The biology, behaviour and survival of pupating false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a citrus pest in South Africa
- Authors: Love, Claire Natalie
- Date: 2015
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Larvae -- Behavior , Citrus -- Diseases and pests , Citrus -- Diseases and pests -- Biological control , Biological pest control agents , Entomopathogenic fungi , Insect nematodes , Pupae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5941 , http://hdl.handle.net/10962/d1018907
- Description: Control of the citrus pest, false codling moth (FCM), Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is crucial for the South African citrus industry. The economic losses and phytosanitary status of this pest, coupled with increased consumer awareness and demands, has created a need for effective, IPM-compatible control measures for use against the soil-dwelling life stages of FCM. Promising developments in the field of microbial control through the use of entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPNs) have highlighted the need for research regarding pupation biology, behaviour and survival of FCM, as a good understanding of biology of the target organism is an important component of any biological control programme. The aim of this study was to improve the current understanding of FCM pupation habits through the manipulation of soil texture class, ground cover, shading, soil compaction, air temperature, and soil moisture in the laboratory. These findings would then be used to aid the biological control programmes using EPF and EPNs against FCM in the soil. Three soil texture classes (sandy loam, silt loam and silty clay loam) were obtained from orchards for use in the study. FCM larvae were allowed to drop into the soil of their own accord and the pupation behaviour that followed was then captured on film with pupae formed in the soil being kept in order to measure adult eclosion. In general, very few abiotic factors had a clear influence on FCM pupation. Larval wandering time and distance was short, but also variable between individuals. Distance did increase when soils were moist. Pupation depth was shallow, with pupal cocoons generally being formed on the soil surface. Depth of pupation was less than one centimetre for all abiotic conditions, with little burrowing into soil. Eclosion success was higher for sandier soils when these were dry and uncompacted, but the addition of both moisture and soil compaction increased FCM eclosion success. FCM was sensitive to desiccation when the soils were dry and temperature limits of 15 °C and 32 °C had a strongly negative impact on eclosion success. Preferences for particular abiotic conditions were limited to only certain moisture conditions when interacting with soil texture class and a preference for pupating in soil when it is available. Limited preference was found for particular soil textures despite this having a strong influence on eclosion success, but individuals did appear to pupate in close proximity to one another. Viable direct habitat manipulation for FCM control could not be identified. These results and all of the abiotic variables measured have important implications for EPF and EPN application, survival and persistence in the soil in order to improve the ability of these biological control agents to control FCM. These are discussed in each chapter.
- Full Text:
- Date Issued: 2015
- Authors: Love, Claire Natalie
- Date: 2015
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Larvae -- Behavior , Citrus -- Diseases and pests , Citrus -- Diseases and pests -- Biological control , Biological pest control agents , Entomopathogenic fungi , Insect nematodes , Pupae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5941 , http://hdl.handle.net/10962/d1018907
- Description: Control of the citrus pest, false codling moth (FCM), Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is crucial for the South African citrus industry. The economic losses and phytosanitary status of this pest, coupled with increased consumer awareness and demands, has created a need for effective, IPM-compatible control measures for use against the soil-dwelling life stages of FCM. Promising developments in the field of microbial control through the use of entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPNs) have highlighted the need for research regarding pupation biology, behaviour and survival of FCM, as a good understanding of biology of the target organism is an important component of any biological control programme. The aim of this study was to improve the current understanding of FCM pupation habits through the manipulation of soil texture class, ground cover, shading, soil compaction, air temperature, and soil moisture in the laboratory. These findings would then be used to aid the biological control programmes using EPF and EPNs against FCM in the soil. Three soil texture classes (sandy loam, silt loam and silty clay loam) were obtained from orchards for use in the study. FCM larvae were allowed to drop into the soil of their own accord and the pupation behaviour that followed was then captured on film with pupae formed in the soil being kept in order to measure adult eclosion. In general, very few abiotic factors had a clear influence on FCM pupation. Larval wandering time and distance was short, but also variable between individuals. Distance did increase when soils were moist. Pupation depth was shallow, with pupal cocoons generally being formed on the soil surface. Depth of pupation was less than one centimetre for all abiotic conditions, with little burrowing into soil. Eclosion success was higher for sandier soils when these were dry and uncompacted, but the addition of both moisture and soil compaction increased FCM eclosion success. FCM was sensitive to desiccation when the soils were dry and temperature limits of 15 °C and 32 °C had a strongly negative impact on eclosion success. Preferences for particular abiotic conditions were limited to only certain moisture conditions when interacting with soil texture class and a preference for pupating in soil when it is available. Limited preference was found for particular soil textures despite this having a strong influence on eclosion success, but individuals did appear to pupate in close proximity to one another. Viable direct habitat manipulation for FCM control could not be identified. These results and all of the abiotic variables measured have important implications for EPF and EPN application, survival and persistence in the soil in order to improve the ability of these biological control agents to control FCM. These are discussed in each chapter.
