Field-based ecological studies to assess prospective biological control agents for invasive alien plants: An example from giant rat's tail grass
- Authors: Sutton, Guy F , Canavan, Kim N , Day, Michael M , Paterson, Iain D
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423756 , vital:72091 , xlink:href="https://doi.org/10.1111/1365-2664.13834"
- Description: Biological control (biocontrol) of invasive alien plants is a widely utilised weed management tool. Prospective biocontrol agents are typically assessed through host specificity testing and pre-release efficacy studies performed in quarantine. However, rearing of the potential biocontrol agents and/or test plants is often difficult or impossible under quarantine conditions. Moreover, practitioners may attain laboratory artefacts in quarantine, which may result in the potential agent being needlessly rejected. Field-based studies in the weed's indigenous distribution could overcome these issues.
- Full Text:
- Date Issued: 2021
Prioritisation of targets for weed biological control I: a review of existing prioritisation schemes and development of a system for South Africa
- Authors: Downey, Paul O , Paterson, Iain D , Canavan, Kim N , Hill, Martin P
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417763 , vital:71484 , xlink:href="https://doi.org/10.1080/09583157.2021.1918636"
- Description: Biological control is widely utilised for the management of invasive alien plants (IAP). With the ever-increasing number of IAPs, it is important to prioritise targets for biocontrol in order to maximise the use of resources and the chances of success. This paper reviewed 12 previous systems developed to prioritise plant targets for biocontrol. The review underpins the selection of attributes and methodologies for the prioritisation of targets for biocontrol in South Africa. All of the previous systems are purpose-built and context-specific, so a new system is required for the South African setting. Previous prioritisation systems were assessed based on the attributes and methodology adopted. The attributes of previous systems were grouped into three sections, being (1) impact/importance of the target plant, (2) likelihood of achieving success, and (3) investment required. Nineteen attributes from previous systems are included in the new system, while nine were excluded due to a requirement for legislation and/or research, or because they conflicted with objectives of the new system in some way. Two methodological approaches were identified for how systems sourced information, either sourcing information through expert knowledge or the use of available literature and data. This information was then applied through either a quantitative or qualitative scoring method. A quantitative scoring method, with information sourced from available resources, was selected as the most appropriate methodology in the context of the new system for South Africa. This review streamlined the development and testing of the South African Biological Control Target Selection system.
- Full Text:
- Date Issued: 2021
Progress and prospects for the biological control of invasive alien grasses Poaceae) in South Africa
- Authors: Sutton, Guy F , Bownes, Angela , Visser, Vernon , Mapaura, Anthony , Canavan, Kim N
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/414448 , vital:71147 , xlink:href="https://hdl.handle.net/10520/ejc-ento_v29_n3_a12"
- Description: Historically, invasive alien grasses have not been considered a major threat in South Africa, and as a result, very few resources are allocated to their management. However, there is an increasing awareness of the severe environmental and socio-economic impacts of invasive grasses and the need for appropriate management options for their control. South Africa has a long history of successfully implementing weed biological control (biocontrol) to manage invasive alien plants, however much like the rest of the world, invasive grasses do not feature prominently as targets for biocontrol. The implementation and early indicators of success of the few grass biocontrol programmes globally and the finding that grasses can be suitable targets, suggests that biocontrol could start to play an important role in managing invasive alien grasses in South Africa. In this paper, we evaluated the prospects for implementing novel grass biocontrol projects over the next ten years against 48 grasses that have been determined to represent the highest risk based on their current environmental and economic impacts. The grasses were ranked in order of priority using the Biological Control Target Selection system. Five grasses were prioritised – Arundo donax L., Cortaderia jubata (Lem.) Stapf, Cortaderia selloana (Schult and Schult) Asch. and Graebn., Nassella trichotoma (Hack. ex Arech.), and Glyceria maxima (Hartm.) Holmb., based on attributes that make them suitable biocontrol targets. Arundo donax has already been the target of a biocontrol programme in South Africa. We reviewed the progress made towards the biocontrol of this species and discuss how this programme could be developed going forward. Moreover, we outline how biocontrol could be implemented to manage the remaining four high-priority targets. While biocontrol of grasses is not without its challenges (e.g. unresolved taxonomies, conflicts of interest and a lack of supporting legislation), South Africa has an opportunity to learn from existing global research and begin to invest in biocontrol of high-priority species that are in most need of control.
