Understanding and addressing the impact of invasive non-native species in the UK Overseas Territories in the South Atlantic: A review of the potential for biocontrol DEFRA ref: CR 0492 CABI ref: TR10086 Final report

Norbert Maczey, Rob Tanner, Oliver Cheesman and Richard Shaw

December 2012

www.cabi.org KNOWLEDGE FOR LIFE 1

Contents

Executive summary ...... 3

1.1 Background ...... 4

1.2 The South Atlantic UKOTs ...... 4

1.3 Project aims and approach ...... 7

1.4 Biological control of weeds ...... 7

1.5 Biological control of invertebrates ...... 8

2 Methods and project activities ...... 9

2.1 Literature survey and survey of other publicly available sources, species evaluation and project website ...... 9

2.2 Questionnaire, core contacts and stakeholder consultation ...... 9

2.3 Workshop, stakeholder meetings and field site visits on the Falklands and Ascension ...... 10

2.4 Adaptation and implementation of prioritization tool ...... 11

3. Results ...... 14

3.1 Number of assessed species and selection of species for full assessment ...... 14

3.2 Results for individual UKOTs ...... 20

3.2.1 Falkland Islands- Weeds ...... 20

3.2.2 Falkland Islands - Invertebrates ...... 33

3.2.3 South Georgia- Weeds ...... 36

3.2.4 South Georgia - Invertebrates ...... 40

3.2.5 Ascension Island - Weeds ...... 43

3.2.6 Ascension - Invertebrates ...... 57

3.2.7 St. Helena - Weeds ...... 59

3.2.8 St. Helena - Invertebrates ...... 81

3.2.9 Tristan da Cunha - Weeds ...... 88

3.2.10 Tristan da Cunha - Invertebrates ...... 100

Annexes ...... 105

Norbert Maczey Senior Ecologist/Entomologist

CABI Bakeham Lane Egham, Surrey TW20 9TY UK

T: +44 (0) 1491 829029 E: [email protected]

2 Executive summary The DEFRA project CR 0492 has evaluated the potential for classical biological control (CBC) of invasive alien species (terrestrial invertebrates and plants) in the South Atlantic UK Overseas Territories (UKOTs). CBC, the introduction of co-evolved, host specific natural enemies from the target species’ native range, has been utilised for the control of non-native species for over 100 years. The project has been conducted by CABI and administered through the JNCC. It builds on the results of previous work, notably the recently completed South Atlantic Invasive Species (SAIS) project led by the RSPB, complementing strategies and recommendations arising from that project. The main project objectives were to: 1. Assess the potential for CBC of introduced invasive plants on all the South Atlantic UKOTs, using a recently-developed prioritisation tool 2. Conduct a preliminary review of the potential for CBC of invertebrate species prioritised by the SAIS project, using the arthropod biocontrol database held by CABI 3. Use the Falkland Islands and South Georgia as the focus for more detailed assessments (case studies) of priority invasive weeds and invertebrates for which CBC is considered feasible. (This more detailed approach was subsequently extended to Ascension Island).

Individual non–native species were assessed using the method developed by Paynter et al. (2009), which was then modified for application to the South Atlantic UKOTs and further adapted for assessment of invertebrate species. The assessments were based on a review of literature and reports from publicly available sources, and additional information provided by stakeholders involved in conservation on the islands included in this study. Preliminary results were refined through stakeholder workshops and field site visits on the Falkland Islands and Ascension, which also allowed stakeholder attitudes to CBC to be assessed in more detail. A major output of the project was the identification of the highest priority species for which CBC is likely to provide a cost effective and sustainable management option. The case studies for the Falklands, South Georgia and Ascension Island indicate that the following high priority species are particularly suitable for CBC, and recommended for further more detailed assessments:

South Georgia Falklands Ascension Priority weed species - Berberis microphylla Prosopis juliflora Pilosella officinarum Nicotiana glauca Ulex europaeus Argemone mexicana Lantana camara Priority invertebrate - Forficula auricularia Icerya purchasi species

For St. Helena and Tristan da Cunha, a preliminary evaluation of priorities for both non-native plants and terrestrial invertebrates was made without the benefit of field site visits and detailed stakeholder consultations. Consequently, species for which CBC is feasible and recommended are subject to further consideration. Nonetheless, the uptake of CBC measures is provisionally highly recommended for the fast spreading Asparagus densiflorus on St. Helena and the scale insect Pseudococcus viburni currently threatening the endemic gumwood trees on St. Helena.

3 1. Introduction

1.1 Background The UK Overseas Territories (UKOTs) are a diverse and geographically widely-distributed set of small, mostly island, administrations. The two largest regional groupings occur in the Wider Caribbean and the South Atlantic, although UKOTs are also found in the Pacific (Pitcairn Island), the Indian Ocean (British Indian Ocean Territory) and Europe (Gibraltar and the Cyprus Sovereign Base Areas). Collectively, the UKOTs support biodiversity of a much greater global significance than Britain itself, particularly in terms of threatened and endemic taxa (e.g. Pienkowski 2010; Pelembe & Cooper 2011). Despite local capacity constraints, responsibility for environmental policy is largely devolved to UKOT Governments. However, the UK Government is responsible for the UKOTs under international Multilateral Environmental Agreements, such as the Convention on Biological Diversity (CBD), and is committed to supporting environmental protection in the UKOTs, including under a set of bilateral Environment Charters (Defra 2009). Invasive alien species are now widely recognised as one of a group of key, interacting drivers of global biodiversity loss and ecosystem change (e.g. MEA 2005; CBD 2010). Their impacts on the natural environment and human well-being have been particularly severe on islands, and are likely to remain so (e.g. MEA 2005; Wong et al. 2005; CBD 2011). The need to combat invasive species has recently been reinforced under the CBD through the adoption of the Aichi Biodiversity Targets as part of the Strategic Plan for Biodiversity 2011-2020 (e.g. CBD 2011). Aichi Target 9 foresees that: By 2020, invasive alien species and pathways are identified and prioritized, priority species are controlled or eradicated, and measures are in place to manage pathways to prevent their introduction and establishment. Across the UKOTs, invasive species are recognised as a major environmental threat, the management of which poses very serious challenges (e.g. Cheesman et al. 2003; Cheesman & Clubbe 2007; Cheesman & Varnham 2010). Consequently, and given the international commitments noted above, tackling invasive alien species is one of the UK Government’s five strategic priorities for conservation of biodiversity in the UKOTs (Defra 2009). Recently, the relevant information base was greatly enhanced by the collation of records of non-native species of all taxa for the UKOTs, resulting in a report (Varnham 2006) and an accompanying database which was updated in 2009. From a conservation perspective, as on many other islands, much attention in the UKOTs has been devoted to the impact of introduced rodents and other mammalian predators, particularly on bird populations (e.g. Hilton & Cuthbert 2010). Although implementation costs are often high, techniques for the control of such invasive species have been refined in recent years, making eradication of mammalian predators an increasingly realistic proposition. However, different techniques are required for other invasive taxa, including plants and invertebrates. Biological control has a long history of application against agricultural weeds and pests, but is increasingly used against plants and invertebrates that impact primarily on biodiversity and ecosystem function (van Driesche et al. 2010).

