A review of the biocontrol programmes against aquatic weeds in South Africa
- Coetzee, Julie A, Bownes, Angela, Martin, Grant D, Miller, Benjamin E, Smith, Rosalie, Weyl, Philip S R, Hill, Martin P
- Authors: Coetzee, Julie A , Bownes, Angela , Martin, Grant D , Miller, Benjamin E , Smith, Rosalie , Weyl, Philip S R , Hill, Martin P
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406965 , vital:70326 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a18"
- Description: Biological control (biocontrol) against invasive macrophytes is one of the longest standing programmes in South Africa, initiated in the 1970s against water hyacinth, Pontederia crassipes Mart. (Pontederiaceae). Since then, 15 agent species (13 insects, one mite and one pathogen) have been released against six weeds, most of which are floating macrophytes, with excellent levels of success. The release of the water hyacinth planthopper Megamelus scutellaris Berg (Hemiptera: Delphacidae) in particular, has improved biocontrol prospects for water hyacinth since 2018. In the last decade, however, a new suite of submerged and rooted emergent invasive macrophytes has been targeted. The first release against a submerged macrophyte in South Africa, and the first release against Brazilian waterweed, Egeria densa Planch. (Hydrocharitaceae), anywhere in the world, was achieved with the release of a leafmining fly, Hydrellia egeriae Rodrigues-Júnior, Mathis and Hauser (Diptera: Ephydridae). Yellow flag, Iris pseudacorus L. (Iridaceae) and Mexican waterlily, Nymphaea mexicana Zucc. (Nymphaeaceae), have also been targeted for biocontrol for the first time worldwide, and are in the early stages of agent development. Post-release evaluations, long term monitoring and controlled experiments have highlighted the need for a more holistic approach to managing aquatic invasive plants in South Africa, whose presence is largely driven by eutrophication, resulting in regime shifts between floating and submerged invaded states.
- Full Text:
- Date Issued: 2021
- Authors: Coetzee, Julie A , Bownes, Angela , Martin, Grant D , Miller, Benjamin E , Smith, Rosalie , Weyl, Philip S R , Hill, Martin P
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406965 , vital:70326 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a18"
- Description: Biological control (biocontrol) against invasive macrophytes is one of the longest standing programmes in South Africa, initiated in the 1970s against water hyacinth, Pontederia crassipes Mart. (Pontederiaceae). Since then, 15 agent species (13 insects, one mite and one pathogen) have been released against six weeds, most of which are floating macrophytes, with excellent levels of success. The release of the water hyacinth planthopper Megamelus scutellaris Berg (Hemiptera: Delphacidae) in particular, has improved biocontrol prospects for water hyacinth since 2018. In the last decade, however, a new suite of submerged and rooted emergent invasive macrophytes has been targeted. The first release against a submerged macrophyte in South Africa, and the first release against Brazilian waterweed, Egeria densa Planch. (Hydrocharitaceae), anywhere in the world, was achieved with the release of a leafmining fly, Hydrellia egeriae Rodrigues-Júnior, Mathis and Hauser (Diptera: Ephydridae). Yellow flag, Iris pseudacorus L. (Iridaceae) and Mexican waterlily, Nymphaea mexicana Zucc. (Nymphaeaceae), have also been targeted for biocontrol for the first time worldwide, and are in the early stages of agent development. Post-release evaluations, long term monitoring and controlled experiments have highlighted the need for a more holistic approach to managing aquatic invasive plants in South Africa, whose presence is largely driven by eutrophication, resulting in regime shifts between floating and submerged invaded states.
- Full Text:
- Date Issued: 2021
A review of the biological control programmes on Eichhornia crassipes (C. mart.) solms (Pontederiaceae), Salvinia molesta DS Mitch.(Salviniaceae), Pistia stratiotes L.(Araceae), Myriophyllum aquaticum (vell.) verdc.(Haloragaceae) and Azolla filiculoides Lam.(Azollaceae) in South Africa
- Coetzee, Julie A, Hill, Martin P, Byrne, Marcus J
- Authors: Coetzee, Julie A , Hill, Martin P , Byrne, Marcus J
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451285 , vital:75036 , https://hdl.handle.net/10520/EJC32900
- Description: Biological control against water hyacinth, Eichhornia crassipes (C. Mart.) Solms (Pontederiaceae), salvinia, Salvinia molesta D.S. Mitch. (Salviniaceae), water lettuce, Pistia stratiotes L. (Araceae), parrot's feather, Myriophyllum aquaticum (Vell.) Verdc. (Haloragaceae), and red water fern, Azolla filiculoides Lam. (Azollaceae) has been ongoing in South Africa since the release of the first biological control agent on water hyacinth in 1974. This review provides an account of progress for the period from 1999. Post-release evaluations over the last three years have shown that, with the exception of water hyacinth, all of these problematic aquatic plants have been suppressed effectively using classical biological control. In eutrophic water bodies at high elevations that experience cold winters, an integrated approach, that includes herbicide application and augmentive biological control, is required against water hyacinth. The grasshopper Cornops aquaticum (Brüner) (Orthoptera: Acrididae: Leptysminae) has recently been released as a new agent for water hyacinth, and Megamelus scutellaris Berg (Hemiptera: Delphacidae) and Taosa longula Remes Lenicov (Hemiptera: Dictyopharidae) are being considered for release on water hyacinth. The longterm management of alien aquatic plants in South Africa relies on the prevention of new introductions of aquatic plant species that could replace those that have been controlled, and, more importantly, on a reduction in nutrient levels in South Africa's aquatic ecosystems.
- Full Text:
- Date Issued: 2011
- Authors: Coetzee, Julie A , Hill, Martin P , Byrne, Marcus J
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451285 , vital:75036 , https://hdl.handle.net/10520/EJC32900
- Description: Biological control against water hyacinth, Eichhornia crassipes (C. Mart.) Solms (Pontederiaceae), salvinia, Salvinia molesta D.S. Mitch. (Salviniaceae), water lettuce, Pistia stratiotes L. (Araceae), parrot's feather, Myriophyllum aquaticum (Vell.) Verdc. (Haloragaceae), and red water fern, Azolla filiculoides Lam. (Azollaceae) has been ongoing in South Africa since the release of the first biological control agent on water hyacinth in 1974. This review provides an account of progress for the period from 1999. Post-release evaluations over the last three years have shown that, with the exception of water hyacinth, all of these problematic aquatic plants have been suppressed effectively using classical biological control. In eutrophic water bodies at high elevations that experience cold winters, an integrated approach, that includes herbicide application and augmentive biological control, is required against water hyacinth. The grasshopper Cornops aquaticum (Brüner) (Orthoptera: Acrididae: Leptysminae) has recently been released as a new agent for water hyacinth, and Megamelus scutellaris Berg (Hemiptera: Delphacidae) and Taosa longula Remes Lenicov (Hemiptera: Dictyopharidae) are being considered for release on water hyacinth. The longterm management of alien aquatic plants in South Africa relies on the prevention of new introductions of aquatic plant species that could replace those that have been controlled, and, more importantly, on a reduction in nutrient levels in South Africa's aquatic ecosystems.
- Full Text:
- Date Issued: 2011
A stable isotope approach for the early detection and identification of N loading in aquatic ecosystems
- Hill, Jaclyn M, Kaehler, Sven, Hill, Martin P, Coetzee, Julie A
- Authors: Hill, Jaclyn M , Kaehler, Sven , Hill, Martin P , Coetzee, Julie A
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444491 , vital:74245 , https://www.wrc.org.za/wp-content/uploads/mdocs/KV 280.pdf
- Description: Global increases in urbanization and anthropogenic activity within wa-tersheds and catchment areas have resulted in excessive nitrogen loads in aquatic ecosystems. South Africa is deeply dependent on nat-ural resources for its economic health and as a consequence is particu-larly vulnerable to the degradation of its natural capital. Increased nitro-gen loading can result in widespread aquatic ecosystem degradation including: harmful algal blooms, increased turbidity, hypoxia, loss of aquatic vegetation and habitat and fish kills, it is also one of the mecha-nisms driving aquatic weed invasions. Understanding the fate and pro-cessing of anthropogenic nutrients in natural systems is therefore criti-cal for both preserving the well-being and biotic heritage for future gen-erations as well as providing a tremendous opportunity to improve the management driven by science. The objectives of this study were to evaluate the feasibility of mapping anthropogenic pollution through sta-ble isotopes signatures of aquatic plants, to investigate the potential for identifying different pollution sources, concentrations and distributions in a freshwater environment and to determine the utility of these tech-niques in indentifying early eutrophication.