- Full Text:
- Date Issued: 2021
The invasive grass genus Nassella in South Africa: A synthesis
- Authors: Mapaura Anthony , Canavan, Kim N , Richardson, David M , Clark, Vincent R , Steenhuisen, Sandy-Lynn
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424842 , vital:72188 , xlink:href="https://doi.org/10.1016/j.sajb.2020.08.031"
- Description: Three species of Nassella have naturalized in South Africa. Nassella trichotoma and N. tenuissima are declared weeds under category 1b of the National Environmental Management: Biodiversity Act (NEM:BA) and occur mainly in the montane grasslands of the Western and Eastern Cape provinces. Nassella neesiana is not listed in NEM:BA but is naturalized in the Eastern Cape, Western Cape and Free State provinces. Research conducted in the 1970s and 1980s led to vigorous government-funded awareness and control campaigns which ended in 2000. No research on Nassella distribution or control has been undertaken since then. Despite this hiatus, Nassella remains a dangerous genus in southern Africa, given the serious impacts of these species in similar social-ecological systems in Australia and New Zealand. This paper presents a synthesis of available information about Nassella invasions in South Africa and identifies research gaps. It specifically addresses these questions: What identification issues exist? What is the current spatial distribution of Nassella? What is the autecology of the genus? What are the social-ecological impacts of Nassella? What control measures are currently applied and what are their strengths and limitations? What do we know about Nassella distribution and its response to climate change? This paper highlights many knowledge gaps about Nassella, such as the species’ current distribution range, field identification and detection difficulties, and the uncoordinated control efforts that require urgent research to inform an effective management response.
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- Date Issued: 2020
The potential for biological control on cryptic plant invasions
- Authors: Canavan, Kim N , Canavan, Susan , Harms, Nathan E , Lambertini, Carla , Paterson, Iain D , Thum, Ryan
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423562 , vital:72072 , xlink:href="https://doi.org/10.1016/j.biocontrol.2020.104243"
- Description: Cryptic invasions can be defined as ‘the occurrence of an invasive species or genotype that was not previously recognised as alien in origin or not distinguished from other aliens’. Such invasions can result in negative impacts on the recipient ecosystems and disturb the evolutionary history of native plant populations. Many cryptic invasions have become so problematic that there is a need to implement control measures. This paper explores the potential for biological control to be implemented as a means of managing cryptic invasions. Firstly, the paper defines the different forms of cryptic invasion, differentiating between interspecific and intraspecific invasions; this hierarchy influences how to detect, study and ultimately implement biological control when cryptic invasions occur. Secondly, unique challenges associated with biological control programmes for cryptic invasions are addressed, including: the need for intraspecific level host specificity in agents, the occurrence of hybridisation between native species/lineages and the target weed, the role of enemy release in cryptic invasions in the presence of closely related native plant species/lineages, and a review of potential stakeholder conflicts of interest and legislation. Biological control of cryptic invasions has been shown to be possible, however the process will be more difficult and complex than controlling traditional targets and will likely take up more time and resources. If these challenges are overcome, then biological control programmes against cryptic invasions should be able to proceed and maintain the same standards as traditional biological control programmes.
