Augmentation of Aphytis melinus DeBach (Hymenoptera: Aphelinidae) for the control of California red scale Aonidiella aurantii Maskell (Hemiptera: Diaspididae) on citrus
- De Beer, Ernst Friedrich Ludwig
- Authors: De Beer, Ernst Friedrich Ludwig
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435638 , vital:73175 , DOI 10.21504/10962/435638
- Description: Aphytis lingnanensis was reared and tested in South Africa in the early 2000s for augmentation against red scale on citrus and was found to be ineffective. Aphytis melinus is now commercially available and it is important that the efficacy of augmentation thereof on red scale is determined locally. Field trials, fitness assessments and molecular identification on A. melinus from two insectaries were done. Field trials was done in seven, five and six pairs of comparable release and control orchards across the Eastern and Western Cape during the seasons of 2019/2020, 2020/2021 and 2021/2022 respectively. Red scale infestation was monitored and a sample of 20 infested fruit from each orchard was randomly collected every four weeks. Aphytis spp. responsible for parasitism were identified and the percentage parasitism recorded. Results of this study of field trials suggest that the augmentation of A. melinus did not significantly increase the level of parasitism above that of the untreated control. Five repetitions with six replicates of flight and longevity tests were performed with wasps from each insectary. Wasps in the longevity test from two insectaries were kept at 23 °C and 65% RH with honey. Flight tests were performed in tubes of 16 by 30 cm, with a light above a clear, sticky ceiling at 23 °C and 65% RH. On average in five replicates, 65%, 33% and 17% A. melinus wasps were alive on day one, five and 10 respectively. The overall sex ratio was 1.58 for females to males, but 1.05, 2.19 and 2.66 for non-flyers, non-crawlers, crawlers, and flyers respectively. In flight tests for both insectaries combined, only 36.97% of wasps could initiate flight in 24 h while 56.96% remained on the tube floor, and 6.05% attempted to crawl upwards. No significant differences in flight performance were recorded between the two insectaries. Wasps from the local insectary lived significantly longer during the longevity tests but were shorter in transit than wasps from the overseas insectary. COI genes were sequenced and compared against Genbank sequences using BLAST. Molecular identifications did not confirm morphological identifications for all species, indicating unexpected genetic complexity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Authors: De Beer, Ernst Friedrich Ludwig
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435638 , vital:73175 , DOI 10.21504/10962/435638
- Description: Aphytis lingnanensis was reared and tested in South Africa in the early 2000s for augmentation against red scale on citrus and was found to be ineffective. Aphytis melinus is now commercially available and it is important that the efficacy of augmentation thereof on red scale is determined locally. Field trials, fitness assessments and molecular identification on A. melinus from two insectaries were done. Field trials was done in seven, five and six pairs of comparable release and control orchards across the Eastern and Western Cape during the seasons of 2019/2020, 2020/2021 and 2021/2022 respectively. Red scale infestation was monitored and a sample of 20 infested fruit from each orchard was randomly collected every four weeks. Aphytis spp. responsible for parasitism were identified and the percentage parasitism recorded. Results of this study of field trials suggest that the augmentation of A. melinus did not significantly increase the level of parasitism above that of the untreated control. Five repetitions with six replicates of flight and longevity tests were performed with wasps from each insectary. Wasps in the longevity test from two insectaries were kept at 23 °C and 65% RH with honey. Flight tests were performed in tubes of 16 by 30 cm, with a light above a clear, sticky ceiling at 23 °C and 65% RH. On average in five replicates, 65%, 33% and 17% A. melinus wasps were alive on day one, five and 10 respectively. The overall sex ratio was 1.58 for females to males, but 1.05, 2.19 and 2.66 for non-flyers, non-crawlers, crawlers, and flyers respectively. In flight tests for both insectaries combined, only 36.97% of wasps could initiate flight in 24 h while 56.96% remained on the tube floor, and 6.05% attempted to crawl upwards. No significant differences in flight performance were recorded between the two insectaries. Wasps from the local insectary lived significantly longer during the longevity tests but were shorter in transit than wasps from the overseas insectary. COI genes were sequenced and compared against Genbank sequences using BLAST. Molecular identifications did not confirm morphological identifications for all species, indicating unexpected genetic complexity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
An examination of activism and ‘political listening’ during the year of student protest at the University of Cape Town from 9 March 2015 to 9 March 2016
- Mufamadi, Azwihangwisi Eugene
- Authors: Mufamadi, Azwihangwisi Eugene
- Date: 2022-10-04
- Subjects: Student movements South Africa Cape Town , Democracy South Africa , Listening Political aspects , Journalistic ethics , Journalism Political aspects , Communication in social action South Africa Cape Town , University of Cape Town , Cape Times Ltd.
