Natural enemies from South Africa for biological control of Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae) in Europe
- Authors: Baars, Jan-Robert , Coetzee, Julie A , Martin, Grant D , Hill, Martin P , Caffrey, J M
- Date: 2010
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/76914 , vital:30637 , https://doi.org/10.1007/s10750-010-0427-0
- Description: The non-native invasive plant, Lagarosiphon major (Hydrocharitaceae) is a submersed aquatic macrophyte that poses a significant threat to water bodies in Europe. Dense infestations prove difficult to manage using traditional methods. In order to initiate a biocontrol programme, a survey for natural enemies of Lagarosiphon was conducted in South Africa. Several phytophagous species were recorded for the first time, with at least three showing notable promise as candidate agents. Amongst these, a leaf-mining fly, Hydrellia sp. (Ephydridae) that occurred over a wide distribution causes significant leaf damage despite high levels of parasitism by braconid wasps. Another yet unidentified fly was recorded mining the stem of L. major. Two leaf-feeding and shoot boring weevils, cf. Bagous sp. (Curculionidae) were recorded damaging the shoot tips and stunting the growth of the stem. Several leaf-feeding lepidopteran species (Nymphulinae) were frequently recorded, but are expected to feed on a wide range of plant species and are not considered for importation before other candidates are assessed. The discovery of several natural enemies in the country of origin improves the biological control prospects of L. major in Europe.
- Full Text:
- Date Issued: 2010
Nutrient-mediated silica uptake from agricultural runoff in invasive floating macrophytes: implications for biological control
- Authors: Baso, Nompumelelo C , Delport, Garyn A , Coetzee, Julie A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424803 , vital:72185 , xlink:href="https://doi.org/10.1007/s10750-020-04344-5"
- Description: Silica (Si) plays a significant role in alleviating the effects of biotic and abiotic stressors in many plants, especially in an agricultural context. With increased use of Si-based fertilisers, understanding plant responses to the addition of Si to their environment, particularly aquatic environments, is important. We investigated how two invasive macrophytes, Eichhornia crassipes and Pistia stratiotes, responded to different nutrient and Si concentrations, in the presence and absence of herbivory. Both species incorporated Si into their foliage, but uptake of Si did not increase under high nutrient availability but rather decreased, especially in P. stratiotes. Plant quality (i.e. C:N) for both weed species was affected more by nutrient concentrations than Si content, and the addition of Si had a negative effect on plant growth. Eichhornia crassipes increased daughter plant production under high Si conditions, while P. stratiotes plants showed no reproductive response to increased Si except in low nutrient conditions where reproduction was reduced. The addition of Si resulted in increased biomass of E. crassipes, while P. stratiotes was unaffected. These results highlight that runoff of Si from fertiliser alter aquatic plant–insect interactions, which has consequences for biological control.
- Full Text:
- Date Issued: 2020
The effects of elevated atmospheric CO2 concentration on the biological control of invasive aquatic weeds
- Authors: Baso, Nompumelelo C , Coetzee, Julie A , Ripley, Bradford S , Hill, Martin P
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419423 , vital:71643 , xlink:href="https://doi.org/10.1016/j.aquabot.2020.103348"
- Description: There has been a rapid increase in atmospheric CO2 concentration, from pre-industrial values of 280 ppm to more than 400 ppm currently, and this is expected to double by the end of the 21st century. Studies have shown that plants grown at elevated CO2 concentrations have increased growth rates and invest more in carbon-based defences. This has important implications for the management of invasive alien plants, especially using biological control which is mostly dependent on herbivorous insects. The aim of this study was to investigate the effects of elevated atmospheric CO2 on the biological control of four invasive aquatic weeds (Azolla filiculoides, Salvinia molesta, Pistia stratiotes and Myriophyllum aquaticum). These species are currently under successful control by their respective biological control agents (Stenopelmus rufinasus, Cyrtobagous salviniae, Neohydronomus affinis, and Lysathia sp.) in South Africa. The plant species were grown in a two factorial design experiment, where atmospheric CO2 concentrations were set at ambient (400 ppm) or elevated (800 ppm), and plants were either subjected to or not subjected to herbivory by their target biological control agents. There was an overall increase in biomass production and C:N across all species at elevated CO2, both in the absence and presence of biological control, although C:N of M. aquaticum and biomass of A. filiculoides with herbivory were not constant with this trend. Insect feeding damage was reduced by elevated CO2, except for S. molesta. Thus, we can expect that plants will respond differently to CO2 increase, but the general trend suggests that these species will become more challenging to manage through biological control in future.
