Developing a community of practice to promote the use of biological control in the integrated management of Prosopis in South Africa
- Authors: Van Staden, Gretha
- Date: 2024-04-04
- Subjects: Mesquite South Africa Northern Cape , Community of practice , Stakeholder participation , Mesquite Control , Invasive plants Biological control , Prosopis
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434998 , vital:73122
- Description: Prosopis spp. are non-native species present in the arid parts of southern Africa. These trees originated in the Americas and were first introduced as a source of fodder, shade, and wood, but have become invasive, negatively impacting local biodiversity, and disrupting the delivery of ecosystem services. Some species of Prosopis hybridise freely, complicating identification and subsequent control. The control of Prosopis in the Northern Cape Province of South Africa is still contentious, because of the perceived benefits to some landowners. The effectiveness of biological control agents to control the spread of Prosopis has been quantified, more damaging agents have been considered in recent years because of the continued increase in Prosopis density. Research into the establishment of a Community of Practice (CoP) to address the differences in perceptions regarding the control of Prosopis in the Northern Cape Province is considered an appropriate starting point to conceptualise the challenges to the successful integrated management of Prosopis. As farmers are the main stakeholders involved with Prosopis control, understanding the role of farmers and the functioning of farming enterprises in the Northern Cape is imperative for the development of both a CoP as well as the appropriate management of Prosopis. To foster engagement with as many stakeholders as possible, workshops dealing with biological control as part on an integrated approach to the control of Prosopis were held in towns in the Northern Cape Province: Groblershoop, Brandvlei, Kenhardt, Upington, Prieska and Williston. Some of the main concerns of the landusers include the host specificity of the released biocontrol agents, as well as increased transparency and communication. This is especially in regards to the research on present and future biological control agents that will possibly improve the perceptions of stakeholders. The mechanical harvesting and use of biomass as a control method was supported, especially where farmers were removing Prosopis from their properties, leaving large amounts of biomass in the veld. Continued research into Prosopis in the Northern Cape needs to consider the possibility of secondary invasions, especially in areas where native bush encroachment is already a concern. The impact of clearing in terms of natural grazing and animal improvement needs to be quantified, to conceptualise the importance of maintaining better veld quality versus using Prosopis for fodder. Biological control targeting not only the reproductive output of the trees, but also the standing biomass has support from the majority of the land users in the Northern Cape Province following these workshops and this study shows the importance of a socio-ecological approach to the control of landscape scale invasion. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Authors: Van Staden, Gretha
- Date: 2024-04-04
- Subjects: Mesquite South Africa Northern Cape , Community of practice , Stakeholder participation , Mesquite Control , Invasive plants Biological control , Prosopis
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434998 , vital:73122
- Description: Prosopis spp. are non-native species present in the arid parts of southern Africa. These trees originated in the Americas and were first introduced as a source of fodder, shade, and wood, but have become invasive, negatively impacting local biodiversity, and disrupting the delivery of ecosystem services. Some species of Prosopis hybridise freely, complicating identification and subsequent control. The control of Prosopis in the Northern Cape Province of South Africa is still contentious, because of the perceived benefits to some landowners. The effectiveness of biological control agents to control the spread of Prosopis has been quantified, more damaging agents have been considered in recent years because of the continued increase in Prosopis density. Research into the establishment of a Community of Practice (CoP) to address the differences in perceptions regarding the control of Prosopis in the Northern Cape Province is considered an appropriate starting point to conceptualise the challenges to the successful integrated management of Prosopis. As farmers are the main stakeholders involved with Prosopis control, understanding the role of farmers and the functioning of farming enterprises in the Northern Cape is imperative for the development of both a CoP as well as the appropriate management of Prosopis. To foster engagement with as many stakeholders as possible, workshops dealing with biological control as part on an integrated approach to the control of Prosopis were held in towns in the Northern Cape Province: Groblershoop, Brandvlei, Kenhardt, Upington, Prieska and Williston. Some of the main concerns of the landusers include the host specificity of the released biocontrol agents, as well as increased transparency and communication. This is especially in regards to the research on present and future biological control agents that will possibly improve the perceptions of stakeholders. The mechanical harvesting and use of biomass as a control method was supported, especially where farmers were removing Prosopis from their properties, leaving large amounts of biomass in the veld. Continued research into Prosopis in the Northern Cape needs to consider the possibility of secondary invasions, especially in areas where native bush encroachment is already a concern. The impact of clearing in terms of natural grazing and animal improvement needs to be quantified, to conceptualise the importance of maintaining better veld quality versus using Prosopis for fodder. Biological control targeting not only the reproductive output of the trees, but also the standing biomass has support from the majority of the land users in the Northern Cape Province following these workshops and this study shows the importance of a socio-ecological approach to the control of landscape scale invasion. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