1.2 The South Atlantic UKOTs The South Atlantic UKOTs comprise five islands or island groups, extending southwards from Ascension Island (close to the equator, around latitude 8oS) to South Georgia & the South Sandwich Islands (the latter around latitude 58oS). Further south lies British Antarctic Territory (BAT), comprising the Antarctic Peninsula and associated islands. This area, where activities are governed by the Antarctic Treaty System, is not covered by the current project. However, the presence and potential introduction of non-native species are a matter of considerable concern there (e.g. Chown et al. 2012). Brief accounts of the five South Atlantic UKOTs are given below. All are notable breeding centres for seabirds, with some islands supporting colonies that are amongst the most important in the world (e.g. Hilton & Cuthbert 2010). However, each Territory has its own unique features, in terms of landscape and habitats, species-level biodiversity, and human impacts on the environment.

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In the context of invasive species management, the South Atlantic UKOTs have recently benefitted from a major EU-funded initiative, managed by RSPB - the South Atlantic Invasive Species (SAIS) project (SAISP 2010). As well as advancing practical action against a range of invasive species, and contributing to the capacity building required to underpin invasive species management and biosecurity in the Territories, this project generated an extremely useful body of information and a South Atlantic UKOTs Regional Strategy and Action Plan (Shine & Stringer 2010). Unfortunately, since the SAIS project ended, lack of substantial follow-up funding from the EU or other sources has hampered the continuation of a fully co-ordinated, regional programme of work. However, important activities continue at a Territory level, building on SAIS outputs or earlier management plans (e.g. Glass et al. 2006, Pickup 1999, Whitehead 2008) and supported by various conservation bodies and other research institutions, such as RSPB, Royal Botanic Gardens (RBG) Kew and others. Nonetheless, invasive species are still considered to be among the main threats to biodiversity in all of the South Atlantic UKOTs (Pelembe & Cooper 2011). Despite the considerable efforts and achievements of the SAIS project, relatively little attention was given to the prospects for biological control of invasive species that might provide suitable targets, a gap which the current project aims to fill. Indeed, there are relatively few recent examples of biological control being applied against weeds and pests in the South Atlantic UKOTs, particularly for conservation purposes. Notable exceptions include two projects undertaken by CABI in the 1990s. One led to the successful control of the scale insect Orthezia insignis when it was severely threatening endemic gumwood Commidendrum robustum trees on St Helena (see Section 1.3). The other may have contributed to slowing the spread of Mexican thorn Prosopis juliflora, one of the most pernicious invasive weeds on Ascension Island (see Section 3.2.5).

Ascension Island Situated around 1700km from the west coast of Africa in the mid-Atlantic, Ascension Island comprises one main landmass of c.90km2 and a few, small, off-shore islands and stacks. Its relatively recent, volcanic origin is reflected in the “lunar landscape” of the lowland areas, which are naturally barren and punctuated by low hills, lava flows and cinder cones. The main feature at higher altitude is Green Mountain, which is relatively densely vegetated by a mixture of native and non-native plant species. As a relatively young and isolated island, Ascension is not particularly species-rich, but the indigenous flora and fauna support a high proportion of endemic species (e.g. see Ashmole & Ashmole 2000). The island also provides important nesting sites for marine turtles as well as seabirds. The human population of Ascension numbers a just few hundred, mostly local government workers, commercial contractors and military personnel. Nonetheless, there is a very active Conservation Department, and recent conservation successes include the eradication of feral cats as part of an on- going seabird restoration programme.

St Helena Around 1300km to the southeast of Ascension, St Helena comprises a single main island of c.120km2 and a few, small, off-shore islands. Volcanic in origin, but much older than Ascension, St Helena supports a variety of habitats and numerous endemic taxa (e.g. see Ashmole & Ashmole 2000), including around 50 vascular plants and over 400 invertebrates. However, as an important port of call on international trade and other shipping routes for centuries, St Helena has experienced severe habitat degradation (including as a result of non-native species introductions), and many endemic species are under threat. Some 4000 people live on St Helena, a number that has declined in recent years alongside a contraction in the small, local agricultural and horticultural sector. However, the recent approval for construction of an airport may result in a period of relatively rapid development (and increased tourist activity), once access to the island is no longer exclusively by ship.

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The local government has recently restructured its environmental departments, which work closely with the St Helena National Trust, an NGO which co-ordinates a range of conservation projects. Examples include the Millennium Forest initiative, started in 2000, a habitat restoration project centred on the planting of endemic gumwood trees.

Tristan da Cunha Around 2400km south of St Helena, and some 2800km west of South Africa, Tristan da Cunha comprises a very remote, dispersed archipelago of four islands or small island groups: Tristan itself, Nightingale, Inaccessible and Gough (the last two being designated collectively as a World Heritage Site). There are a range of endemic species including, for example, 34 vascular plants and 20 ferns, although some taxa (including many invertebrate groups) are incompletely documented. The population of less than 300 people (one of the most isolated communities in the world) is confined to the c.95km2 main island, which is accessible only by ship. Partly as a consequence of this, small- scale agriculture and horticulture are important local activities. The small local Conservation Department, with support from RSPB in particular, is engaged in a range of environmental monitoring and protection activities. The control of introduced rodents on Gough is increasingly seen as an international conservation priority.

Falkland Islands Lying around 600km east of the southern extreme of South America, the Falklands comprise a quite extensive and complex archipelago of two main islands and over 700 smaller islands and islets, covering around 12,000km2 in total. Endemic taxa identified from the islands include 14 vascular plant species. Around 3000 people live on the Falkland Islands, mostly on East Falkland, in the capital (Stanley) or the military base at Mount Pleasant, although others are distributed across various small farming settlements. Livestock rearing is an important aspect of the local economy, alongside fisheries and an expanding tourist sector based on cruise ships. The Falkland Islands Government’s Environmental Planning Department works in partnership with various local NGOs, notably Falklands Conservation, on a range of environmental initiatives.

South Georgia & the South Sandwich Islands Located around 1400km east of the Falkland Islands, South Georgia comprises a main island of c.3750km2 and numerous, small off-shore islands. The South Sandwich Islands form an archipelago some 500km further southeast.

Once an important centre for whaling, South Georgia has no permanent resident population as such, but is home to a small number of official staff and research scientists, and attracts visits from tourists undertaking Antarctic cruises. Half of the main island is under permanent ice and snow cover, and the local flora is dominated by bryophytes and lichens. The Government of South Georgia & the South Sandwich Islands is based in the Falkland Islands. An Environmental Officer works with NGOs, notably the South Georgia Heritage Trust, on a range of environmental initiatives. These currently include measures to eliminate all non-native vertebrates (including rats and reindeer) from South Georgia. All consignments of goods entering South Georgia must pass through a recently constructed biosecurity facility.

