microbial control agents of the soil-dwelling life stages of a key South African citrus pest, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae)
- Authors: Coombes, Candice Anne
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/507 , vital:19965
- Description: The control of false codling moth (FCM), Thaumatotibia leucotreta (Meyrick, 1912) (Lepidoptera: Tortricidae), in citrus orchards is strongly reliant on the use of integrated pest management as key export markets impose stringent chemical restrictions on exported fruit and have a strict no entry policy towards this phytosanitary pest. Most current, registered control methods target the above-ground life stages of FCM, not the soil-dwelling life stages. As such, entomopathogenic fungi which are ubiquitous, percutaneously infective soil-borne microbes that have been used successfully as control agents worldwide, present ideal candidates as additional control agents. Following an initial identification of 62 fungal entomopathogens isolated from soil collected from citrus orchards in the Eastern Cape Province, South Africa, further laboratory research has highlighted three isolates as having the greatest control potential against FCM subterranean life stages: Metarhizium anisopliae G 11 3 L6 (Ma1), M. anisopliae FCM Ar 23 B3 (Ma2) and Beauveria bassiana G Ar 17 B3 (Bb1). These isolates are capable of causing above 80% laboratory-induced mycosis of FCM fifth instars. Whether this level of efficacy was obtainable under sub-optimal and fluctuating field conditions was unknown. Thus, this thesis aimed to address the following issues with regards to the three most laboratory-virulent fungal isolates: field efficacy, field persistence, optimal application rate, application timing, environmental dependency, compatibility with fungicides and the use of different wetting agents to promote field efficacy. Following fungal application to one hectare treatment blocks in the field, FCM infestation within fruit was reduced by 28.3% to 81.7%. Isolate Bb1 performed best under moderate to high soil moisture whilst Ma2 was more effective under low soil moisture conditions. All isolates, with the exception of Ma2 at one site, were recorded in the soil five months post-application. None of the wetting agents tested were found to be highly toxic to fungal germination and similar physical suspension characteristics were observed. Fungicide toxicity varied amongst isolates and test conditions. However, only Dithane (a.i. mancozeb) was considered incompatible with isolate Ma2. The implication of these results and the way forward is discussed. This study is the first report of the field efficacy of three laboratory-virulent fungal isolates applied to the soil of conventional citrus orchards against FCM soil-dwelling life stages. As such, it provides a foundation on which future research can build to ensure the development and commercialisation of a cost-effective and consistently reliable product.
- Full Text:
- Date Issued: 2016
- Authors: Coombes, Candice Anne
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/507 , vital:19965
- Description: The control of false codling moth (FCM), Thaumatotibia leucotreta (Meyrick, 1912) (Lepidoptera: Tortricidae), in citrus orchards is strongly reliant on the use of integrated pest management as key export markets impose stringent chemical restrictions on exported fruit and have a strict no entry policy towards this phytosanitary pest. Most current, registered control methods target the above-ground life stages of FCM, not the soil-dwelling life stages. As such, entomopathogenic fungi which are ubiquitous, percutaneously infective soil-borne microbes that have been used successfully as control agents worldwide, present ideal candidates as additional control agents. Following an initial identification of 62 fungal entomopathogens isolated from soil collected from citrus orchards in the Eastern Cape Province, South Africa, further laboratory research has highlighted three isolates as having the greatest control potential against FCM subterranean life stages: Metarhizium anisopliae G 11 3 L6 (Ma1), M. anisopliae FCM Ar 23 B3 (Ma2) and Beauveria bassiana G Ar 17 B3 (Bb1). These isolates are capable of causing above 80% laboratory-induced mycosis of FCM fifth instars. Whether this level of efficacy was obtainable under sub-optimal and fluctuating field conditions was unknown. Thus, this thesis aimed to address the following issues with regards to the three most laboratory-virulent fungal isolates: field efficacy, field persistence, optimal application rate, application timing, environmental dependency, compatibility with fungicides and the use of different wetting agents to promote field efficacy. Following fungal application to one hectare treatment blocks in the field, FCM infestation within fruit was reduced by 28.3% to 81.7%. Isolate Bb1 performed best under moderate to high soil moisture whilst Ma2 was more effective under low soil moisture conditions. All isolates, with the exception of Ma2 at one site, were recorded in the soil five months post-application. None of the wetting agents tested were found to be highly toxic to fungal germination and similar physical suspension characteristics were observed. Fungicide toxicity varied amongst isolates and test conditions. However, only Dithane (a.i. mancozeb) was considered incompatible with isolate Ma2. The implication of these results and the way forward is discussed. This study is the first report of the field efficacy of three laboratory-virulent fungal isolates applied to the soil of conventional citrus orchards against FCM soil-dwelling life stages. As such, it provides a foundation on which future research can build to ensure the development and commercialisation of a cost-effective and consistently reliable product.