The effects of elevated CO2 on feeding guild responses of biological control agents of Pontederia crassipes Mart. (Pontederiaceae)
- Authors: Paper, Matthew Keenan
- Date: 2022-04-06
- Subjects: Carbon dioxide , Pontederia crassipes , Biological pest control agents , Invasive plants Biological control , Pontederiaceae Climatic factors
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/455338 , vital:75422
- Description: Elevated CO2 (eCO2) and rising global temperatures have the potential to alter plant-insect interactions with important implications for plant community structure and function. Previous studies on plant-insect interactions have shown that eCO2 will affect insect feeding guilds differently, impacting negatively, positively or having very little effect. The implications of this on the global invasive plant biological control programme is largely unknown. This study investigates the response of one of the world’s most invasive aquatic plants, Pontederia ( = Eichhornia) crassipes Mart. (Pontederiaceae), to predicted eCO2 conditions of 800 ppm and how this may affect the feeding response of two biological control agents representing different feeding guilds; the leaf chewing Cornops aquaticum Brüner (Orthoptera: Acrididae) and the phloem-feeding Megamelus scutellaris Berg (Hemiptera: Delphacidae). A factorial eCO2 x feeding impact study was conducted at the Rhodes University Elevated CO2 Facility in the Eastern Cape Province of South Africa over 13 weeks in the growing season of 2019. The effect of insect herbivory by C. aquaticum and M. scutellaris at two atmospheric CO2 concentrations, representing current and future predicted concentrations (400 ppm and 800 ppm) on P. crassipes was examined through both biomass and ecophysiological measures. Assimilation rates, C:N ratio, total dry weight and relative growth rate of P. crassipes were unaffected by eCO2 conditions, and plants experienced no CO2 fertilization in eutrophic water conditions representative of South African waterways. Effects of eCO2 on insect herbivory varied depending on the feeding guild. Pontederia crassipes showed compensatory growth responses when exposed to C. aquaticum herbivory regardless of CO2 treatment, but chewing herbivory damage remained constant, and the agent maintained efficacy. Pontederia crassipes showed down-regulation of photosynthesis when exposed to M. scutellaris due to eCO2-related feeding responses by M. scutellaris increasing substantially through a significant (30%) increase in adult population density under eCO2 conditions. These results indicate that the plant-insect interactions that underpin biological control programmes for P. crassipes should remain successful under future CO2 conditions. Phloem-feeding insect damage (M. scutellaris) was significantly greater than chewing damage in this study, suggesting that invasive plant biological control programmes will need to shift focus away from the charismatic chewing insect herbivores and onto the often-neglected phloem-feeding biological control agents due to their overwhelmingly positive response to eCO2. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2022
- Full Text:
- Authors: Paper, Matthew Keenan
- Date: 2022-04-06
- Subjects: Carbon dioxide , Pontederia crassipes , Biological pest control agents , Invasive plants Biological control , Pontederiaceae Climatic factors
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/455338 , vital:75422
- Description: Elevated CO2 (eCO2) and rising global temperatures have the potential to alter plant-insect interactions with important implications for plant community structure and function. Previous studies on plant-insect interactions have shown that eCO2 will affect insect feeding guilds differently, impacting negatively, positively or having very little effect. The implications of this on the global invasive plant biological control programme is largely unknown. This study investigates the response of one of the world’s most invasive aquatic plants, Pontederia ( = Eichhornia) crassipes Mart. (Pontederiaceae), to predicted eCO2 conditions of 800 ppm and how this may affect the feeding response of two biological control agents representing different feeding guilds; the leaf chewing Cornops aquaticum Brüner (Orthoptera: Acrididae) and the phloem-feeding Megamelus scutellaris Berg (Hemiptera: Delphacidae). A factorial eCO2 x feeding impact study was conducted at the Rhodes University Elevated CO2 Facility in the Eastern Cape Province of South Africa over 13 weeks in the growing season of 2019. The effect of insect herbivory by C. aquaticum and M. scutellaris at two atmospheric CO2 concentrations, representing current and future predicted concentrations (400 ppm and 800 ppm) on P. crassipes was examined through both biomass and ecophysiological measures. Assimilation rates, C:N ratio, total dry weight and relative growth rate of P. crassipes were unaffected by eCO2 conditions, and plants experienced no CO2 fertilization in eutrophic water conditions representative of South African waterways. Effects of eCO2 on insect herbivory varied depending on the feeding guild. Pontederia crassipes showed compensatory growth responses when exposed to C. aquaticum herbivory regardless of CO2 treatment, but chewing herbivory damage remained constant, and the agent maintained efficacy. Pontederia crassipes showed down-regulation of photosynthesis when exposed to M. scutellaris due to eCO2-related feeding responses by M. scutellaris increasing substantially through a significant (30%) increase in adult population density under eCO2 conditions. These results indicate that the plant-insect interactions that underpin biological control programmes for P. crassipes should remain successful under future CO2 conditions. Phloem-feeding insect damage (M. scutellaris) was significantly greater than chewing damage in this study, suggesting that invasive plant biological control programmes will need to shift focus away from the charismatic chewing insect herbivores and onto the often-neglected phloem-feeding biological control agents due to their overwhelmingly positive response to eCO2. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2022
- Full Text:
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