6 1.3 Project aims and approach A major component of this study is a desk-based review assessing the impact of non-native plant and invertebrate species in the South Atlantic UKOTs. We rank the need and suitability for biological control of individual invasive species, from high to low, using a recently-developed weed biocontrol prioritisation tool (Paynter et al 2009), developed initially for Australia, but already proving to be very useful on the islands in the South Pacific (Paynter 2010). Priority species are selected based on their population dynamics, reported impact on biodiversity, impact on livelihoods, the costs of on-going control by other means, and other criteria. At the outset of the project, it was planned that two detailed case studies would evaluate the potential of implementing a biological control programme against priority species for the Falklands and South Georgia in particular. An additional stopover visit, including field site visits and stakeholder consultations, allowed this approach to be extended to include Ascension Island as well. These detailed assessments combine all current information about the target pest species, including information on their native range, areas of introduction and recorded natural enemies in their areas of origin. Ranked in order of priority, and underpinned with the more detailed information from the case studies, detailed recommendations are given for each priority target species. During field site visits to the Falkland Islands and Ascension Island, dialogue with stakeholders allowed local attitudes towards biological control to be assessed. We hoped to underpin this part of the feasibility study through a questionnaire completed by stakeholders, including on the Territories that were not featured in the detailed case studies. However, the response to this approach was disappointing, and direct dialogue quickly turned out to be a far better way to assess stakeholder’s attitudes. In addition, the need for pilot projects to demonstrate the benefits of effective weed management on associated trophic levels were assessed for the Falkland Islands, South Georgia and Ascension Island. This included appraisal of needs for information and training materials amongst land managers, particularly with respect to actions required to restore habitats after successful biological control of target species.

1.4 Biological control of weeds A major focus of this study is the assessment of invasive weeds on all South Atlantic UKOTs, as these are often the most numerous, widespread and damaging introduced non-native species, with the potential significantly to alter whole ecosystems. Mechanical or chemical methods often fail to effect persistent control (needing to be repeatedly applied throughout seasons and year-on-year), and may not be feasible owing to the extent or location of populations of the target species. Consequently, biological control is often the only available practical and economically feasible option. It can be applied over a large geographical area, and impacts very little on the environment, in contrast to the disturbance caused by manual or other mechanical clearing, or the application of herbicides. When successful, biological control is permanent and self-sustaining (Wittenberg & Cock 2001). On average, more than 75% of target weeds have been significantly or permanently controlled using biocontrol in the past century. Success rates range from 50% to 87% depending heavily on the amount of effort and funding applied to required research (Myers & Bazely 2003, McFadyen 1998, Hoffmann 1995, Fowler et al. 2000). A recent meta-analysis has demonstrated the positive impacts of classical biocontrol and, in particular, its positive impact on the re-establishment of native plants in a broad range of systems (Clewley et al., in press). Integrated biological control can be regarded as a very safe and cost efficient method, provided that adequate risk assessment procedures and current protocols such as the International Plant Protection Convention's Code of Conduct for the Import and Release of Exotic Biological Control Agents (IPPC 1996, 2006) are followed. Possible non-target effects are predictable and can be avoided by application of the safety-testing methods that are now routinely carried out under biological control programmes (Pemberton 2000). However, we also recognise that the introduction of a biocontrol agent without considering potential conflicts of interest is unwise and ultimately unproductive. Hence the consideration of attitudes to

7 invasive species and biological control as an important part of the detailed feasibility assessments conducted for the Falklands Islands, South Georgia and Ascension. This project started with a desk-based review, for which results of the recently completed, EU-funded South Atlantic Invasive Species Project (SAISP 2010) provided particularly useful baseline information. In addition, CABI has collated information on the impacts of non-native plants and invertebrates using literature reviews and current relevant databases and combined this with the results of other recent surveys and reviews. Based on this information, non-native species recorded from the South Atlantic UKOTs were ranked, to form a list of potential priorities for future biological control programmes using the weed biocontrol prioritisation tool developed by Paynter et al. (2009). This incorporates many factors associated with weed biocontrol, and produces an overall prioritisation score to aid decision makers in the allocation of limited resources, based on the scale of the species’ impacts and the likelihood of achieving successful management of the problem through a biological control programme. Such factors include:

• Is opposition to biological control likely? • Does the weed species have socioeconomic value? • Is the weed sufficiently widespread/intractable/important to justify investment in biological control? • Has the weed been/is it the subject of adequately resourced biological control programmes elsewhere? • What is the accessibility and ease of working in its native range? • Is literature available regarding natural enemies; is it well known/accessible? • How closely related to indigenous/valued plants is the target weed? • Which habitats are invaded? • Is it growing in competitive environment (agricultural vs. environmental)? • Is it a native/valued exotic congener?

After eradication of an invasive plant, habitat management is essential to aid restoration of the area to its former state. Invasive plants can impact on the soil microbial community, including by adversely affecting fungi beneficial to native species. As a result, native plant species can struggle to recolonise invaded areas. To address this aspect of weed control, where appropriate, CABI included the potential for integrated approaches into recommendations for the control of individual species for the Falkland Islands, South Georgia and Ascension. This can, in some cases, include future efforts to evaluate the ecology of native and introduced plants in trial sites, in order to deliver the best management practices and remedial actions to support native plant restoration.

1.5 Biological control of invertebrates Introduced invertebrates can cause widespread and serious problems on islands, including threats to indigenous biodiversity, reduced agricultural productivity, and direct impacts on human health and quality of life. For example, on St Helena, the introduced ensign scale Orthezia insignis not only threatened many horticultural plants but was severely damaging (and in many cases killing) the national tree, the endemic gumwood Commidendrum robustum (Asteraceae). Thankfully, the specialist coccinellid beetle Hyperaspis pantherina had been used successfully against this pest elsewhere in the world and CABI was able to facilitate its introduction to St Helena in the 1990s. This action is believed to have saved the tree from extinction (Booth et al. 1995, 2001; Fowler 1996, 2004). Under the current project, the feasibility of biological control against introduced invasive terrestrial invertebrates was assessed in the same way as for non-native weeds, and only small adaptations to the prioritisation tool were required. Although the in-depth data for many non-native invertebrates in the UKOTs is patchy, a good preliminary list exists in most cases. Also, CABI holds an extensive database (BIOCAT 2010) on previous insect biocontrol activities around the globe, and this was used to determine whether key invertebrate pests in the South Atlantic UKOTs had historically been subject to attention elsewhere. Target species were again prioritised based on the severity of their impacts and the likelihood of successful management using biological control.

8 2 Methods and project activities

2.1 Literature survey and survey of other publicly available sources, species evaluation and project website The available literature and reports from publicly available sources (as well as a number of unpublished documents) have been reviewed, and a full list of references is given in Annex 4. The surveyed literature has provided the required background data, against which an evaluation of the environmental impacts of target species has been conducted. Aside from some recent action plans and risk assessments, two particularly important sources of information on the current status of non- native species in the South Atlantic UKOTs have been included. These are the ’2009 UKOT/CD non- native database’ compiled by Karen Varnham (initially in 2005, then updated in 2009) and made available on-line by JNCC, and the various annexes to the recent report of the SAIS Project (SAISP 2010) kindly provided by RSPB. In addition to new data collected through field surveys under the SAIS Project, these resources draw together an extensive body of information from previous publications. Major sources of information on the current status of biological control of the species assessed have been the ‘CABI Invasive Species Compendium’ (CABI ISC 2012) and the ‘Global Invasive Species Database’ (GISD 2012), both publicly available online resources. Another important source of information has been the so far unpublished ‘BIOCAT’ database (2010) held by CABI, which includes extensive historical information on previous and on-going biocontrol projects using invertebrates.