- Full Text:
- Date Issued: 2011
- Authors: Hill, Jaclyn M , Kaehler, Sven , Hill, Martin P , Coetzee, Julie A
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444491 , vital:74245 , https://www.wrc.org.za/wp-content/uploads/mdocs/KV 280.pdf
- Description: Global increases in urbanization and anthropogenic activity within wa-tersheds and catchment areas have resulted in excessive nitrogen loads in aquatic ecosystems. South Africa is deeply dependent on nat-ural resources for its economic health and as a consequence is particu-larly vulnerable to the degradation of its natural capital. Increased nitro-gen loading can result in widespread aquatic ecosystem degradation including: harmful algal blooms, increased turbidity, hypoxia, loss of aquatic vegetation and habitat and fish kills, it is also one of the mecha-nisms driving aquatic weed invasions. Understanding the fate and pro-cessing of anthropogenic nutrients in natural systems is therefore criti-cal for both preserving the well-being and biotic heritage for future gen-erations as well as providing a tremendous opportunity to improve the management driven by science. The objectives of this study were to evaluate the feasibility of mapping anthropogenic pollution through sta-ble isotopes signatures of aquatic plants, to investigate the potential for identifying different pollution sources, concentrations and distributions in a freshwater environment and to determine the utility of these tech-niques in indentifying early eutrophication.
- Full Text:
- Date Issued: 2011
Assessing the morphological and physiological adaptations of the parasitoid wasp E chthrodesis lamorali for survival in an intertidal environment
- Owen, Candice A, Coetzee, Julie A, van Noort, Simon, Austin, Andrew D
- Authors: Owen, Candice A , Coetzee, Julie A , van Noort, Simon , Austin, Andrew D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123178 , vital:35412 , https://doi.org/10.1111/phen.12187
- Description: As a result of a variety of chemical, environmental, mechanical and physiological difficulties, insects that spend their entire life spans in the marine or intertidal region are relatively rare. The present study assesses whether morphological and physiological adaptations have evolved in a maritime parasitoidwasp species Echthrodesis lamorali Masner, 1968 (Hymenoptera: Platygastridae, Scelioninae), in response to environmental pressures on its respiratory functioning. Scanning electron and light microscopy of whole and sectioned specimens show the presence of structure-retaining taenidia in the tracheal tubes, although there is an absence of other major adaptations associated with the trachea or spiracles. Histological sectioning reveals the presence of unusual sacs in the female metasoma whose role is unknown, although they are hypothesized to most likely be linked to ovipositor control. Respirometry experiments illustrate the formation of a plastron when submerged, with the longevity of the wasps being increased by quiescence. The critical thermal range of E. lamorali is shown to be large: from −1.1 ∘C±0.16 to 45.7 ∘C±0.26 (mean±SE). Behavioural and physiological adaptations in E. lamorali appear to have evolved in response to exposure to the heterogeneous environmental conditions experienced within the intertidal zone.
- Full Text:
- Date Issued: 2017
- Authors: Owen, Candice A , Coetzee, Julie A , van Noort, Simon , Austin, Andrew D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123178 , vital:35412 , https://doi.org/10.1111/phen.12187
- Description: As a result of a variety of chemical, environmental, mechanical and physiological difficulties, insects that spend their entire life spans in the marine or intertidal region are relatively rare. The present study assesses whether morphological and physiological adaptations have evolved in a maritime parasitoidwasp species Echthrodesis lamorali Masner, 1968 (Hymenoptera: Platygastridae, Scelioninae), in response to environmental pressures on its respiratory functioning. Scanning electron and light microscopy of whole and sectioned specimens show the presence of structure-retaining taenidia in the tracheal tubes, although there is an absence of other major adaptations associated with the trachea or spiracles. Histological sectioning reveals the presence of unusual sacs in the female metasoma whose role is unknown, although they are hypothesized to most likely be linked to ovipositor control. Respirometry experiments illustrate the formation of a plastron when submerged, with the longevity of the wasps being increased by quiescence. The critical thermal range of E. lamorali is shown to be large: from −1.1 ∘C±0.16 to 45.7 ∘C±0.26 (mean±SE). Behavioural and physiological adaptations in E. lamorali appear to have evolved in response to exposure to the heterogeneous environmental conditions experienced within the intertidal zone.
- Full Text:
- Date Issued: 2017
Best of both worlds: The thermal physiology of Hydrellia egeriae, a biological control agent for the submerged aquatic weed, Egeria densa in South Africa
- Smith, Rosali, Coetzee, Julie A, Hill, Martin P
- Authors: Smith, Rosali , Coetzee, Julie A , Hill, Martin P
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417913 , vital:71494 , xlink:href="https://doi.org/10.1007/s10526-022-10142-w"
- Description: The submerged aquatic weed, Egeria densa Planch. (Hydrocharitaceae) or Brazilian waterweed, is a secondary invader of eutrophic freshwater systems in South Africa, following the successful management of floating aquatic weeds. In 2018, the leaf and stem-mining fly, Hydrellia egeriae Rodrigues-Júnior, Mathis and Hauser (Diptera: Ephydridae), was released against E. densa, the first agent released against a submerged aquatic weed in South Africa. During its life stages, the biological control agent is exposed to two environments, air and water. The thermal physiology of both life stages was investigated to optimize agent establishment through fine-tuned release strategies. The thermal physiological limits of H. egeriae encompassed its host plant’s optimal temperature range of 10 to 35 °C, with lower and upper critical temperatures of 2.6 to 47.0 °C, lower and upper lethal temperatures of − 5.6 and 40.6 °C for adults, and − 6.3 to 41.3 °C for larvae. Results from development time experiments and degree-day accumulation showed that the agent is capable of establishing at all E. densa sites in South Africa, with between 6.9 and 8.3 generations per year. However, cold temperatures (14 °C) prolonged the agent’s development time to three months, allowing it to only develop through one generation in winter. Predictions obtained from laboratory thermal physiology experiments corroborates field data, where the agent has established at all the sites it was released.
- Full Text:
- Date Issued: 2022
- Authors: Smith, Rosali , Coetzee, Julie A , Hill, Martin P
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417913 , vital:71494 , xlink:href="https://doi.org/10.1007/s10526-022-10142-w"
- Description: The submerged aquatic weed, Egeria densa Planch. (Hydrocharitaceae) or Brazilian waterweed, is a secondary invader of eutrophic freshwater systems in South Africa, following the successful management of floating aquatic weeds. In 2018, the leaf and stem-mining fly, Hydrellia egeriae Rodrigues-Júnior, Mathis and Hauser (Diptera: Ephydridae), was released against E. densa, the first agent released against a submerged aquatic weed in South Africa. During its life stages, the biological control agent is exposed to two environments, air and water. The thermal physiology of both life stages was investigated to optimize agent establishment through fine-tuned release strategies. The thermal physiological limits of H. egeriae encompassed its host plant’s optimal temperature range of 10 to 35 °C, with lower and upper critical temperatures of 2.6 to 47.0 °C, lower and upper lethal temperatures of − 5.6 and 40.6 °C for adults, and − 6.3 to 41.3 °C for larvae. Results from development time experiments and degree-day accumulation showed that the agent is capable of establishing at all E. densa sites in South Africa, with between 6.9 and 8.3 generations per year. However, cold temperatures (14 °C) prolonged the agent’s development time to three months, allowing it to only develop through one generation in winter. Predictions obtained from laboratory thermal physiology experiments corroborates field data, where the agent has established at all the sites it was released.