- Full Text:
- Date Issued: 2021
Effect of water trophic level on the impact of the water hyacinth moth Niphograpta albiguttalis on Eichhornia crassipes
- 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
The role of eutrophication in the biological control of water hyacinth, Eichhornia crassipes, in South Africa
- Authors: Coetzee, Julie A , Hill, Martin P
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69263 , vital:29474 , https://doi.org/10.1007/s10526-011-9426-y
- Description: South Africa has some of the most eutrophic aquatic systems in the world, as a result of the adoption of an unnecessarily high 1 mg l-1 phosphorus (P) standard for all water treatment works in the 1970 s. The floating aquatic macrophyte, water hyacinth (Eichhornia crassipes (Mart.) Solms (Pontederiaceae), has taken advantage of these nutrient rich systems, becoming highly invasive and damaging. Despite the implementation of a biological control programme in South Africa, water hyacinth remains the worst aquatic weed. A meta-analysis of published and unpublished laboratory studies that investigated the combined effect of P and nitrogen (N) water nutrient concentration and control agent herbivory showed that water nutrient status was more important than herbivory in water hyacinth growth. Analysis of long-term field data collected monthly from 14 sites around South Africa between 2004 and 2005 supported these findings. Therefore, the first step in any water hyacinth control programme should be to reduce the nutrient status of the water body.
- Full Text:
- Date Issued: 2011
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
- 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
Prospects for the biological control of submerged macrophytes in South Africa
- Authors: Coetzee, Julie A , Bownes, Angela , Martin, Grant D
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452295 , vital:75118 , https://hdl.handle.net/10520/EJC32899
- Description: Historically, biological control efforts against aquatic plants in South Africa have focused on floating species, and as a result, there has been a dearth of research into the invasion and control of submerged macrophytes. With numerous submerged invasive species already established in South Africa, thriving horticultural and aquarium industries, nutrient-rich water systems, and a limited knowledge of the drivers of invasions of submerged macrophytes, South Africa is highly vulnerable to a second phase of aquatic plant problems. Experience gained in the U.S.A. on biological control against submerged weeds, such as hydrilla, Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) and spiked / Eurasian watermilfoil, Myriophyllum spicatum L. (Haloragaceae), have provided South African researchers with the necessary foundation to initiate programmes against these weeds. Research in South Africa is currently focused on pre-release studies on the biological control of H. verticillata, using an undescribed fly, Hydrellia sp. (Diptera: Ephydridae) and a weevil, Bagous hydrillae O'Brien (Coleoptera: Curculionidae); and on M. spicatum using a North American weevil, Euhrychiopsis lecontei Dietz (Coleoptera: Curculionidae). Feasibility studies into biological control of some incipient submerged weeds are also being conducted, including Brazilian water weed, Egeria densa Planch. (Hydrocharitaceae), Canadian water weed, Elodea canadensis Mitch. (Hydrocharitaceae) and cabomba, Cabomba caroliniana A. Gray (Cabombaceae). Progress with, and potential constraints that may limit these programmes, are discussed.