2.2 Questionnaire, core contacts and stakeholder consultation At the outset of the project, a group of 23 core contacts was identified, encompassing relevant parties (environmental officers, etc.) within the governments of the five South Atlantic UKOTs, key local and international NGOs, cross-Territory bodies and individual specialists. An introductory e-mail was sent to each of these contacts, explaining the aims and approach of the project, seeking their engagement and inviting participation in on-going discussions. In particular, contacts were encouraged to distribute information about the project to other interested parties within their respective organisations, local communities and stakeholders on the islands in question (where contacts were based in-Territory) and to the wider scientific community. Dialogue was maintained with core contacts who responded directly to the introductory e-mail. In addition, regular project updates were disseminated via meetings of the Southern Oceans Working Group (SOWG) of the UK Overseas Territories Conservation Forum (UKOTCF) during 2011 and 2012. Core contacts and/or other representatives of their respective organisations are members of this Group, which also encompasses a wider set of contacts with interests in conservation in the South Atlantic UKOTs. To provide a focus for broader awareness-raising of the project, a dedicated webpage was established (http://www.cabi.org/Default.aspx?site=170&page=4330). This outlined the rationale for exploring the potential of biological control against invasive species in the South Atlantic UKOTs, detailed the aims and approach of the project, and provided contact details for those wishing to engage with the project team. In order to seek views on invasive species issues as they affected the five South Atlantic UKOTs, and (in particular) to examine attitudes to biological control, an on-line questionnaire was established on the Surveymonkey platform. Core contacts were asked to raise awareness of the questionnaire, particularly within the UKOTs concerned, resulting in announcements being distributed through local media, e.g. Penguin News (Falkland Islands) and The St Helena Independent. A link to the questionnaire was made available on the project webpage. Unfortunately, despite these efforts, the number of completed returns was low. This is not unusual when attempting to gather views using a questionnaire-based approach, and some useful information was obtained nonetheless (see below).

9 In order to compensate for the low rate of questionnaire returns, telephone interviews were considered. However, while evaluating the logistics of telephone interviews with stakeholders, it was decided that a better approach would be to hold these interviews in person during site visit to the Falklands and Ascension in March 2012 (see Section 2.3). This enabled engagement not only with local conservation scientists and officials, but also with land managers who were directly affected by invasive plant and invertebrate species. In addition, in the Falklands, face-to-face interviews were conducted with a number of Stanley residents regarding the impact of the European earwig. In total, five specific questionnaire responses were received from the Falkland Islands, one from Tristan da Cunha, two from St Helena and two where the respondent referred to more than one UKOT. With such low return rates, feedback cannot be regarded as representative of the collective views of stakeholders or the wider community within or across Territories. However, all of the questionnaire respondents considered that invasive non-native species were having a direct negative impact on the UKOTs concerned. Impacts spanned across all sectors, including agriculture, conservation, tourism and local infrastructure. The majority of the specific information provided on invasive species locally came from representatives of relevant government departments and NGOs working within the Territories. Most of the questionnaire respondents acknowledged the potential of biological control as a management tool for invasive weeds and invertebrates, and agreed that it should be considered as part of an integrated approach to invasive species management. However, most highlighted that further information would be beneficial, to aid decision making. Potentially, as with other information on invasive species, a straightforward introduction to biological control, alongside a more detailed analysis of the costs and benefits of this approach in particular cases, could be disseminated via government departments and NGOs to a wide audience.

2.3 Workshop, stakeholder meetings and field site visits on the Falklands and Ascension Falklands The CABI team (Rob Tanner, Norbert Maczey) visited the Falkland Islands from the 17th to the 27th of March 2012. Amongst others, Nick Rendell (Environmental Officer, Environmental Planning Department, FIG), Martin Collins (Chief Executive & Director of Fisheries, GoSG) and Richard McKee (Executive Officer GoSG) were particular helpful with co-ordination during the run-up to this visit, and in providing logistic support during the visit. A one day workshop was held at the Chamber of Commerce meeting room in Stanley on the 20th of March 2012. Stakeholders with a known interest in the uptake of biological control in the Falklands or South Georgia were invited directly via e-mail, and provided with background information including preliminary results of the study. In addition, an open invitation was published in the local Stanley newspaper Penguin News. Sixteen people attended the workshop itself and additional meetings with stakeholders unable to attend on the 20th were held in the days after the workshop. The workshop programme covered a range of objectives: • To provide an introduction to biological control • To emphasise the importance of stakeholder acceptance • To explain methods used to assess feasibility of individual species for biological control • To present preliminarily results of the study for Falklands and South Georgia • To compare the outputs of the prioritization analysis to the actual experience of stakeholders on the islands • To discuss future research on priority species for biological control

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During a number of smaller meetings at the government facilities of the Falklands and South Georgia, including a short presentation to a meeting of the ‘Environment Committee’, biological control options for invasive species based on the results of the workshops were discussed in more detail. The outcomes of the workshop were also presented during two short interviews for Falkland Islands TV (FITV) and the Stanley radio station. Field site visits to areas worst impacted by invasive weeds included a visit to Port Stephens (infestation with Pilosella officinalis) and Port Sussex (infestation of Berberis microphylla). The overall benefits of the visit to the Falkland Islands can be divided into two broad areas. Firstly, during evidence-based discussions, a substantial degree of scepticism could be addressed and stakeholders became more receptive to the idea of future biological control projects. As a direct consequence of this, the process of putting forward a package of more detailed information on the prospects for control of European earwigs and Calafate has been initiated, with the intention of developing full project proposals. In addition, a collaboration looking into the possibilities of biological control of Mouse-eared Hawkweed has been established between the FIG, Kew and CABI. The second area where the field site visits and stakeholder consultation proved to be absolutely vital was in the updating of information on individual invasive species. This allowed preliminary results from the ‘Paynter’ tool analysis (based on publications and grey literature) to be refined, leading to adjustments of the initial priority setting, as reflected in the results for the Falklands and South Georgia presented below.