- Full Text:
- Date Issued: 2022
Biological control of Salvinia molesta (DS Mitchell) drives aquatic ecosystem recovery
- Motitsoe, Samuel N, Coetzee, Julie A, Hill, Jaclyn M, Hill, Martin P
- Authors: Motitsoe, Samuel N , Coetzee, Julie A , Hill, Jaclyn M , Hill, Martin P
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444515 , vital:74247 , https://doi.org/10.3390/d12050204
- Description: Salvinia molesta D.S. Mitchell (Salviniaceae) is a damaging free-floating invasive alien macrophyte native to South America. The biological control programme against S. molesta by the weevil Cyrtobagous salviniae Calder and Sands (Erirhinidae) has been successful in controlling S. molesta infestations in the introduced range, however, there is some debate as to how biological control success is measured. This study measured the response of epilithic algae and aquatic macroinvertebrate communities in a S. molesta-dominated state and subsequently where the weed had been cleared by biological control, as a proxy for ecosystem recovery in a before–after control–impact mesocosm experiment.
- Full Text:
- Date Issued: 2020
- Authors: Motitsoe, Samuel N , Coetzee, Julie A , Hill, Jaclyn M , Hill, Martin P
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444515 , vital:74247 , https://doi.org/10.3390/d12050204
- Description: Salvinia molesta D.S. Mitchell (Salviniaceae) is a damaging free-floating invasive alien macrophyte native to South America. The biological control programme against S. molesta by the weevil Cyrtobagous salviniae Calder and Sands (Erirhinidae) has been successful in controlling S. molesta infestations in the introduced range, however, there is some debate as to how biological control success is measured. This study measured the response of epilithic algae and aquatic macroinvertebrate communities in a S. molesta-dominated state and subsequently where the weed had been cleared by biological control, as a proxy for ecosystem recovery in a before–after control–impact mesocosm experiment.
- Full Text:
- Date Issued: 2020
Biological control of Salvinia molesta in South Africa revisited
- Martin, Grant D, Coetzee, Julie A, Weyl, Philip S R, Parkinson, Matthew C, Hill, Martin P
- Authors: Martin, Grant D , Coetzee, Julie A , Weyl, Philip S R , Parkinson, Matthew C , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103878 , vital:32318 , https://doi.org/10.1016/j.biocontrol.2018.06.011
- Description: The aquatic weed Salvinia molesta D.S. Mitch. (Salviniaceae) was first recorded in South Africa in the early 1900s, and by the 1960s was regarded as one of South Africa’s worst aquatic weeds. Following the release of the weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) in 1985, the weed is now considered under successful biological control. However, the post-release evaluation of this biological control programme has been ad hoc, therefore, to assess the efficacy of the agent, annual quantitative surveys of South African freshwater systems have been undertaken since 2008. Over the last ten years, of the 57 S. molesta sites visited annually in South Africa, the weevil has established at all of them. Eighteen sites are under successful biological control, where the weed no longer poses a threat to the system and 19 are under substantial biological control, where biological control has reduced the impact of the weed. Since 2008, the average percentage weed cover at sites has declined significantly from 51–100% cover to 0–5% cover in 2017 (R2 = 0.78; P < 0.05). Observations of site-specific characteristics suggest that biological control is most effective at small sites and more difficult at larger and shaded sites. Our findings show that S. molesta remains under good biological control in South Africa, however, some sites require intermittent strategic management, such as augmentative releases of C. salviniae.
- Full Text:
- Date Issued: 2018
- Authors: Martin, Grant D , Coetzee, Julie A , Weyl, Philip S R , Parkinson, Matthew C , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103878 , vital:32318 , https://doi.org/10.1016/j.biocontrol.2018.06.011
- Description: The aquatic weed Salvinia molesta D.S. Mitch. (Salviniaceae) was first recorded in South Africa in the early 1900s, and by the 1960s was regarded as one of South Africa’s worst aquatic weeds. Following the release of the weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) in 1985, the weed is now considered under successful biological control. However, the post-release evaluation of this biological control programme has been ad hoc, therefore, to assess the efficacy of the agent, annual quantitative surveys of South African freshwater systems have been undertaken since 2008. Over the last ten years, of the 57 S. molesta sites visited annually in South Africa, the weevil has established at all of them. Eighteen sites are under successful biological control, where the weed no longer poses a threat to the system and 19 are under substantial biological control, where biological control has reduced the impact of the weed. Since 2008, the average percentage weed cover at sites has declined significantly from 51–100% cover to 0–5% cover in 2017 (R2 = 0.78; P < 0.05). Observations of site-specific characteristics suggest that biological control is most effective at small sites and more difficult at larger and shaded sites. Our findings show that S. molesta remains under good biological control in South Africa, however, some sites require intermittent strategic management, such as augmentative releases of C. salviniae.
- Full Text:
- Date Issued: 2018
Biological control of South African plants that are invasive elsewhere in the world: A review of earlier and current programmes
- Olckers, Terence, Coetzee, Julie A, Egli, Daniella, Martin, Grant D, Paterson, Iain D, Sutton, Guy F, Wood, Alan R
- Authors: Olckers, Terence , Coetzee, Julie A , Egli, Daniella , Martin, Grant D , Paterson, Iain D , Sutton, Guy F , Wood, Alan R
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414336 , vital:71137 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a21"
- Description: South Africa supports a rich floral diversity, with 21 643 native plant taxa that include a high proportion (76.3%) of endemic species, and many of these favoured as ornamentals, both locally and globally. Consequently, South Africa has contributed substantially to global plant invasions, with 1093 native taxa (5% of all species) naturalized in other countries. At least 80 taxa are invasive in natural or semi-natural ecosystems elsewhere, while an additional 132 taxa are potentially invasive. Of the global naturalized flora, 8.2% originate from South Africa and largely comprise species of Poaceae, Asteraceae, Iridaceae and Fabaceae. Australia, in particular, but also Europe and North America are major recipients of South African weeds. However, few countries have targeted South African plants for biological control (biocontrol), with most efforts undertaken by Australia. Previous and current targets have involved only 26 species with 17 agents (15 insects, one mite and one rust fungus) of South African origin released on five target species in Australia and the United States of America. South Africa’s history of weed biocontrol, together with a large cohort of active scientists, is currently facilitating several internationally funded programmes targeting invasive plants of South African origin. In particular, the recently inaugurated Centre for Biological Control at Rhodes University and the University of KwaZulu-Natal have provided the impetus for novel efforts on five new target species and renewed efforts on four previously targeted species. In this contribution, we review the history of earlier biocontrol programmes against weeds of South African origin and the status of projects currently in progress in South Africa.
- Full Text:
- Date Issued: 2021
- Authors: Olckers, Terence , Coetzee, Julie A , Egli, Daniella , Martin, Grant D , Paterson, Iain D , Sutton, Guy F , Wood, Alan R
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414336 , vital:71137 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a21"
- Description: South Africa supports a rich floral diversity, with 21 643 native plant taxa that include a high proportion (76.3%) of endemic species, and many of these favoured as ornamentals, both locally and globally. Consequently, South Africa has contributed substantially to global plant invasions, with 1093 native taxa (5% of all species) naturalized in other countries. At least 80 taxa are invasive in natural or semi-natural ecosystems elsewhere, while an additional 132 taxa are potentially invasive. Of the global naturalized flora, 8.2% originate from South Africa and largely comprise species of Poaceae, Asteraceae, Iridaceae and Fabaceae. Australia, in particular, but also Europe and North America are major recipients of South African weeds. However, few countries have targeted South African plants for biological control (biocontrol), with most efforts undertaken by Australia. Previous and current targets have involved only 26 species with 17 agents (15 insects, one mite and one rust fungus) of South African origin released on five target species in Australia and the United States of America. South Africa’s history of weed biocontrol, together with a large cohort of active scientists, is currently facilitating several internationally funded programmes targeting invasive plants of South African origin. In particular, the recently inaugurated Centre for Biological Control at Rhodes University and the University of KwaZulu-Natal have provided the impetus for novel efforts on five new target species and renewed efforts on four previously targeted species. In this contribution, we review the history of earlier biocontrol programmes against weeds of South African origin and the status of projects currently in progress in South Africa.