- Full Text:
- Date Issued: 2015
Rights, duties and remedies under the United Nations Convention on Contracts for the International Sale of Goods: an investigation into the CISG's compatibility with South African law
- Authors: Oosthuizen, Beverley-Claire
- Date: 2009
- Subjects: United Nations Convention on Contracts for the International Sale of Goods (1980) , Sales -- South Africa , Commercial law -- South Africa , South Africa -- Law and legislation
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3691 , http://hdl.handle.net/10962/d1003206 , United Nations Convention on Contracts for the International Sale of Goods (1980) , Sales -- South Africa , Commercial law -- South Africa , South Africa -- Law and legislation
- Description: This thesis analyses the compatibility of the United Nations Convention on Contracts for the International Sale of Goods (CISG) with the South African law of sale. An initial examination of the historical development of the CISG reveals its ambitions of becoming the primary source of law governing international contracts of sale. The goal of this research is to determine whether South Africa should ratify the CISG. The CISG has been ratified by most of the leading trading States in the world. In order to gain a better understanding of the advantages and disadvantages of ratification, a comparative study has been undertaken. The stance taken toward the CISG by the United Kingdom and Germany has been examined. The United Kingdom has staunchly avoided ratifying the CISG, despite having agreed thereto a number of years ago. Germany however has taken a different approach and has welcomed the CISG. The experiences of these foreign States serve as a useful guide when assessing the specific challenges that exist in South Africa concerning the adoption of the CISG. The most important aspect of this study is the direct comparison between the legal provisions housed in the CISG and their counterparts under South African law. A careful investigation has been conducted into the rights, duties, and remedies under the CISG. This investigation is followed by an examination of the corresponding rights, duties, and remedies under the South African domestic law of sale. It is evident from these explorations that the rights and duties under the CISG strongly resemble those under South African law. The direct comparison revealed however that certain remedies found in the CISG do not have a counterpart under South African law. Despite this discrepancy, there are no legal principles in the CISG that are completely unknown in South African law. While certain remedies housed in the CISG cannot be found in an identical form under South African law, sufficiently similar legal principles can be found, which frequently lead to the same results as those under the CISG. This study is concluded with a recommendation concerning South Africa’s adoption of the CISG.
- Full Text:
- Date Issued: 2009
- Authors: Oosthuizen, Beverley-Claire
- Date: 2009
- Subjects: United Nations Convention on Contracts for the International Sale of Goods (1980) , Sales -- South Africa , Commercial law -- South Africa , South Africa -- Law and legislation
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3691 , http://hdl.handle.net/10962/d1003206 , United Nations Convention on Contracts for the International Sale of Goods (1980) , Sales -- South Africa , Commercial law -- South Africa , South Africa -- Law and legislation
- Description: This thesis analyses the compatibility of the United Nations Convention on Contracts for the International Sale of Goods (CISG) with the South African law of sale. An initial examination of the historical development of the CISG reveals its ambitions of becoming the primary source of law governing international contracts of sale. The goal of this research is to determine whether South Africa should ratify the CISG. The CISG has been ratified by most of the leading trading States in the world. In order to gain a better understanding of the advantages and disadvantages of ratification, a comparative study has been undertaken. The stance taken toward the CISG by the United Kingdom and Germany has been examined. The United Kingdom has staunchly avoided ratifying the CISG, despite having agreed thereto a number of years ago. Germany however has taken a different approach and has welcomed the CISG. The experiences of these foreign States serve as a useful guide when assessing the specific challenges that exist in South Africa concerning the adoption of the CISG. The most important aspect of this study is the direct comparison between the legal provisions housed in the CISG and their counterparts under South African law. A careful investigation has been conducted into the rights, duties, and remedies under the CISG. This investigation is followed by an examination of the corresponding rights, duties, and remedies under the South African domestic law of sale. It is evident from these explorations that the rights and duties under the CISG strongly resemble those under South African law. The direct comparison revealed however that certain remedies found in the CISG do not have a counterpart under South African law. Despite this discrepancy, there are no legal principles in the CISG that are completely unknown in South African law. While certain remedies housed in the CISG cannot be found in an identical form under South African law, sufficiently similar legal principles can be found, which frequently lead to the same results as those under the CISG. This study is concluded with a recommendation concerning South Africa’s adoption of the CISG.