Ascension Island In collaboration with the Ascension Island Government (AIG) Conservation Office, a stopover visit to Ascension was arranged for the 27th – 30th March 2012, on the return journey from the Falklands. Particular thanks are due to Stedson Stroud (AIG Conservation Officer) and Jolene Sim (AIG Assistant Conservation Officer) for their support in making this possible. The programme for the visit included introductory meetings with Stedson Stroud, Miles Miller (AIG Director of Operations) and Colin Wells (Ascension Island Administrator). These were followed by a meeting with stakeholders from local organisations (AIG, CSR [Computer Sciences Raytheon], Babcock, IDL [Interserve Defence Limited], Serco, CSO [Composite Signals Organisation], C&W [Cable & Wireless]), to address the same objectives as the stakeholder meeting in the Falklands. In addition, a presentation was given and discussions held on the subject of invasive species and the principles of biological control at the local school in Two Boats village. After the stakeholder meeting, field site visits were conducted to areas worst impacted by invasive weeds, including to observe any on-going biological control (Prosopis, Opuntia). Benefits of the visit to Ascension Island were similar to those arising from the visit to the Falklands. Again, evidence-based discussions were able to dispel much scepticism over biological control. As a direct consequence, concepts for the enhanced control of Mexican Thorn and the control of Wild Tobacco were developed and forwarded to the AIG for consideration. In addition, an article on future biological control on Ascension based on this visit was published in Ascension Island Conservation Quarterly Issue 38 (http://www.conservation-ascension-island.gov.ac/conservation-quarterly-issue-38). Also as in the Falklands, the visit allowed for refinement of preliminary results from the desk-based study, in particular via the updating of information on individual invasive species, both through stakeholder discussions and field site visits. This refinement is reflected in the results for Ascension presented further below.

2.4 Adaptation and implementation of prioritization tool In this study, we use Paynter et al. (2009) as a tool to assess the feasibility for biological control of weeds and invertebrates on the South Atlantic UKOTs. An example of the assessment framework,

11 based on three component modules, is given in Annex 1. Paynter et al. (2009) use a scoring system widely established in Australia through their Weeds of National Significance (WoNS) system. A comparable system for the UKOTs does not yet exist. The scoring system developed by Whitebread (2008) for the Falkland Islands assesses the risk of invasiveness but not the actual impact, and therefore cannot be used for an accurate adjustment of the Paynter method. The development of impact assessment systems comparable to WoNS in Australia is complex and relies on the accumulation of a large body of data by many experts over a long period, to establish the necessary background information. As a workable substitute, we developed a slightly simplified approach, which still allows the accurate ranking of priority species feasible for biological control, based on the following adjustments within the three main modules of the Paynter tool:

Module 1: Weed importance and desirability of biocontrol Based on the information available from the SAIS project, the JNCC database and additional literature covering reported impacts of relevant species in other countries, we adopted the scoring system described in Table 1 to estimate weed importance under Question 6:

Table 1: Factors determining whether a species is sufficiently widespread/intractable/important to justify investment in biocontrol. Score if question Question is answered with yes Is the species only recently introduced/recorded on the island(s)? 5 (0-no, or no data available; 5-yes) Does the species currently have a widespread recorded distribution on the island(s)? 5 (0-no, or no data available; 5-yes) Is the species currently expanding its range on the island(s)? 5 (0-no, or no data available; 5-yes) Is the species known to be invasive in other geographical regions? 5 (0-no, or no data available; 5-yes) Is the species known to have negative impacts on biodiversity in other geographical regions? 5 (0-no, or no data available; 5-yes) Is the species known to cause economic damage in other geographical regions? 5 (0-no, or no data available; 5-yes) Is the species known to cause threats to human or animal health in other geographical regions? 5 (0-no, or no data available; 5-yes) Are habitats on the island(s) which can potentially be invaded of conservation importance? 5 (0-no, or no data available; 5-yes) Does the SAIS assessment suggest a likely negative impact on biodiversity, agriculture or health? 5 (0-no; 5-yes) Have ecological impacts been recorded on the island(s) for this species? 10 (0-no; 10-yes) Have economic impacts (agriculture and others) been recorded on the island(s) for this species? 10 (0-no; 10-yes) Have impacts on human or animal health recorded on the island(s) for this species? 10 (0-no; 10-yes)

Only species scoring at least 20 using this modified assessment were considered suitable targets for biocontrol and further assessed. One additional option would have been to consider aspects of current

12 control methods in the above, something that Paynter et al. (2009) have suggested themselves as a possible refinement of their method as applied to Australian weeds. However, the acquisition of such information for each species turned out to be beyond the scope of this project. It may also have been appropriate to place greater emphasis on public perception, as a nuisance species might have more support for biocontrol than one actually causing economic or ecological harm.

Module 2: Effort required to obtain and host-range test biocontrol agents We kept this this module unchanged. Paynter et al. (2009) give a minimum score for each question in this module, because (even where successful biological control programmes against a weed exist elsewhere) the unique flora of Australia means that a certain amount of additional testing is required. We most likely can assume this also for the South Atlantic UKOTs. Due to their unique indigenous flora, similar efforts for host-range testing to those required in Australia can be assumed.

Module 3: Predicting the potential impact of biocontrol Again, we kept this this module unchanged. There was the option to apply different weightings for Questions 9-14. Since the weightings within Paynter et al. (2009) are based on large combined data sets from Australia, South Africa and North America, one can assume that no other, better datasets exist, which could provide weightings more suited to the flora of the South Atlantic UKOTs.

Adaptation for invasive alien invertebrate species We used a similar approach as for weed species. The only difference being the deletion of Questions 9-11 within Module 3. These questions are not suitable for invertebrates, and no datasets exists to provide equivalent questions with a corresponding weighting system. We did, however, add one new question: Asking whether biological control programmes have been conducted (successfully or unsuccessfully) for closely related species. Information derived from such programmes might increase the probability of successful control efforts against the species being assessed. If no biological control of even related species had been recorded, then the species was regarded as currently unsuitable for biological control.

13 3. Results

3.1 Number of assessed species and selection of species for full assessment According to the available sources of information, the following numbers of weed and invertebrate species have been recorded at some stage as introduced and naturalized (or at least showing a high potential for spread beyond deliberate cultivation) on the five target islands/island groups:

• Falklands: invertebrates (15); plants (261) • South Georgia: invertebrates (30); plants (36) • St Helena: invertebrates (175); plants (392) • Ascension: invertebrates (68); plants (414) • Tristan: invertebrates (111); plants (138)

All these non-native species were put through Module 1 of the evaluation process, to assess their current level of impact and the desirability of biological control. Only species scoring at least 20 were considered further, with an assessment of the feasibility of biological control conducted using Modules 2 and 3. The proportion of species scoring at least 20 owing to their impact is given for each UKOT in Figures 1 and 2 below. A summary and a list of individual species scoring at least 20 is given for each Territory in Tables 2 and 3.

14 Weeds on South Georgia Weeds on Falklands

32; 8; 22% 12%

28; 78% 229; 88%

Weeds on Ascension Weeds on St Helena

42; 9% 61; 15%

335; 85% 403; 91%

Weeds on Tristan number of recorded alien plant species with impact score <20

number of alien plant species with impact scoring ≥20; justifying feasibility assessment for BC

47; 34%

91; 66%

Figure 1: Number and proportion of non-native plant species with an impact score justifying further feasibility assessment for biological control.

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Non-native invertebrates on South Non‐native invertebrates on Falklands Georgia

6; 20% 4; 27%

24; 80% 11; 73%

Non‐native invertebrates on Ascension Non‐native invertebrates on St Helena

9; 13% 24; 14%

59; 87% 151; 86%

Non‐native invertebrates on Tristan number of recorded alien invertebrate taxa with impact 5; 5% score <20

number of alien invertebrate taxa with impact scoring ≥20; justifying feasibility assessment for BC

106; 95%

Figure 2: Number and proportion of invertebrate species with an impact score justifying further feasibility assessment for biological control.