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/327144 , vital:61085 , DOI 10.21504/10962/327144
- Description: This study sets out to examine democratic participation in South Africa and the role that ‘political listening’ could play in making participation more equitable. It considers protest action on a South African university campus, which at times not only resulted in significant and swift concessions from the university leadership but also sparked national political action which got an equally swift response from the South African government. It considers the social movement, the RhodesMustFall movement (RMF), as one way in which students can organise themselves to get a better hearing from the University of Cape Town (UCT) management in their attempt to make a meaningful contribution to the university’s micro democracy. This study examines whether the interaction between the UCT management and RMF could be considered ‘political listening’, and the possible role of the Cape Times newspaper within this context of participation. Using data gathered through interviews, written communications, observation and newspaper articles, the study shows that in all of the interactions between RMF and the UCT management, both groups were seldom willing to forego their power to engage in genuine listening. Instead, the two parties guessed at what power the other party might have and acted to reduce that power. It is in this context of guessing at and figuring what power the other party has that listening occurs. Furthermore, the study shows that during the RMF protest, the UCT management viewed their responsibility for the institution mainly through the lens of Private Property Law which framed protest as something to be dealt with by restoring law and order. The study also details the role of the Cape Times newspaper in the interactions between RMF and the UCT management and considers if this role could be political listening. The study is exploratory and demonstrates how political listening could work more optimally in real-life instances. , Thesis (PhD) -- Faculty of Humanities, Journalism and Media Studies, 2022
- Full Text:
- Authors: Mufamadi, Azwihangwisi Eugene
- Date: 2022-10-04
- Subjects: Student movements South Africa Cape Town , Democracy South Africa , Listening Political aspects , Journalistic ethics , Journalism Political aspects , Communication in social action South Africa Cape Town , University of Cape Town , Cape Times Ltd.
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/327144 , vital:61085 , DOI 10.21504/10962/327144
- Description: This study sets out to examine democratic participation in South Africa and the role that ‘political listening’ could play in making participation more equitable. It considers protest action on a South African university campus, which at times not only resulted in significant and swift concessions from the university leadership but also sparked national political action which got an equally swift response from the South African government. It considers the social movement, the RhodesMustFall movement (RMF), as one way in which students can organise themselves to get a better hearing from the University of Cape Town (UCT) management in their attempt to make a meaningful contribution to the university’s micro democracy. This study examines whether the interaction between the UCT management and RMF could be considered ‘political listening’, and the possible role of the Cape Times newspaper within this context of participation. Using data gathered through interviews, written communications, observation and newspaper articles, the study shows that in all of the interactions between RMF and the UCT management, both groups were seldom willing to forego their power to engage in genuine listening. Instead, the two parties guessed at what power the other party might have and acted to reduce that power. It is in this context of guessing at and figuring what power the other party has that listening occurs. Furthermore, the study shows that during the RMF protest, the UCT management viewed their responsibility for the institution mainly through the lens of Private Property Law which framed protest as something to be dealt with by restoring law and order. The study also details the role of the Cape Times newspaper in the interactions between RMF and the UCT management and considers if this role could be political listening. The study is exploratory and demonstrates how political listening could work more optimally in real-life instances. , Thesis (PhD) -- Faculty of Humanities, Journalism and Media Studies, 2022
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Language Learning Anxiety: a bometric investigation of stress and language learning using wearable devices
- Authors: MacDonald, William Tait
- Date: 2022-10-04
- Subjects: Language and languages Study and teaching Psychological aspects , Wearable technology , Heart rate monitoring , Stress (Psychology) Testing , Anxiety Testing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/327133 , vital:61084 , DOI 10.21504/10962/327133