- Full Text:
- Date Issued: 2016
Managing change in organisational environment
- Authors: Markova, Elena
- Date: 2016
- Subjects: Organizational change , Conflict management , Teams in the workplace
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8129 , vital:25017
- Description: Twentieth century has set an unprecedented pace of change, which seems to be ever increasing. The changes are transforming every sphere of social life including business and organisational life. Globalisation has made organisational structures flatter but wider in reach. Advancements in information and communication technologies have made teams larger through vast and powerful information networks. These forces are triggering the reshaping and restructuring of every major industry worldwide nowadays. The main research aim of this study is to explore how organisational conflict is affected by change (and vice versa) in order to work out a set of recommendations which shall take form of practical intervention strategies for the improvement of organizational effectiveness by mitigating the dysfunctions of a conflict and adjusting employees' styles of handling interpersonal and intergroup conflict. Workplace conflict is an everyday reality. It is an inevitable result of human interaction in a competitive environment of the workplace. So, according to this assumption, conflict is not something vicious and destructive, but an intrinsic part of human interaction. Then, the conflict is not a problem in itself, the way it is managed is what defines whether the conflict is destructive or not.
- Full Text:
- Date Issued: 2016
- Authors: Markova, Elena
- Date: 2016
- Subjects: Organizational change , Conflict management , Teams in the workplace
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8129 , vital:25017
- Description: Twentieth century has set an unprecedented pace of change, which seems to be ever increasing. The changes are transforming every sphere of social life including business and organisational life. Globalisation has made organisational structures flatter but wider in reach. Advancements in information and communication technologies have made teams larger through vast and powerful information networks. These forces are triggering the reshaping and restructuring of every major industry worldwide nowadays. The main research aim of this study is to explore how organisational conflict is affected by change (and vice versa) in order to work out a set of recommendations which shall take form of practical intervention strategies for the improvement of organizational effectiveness by mitigating the dysfunctions of a conflict and adjusting employees' styles of handling interpersonal and intergroup conflict. Workplace conflict is an everyday reality. It is an inevitable result of human interaction in a competitive environment of the workplace. So, according to this assumption, conflict is not something vicious and destructive, but an intrinsic part of human interaction. Then, the conflict is not a problem in itself, the way it is managed is what defines whether the conflict is destructive or not.
- Full Text:
- Date Issued: 2016
The design of an airport terminal in Somerset East, province of the Eastern Cape
- Authors: Karihindi, Kounikui
- Date: 2016
- Subjects: Aeronautical museums -- South Africa -- Eastern Cape -- Designs and plans , Airport buildings -- South Africa -- Eastern Cape , Airports -- South Africa -- Eastern Cape -- Designs and plans
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/18886 , vital:28743
- Description: In addressing the stunted growth of the town of Somerset East, the treatise suggests that the model of an aerotropolis be used as means to spur economic growth an development of the town. The treatise proposes the design of an air terminal facility, to act as a catalyst, for which growth of a mini-Aerotropolis will happen around as well as a northern gateway for tourism to two of South Africa's popular national parks; Addo Elephant National Park and Mountain Zebra National park. The challenge being the creation of a building type that incorporates several would be segregated activities into one hybrid that generates public space within an interface or transcient space.
- Full Text:
- Date Issued: 2016
- Authors: Karihindi, Kounikui
- Date: 2016
- Subjects: Aeronautical museums -- South Africa -- Eastern Cape -- Designs and plans , Airport buildings -- South Africa -- Eastern Cape , Airports -- South Africa -- Eastern Cape -- Designs and plans
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/18886 , vital:28743
- Description: In addressing the stunted growth of the town of Somerset East, the treatise suggests that the model of an aerotropolis be used as means to spur economic growth an development of the town. The treatise proposes the design of an air terminal facility, to act as a catalyst, for which growth of a mini-Aerotropolis will happen around as well as a northern gateway for tourism to two of South Africa's popular national parks; Addo Elephant National Park and Mountain Zebra National park. The challenge being the creation of a building type that incorporates several would be segregated activities into one hybrid that generates public space within an interface or transcient space.
- Full Text:
- Date Issued: 2016
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