16 Table 2: Numbers of assessed plant species and alien invasive plant species with impact scores of 20 or higher

Summary: South Georgia Falklands Ascension St Helena Tristan assessed non‐native 36 261 414 392 138 plant species taxa scoring ≥20 8 32 41 61 47

Individual scores: South Georgia • Casuarina equisetifolia 25 • Chenopodium murale 25 • Agrostis capillaris syn. tenuis 40 • Clidemia hirta 20 • Cardamine glaclalis 30 • Commelina diffusa 30 • Cerastium fontanum 20 • Conyza bonariensis 25 • Poa annua 25 • Cynodon dactylon 30 • Poa pratensis 25 • Digitaria ciliaris/ sanguinalis 25 • Ranunculus repens 35 • Eleusine indica 20 • Rumex acetosella 35 • Euphorbia hirta 30 • Taraxacum officinale 30 • Heliotropium curassavicum 40 • Juniperus bermudiana 25 Falkland Islands • Lantana camara 45 • Leucaena leucocephala 25 • Ammophila arenaria 45 • Melinis minutiflora 30 • Atriplex patula 20 • Nicotiana glauca 50 • Berberis microphylla 30 • Paspalum scrobiculatum 30 • Calluna vulgaris 25 • Pennisetum clandestinum 35 • Cerastium fontanum ssp. vulgare 20 • Pennisetum macrourum 35 • Cirsium arvense 35 • Piper aduncum 30 • Cirsium vulgare 40 • Plantago lanceolata 25 • Cytisus scoparius 20 • Prosopis juliflora 55 • Equisetum arvense 25 • Psidium guajava 40 • Hedera helix 25 • Ricinus communis 25 • Lupinus arboreus 30 • Rubus pinnatus 30 • Myosotis discolor 20 • Rubus rosifolius/nanus 35 • Pilosella aurantiaca 25 • Setaria verticillata 25 • Pilosella officinarum 35 • Solanum nigrum 30 • Plantago lanceolata 30 • Sonchus asper 25 • Poa annua 20 • Sonchus oleraceus 20 • Poa pratensis 20 • Tecoma stans 30 • Poa trivialis 20 • Vitex trifolia 20 • Rosa canina 20 • Waltheria indica 20 • Rosa rugosa 20 • Rumex crispus 35 St. Helena • Rumex obtusifolius 35 • Sedum acre 25 • Acacia cyclops 20 • Senecio squalidus 30 • Acacia longifolia 25 • Senecio sylvaticus 20 • Acacia mearnsii 25 • Senecio vulgaris 30 • Acacia melanoxylon 25 • Sonchus asper 30 • Ageratum conyzoides 25 • Sonchus oleraceus 20 • Alpinia zerumbet 25 • Stellaria media 20 • Anredera cordifolia 25 • Taraxacum officinale 25 • Argemone mexicana 25 • Ulex europaeus 45 • Arundo donax 40 • Asparagus asparagoides 40 Ascension Island • Asparagus densiflorus 30 • Austroeupatorium inulaefolium 30 • Acacia farnesiana 20 • Bidens pilosa 25 • Adiantum raddianum/ capillus-veneris 30 • Buddleja madagascariensis 20 • Ageratum conyzoides 30 • Carpobrotus edulis 40 • Alpinia zerumbet 35 • Chrysanthemoides monilifera 30 • Argemone mexicana 30 • Cynodon dactylon 30 • Begonia hirtella 30 • Cyperus rotundus 30 • Borreria verticillata 30 • Digitaria ciliaris 30 • Buddleja madagascariensis 20 • Eleusine indica 30

17 • Furcraea foetida 20 • Agrostis tenuis . 40 • Hedychium coronarium 25 • Centella asiatica 35 • Ipomoea indica 30 • Conyza sumatrensis 35 • Juncus capillaceus 20 • Coronopus didymus 25 • Juncus tenuis 30 • Crepis capillaris 20 • Kalanchoe delagoensis 25 • Cynodon dactylon 25 • Kalanchoe pinnata 30 • Cyperus esculentus 40 • Lantana camara 35 • Euphorbia peplus 30 • Leucaena leucocephala 45 • Gnaphalium luteo- album 25 • Lonicera japonica 25 • Gnaphalium purpureum 25 • Nicotiana glauca 20 • Holcus lanatus 25 • Olea europaea ssp. africana 35 • Juncus effusus 20 • Opuntia ficus-indica 25 • Juncus tenuis 35 • Opuntia stricta var. dillenii ) 35 • Leucanthemum vulgare 20 • Oxalis pes-caprae 25 • Mariscus congestus 35 • Panicum maximum 30 • Oenothera glazioviana 25 • Paspalum scrobiculatum 25 • Oxalis corniculata 20 • Pennisetum clandestinum 35 • Paspalum dilatatum 30 • Pennisetum macrourum 35 • Paspalum notatum 25 • Pennisetum setaceum 25 • Pennisetum clandestinum 40 • Phormium tenax 30 • Plantago lanceolata 30 • Physalis peruviana 20 • Poa annua 35 • Pinus pinaster 20 • Poa humilis 20 • Plantago major 20 • Poa pratensis 25 • Poa annua 20 • Poa trivialis 20 • Poa pratensis 20 • Polycarpon tetraphyllum . 30 • Populus alba 25 • Prunella vulgaris 20 • Psidium guajava 30 • Rubus loganobaccus 20 • Rubus pinnatus 25 • Rumex acetosella 40 • Rubus rosifolius 25 • Rumex obtusifolius 40 • Schinus molle 25 • Sagina procumbens 35 • Schinus terebinthifolius 25 • Senecio pterophorus 30 • Setaria verticillata 20 • Senecio vulgaris 20 • Solanum mauritianum 25 • Solanum nigrum 30 • Sonchus asper 20 • Sonchus asper 40 • Sonchus oleraceus 30 • Sonchus oleraceus 30 • Sporobolus africanus 40 • Sporobolus africanus 30 • Tagetes minuta 20 • Taraxacum officinale 35 • Tecoma stans 30 • Trifolium cernuum 20 • Ulex europaeus 35 • Trifolium dubium 20 • Watsonia borbonica 20 • Trifolium glomeratum 20 • Trifolium micranthum 20 Tristan da Cunha • Vellereophyton dealbatum t 20 • Veronica serpyllifolia 20 • Agrostis castellana 20 • Vulpia bromoides 20 • Agrostis stolonifera 40

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Table 3: Assessed invertebrate species, alien invasive invertebrate species with impact scores of 20 or higher

Summary: South Georgia Falklands Ascension St Helena Tristan assessed non‐native 30 15 68 175 111 invertebrate species taxa scoring ≥20 6 4 9 24 5

Individual scores:

South Georgia • Ceratitis capitata 30 • Aptinothrips stylifer 20 • Cosmopolites sordidus 20 • Calliphora vicina 30 • Cryptotermes brevis 20 • Dendrodrilus rubidus 20 • Dysdera crocota 30 • Oopterus soledadinus 20 • Galleria mellonella 25 • Scatopse notata 20 • Helix aspersa 30 • Trechisibus antarcticus 25 • Herpetogramma licarsisalis 30 • Heteronychus arator 30 Falklands • Heterotermes perfidus 40 • Linepithema humile 20 • Forficula auricularia 40 • Lucilia sericata 20 • Lucilia sericata 35 • Musca domestica 20 • Protophormia terraenovae 35 • Paratrechina bourbonica 20 • Tenuiphantes tenuis 20 • Paratrechina longicornis 25 Ascension • Pheidole megacephala 30 • Phthorimaea operculella 20 • Cryptophlebia leucotreta 25 • Plutella xylostella 20 • Cryptotermes brevis 20 • Pseudococcus viburni 35 • Erechthias minuscula 20 • Scolopendra morsitans 25 • Icerya purchasi 35 • Stegobium paniceum 20 • Musca domestica 20 • Stomoxys calcitrans 30 • Paratrechina longicornis 25 • Trioza erytreae 20 • Periplaneta americana 30 • Vespula vulgaris 35 • Pheidole megacephala 30 • Scolopendra morsitans 25 Tristan da Cunha

St Helena • Dendrodrilus rubidus 20 • Deroceras reticulatum 20 • Acanthoscelides obtectus 20 • Lehmannia valentiana 30 • Adoretus versutus 30 • Lumbricus rubellus 20 • Brevicoryne brassicae 25 • Milax gagetes 25 • Porcellio scaber 25

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3.2 Results for individual UKOTs Sections below for each Territory are separated into weeds and invertebrates. Only species with an impact factor of 20 and above are discussed in detail. As a cut-off point below which we regard biological control not to be feasible, we have chosen an overall score of 50. However, a high overall score for a species does not automatically result in an immediate recommendation for biological control. This needs to be considered in more detail on a case-by-case basis, taking additional factors such other control options and costs versus benefits into account. Equally, in a number of cases, field site visits and direct stakeholder consultations have provided additional information that needs to be considered in tandem with the overall score generated by the modified Paynter tool. As such, recommendations for St. Helena and Tristan da Cunha, where such stakeholder consultations and visits were not part of the current project, should be considered preliminary.

3.2.1 Falkland Islands- Weeds Thirty one non-native plant species had an initial impact score of 20 or above and were evaluated further with the prioritisation tool. Results of the full assessment are given in Table 4. Ulex europaeus, Cytisus scoparius and Calluna vulgaris all achieved an overall score higher than 300, suggesting that these species are very suitable candidates for classical biological control. Indeed, all three species have been the subject of biological control programmes in other geographical regions. Hence, ‘off-the- shelf’ biocontrol agents would be available, significantly reducing the costs of implementing programmes against these species on the Falkland Islands. However, Ulex europaeus is regarded as having substantial benefits to the Falklands, notably providing shelter for farming purposes. In addition, over a long period, Gorse has acquired significant cultural and ornamental value. Therefore, with regards to the potential control of this species, a detailed cost-benefit analysis and careful stakeholder consultations are required to determine the balance between perceived value and any negative impacts this species has. Of the three species scoring highest, Cytisus scoparius currently shows a very low tendency for naturalisation or spread beyond gardens; stakeholder consultation therefore gave this species a low priority for biological control. One species initially scoring relatively highly (based on available data at the time) was Senecio jacobea. However, recent surveys indicate that this species does not grow on the Falklands anymore, making control efforts of any kind somewhat obsolete. For some species, readily available biological control agents have been tested but not proven to be effective, or are only partially effective. To this group of species, which are generally difficult to manage with biological control, belong Cirsium vulgare and C. arvense. Some potentially effective control agents are not host specific enough to be released in countries with native thistles, but may turn out to provide suitable options for the Falklands, where no native close relatives exist. Equally, research into these two species is still on-going with regards to alternative control agents, which may become available in the near future. For some species, no biological control agents have been tested and proven to be effective as yet, but research efforts are on-going as these species cause severe problems in other geographical regions. This group includes Pilosella aurantiaca, Pilosella officinarum and Sonchus asper. For these species, suitable agents may become available in the near future. In particular, the implementation of control measures against P. officinarum may be able slow down further spread and contain negative impacts caused by this species (see details below). Alternatively, independently funded scoping studies and host-range testing could be initiated for the Falklands. Such larger scale projects need, of course, to be considered carefully in relation to the current or imminent threats these species pose to indigenous species and habitats. Berberis microphylla generated a relatively low score, principally because biological control has never previously been undertaken for this species. However, it is a weed of great concern in the Falklands, due to a recently substantially increased rate of spread, potentially substantial threats to the environment and wool production, and the difficulty of control by chemical or mechanical means.

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Based on this, we highly recommend the initiation of scoping studies, surveying suitable biological control agents for Calafate as soon as possible. Although they generated relatively low overall scores, it may be worth further exploration of the potential of biological control of Rumex crispus and Rumex obtusifolius. Both species have been the subject of research into the potential for biological control, but as yet little is known about the efficacy of control agents studied so far. However, with the ease of working in the native range, and only one closely related species (Rumex magellanicus) being native to the islands, biocontrol may be an option in the future if the impact of the species is considered high and initial tests would confirm a good host specificity safeguarding the native congener. Ammophila arenaria, Lupinus arboreus and Equisetum arvense belong to a group for which there is no (or only a limited) history of biological control elsewhere. Initiating new control projects would be costly compared to ‘off the shelf’ solutions and would need to be justified on a case-by-case basis, according to the scale of current and expected impacts. We currently regard the impact of these species on the indigenous biodiversity of the Falklands as too low to justify the implementation of full scale biological control projects. However, this preliminary judgement may turn out to be unjustified for some of these species and remains open for reassessment at any time. This is also true for a number of other species such as Hedera helix, Myosotis discolour, Bellis perennis, Atriplex patula, Sonchus oleraceus, Sedum acre, Senecio squalidus, Plantago major or Senecio sylvaticus. These all have an overall score below 50, which does not suggest that research into biological control is warranted. The feasibility of biological control against all species with a high impact score is described in Table 3, where species are considered in order of their overall assessment score. However, this is not the actual priority order of species for biological control. Based on stakeholder consultation, and taking all other available information into account, biological control is currently most strongly recommended for the following three species (in order of priority):

1. Calafate (Berberis microphylla) 2. Mouse-eared Hawkweed (Pilosella officinarum) 3. Gorse (Ulex europaeus)

In addition, current control efforts against Cirsium vulgare are likely to benefit from reinforcement by additional biological control measures.