- Full Text:
- Date Issued: 2020
Investigating herbivory and plant origin on tall-statured grasses in South Africa
- Authors: Canavan, Kim N
- Date: 2017
- Subjects: Insects as biological pest control agents -- South Africa , Arundo donax , Giant reed -- South Africa , Giant reed -- Biological control -- South Africa , Phragmites australis , Phragmites mauritianus , Phragmites , Tetramesa romana , Biological invasions -- South Africa , Wasps -- Host plants , Wasps -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/6147 , vital:21051
- Description: South African riparian zones have been heavily degraded through anthropogenic activities such as dam construction and extraction of water for irrigation, which has resulted in a loss of ecosystem services and functioning. A consequence of such disturbances to riparian areas is in their susceptibility to invasive alien species (IAS). One such IAS is the giant reed, Arundo donax L. (Poaceae), introduced to South Africa in the 1700s largely for erosion control. Arundo donax has since greatly expanded in the country and is now one of the most abundant IAS. Arundo donax has been found to displace native vegetation and in South Africa this will most likely lead to the displacement of the native tall-statured grasses, Phragmites australis (Cav.) Trin. ex Steud. and Phragmites mauritianus Kunth. This study aimed to enhance our understanding of the tall-statured grasses A. donax, P. australis and P. mauritianus to better manage them in riparian areas. For A. donax, biological control is seen as the most viable option to control stands in the long-term. However, before such a programme is put in place, it is important to first collect baseline data that can be used to guide the direction of the biological control project in South Africa. For the Phragmites spp., despite being a dominant vegetative type in riparian areas, very little is known about their status in South Africa. Furthermore, there have been increasing reports of both Phragmites species having an expansion of their range and abundance. In North America, there has been a similar trend of reed expansion and through molecular work it was determined that a cryptic invasion has occurred with the introduction of an invasive non-native haplotype from Europe. It is therefore unknown if Phragmites spp. populations are expanding due to anthropogenic activities or due to a cryptic invasion. To address these shortfalls in knowledge the study investigated the tall-statured grasses in two parts; firstly, molecular techniques are used to explore the plant origin and genetic diversity of A. donax, P. australis and P. mauritianus and secondly using the Enemy Release Hypothesis as a framework, herbivore assemblages for each reed was determined across their distribution in South Africa. Molecular-techniques determined that both P. australis and P. mauritianus had only one haplotype - known as haplotype K and haplotype V respectively, across their distribution. For P. australis, haplotype K shares a close connection with populations from a Mediterranean lineage and this was further confirmed with a shared grass-waxy band. The direction and timing of genetic exchange between the two regions could not be ascertained and thus still remains unknown. Microsatellite analysis determined that both Phragmites spp. had a high genetic diversity compared to worldwide lineages. With no evidence of any cryptic invasions of haplotypes from other regions, both Phragmites spp. populations are likely to be native to South Africa. For A. donax all populations across South Africa were determined to be haplotype M1; a cosmopolitan haplotype that has an ancient native range in Afghanistan and Pakistan (Indus Valley). Populations were found to have no genetic diversity and thus can be considered one clone. A pre-introductory survey determined a list of herbivores associated with each tall- statured grass. For A. donax, a total of seven herbivores were found. Of these, one herbivore, a galling wasp, Tetramesa romana Walker (Hymenoptera: Eurytomidae) was found to be highly abundant and widely distributed in South Africa. Tetramesa romana is already a biological control agent in North America and thus is likely exerting some pressure on A. donax populations in South Africa. For both Phragmites spp. a total of ten herbivores were found, although having higher species richness compared to A. donax, when compared to other regions, these native species have a relatively low species richness. Providing baseline data on plant origin, genetic diversity and herbivory on A. donax, P. australis and P. mauritianus has provided important information on managing these species in riparian ecosystems in South Africa. For the Phragmites spp. with no evidence of any cryptic invasions, it is recommended that reed stands continue to be managed as native species. Phragmites spp. are important dominant vegetative species and thus should be protected; however, if reed stands become expansive, control methods can be put in place to focus on managing spread and abundance. For A. donax, this study was able to provide pivotal information in guiding the biological control programme. By determining the ancient lineage of South African populations, research can be focused in this area to find potential biological control agents. Lastly, the pre-introductory survey determined that a biological control agent, T. romana was already established with an unknown introduction and also highlighted potential plant parts that should be targeted. In particular, no rhizome feeding herbivores were found in South Africa and therefore this highlights an important niche that should be explored in biological control agents.
- Full Text:
- Date Issued: 2017
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.
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- Date Issued: 2014
The herbivorous arthropods associated with the invasive alien plant, Arundo donax, and the native analogous plant, Phragmites australis, in the Free State Province, South Africa s
- Authors: Canavan, Kim N , Paterson, Iain D , Hill, Martin P
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406155 , vital:70243 , xlink:href="https://hdl.handle.net/10520/EJC155690"
- Description: The Enemy Release Hypothesis (ERH) predicts that when plant species are introduced outside their native range there is a release from natural enemies resulting in the plants becoming problematic invasive alien species (Lake and Leishman 2004; Puliafico et al. 2008). The release from natural enemies may benefit alien plants more than simply reducing herbivory because, according to the Evolution of Increased Competitive Ability (EICA) hypothesis, without pressure from herbivores more resources that were previously allocated to defence can be allocated to reproduction (Blossey and Notzold 1995). Alien invasive plants are therefore expected to have simpler herbivore communities with fewer specialist herbivores (Frenzel and Brandl 2003; Heleno et al. 2008; Heger and Jeschke 2014).
- Full Text:
- Date Issued: 2014