- Full Text:
- Date Issued: 2009
The measurement of genetic diversity in mycobacterium tuberculosis using random amplified polymorphic DNA profiling
- Authors: Richner, Sharon M
- Date: 2000
- Subjects: Tuberculosis -- History -- 20th century , Tuberculosis -- Africa, Southern , Tuberculosis -- Treatment , Tuberculosis -- Africa , Tuberculosis -- Prevention , Tuberculosis -- Pathogenesis , Mycobacterium tuberculosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4008 , http://hdl.handle.net/10962/d1004068 , Tuberculosis -- History -- 20th century , Tuberculosis -- Africa, Southern , Tuberculosis -- Treatment , Tuberculosis -- Africa , Tuberculosis -- Prevention , Tuberculosis -- Pathogenesis , Mycobacterium tuberculosis
- Description: Mycobacterium tuberculosis has caused a resurgence in pulmonary disease in both developed and developing countries in recent times, particularly amongst people infected with the human immunodeficiency virus. The disease has assumed epidemic proportions in South Africa and in the Eastern Cape Province in particular. Of further concern is the isolation of increasing numbers of multiply drug resistant strains. Knowledge of the genetic capability of this organism is essential for the successful development of novel antibiotics and vaccines in an attempt to bring the global pandemic under control. Measurement of the genetic diversity of the organism may significantly contribute to such knowledge, and is of vital importance in monitoring epidemics and in improving treatment and control of the disease. This will entail answering a number of questions related to the degree of genetic diversity amongst strains, to the difference between urban and rural strains, and between drug resistant and drug sensitive strains, and to the geographical distribution of strains. In order to establish such baseline information, RAPD profiling of a large population of isolates from the western and central regions of the Eastern Cape Province was undertaken. A smaller number of drug resistant strains from a small area of KwaZulu-Natal were also analysed, with a view to establishing the genetic difference between strains from the two provinces. Cluster analysis, analysis of molecular variance and Geographical Information Systems technology were used to analyse the RAPD profiles generated. An unexpectedly high degree of genetic diversity was detected in strains from both provinces. While no correlation was seen between genetic diversity and either urban-rural situation or geographical location, a small degree of population structure could be correlated with drug resistance in the Eastern Cape. Furthermore, a significant degree of population structure was detected between strains from the two provinces, although this was still within the parameters for conspecific populations. Future work is necessary to further characterise strains from rural areas of both provinces, as well as from the eastern region of the Eastern Cape in an attempt to pinpoint the cause of the separation of the provincial populations.
- Full Text:
- Date Issued: 2000
- Authors: Richner, Sharon M
- Date: 2000
- Subjects: Tuberculosis -- History -- 20th century , Tuberculosis -- Africa, Southern , Tuberculosis -- Treatment , Tuberculosis -- Africa , Tuberculosis -- Prevention , Tuberculosis -- Pathogenesis , Mycobacterium tuberculosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4008 , http://hdl.handle.net/10962/d1004068 , Tuberculosis -- History -- 20th century , Tuberculosis -- Africa, Southern , Tuberculosis -- Treatment , Tuberculosis -- Africa , Tuberculosis -- Prevention , Tuberculosis -- Pathogenesis , Mycobacterium tuberculosis
- Description: Mycobacterium tuberculosis has caused a resurgence in pulmonary disease in both developed and developing countries in recent times, particularly amongst people infected with the human immunodeficiency virus. The disease has assumed epidemic proportions in South Africa and in the Eastern Cape Province in particular. Of further concern is the isolation of increasing numbers of multiply drug resistant strains. Knowledge of the genetic capability of this organism is essential for the successful development of novel antibiotics and vaccines in an attempt to bring the global pandemic under control. Measurement of the genetic diversity of the organism may significantly contribute to such knowledge, and is of vital importance in monitoring epidemics and in improving treatment and control of the disease. This will entail answering a number of questions related to the degree of genetic diversity amongst strains, to the difference between urban and rural strains, and between drug resistant and drug sensitive strains, and to the geographical distribution of strains. In order to establish such baseline information, RAPD profiling of a large population of isolates from the western and central regions of the Eastern Cape Province was undertaken. A smaller number of drug resistant strains from a small area of KwaZulu-Natal were also analysed, with a view to establishing the genetic difference between strains from the two provinces. Cluster analysis, analysis of molecular variance and Geographical Information Systems technology were used to analyse the RAPD profiles generated. An unexpectedly high degree of genetic diversity was detected in strains from both provinces. While no correlation was seen between genetic diversity and either urban-rural situation or geographical location, a small degree of population structure could be correlated with drug resistance in the Eastern Cape. Furthermore, a significant degree of population structure was detected between strains from the two provinces, although this was still within the parameters for conspecific populations. Future work is necessary to further characterise strains from rural areas of both provinces, as well as from the eastern region of the Eastern Cape in an attempt to pinpoint the cause of the separation of the provincial populations.
- Full Text:
- Date Issued: 2000
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