- Full Text:
- Date Issued: 2011
A review of the biocontrol programmes against aquatic weeds in South Africa
- 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
It's a numbers game: inundative biological control of water hyacinth (Pontederia crassipes), using Megamelus scutellaris (Hemiptera: Delphacidae) yields success at a high elevation, hypertrophic reservoir in South Africa
- Authors: Coetzee, Julie A , Miller, Benjamin E , Kinsler, David , Sebola, Keneilwe , Hill, Martin P
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417749 , vital:71483 , xlink:href="https://doi.org/10.1080/09583157.2022.2109594"
- Description: Classical biological control of water hyacinth in South Africa has been constrained by cool winter temperatures that limit population growth of the biological control agents, and highly eutrophic waters which enhance plant growth. However, inundative releases of the control agent, Megamelus scutellaris (Hemiptera: Delphacidae), at the Hartbeespoort Dam, South Africa, suggest that water hyacinth can be managed successfully using biological control as a standalone intervention for the first time in the absence of herbicide operations, despite eutrophication and a temperate climate. Sentinel-2 satellite images were used to measure the reduction in water hyacinth cover from over 37% to less than 6% over two consecutive years since M. scutellaris was first released on the dam in 2018, while site surveys confirmed a corresponding increase in M. scutellaris population density from fewer than 500 insects/m2 in October 2019, to more than 6000 insects/m2 by March 2020. Inundative release strategies are recommended for the control of water hyacinth in South Africa at key stages of its invasion, particularly after winter, and flooding events.
- Full Text:
- Date Issued: 2022
Biological control of water lettuce, Pistia stratiotes L., facilitates macroinvertebrate biodiversity recovery: a mesocosm study
- 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
Performance and field host range of the life stages of Cornops aquaticum, a biological control agent of water hyacinth
- Authors: Franceschini, M Celeste , Hill, Martin P , Fuentes-Rodríguez, Daniela , Gervazoni, Paula B , Sabater, Lara M , Coetzee, Julie A
- Date: 2023
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424814 , vital:72186 , xlink:href="https://doi.org/10.1111/eea.13354"
- Description: Host specificity determination of weed biocontrol agents has historically relied on evidence generated through quarantine trials in the region of introduction. These trials could give ‘false positive’ results due to a maximum type I error probability, and where possible, more research under field conditions should be conducted in the region of origin. The oligophagous, semiaquatic grasshopper, Cornops aquaticum Bruner (Orthoptera: Acrididae, Tetrataeniini), was released in South Africa for the biological control of Pontederia crassipes Pellegrini and Horn (Pontederiaceae). The aim of this study was to assess how the performance and field host range of C. aquaticum varies according to its stages of development, and how this contributes to the understanding of the relationship between the fundamental (laboratory-based) and the ecological (field-based) host range of this grasshopper, and its implications for water hyacinth biocontrol. We conducted post-release laboratory no-choice trials, confining early instars (instars 1 and 2), later instars (instars 3–6), and adult females and males in mesh cages, to determine insect performance on wetland plants growing in sympatry with P. crassipes. Also, gut analysis from field-collected C. aquaticum was done to determine the ecological host range of this insect, identifying epidermal tissue of consumed plants. In no-choice trials, survival rates of the later instars and adult C. aquaticum were similar on Pistia stratiotes L. (Araceae), Oxycaryum cubense (Poepp. and Kunth) Lye (Cyperaceae), and P. crassipes. However, under field conditions, P. crassipes and the congeneric Pontederia azurea Sw. were the only plant contents in the guts of early instars and the most abundant species in later instars and adults. The results support the hypothesis that C. aquaticum is an oligophagous insect on the genus Pontederia, and that different life stages should be considered when conducting host-specificity trials in externally feeding mobile herbivore species. Diet composition of field-collected insects thus could help detect false positives in laboratory trials, being an additional and realistic approach in understanding and predicting the selection processes of the insect in the new environment. Retrospective analysis of potential agents that were rejected due to lack of host-specificity, using the methods from this study, could add a suite of additional agents to programs where invasive weeds remain unmanaged.