- Full Text:
- Date Issued: 2021
Biological control of water lettuce, Pistia stratiotes L., facilitates macroinvertebrate biodiversity recovery: a mesocosm study
- Coetzee, Julie A, Langa, Susana D, Motitsoe, Samuel N, Hill, Martin P
- Authors: Coetzee, Julie A , Langa, Susana D , Motitsoe, Samuel N , Hill, Martin P
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423967 , vital:72112 , xlink:href="https://doi.org/10.1007/s10750-020-04369-w"
- Description: Floating aquatic weed infestations have negative socio-economic and environmental consequences to the ecosystems they invade. Despite the long history of invasion by macrophytes, only a few studies focus on their impacts on biodiversity, while the ecological benefits of biological control programmes against these species have been poorly quantified. We investigated the process of biotic homogenization following invasion by Pistia stratiotes on aquatic biodiversity, and recovery provided by biological control of this weed. Biotic homogenization is the increased similarity of biota as a result of introductions of non-native species. The study quantified the effect of P. stratiotes, and its biological control through the introduction of the weevil, Neohydronomus affinis on recruitment of benthic macroinvertebrates to artificial substrates. Mats of P. stratiotes altered the community composition and reduced diversity of benthic macroinvertebrates in comparison to an uninvaded control. However, reduction in percentage cover of the weed through biological control resulted in a significant increase in dissolved oxygen, and recovery of the benthic macroinvertebrate community that was comparable to the uninvaded state. This highlights the process of homogenization by an invasive macrophyte, providing a justification for sustained ecological and restoration efforts in the biological control of P. stratiotes where this plant is problematic.
- Full Text:
- Date Issued: 2020
- Authors: Coetzee, Julie A , Langa, Susana D , Motitsoe, Samuel N , Hill, Martin P
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423967 , vital:72112 , xlink:href="https://doi.org/10.1007/s10750-020-04369-w"
- Description: Floating aquatic weed infestations have negative socio-economic and environmental consequences to the ecosystems they invade. Despite the long history of invasion by macrophytes, only a few studies focus on their impacts on biodiversity, while the ecological benefits of biological control programmes against these species have been poorly quantified. We investigated the process of biotic homogenization following invasion by Pistia stratiotes on aquatic biodiversity, and recovery provided by biological control of this weed. Biotic homogenization is the increased similarity of biota as a result of introductions of non-native species. The study quantified the effect of P. stratiotes, and its biological control through the introduction of the weevil, Neohydronomus affinis on recruitment of benthic macroinvertebrates to artificial substrates. Mats of P. stratiotes altered the community composition and reduced diversity of benthic macroinvertebrates in comparison to an uninvaded control. However, reduction in percentage cover of the weed through biological control resulted in a significant increase in dissolved oxygen, and recovery of the benthic macroinvertebrate community that was comparable to the uninvaded state. This highlights the process of homogenization by an invasive macrophyte, providing a justification for sustained ecological and restoration efforts in the biological control of P. stratiotes where this plant is problematic.
- Full Text:
- Date Issued: 2020
Biotic resistance towards Hydrellia egeriae, a biological control agent for the aquatic weed Egeria densa, in South Africa
- Moffat, Rosali, van Noort, Simon, Coetzee, Julie A, Hill, Martin P
- Authors: Moffat, Rosali , van Noort, Simon , Coetzee, Julie A , Hill, Martin P
- Date: 2024
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451299 , vital:75038 , http://dx.doi.org/10.17159/2254-8854/2024/a15718
- Description: Egeria densa is a submerged aquatic weed that can grow into dense monocultures in rivers and dams in South Africa, which negatively affects ecosystem functioning and services. The biological control agent Hydrellia egeriae Rodrigues-Júnior (Diptera: Ephydridae) was first released against Egeria densa Planchon (Hydrocharitaceae) in South Africa in 2018. Biotic resistance in an introduced range can have negative impacts on the ability of a biological control agent to establish and exert top-down pressure. Dipteran and lepidopteran species that are used as biological control agents are often susceptible to higher levels of parasitism in their introduced range than biological control agents from other insect orders. In addition, ecological analogues that are present in South Africa, make H. egeriae particularly vulnerable to biotic resistance. Considering this, post-release surveys were conducted to investigate if native parasitoids will extend their host range to include H. egeriae. Chaenusa seminervata van Achterberg, C. anervata van Achterberg (Braconidae: Alysiinae: Dacnusini) and Ademon lagarosiphonae van Achterberg (Braconidae: Opiinae) were reared from field-collected H. egeriae pupae, within a year of its release. These braconid parasitoids were previously recorded from a native herbivore, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae).
- Full Text:
- Date Issued: 2024
- Authors: Moffat, Rosali , van Noort, Simon , Coetzee, Julie A , Hill, Martin P
- Date: 2024
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/451299 , vital:75038 , http://dx.doi.org/10.17159/2254-8854/2024/a15718
- Description: Egeria densa is a submerged aquatic weed that can grow into dense monocultures in rivers and dams in South Africa, which negatively affects ecosystem functioning and services. The biological control agent Hydrellia egeriae Rodrigues-Júnior (Diptera: Ephydridae) was first released against Egeria densa Planchon (Hydrocharitaceae) in South Africa in 2018. Biotic resistance in an introduced range can have negative impacts on the ability of a biological control agent to establish and exert top-down pressure. Dipteran and lepidopteran species that are used as biological control agents are often susceptible to higher levels of parasitism in their introduced range than biological control agents from other insect orders. In addition, ecological analogues that are present in South Africa, make H. egeriae particularly vulnerable to biotic resistance. Considering this, post-release surveys were conducted to investigate if native parasitoids will extend their host range to include H. egeriae. Chaenusa seminervata van Achterberg, C. anervata van Achterberg (Braconidae: Alysiinae: Dacnusini) and Ademon lagarosiphonae van Achterberg (Braconidae: Opiinae) were reared from field-collected H. egeriae pupae, within a year of its release. These braconid parasitoids were previously recorded from a native herbivore, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae).
- Full Text:
- Date Issued: 2024
Chlorophyll fluorometry as a method of determining the effectiveness of a biological control agent in post-release evaluations
- Miller, Benjamin E, Coetzee, Julie A, Hill, Martin P
- Authors: Miller, Benjamin E , Coetzee, Julie A , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417438 , vital:71453 , xlink:href="https://doi.org/10.1080/09583157.2019.1656165"
- Description: The impact of the planthopper Megamelus scutellaris, a biocontrol agent of water hyacinth in South Africa, was assessed using chlorophyll fluorometry in a greenhouse study under two different eutrophic nutrient treatments and agent densities (high and low). The results indicated that plants grown in low nutrients with high densities of M. scutellaris showed the greatest reduction in the fluorescence parameters Fv/Fm and PIabs. The successful use of chlorophyll fluorometry for the detection of subtle insect damage to water hyacinth leaves could have future application in post-release studies to measure the impact of M. scutellaris in the field.