- Description: As Sapolsky (2015) notes, stress research has long been characterised by definitional debates that gave rise to a lack of agreement between theorists. An example of this definitional confusion can be seen in the area of Language Learning Anxiety, where there appears to be confusion in the literature over terms such as anxiety and stress. This study investigated the link between stress and language learning using wearable devices measuring heart rate variance, as a means of establishing the feasibility of using this new technology in stress research. The results indicate that the contextualised longitudinal data delivered by wearable devices mitigates against the current dominant paradigm in Language Learning Anxiety, which postulates a straight-line negative correlation between stress and learning. Instead, the inverted U stress relationship proposed by theorists such as Hebb (1955) seem to be a better fit for the data. The nature of the contextualised data generated in this study allowed for comparisons between participants’ stress readings in academic contexts, such as language and non-language classes, and their free time. The findings suggest that certain long-held assumptions about heightened stress in academic contexts may not hold true. While the findings of this study did not reach the levels of statistical significance, they constitute proof of concept that the type of contextualised data delivered by wearable devices may allow for a new type of stress research that incorporates contextualising longitudinal perspectives on participants’ stress levels. In this study the inclusion of contextualising data led to fundamentally different conclusions about the relationship between stress and language learning. The same may be true of many areas of stress research. The findings presented in this study have broader paradigm-altering implications not only for educational policy, but also for stress research in general. Perhaps equally important was that the type of data delivered by wearable devices was qualitatively different from that normally associated with quantitative studies. This presented challenges in data analysis in this study, but also opens intriguing possibilities regarding a means of reconciling the qualitative and quantitative split in research modalities. The use of wearable devices is not without issues, and some of the issues, ranging from practical considerations to ethical conundrums, are presented for the reader’s consideration and to inform future researchers regarding potential pitfalls. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Authors: MacDonald, William Tait
- Date: 2022-10-04
- Subjects: Language and languages Study and teaching Psychological aspects , Wearable technology , Heart rate monitoring , Stress (Psychology) Testing , Anxiety Testing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/327133 , vital:61084 , DOI 10.21504/10962/327133
- Description: As Sapolsky (2015) notes, stress research has long been characterised by definitional debates that gave rise to a lack of agreement between theorists. An example of this definitional confusion can be seen in the area of Language Learning Anxiety, where there appears to be confusion in the literature over terms such as anxiety and stress. This study investigated the link between stress and language learning using wearable devices measuring heart rate variance, as a means of establishing the feasibility of using this new technology in stress research. The results indicate that the contextualised longitudinal data delivered by wearable devices mitigates against the current dominant paradigm in Language Learning Anxiety, which postulates a straight-line negative correlation between stress and learning. Instead, the inverted U stress relationship proposed by theorists such as Hebb (1955) seem to be a better fit for the data. The nature of the contextualised data generated in this study allowed for comparisons between participants’ stress readings in academic contexts, such as language and non-language classes, and their free time. The findings suggest that certain long-held assumptions about heightened stress in academic contexts may not hold true. While the findings of this study did not reach the levels of statistical significance, they constitute proof of concept that the type of contextualised data delivered by wearable devices may allow for a new type of stress research that incorporates contextualising longitudinal perspectives on participants’ stress levels. In this study the inclusion of contextualising data led to fundamentally different conclusions about the relationship between stress and language learning. The same may be true of many areas of stress research. The findings presented in this study have broader paradigm-altering implications not only for educational policy, but also for stress research in general. Perhaps equally important was that the type of data delivered by wearable devices was qualitatively different from that normally associated with quantitative studies. This presented challenges in data analysis in this study, but also opens intriguing possibilities regarding a means of reconciling the qualitative and quantitative split in research modalities. The use of wearable devices is not without issues, and some of the issues, ranging from practical considerations to ethical conundrums, are presented for the reader’s consideration and to inform future researchers regarding potential pitfalls. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2022
- Full Text:
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