- Full Text:
- Date Issued: 2023
The thermal physiology of Lysathia sp.(Coleoptera: Chrysomelidae), a biocontrol agent of parrot’s feather in South Africa, supports its success
- Authors: Goddard, Matthew , Owen, Candice A , Martin, Grant D , Coetzee, Julie A
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417806 , vital:71487 , xlink:href="https://doi.org/10.1080/09583157.2022.2054949"
- Description: The establishment success of biocontrol agents originating from tropical regions is often limited by climate when introduced in temperate regions. However, the flea beetle, Lysathia sp. (Coleoptera: Chrysomelidae), a biocontrol agent of Myriophyllum aquaticum (Vell.) Verdc. (Haloragaceae) in South Africa, is an effective agent in regions where other biocontrol agents of tropical aquatic weeds have failed due to winter-induced mortality. The development (degree-day model) and thermal tolerance (critical thermal minimum/maximum [CTmin/max] and lower/upper lethal limits [LLT/ULT50]) of Lysathia sp. were investigated to explain this success. The model predicted that Lysathia sp. could complete 6 to 12 generations per year in the colder regions of the country. The lower threshold for development (t0) was 13.0 °C and thermal constant (K) was 222.4 days, which is considerably lower than the K values of other biocontrol agents of aquatic weeds in South Africa. This suggests that above the temperature threshold, Lysathia sp. can develop faster than those other species and complete multiple life cycles in the cooler winter months, allowing for rapid population growth and thus improving M. aquaticum control. Furthermore, the CTmin of Lysathia sp. was 2.3 ± 0.2 °C and the CTmax was 49.0 ± 0.5 °C. The LLT50 was calculated as ∼ −7.0 °C and the ULT50 as ∼ 43.0 °C. These wide tolerance ranges and survival below freezing show why Lysathia sp. has established at cool sites and suggest that it may be a suitable agent for other cold countries invaded by M. aquaticum.
- Full Text:
- Date Issued: 2022
Thermal plasticity and microevolution enhance establishment success and persistence of a water hyacinth biological control agent
- Authors: Griffith, Tamzin C , Paterson, Iain D , Owen, Candice A , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424866 , vital:72190 , xlink:href="https://doi.org/10.1111/eea.12814"
- Description: Aspects of the thermal physiology of the water hyacinth biological control agent Eccritotarsus catarinensis Carvalho (Hemiptera: Miridae) have been extensively investigated over the past 20 years to understand and improve post-release establishment in the field. Thermal physiology studies predicted that the agent would not establish at a number of cold sites in South Africa, where it has nonetheless subsequently established and thrived. Recently, studies have begun to incorporate the plastic nature of insect thermal physiology into models of agent establishment. This study determined whether season and locality influenced the thermal physiology of two field populations of E. catarinensis, one collected from the hottest site where the agent has established in South Africa, and one from the coldest site. The thermal physiology of E. catarinensis was significantly influenced by season and site, demonstrating a degree of phenotypic plasticity, and that some post-release local adaptation to climatic conditions has occurred through microevolution. We then determined whether cold acclimation under laboratory conditions was possible. Successfully cold-acclimated E. catarinensis had a significantly lower critical thermal minimum (CTmin) compared to the field cold-acclimated population. This suggests that cold acclimation of agents could be conducted in the laboratory before future releases to improve their cold tolerance, thereby increasing their chance of establishment at cold sites and allowing further adaptation to colder climates to occur in the field. Although the thermal tolerance of E. catarinensis is limited by local adaptations to climatic conditions in the native range, the plastic nature of the insect's thermal physiology has allowed it to survive in the very different climatic conditions of the introduced range, and there has been some adaptive change to the insect's thermal tolerance since establishment. This study highlights the importance of plasticity and microevolutionary processes in the success of biological control agents under the novel climatic conditions in the introduced range.