- Full Text:
- Date Issued: 2019
- Authors: Miller, Benjamin E , Coetzee, Julie A , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417438 , vital:71453 , xlink:href="https://doi.org/10.1080/09583157.2019.1656165"
- Description: The impact of the planthopper Megamelus scutellaris, a biocontrol agent of water hyacinth in South Africa, was assessed using chlorophyll fluorometry in a greenhouse study under two different eutrophic nutrient treatments and agent densities (high and low). The results indicated that plants grown in low nutrients with high densities of M. scutellaris showed the greatest reduction in the fluorescence parameters Fv/Fm and PIabs. The successful use of chlorophyll fluorometry for the detection of subtle insect damage to water hyacinth leaves could have future application in post-release studies to measure the impact of M. scutellaris in the field.
- Full Text:
- Date Issued: 2019
Climatic suitability and compatibility of the invasive Iris pseudacorus L.(Iridaceae) in the Southern Hemisphere: Considerations for biocontrol
- Minuti, Gianmarco, Stiers, Iris, Coetzee, Julie A
- Authors: Minuti, Gianmarco , Stiers, Iris , Coetzee, Julie A
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423293 , vital:72045 , xlink:href="https://doi.org/10.1016/j.biocontrol.2022.104886"
- Description: Iris pseudacorus L. (Iridaceae) is an emergent macrophyte native to Europe, North Africa and western Asia. Considered invasive in wetland habitats around the world, this species is now the target of a biocontrol programme in the Southern Hemisphere. Native range surveys of the weed led to the selection of the flea beetle, Aphthona nonstriata Goeze (Coleoptera: Chrysomelidae), as a candidate biocontrol agent. An important aspect to consider in weed biocontrol is the ability of an agent to establish and thrive in the environment where it is released. Climatic incompatibility between source and intended release sites can in fact limit the success of a biocontrol programme. In the current study, the potential climatic niche of I. pseudacorus and A. nonstriata in the Southern Hemisphere was analysed. The ecological niche modelling software MaxEnt was used to map the climatic suitability of both organisms across invaded regions in South America, southern Africa and Australasia. Furthermore, occurrence records from each invaded range were used independently to model the climatic compatibility of I. pseudacorus in Europe, in order to prioritize areas of the native range to explore during future surveys for potential biocontrol agents. The models identified areas at high risk of invasion by I. pseudacorus in northern Argentina, Uruguay, southern Brazil and central Chile, as well as numerous provinces of eastern South Africa, Lesotho, southern Australia and New Zealand. Accordingly, the highest climatic suitability for A. nonstriata was predicted across the humid temperate climates of north-east Argentina, Uruguay, southern Brazil, southern South Africa, south-east Australia and New Zealand. These results can eventually be used in future release plans to prioritize areas where establishment and survival of the agent is expected to be highest. At the same time, it may be useful to search the native range of the weed for biological control agents showing high climatic adaptation towards the intended release sites of each invaded range. In this regards, our climatic compatibility models identified high-priority areas across the Mediterranean regions of Italy and southern France, as well as the temperate regions of central and western Europe. Altogether, the current study provides useful new information to tackle the invasion and advance the biocontrol programme of I. pseudacorus in the Southern Hemisphere.
- Full Text:
- Date Issued: 2022
- Authors: Minuti, Gianmarco , Stiers, Iris , Coetzee, Julie A
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423293 , vital:72045 , xlink:href="https://doi.org/10.1016/j.biocontrol.2022.104886"
- Description: Iris pseudacorus L. (Iridaceae) is an emergent macrophyte native to Europe, North Africa and western Asia. Considered invasive in wetland habitats around the world, this species is now the target of a biocontrol programme in the Southern Hemisphere. Native range surveys of the weed led to the selection of the flea beetle, Aphthona nonstriata Goeze (Coleoptera: Chrysomelidae), as a candidate biocontrol agent. An important aspect to consider in weed biocontrol is the ability of an agent to establish and thrive in the environment where it is released. Climatic incompatibility between source and intended release sites can in fact limit the success of a biocontrol programme. In the current study, the potential climatic niche of I. pseudacorus and A. nonstriata in the Southern Hemisphere was analysed. The ecological niche modelling software MaxEnt was used to map the climatic suitability of both organisms across invaded regions in South America, southern Africa and Australasia. Furthermore, occurrence records from each invaded range were used independently to model the climatic compatibility of I. pseudacorus in Europe, in order to prioritize areas of the native range to explore during future surveys for potential biocontrol agents. The models identified areas at high risk of invasion by I. pseudacorus in northern Argentina, Uruguay, southern Brazil and central Chile, as well as numerous provinces of eastern South Africa, Lesotho, southern Australia and New Zealand. Accordingly, the highest climatic suitability for A. nonstriata was predicted across the humid temperate climates of north-east Argentina, Uruguay, southern Brazil, southern South Africa, south-east Australia and New Zealand. These results can eventually be used in future release plans to prioritize areas where establishment and survival of the agent is expected to be highest. At the same time, it may be useful to search the native range of the weed for biological control agents showing high climatic adaptation towards the intended release sites of each invaded range. In this regards, our climatic compatibility models identified high-priority areas across the Mediterranean regions of Italy and southern France, as well as the temperate regions of central and western Europe. Altogether, the current study provides useful new information to tackle the invasion and advance the biocontrol programme of I. pseudacorus in the Southern Hemisphere.
- Full Text:
- Date Issued: 2022
Community entomology: insects, science and society
- Weaver, Kim N, Hill, Jaclyn M, Martin, Grant D, Paterson, Iain D, Coetzee, Julie A, Hill, Martin P
- Authors: Weaver, Kim N , Hill, Jaclyn M , Martin, Grant D , Paterson, Iain D , Coetzee, Julie A , Hill, Martin P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123343 , vital:35429 , https://hdl.handle.net/10520/EJC-c859bebd5
- Description: Educative outreach programmes have been found to be effective ways in which to raise awareness around basic scientific concepts. The Biological Control Research Group (BCRG) in the Department of Zoology and Entomology at Rhodes University, South Africa, is involved in community engaged initiatives that aim to be interactive and informative around entomology, and more specifically, the use of biological control against invasive alien plants. As a higher education institution, Rhodes University has a civic responsibility to engage with local communities and work with them around local challenges. Three groups of activities undertaken by the BCRG in partnership with local schools and other community partners are described and assessed in this paper as a way of assessing them and exploring future research areas around the aims and outcomes of these programmes.
- Full Text:
- Date Issued: 2017
- Authors: Weaver, Kim N , Hill, Jaclyn M , Martin, Grant D , Paterson, Iain D , Coetzee, Julie A , Hill, Martin P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123343 , vital:35429 , https://hdl.handle.net/10520/EJC-c859bebd5
- Description: Educative outreach programmes have been found to be effective ways in which to raise awareness around basic scientific concepts. The Biological Control Research Group (BCRG) in the Department of Zoology and Entomology at Rhodes University, South Africa, is involved in community engaged initiatives that aim to be interactive and informative around entomology, and more specifically, the use of biological control against invasive alien plants. As a higher education institution, Rhodes University has a civic responsibility to engage with local communities and work with them around local challenges. Three groups of activities undertaken by the BCRG in partnership with local schools and other community partners are described and assessed in this paper as a way of assessing them and exploring future research areas around the aims and outcomes of these programmes.
- Full Text:
- Date Issued: 2017
Comparisons of the thermal physiology of water hyacinth biological control agents: predicting establishment and distribution pre-and post-release
- May, Bronwen, Coetzee, Julie A
- Authors: May, Bronwen , Coetzee, Julie A
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123476 , vital:35446 , https://doi.10.1111/eea.120628
- Description: Investigations into the thermal physiology of weed biological control agents may elucidate reasons for establishment failure following release. Such studies have shown that the success of water hyacinth biological control in South Africa remains variable in the high-lying interior Highveld region, because the control agents are restricted to establishment and development due to extreme winter conditions. To determine the importance of thermal physiology studies, both pre- and post-release, this study compared the known thermal requirements of Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) released in 1996, with those of an agent released in 1990, Niphograpta albiguttalis (Warren) (Lepidoptera: Pyralidae) and a candidate agent, Megamelus scutellaris Berg (Hemiptera: Delphacidae), which is currently under consideration for release. The lower developmental threshold (to) and rate of development (K) were determined for N. albiguttalis and M. scutellaris, using a reduced axis regression, and incorporated into a degree-day model which compared the number of generations that E. catarinensis, N. albiguttalis, and M. scutellaris are capable of producing annually at any given site in South Africa. The degree-day models predicted that N. albiguttalis (K = 439.43, to = 9.866) can complete 4–11 generations per year, whereas M. scutellaris (K = 502.96, to = 11.458) can only complete 0–10 generations per year, compared with E. catarinensis (K = 342, to = 10.3) which is predicted to complete 3–14 generations per year. This suggests that the candidate agent, M. scutellaris, will not fare better in establishment than the other two agents that have been released in the Highveld, and that it may not be worth releasing an agent with higher thermal requirements than the agents that already occur in these high-lying areas. Thermal physiology studies conducted prior to release are important tools in biological control programmes, particularly those in resource-limited countries, to prevent wasting efforts in getting an agent established.
- Full Text:
- Date Issued: 2013
- Authors: May, Bronwen , Coetzee, Julie A
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123476 , vital:35446 , https://doi.10.1111/eea.120628
- Description: Investigations into the thermal physiology of weed biological control agents may elucidate reasons for establishment failure following release. Such studies have shown that the success of water hyacinth biological control in South Africa remains variable in the high-lying interior Highveld region, because the control agents are restricted to establishment and development due to extreme winter conditions. To determine the importance of thermal physiology studies, both pre- and post-release, this study compared the known thermal requirements of Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) released in 1996, with those of an agent released in 1990, Niphograpta albiguttalis (Warren) (Lepidoptera: Pyralidae) and a candidate agent, Megamelus scutellaris Berg (Hemiptera: Delphacidae), which is currently under consideration for release. The lower developmental threshold (to) and rate of development (K) were determined for N. albiguttalis and M. scutellaris, using a reduced axis regression, and incorporated into a degree-day model which compared the number of generations that E. catarinensis, N. albiguttalis, and M. scutellaris are capable of producing annually at any given site in South Africa. The degree-day models predicted that N. albiguttalis (K = 439.43, to = 9.866) can complete 4–11 generations per year, whereas M. scutellaris (K = 502.96, to = 11.458) can only complete 0–10 generations per year, compared with E. catarinensis (K = 342, to = 10.3) which is predicted to complete 3–14 generations per year. This suggests that the candidate agent, M. scutellaris, will not fare better in establishment than the other two agents that have been released in the Highveld, and that it may not be worth releasing an agent with higher thermal requirements than the agents that already occur in these high-lying areas. Thermal physiology studies conducted prior to release are important tools in biological control programmes, particularly those in resource-limited countries, to prevent wasting efforts in getting an agent established.
- Full Text:
- Date Issued: 2013
Competition between two aquatic macrophytes, Lagarosiphon major (Ridley) Moss (Hydrocharitaceae) and Myriophyllum spicatum Linnaeus (Haloragaceae) as influenced by substrate sediment and nutrients
- Martin, Grant D, Coetzee, Julie A
- Authors: Martin, Grant D , Coetzee, Julie A
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76925 , vital:30641 , https://doi.org/10.1016/j.aquabot.2013.11.001
- Description: Competition between two globally economic and ecologically important submerged aquatic macrophytes, Lagarosiphon major (Rid.) Moss ex Wager and Myriophyllum spicatum L., was studied in response to growing in different substrate nutrient and sediment treatments. Addition series experiments were conducted with mixed plantings of L. major and M. spicatum grown under two soil nutrient concentrations (high vs. low) and two sediment treatments (sand vs. loam). Competitive ability of the plants was determined using an inverse linear model of the total dry weights as the yield variable. In high nutrient sediment treatments, L. major was the stronger competitor relative to M. spicatum, with one L. major plant being competitively equivalent to 2.5 M. spicatum plants in terms of their respective ability to reduce L. major biomass. In the loam sediment treatments, L. major was an even stronger competitor relative to M. spicatum with one L. major being equivalent to 10 M. spicatum plants. Additionally, L. major had a faster relative growth rate (RGR) than M. spicatum when grown in mixed cultures, a loam sediment type and at both high and low planting densities. The results indicated that L. major is a superior competitor to M. spicatum and that both nutrient and sediment conditions significantly affect the competitive ability of both species. The results contribute to the understanding of competition between submerged invasive macrophytes, and provide insight into the establishment and spread of invasive submerged macrophytes.
- Full Text:
- Date Issued: 2014
- Authors: Martin, Grant D , Coetzee, Julie A
- Date: 2014
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76925 , vital:30641 , https://doi.org/10.1016/j.aquabot.2013.11.001
- Description: Competition between two globally economic and ecologically important submerged aquatic macrophytes, Lagarosiphon major (Rid.) Moss ex Wager and Myriophyllum spicatum L., was studied in response to growing in different substrate nutrient and sediment treatments. Addition series experiments were conducted with mixed plantings of L. major and M. spicatum grown under two soil nutrient concentrations (high vs. low) and two sediment treatments (sand vs. loam). Competitive ability of the plants was determined using an inverse linear model of the total dry weights as the yield variable. In high nutrient sediment treatments, L. major was the stronger competitor relative to M. spicatum, with one L. major plant being competitively equivalent to 2.5 M. spicatum plants in terms of their respective ability to reduce L. major biomass. In the loam sediment treatments, L. major was an even stronger competitor relative to M. spicatum with one L. major being equivalent to 10 M. spicatum plants. Additionally, L. major had a faster relative growth rate (RGR) than M. spicatum when grown in mixed cultures, a loam sediment type and at both high and low planting densities. The results indicated that L. major is a superior competitor to M. spicatum and that both nutrient and sediment conditions significantly affect the competitive ability of both species. The results contribute to the understanding of competition between submerged invasive macrophytes, and provide insight into the establishment and spread of invasive submerged macrophytes.
- Full Text:
- Date Issued: 2014
Contrasting effects of climate change on the invasion risk and biocontrol potential of the invasive Iris pseudacorus L. between Northern and Southern Hemisphere
- Minuti, Gianmarco, Coetzee, Julie A, Stiers, Iris
- Authors: Minuti, Gianmarco , Coetzee, Julie A , Stiers, Iris
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423329 , vital:72048 , xlink:href="https://doi.org/10.1016/j.biocontrol.2023.105290"
- Description: Iris pseudacorus is both a prized ornamental and an invasive aquatic plant that tends to grow dense monospecific stands, displacing the local vegetation and altering the hydrology of freshwater ecosystems. Originally from Europe, this species has historically invaded North America, China and Japan, and more recently spread through Argentina, South Africa and Australasia, where it is now a target for biological control. Field surveys within its native range have led to the selection of three candidate biocontrol agents. Prioritizing the best candidates for different regions constitutes a critical step, which could save significant time and resources before further cost-intensive experimental studies are conducted. Climate change is seldom taken into consideration in the prioritization process. In this regard, climatic suitability can be used to model the potential distributions of weeds and their candidate agents, both in space and time, thus allowing to identify areas at risk of invasion and predict where agents will be able to establish long-term. Accordingly, the objectives of this work were (i) to predict I. pseudacorus invasions and range shifts in the context of climate change; (ii) to identify wetland areas most at risk of invasion under present and future climatic conditions; and (iii) to prioritize the best suite of candidate biocontrol agents for different invaded ranges, worldwide. To do so, we modelled the present and future (2040–2060) climatic suitability of I. pseudacorus and its candidate agents using the software MaxEnt. Our results highlight a clear distinction between predictions for the Northern and Southern Hemispheres. In North America and eastern Asia, the area climatically suitable for I. pseudacorus is expected to increase and shift northwards. As for its biocontrol agents, very low suitability is predicted across these regions, further decreasing under future climatic conditions. On the other hand, climatically suitable areas for the plant in South America, southern Africa and Australasia are predicted, on average, to reduce in response to climate change. A decrease in climatic suitability is also expected for its candidate biocontrol agents which, however, would still maintain a significant range overlap with their host. These results can be used to prioritize areas most at risk of invasion and identify which combination of candidates could potentially provide the best level of control across different invaded ranges.