- Full Text:
- Date Issued: 2019
A stable isotope approach for the early detection and identification of N loading in aquatic ecosystems
- 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
The biological control of aquatic weeds in South Africa: current status and future challenges
- Authors: Hill, Martin P , Coetzee, Julie A
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59909 , vital:27706 , https://doi.org/10.4102/abc.v47i2.2152
- Description: Aquatic ecosystems in South Africa have been prone to invasion by introduced macrophytes since the late 1800s, when water hyacinth, Eichhornia crassipes (Mart.) Solms-Laub. (Pontederiaceae), was first recorded as naturalised in KwaZulu-Natal (Cilliers 1991). Several other species of freshwater aquatic plants, all notorious weeds in other parts of the world, have also become invasive in many of the rivers, man-made impoundments, lakes and wetlands of South Africa (Hill 2003). These are Pistia stratiotes L. (Araceae) (water lettuce); Salvinia molesta D.S. Mitch. (Salviniaceae) (salvinia); Myriophyllum aquaticum (Vell. Conc.) Verd. (parrot's feather); and Azolla filiculoides Lam. (Azollaceae) (red water fern) (Hill 2003), which along with water hyacinth comprise the 'Big Bad Five' (Henderson & Cilliers 2002). Recently, new invasive aquatic plant species have been recorded which are still at their early stages of invasion, including the submerged species, Egeria densa Planch. (Hydrocharitaceae) (Brazilian water weed) and Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae); the emergent species, Sagittaria platyphylla (Engelm.) J.G.Sm. and S. latifolia Willd. (Alismataceae); Lythrum salicaria L. (Lythraceae) (purple loosestrife), Nasturtium officinale W.T. Aiton. (Brassicaceae) (watercress); Iris pseudacorus L. (Iridaceae) (yellow flag); and Hydrocleys nymphoides (Humb. & Bonpl. ex Willd.) Buchenau (Alismataceae) (water poppy); and the new floating weeds, Salvinia minima Baker (Salviniaceae) and Azolla cristata Kaulf. (Azollaceae) (Mexican azolla); and the rooted floating Nymphaea mexicana Zucc. (Nymphaeceae) (Mexican water lily) (Coetzee et al. 2011a; Coetzee, Bownes & Martin 2011b). The mode of introduction of these species is mainly through the horticultural and aquarium trade (Martin & Coetzee 2011), and two issues contribute to the invasiveness of these macrophytes following establishment: the lack of co-evolved natural enemies in their adventive range (McFadyen 1998); and disturbance, the presence of nitrate- and phosphate-enriched waters, associated with urban, agricultural and industrial pollution that promotes plant growth (Coetzee & Hill 2012).
- Full Text:
- Date Issued: 2017
Invasive alien aquatic plants in South African freshwater ecosystems:
- Authors: Hill, Martin P , Coetzee, Julie A , Martin, Grant D , Smith, Rosali , Strange, Emily F
- Date: 2020
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/176271 , vital:42680 , ISBN 978-3-030-32394-3 , 10.1007/978-3-030-32394-3
- Description: South Africa has a long history of managing the establishment and spread of invasive fioating macrophytes. The past thirty years of research and the implementation of nation-wide biological and integrated control programmes has led to widespread control of these species in many degraded freshwater ecosystems. Such initiatives are aimed at restoring access to potable freshwater and maintaining native biodiversity.
- Full Text: false
- Date Issued: 2020
The role of mass-rearing in weed biological control projects in South Africa
- Authors: Hill, Martin P , Conlong, Desmond , Zachariades, Costas , Coetzee, Julie A , Paterson, Iain D , Miller, Benjamin E , Foxcroft, Llewellyn , van der Westhuizen, L
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/407094 , vital:70335 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a22"
- Description: It has been documented that the continual release of high numbers of biological control (biocontrol) agents for weeds increases the likelihood of agent establishment and has been shown to reduce the time between the first release and subsequent control of the target weed. Here we review the mass-rearing activities for weed biocontrol agents in South Africa between 2011 and 2020. Some 4.7 million individual insects from 40 species of biocontrol agent have been released on 31 weed species at over 2000 sites throughout South Africa during the last decade. These insects were produced at mass-rearing facilities at eight research institutions, five schools and 10 Non-Governmental Organizations. These mass-rearing activities have created employment for 41 fulltime, fixed contract staff, of which 11 are people living with physical disabilities. To improve the uptake of mass-rearing through community engagement, appropriate protocols are required to ensure that agents are produced in high numbers to suppress invasive alien plant populations in South Africa.