- Full Text:
- Date Issued: 2023
- Authors: Minuti, Gianmarco , Coetzee, Julie A , Stiers, Iris
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423329 , vital:72048 , xlink:href="https://doi.org/10.1016/j.biocontrol.2023.105290"
- Description: Iris pseudacorus is both a prized ornamental and an invasive aquatic plant that tends to grow dense monospecific stands, displacing the local vegetation and altering the hydrology of freshwater ecosystems. Originally from Europe, this species has historically invaded North America, China and Japan, and more recently spread through Argentina, South Africa and Australasia, where it is now a target for biological control. Field surveys within its native range have led to the selection of three candidate biocontrol agents. Prioritizing the best candidates for different regions constitutes a critical step, which could save significant time and resources before further cost-intensive experimental studies are conducted. Climate change is seldom taken into consideration in the prioritization process. In this regard, climatic suitability can be used to model the potential distributions of weeds and their candidate agents, both in space and time, thus allowing to identify areas at risk of invasion and predict where agents will be able to establish long-term. Accordingly, the objectives of this work were (i) to predict I. pseudacorus invasions and range shifts in the context of climate change; (ii) to identify wetland areas most at risk of invasion under present and future climatic conditions; and (iii) to prioritize the best suite of candidate biocontrol agents for different invaded ranges, worldwide. To do so, we modelled the present and future (2040–2060) climatic suitability of I. pseudacorus and its candidate agents using the software MaxEnt. Our results highlight a clear distinction between predictions for the Northern and Southern Hemispheres. In North America and eastern Asia, the area climatically suitable for I. pseudacorus is expected to increase and shift northwards. As for its biocontrol agents, very low suitability is predicted across these regions, further decreasing under future climatic conditions. On the other hand, climatically suitable areas for the plant in South America, southern Africa and Australasia are predicted, on average, to reduce in response to climate change. A decrease in climatic suitability is also expected for its candidate biocontrol agents which, however, would still maintain a significant range overlap with their host. These results can be used to prioritize areas most at risk of invasion and identify which combination of candidates could potentially provide the best level of control across different invaded ranges.
- Full Text:
- Date Issued: 2023
Cryptic species of a water hyacinth biological control agent revealed in South Africa: host specificity, impact, and thermal tolerance
- Paterson, Iain D, Coetzee, Julie A, Weyl, Philip S R, Griffith, Tamzin C, Voogt, Nina, Hill, Martin P
- Authors: Paterson, Iain D , Coetzee, Julie A , Weyl, Philip S R , Griffith, Tamzin C , Voogt, Nina , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423982 , vital:72113 , xlink:href="https://doi.org/10.1111/eea.12812"
- Description: The discovery that cryptic species are more abundant than previously thought has implications for weed biological control, as there is a risk that cryptic species may be inadvertently released with consequences for the safety of the practice. A cryptic species of a biological control agent released for the control of the invasive alien macrophyte, water hyacinth, Eichhornia crassipes (C. Mart.) Solms. (Pontederiaceae), was recently discovered in South Africa. The two species were considered a single species prior to genetic analysis and interbreeding experiments. The original biological control agent retains the name Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) whereas the new species has been described as Eccritotarsus eichhorniae Henry. In this study, we compared the host specificity, efficacy, and thermal physiologies of the two species. The host specificity of the two species within the Pontederiaceae was very similar and both are safe for release in South Africa. Comparison of the per capita impact of the two species indicated that E. eichhorniae was the more damaging species but this is likely to be influenced by temperature, with E. catarinensis being more effective under lower temperatures and E. eichhorniae being more effective under higher temperatures. Releasing the correct species for the thermal environment of each release site will improve the level of control of water hyacinth in South Africa. This example highlights the need to keep populations of biological control agents from different native range collection localities separate, and to screen for host specificity and efficacy.
- Full Text:
- Date Issued: 2019
- Authors: Paterson, Iain D , Coetzee, Julie A , Weyl, Philip S R , Griffith, Tamzin C , Voogt, Nina , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423982 , vital:72113 , xlink:href="https://doi.org/10.1111/eea.12812"
- Description: The discovery that cryptic species are more abundant than previously thought has implications for weed biological control, as there is a risk that cryptic species may be inadvertently released with consequences for the safety of the practice. A cryptic species of a biological control agent released for the control of the invasive alien macrophyte, water hyacinth, Eichhornia crassipes (C. Mart.) Solms. (Pontederiaceae), was recently discovered in South Africa. The two species were considered a single species prior to genetic analysis and interbreeding experiments. The original biological control agent retains the name Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) whereas the new species has been described as Eccritotarsus eichhorniae Henry. In this study, we compared the host specificity, efficacy, and thermal physiologies of the two species. The host specificity of the two species within the Pontederiaceae was very similar and both are safe for release in South Africa. Comparison of the per capita impact of the two species indicated that E. eichhorniae was the more damaging species but this is likely to be influenced by temperature, with E. catarinensis being more effective under lower temperatures and E. eichhorniae being more effective under higher temperatures. Releasing the correct species for the thermal environment of each release site will improve the level of control of water hyacinth in South Africa. This example highlights the need to keep populations of biological control agents from different native range collection localities separate, and to screen for host specificity and efficacy.
- Full Text:
- Date Issued: 2019
Distributional range of the South African maritime spider-egg parasitoid wasp, Echthrodesis lamorali (Hymenoptera: Platygastridae Scelioninae) insecta hymenoptera
- Owen, Candice A, Coetzee, Julie A, van Noort, Simon
- Authors: Owen, Candice A , Coetzee, Julie A , van Noort, Simon
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444407 , vital:74238 , https://hdl.handle.net/10520/EJC161753
- Description: The southern African coastline plays host to nine spider species. Two of these, namely Desis formidabilis (O. P.-Cambridge, 1890) (Araneae: Desidae) and Amaurobioides africanus Hewitt, 1917 (Araneae: Anyphaenidae), are recorded as hosts for an intertidal spider egg parasitoid, Echthrodesis lamorali Masner, 1968 (Hymenoptera: Platygastridae: Scelioninae). These two spider species occur from Lüderitz (Namibia) along the coast to East London (Eastern Cape Province, South Africa), while their parasitoid has been known from only a single locality on the Cape Peninsula. The South African coastline was surveyed from Jacobsbaai (Western Cape Province) to East London in an attempt to determine the full distribution of E. lamorali. The wasp was only reared from host eggs collected on the Cape Peninsula, confirming a high degree of endemism for this species.
- Full Text:
- Date Issued: 2014
- Authors: Owen, Candice A , Coetzee, Julie A , van Noort, Simon
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444407 , vital:74238 , https://hdl.handle.net/10520/EJC161753
- Description: The southern African coastline plays host to nine spider species. Two of these, namely Desis formidabilis (O. P.-Cambridge, 1890) (Araneae: Desidae) and Amaurobioides africanus Hewitt, 1917 (Araneae: Anyphaenidae), are recorded as hosts for an intertidal spider egg parasitoid, Echthrodesis lamorali Masner, 1968 (Hymenoptera: Platygastridae: Scelioninae). These two spider species occur from Lüderitz (Namibia) along the coast to East London (Eastern Cape Province, South Africa), while their parasitoid has been known from only a single locality on the Cape Peninsula. The South African coastline was surveyed from Jacobsbaai (Western Cape Province) to East London in an attempt to determine the full distribution of E. lamorali. The wasp was only reared from host eggs collected on the Cape Peninsula, confirming a high degree of endemism for this species.
- Full Text:
- Date Issued: 2014
Do thermal requirements of Dichrorampha odorata, a shoot-boring moth for the biological control of Chromolaena odorata, explain its failure to establish in South Africa?
- Nqayi, Slindile B, Zachariades, Costas, Coetzee, Julie A, Hill, Martin P, Chidawanyika, Frank, Uyi, Osariyekemwen O, McConnachie, Andrew J
- Authors: Nqayi, Slindile B , Zachariades, Costas , Coetzee, Julie A , Hill, Martin P , Chidawanyika, Frank , Uyi, Osariyekemwen O , McConnachie, Andrew J
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416851 , vital:71391 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v31_n1_a14"
- Description: Chromolaena odorata (L.) RM King and H Rob. (Asteraceae) has been subject to a biological control programme in South Africa for over three decades. A shoot-tip boring moth, Dichrorampha odorata Brown and Zachariades (Lepidoptera: Tortricidae), originating from Jamaica, was released as a biological control agent in 2013 but despite the release of substantial numbers of the insect, it has not established a permanent field population. Because climate incompatibility is a major constraint for classical biological control of invasive plants, and based on the differences in climate between Jamaica and South Africa and field observations at release sites, aspects of the thermal physiology of D. odorata were investigated to elucidate reasons for its failure to establish. Developmental time decreased with increasing temperatures ranging from 20 °C to 30 °C, with incomplete development for immature stages at 18 °C and 32 °C. The developmental threshold, t, was calculated as 8.45 °C with 872.4 degree-days required to complete development (K). A maximum of 6.5 generations per year was projected for D. odorata in South Africa, with the heavily infested eastern region of the country being the most eco-climatically suitable for establishment. The lower lethal temperature (LLT50) of larvae and adults was –4.5 and 1.8 °C, respectively. The upper lethal temperature (ULT50) for larvae was 39.6 °C whilst that of adults was 41.0 °C. Larvae thus had better cold tolerance compared to adults whereas adults had better heat tolerance compared to larvae. The critical thermal (CT) limits for adults were 3.4 ± 0.07 to 43.7 ± 0.12 °C. Acclimation at 20 °C for 7 days resulted in increased cold and heat tolerance with a CTmin and CTmax of 1.9 ± 0.06 and 44.4 ± 0.07 °C respectively, compared to the relative control, acclimated at 25 °C. Acclimation at 30 °C improved neither cold (CTmin: 5.9 ± 0.08 °C) nor heat tolerance (CTmax: 42.9 ± 0.10 °C). These results suggest that thermal requirements fall within field temperatures and are thus not the main constraining factor leading to poor establishment of D. odorata in South Africa.
- Full Text:
- Date Issued: 2023
- Authors: Nqayi, Slindile B , Zachariades, Costas , Coetzee, Julie A , Hill, Martin P , Chidawanyika, Frank , Uyi, Osariyekemwen O , McConnachie, Andrew J
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416851 , vital:71391 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v31_n1_a14"
- Description: Chromolaena odorata (L.) RM King and H Rob. (Asteraceae) has been subject to a biological control programme in South Africa for over three decades. A shoot-tip boring moth, Dichrorampha odorata Brown and Zachariades (Lepidoptera: Tortricidae), originating from Jamaica, was released as a biological control agent in 2013 but despite the release of substantial numbers of the insect, it has not established a permanent field population. Because climate incompatibility is a major constraint for classical biological control of invasive plants, and based on the differences in climate between Jamaica and South Africa and field observations at release sites, aspects of the thermal physiology of D. odorata were investigated to elucidate reasons for its failure to establish. Developmental time decreased with increasing temperatures ranging from 20 °C to 30 °C, with incomplete development for immature stages at 18 °C and 32 °C. The developmental threshold, t, was calculated as 8.45 °C with 872.4 degree-days required to complete development (K). A maximum of 6.5 generations per year was projected for D. odorata in South Africa, with the heavily infested eastern region of the country being the most eco-climatically suitable for establishment. The lower lethal temperature (LLT50) of larvae and adults was –4.5 and 1.8 °C, respectively. The upper lethal temperature (ULT50) for larvae was 39.6 °C whilst that of adults was 41.0 °C. Larvae thus had better cold tolerance compared to adults whereas adults had better heat tolerance compared to larvae. The critical thermal (CT) limits for adults were 3.4 ± 0.07 to 43.7 ± 0.12 °C. Acclimation at 20 °C for 7 days resulted in increased cold and heat tolerance with a CTmin and CTmax of 1.9 ± 0.06 and 44.4 ± 0.07 °C respectively, compared to the relative control, acclimated at 25 °C. Acclimation at 30 °C improved neither cold (CTmin: 5.9 ± 0.08 °C) nor heat tolerance (CTmax: 42.9 ± 0.10 °C). These results suggest that thermal requirements fall within field temperatures and are thus not the main constraining factor leading to poor establishment of D. odorata in South Africa.
- Full Text:
- Date Issued: 2023
Effect of water trophic level on the impact of the water hyacinth moth Niphograpta albiguttalis on Eichhornia crassipes
- Canavan, Kim N, Coetzee, Julie A, Hill, Martin P, Paterson, Iain D
- Authors: Canavan, Kim N , Coetzee, Julie A , Hill, Martin P , Paterson, Iain D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423740 , vital:72090 , xlink:href="https://doi.org/10.2989/16085914.2014.893225"
- Description: Eutrophication contributes to the proliferation of alien invasive weed species such as water hyacinth Eichhornia crassipes. Although the South American moth Niphograpta albiguttalis was released in South Africa in 1990 as a biological control agent against water hyacinth, no post-release evaluations have yet been conducted here. The impact of N. albiguttalis on water hyacinth growth was quantified under low-, medium- and high-nutrient concentrations in a greenhouse experiment. Niphograpta albiguttalis was damaging to water hyacinth in all three nutrient treatments, but significant damage in most plant parameters was found only under high-nutrient treatments. However, E. crassipes plants grown in high-nutrient water were healthier, and presumably had higher fitness, than plants not exposed to herbivory at lower-nutrient levels. Niphograpta albiguttalis is likely to be most damaging to water hyacinth in eutrophic water systems, but the damage will not result in acceptable levels of control because of the plant's high productivity under these conditions. Niphograpta albiguttalis is a suitable agent for controlling water hyacinth infestations in eutrophic water systems, but should be used in combination with other biological control agents and included in an integrated management plan also involving herbicidal control and water quality management.
- Full Text:
- Date Issued: 2014
- Authors: Canavan, Kim N , Coetzee, Julie A , Hill, Martin P , Paterson, Iain D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423740 , vital:72090 , xlink:href="https://doi.org/10.2989/16085914.2014.893225"
- Description: Eutrophication contributes to the proliferation of alien invasive weed species such as water hyacinth Eichhornia crassipes. Although the South American moth Niphograpta albiguttalis was released in South Africa in 1990 as a biological control agent against water hyacinth, no post-release evaluations have yet been conducted here. The impact of N. albiguttalis on water hyacinth growth was quantified under low-, medium- and high-nutrient concentrations in a greenhouse experiment. Niphograpta albiguttalis was damaging to water hyacinth in all three nutrient treatments, but significant damage in most plant parameters was found only under high-nutrient treatments. However, E. crassipes plants grown in high-nutrient water were healthier, and presumably had higher fitness, than plants not exposed to herbivory at lower-nutrient levels. Niphograpta albiguttalis is likely to be most damaging to water hyacinth in eutrophic water systems, but the damage will not result in acceptable levels of control because of the plant's high productivity under these conditions. Niphograpta albiguttalis is a suitable agent for controlling water hyacinth infestations in eutrophic water systems, but should be used in combination with other biological control agents and included in an integrated management plan also involving herbicidal control and water quality management.
- Full Text:
- Date Issued: 2014