- Full Text:
- Date Issued: 2021
More than a century of biological control against invasive alien plants in South Africa: a synoptic view of what has been accomplished
- Authors: Hill, Martin P , Moran, V Clifford , Hoffmann, John H , Neser, Stefan , Zimmermann, Helmuth G , Simelane, David O , Klein, Hildegard , Zachariades, Costas , Wood, Alan R , Byrne, Marcus J , Paterson, Iain D , Martin, Grant D , Coetzee, Julie A
- Date: 2020
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/176260 , vital:42679 , ISBN 978-3-030-32394-3 , 10.1007/978-3-030-32394-3
- Description: Invasive alien plant species negatively affect agricultural production, degrade conservation areas, reduce water supplies, and increase the intensity of wild fires. Since 1913, biological control agents ie plant-feeding insects, mites, and fungal pathogens, have been deployed in South Africa to supplement other management practices (herbicides and mechanical controls) used against these invasive plant species. We do not describe the biological control agent species.
- Full Text: false
- Date Issued: 2020
On the move: New insights on the ecology and management of native and alien macrophytes
- Authors: Hofstra, Deborah , Schoelynck, Jonas , Ferrell, Jason , Coetzee, Julie A , de Winton, Mary , Bickel, Tobias O , Champion, Paul , Madsen, John , Bakker, Elisabeth S , Hilt, Sabine , Matheson, Fleur , Netherland, Mike , Gross, Elisabeth M
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419346 , vital:71636 , xlink:href=" https://doi.org/10.1016/j.aquabot.2019.103190"
- Description: Globally, freshwater ecosystems are under threat. The main threats come from catchment land-use changes, altered water regimes, eutrophication, invasive species, climate change and combinations of these factors. We need scientific research to respond to these challenges by providing solutions to halt the deterioration and improve the condition of our valuable freshwaters. This requires a good understanding of aquatic ecosystems, and the nature and scale of changes occurring. Macrophytes play a fundamental role in aquatic systems. They are sensitive indicators of ecosystem health, as they are affected by run-off from agricultural, industrial or urban areas. On the other hand, alien macrophytes are increasingly invading aquatic systems all over the world. Improving our knowledge on the ecology and management of both native and alien plants is indispensable to address threats to freshwaters in order to protect and restore aquatic habitats. The International Aquatic Plants Group (IAPG) brings together scientists and practitioners based at universities, research and environmental organisations around the world. The main themes of the 15th symposium 2018 in New Zealand were biodiversity and conservation, management, invasive species, and ecosystem response and restoration. This Virtual Special Issue provides a comprehensive review from the symposium, addressing the ecology of native macrophytes, including those of conservation concern, and highly invasive alien macrophytes, and the implications of management interventions. In this editorial paper, we highlight insights and paradigms on the ecology and management of native and alien macrophytes gathered during the meeting.
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- Date Issued: 2020
Simulated global increases in atmospheric CO2 alter the tissue composition, but not the growth of some submerged aquatic plant bicarbonate users growing in DIC rich waters
- Authors: Hussner, Andreas , Smith, Rosali , Mettler-Altmann, Tabea , Hill, Martin P , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419388 , vital:71640 , xlink:href="https://doi.org/10.1016/j.aquabot.2018.11.009"
- Description: Current global change scenarios predict an increase in atmospheric CO2 from the current 380 ppm to a value ranging from 540 ppm to 960 ppm by the year 2100. The effects of three air CO2 levels (400, 600 and 800 ppm) on five submerged aquatic plants that utilize HCO3− were studied, using the elevated CO2 Open Top Chamber facility at Rhodes University (Grahamstown, South Africa). Plants grew in water with two different initial dissolved inorganic carbon (DIC) concentrations of 1.5 and 3.0 mM. Overall, the growth rates and biomass allocation to roots were not affected by the initial DIC and air CO2, even though differences between the species were found. Furthermore, no overall effects were found on net photosynthesis, chlorophyll and starch content, even though significant effects of CO2 and DIC were observed in some species. In contrast, with increasing DIC and air CO2 a significant global decline in leaf nitrogen content linked with an increased C:N molar ratio was observed. The results indicate that submerged aquatic HCO3− users will be less affected by atmospheric CO2 increases when growing in DIC rich waters, in comparison to obligate CO2 users growing under CO2 limiting conditions as documented in previous studies. However, the changes found in plant nitrogen illustrate that atmospheric CO2 increases will affect nitrogen absorption by submerged plants, with subsequent ecosystem level effects.
- Full Text:
- Date Issued: 2019