Table 4: Assessment of non-native plant species on the Falkland Islands for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol x TOTAL BIOCONTROL FEASIBILITY EFFORT IMPACT Ulex europaeus Fabaceae 45 5 100 900.0

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BC feasible: Yes Ulex europaeus has a long history as a target of classical biological control, mainly from programmes conducted in New Zealand and Australia (CABI ISC 2012). The gorse seed weevil Exapion ulicis was the first biological control agent used against U. europaeus. Introduced to New Zealand in 1931, it was widely established by 1935 and has destroyed approximately 35% of the seed crop annually since then (Miller 1970; Cowley 1983). A further six control agents have been introduced to New Zealand (Hill et al. 2000). The gorse spider mite Tetranychus lintearius was introduced in 1989 and it has become widely established (Hill et al. 1993). The thrips Sericothrips staphylinus was released in New Zealand in 1990 and is spreading slowly (Hill et al. 2001). Three foliage‐feeding Lepidoptera have been introduced. Agonopterix ulicetella was released in 1990 (Hill et al. 1995) but, although firmly established, no populations have yet reached damaging proportions. Scythris grandipennis was released in 1993 but did not establish and Pempelia genistella was released in 1995 but has established at only two sites to date (Hill et al. 2000). The bivoltine seed‐feeding moth Cydia succedana was introduced in 1992 to augment the seed predation provided by Exapion ulicis and it has spread rapidly and become abundant in New Zealand (Hill & Gourlay 2002). Seed losses to predation by both insects exceed those from E. ulicis alone, but the effect on the annual seed crop has yet to be assessed (Hill et al. 2000). Exapion ulicis was introduced to the island of Maui, Hawaii, in 1956 and was established on the island of Hawaii in 1984, attacking 78% of seed pods by 1994. The gall‐forming weevil Perapion scutellare was released in 1961 and again from 1989 but has not established. Agonopterix ulicetella was released in 1988 and, unlike in New Zealand, this moth has become abundant on the island of Hawaii and larvae destroy a high proportion of growing tips. The rust fungus Uromyces pisi f.sp. europaei was also released in Hawaii (Markin et al. 2002) but has been recovered only once. Tetranychus lintearius was released on St Helena in 1995, but again appears to be regulated by predatory mites (Julien & Griffiths 1998). Exapion ulicis was released in Tasmania, Australia, in 1939, but has not prevented the spread of U. europaeus (Julien & Griffiths 1998). Tetranychus lintearius and Sericothrips staphylinus have also been released there (Ireson et al. 2003). E. ulicis, T. lintearius, and Agonopterix ulicetella have been released in Chile (Norambuena et al. 2001). The fungus Fusarium tumidum (Gibberella tumidum) is being developed as a bioherbicide for use against U. europaeus worldwide (Fröhlich & Gianotti 2000; CABI ISC 2012).

BC recommendable at this point: Yes It was agreed during stakeholder consultations in Stanley that gorse was probably not the first choice for a BC project on the Falklands, due to positive public perception of the species. However, there is a worrying ongoing spread of the plant, in particular on smaller islands, after reduction or cessation of grazing. Less effort than previously is now put into cutting of gorse hedges during winter, and it is predicted that it will eventually spread along coastal habitats (as in Scottish habitats). Recently, the spread seems to have accelerated (probably due to a higher rate of seeding) and it is possible that this will result in a greater threat in the future. Within the spreading stands, gorse is also altering the character of the original ecological system by fixation of nitrogen.

Currently, public opinion is mostly against control, due to a number of perceived benefits of the plant: • Gorse provides an attractive and characteristic landscape feature in summer when in bloom. • Gorse provides shelter for sheep and, although rarely used for fencing as such, it has been traditionally planted along fence lines. • Native boxwood is not suitable to replace gorse as it is grazed by livestock. • Gorse provides shelter for native animals and nesting habitat for birds (in particular, barn owls). It was, however, agreed that these would still be able to survive in the original habitat without gorse. In this respect gorse benefits diversity only on a small very localised scale.

Given the perceived and real benefits of gorse, biological control efforts need to be well‐targeted and would require initial public education for higher acceptance levels. During the workshop consultations, it was pointed out that the release of host‐specific seed‐eating agents may be a viable option, as this would preserve existing stands but slow further spread; diminished germination of seedlings would also underpin other integrated control efforts.

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Calluna vulgaris 25 5 80 400.0 Ericaceae

BC feasible: Yes In New Zealand, a biological control programme against heather using the heather beetle Lochmaea suturalis was implemented in 1990. While success was initially poor at high altitude sites, by 2009 beetle populations were high and substantial damage was occurring at all release sites. Researchers expect beetle populations will continue to grow and disperse in subsequent years (Landcare Research 2007a, 2008a, 2009, 2011; GISD 2012).

BC recommendable at this point: No Since its introduction in the early 1900s, Calluna has spread only slowly, and still occurs on only a very localised scale. On this basis, eradication is still considered to be possible. However, this is certainly a species which will need to be closely monitored because of the high risk (as a heathland species) of it invading vast areas of native heathland habitats should its rate of spread increase.

Cytisus scoparius 20 5 100 400.0 Fabaceae

BC feasible: Yes Biological control activities targeted at scotch broom started in 1951 in Europe (CABI ISC 2012). The twig‐ mining moth Leucoptera spartifoliella and the weevil Exapion fuscirostre were released in the field in California, USA, in 1960 and 1964, respectively and then widely redistributed (Andres et al. 1967). The weevil has been recorded destroying between 60 and 90% of seed produced, with attack rates of three weevils per pod (Syrett et al. 1999). L. spartifoliella initially caused severe damage, but was then discovered to have been present in Washington State (along with its European parasitoid) since at least 1941, and soon failed to maintain the high population levels reported regularly in New Zealand. L. spartifoliella was introduced to Australia from New Zealand in 1993, where it has established at several release sites and has reached densities that are starting to stunt broom growth. The seed beetle Bruchus villosus was released in New Zealand in 1987 and in Australia in 1996 (Syrett et al. 1999). The beetle has established in both countries and, in New Zealand, up to 60% seed loss has been recorded at early release sites. The psyllid Arytainilla spartiophila was first released in 1993 in New Zealand and in 1995 in Australia and is now established in both countries (Syrett et al. 1999). As well as classical biological control, mycoherbicides are being considered for use against C. scoparius (Fröhlich & Gianotti 2000; Prasad 2002a; CABI ISC 2012).

BC recommendable at this point: No Currently, Cytisus scoparius poses no threat to biodiversity as only very few specimens exist in gardens without showing a tendency to spread further.

Pilosella officinarum 35 21 79 131.7 Asteraceae

BC feasible: Yes The rust fungus Puccinia hieracii var. piloselloidarum was chosen as a potential agent for the biological control of P. officinarum in New Zealand (CABI ISC 2012). However, during investigations prior to its introduction, it was detected in the field in New Zealand. Nonetheless, further strains may need to be tested and released to inoculate the various biotypes of P. officinarum (Morin & Syrett 1996). Apart from this rust fungus, five herbivorous insects of European origin have been studied as potential biological control agents of P. officinarum and have been approved for release in New Zealand (Syrett et al. 1999; Grosskopf et al. 2002; Klöppel et al. 2003). Four of them, Oxyptilus pilosellae (Lepidoptera, Pterophoridae), Aulacidea subterminalis (Hymenoptera, Cynipidae), Macrolabis pilosellae (Diptera, Cecidomyiidae) and Cheilosia urbana (Diptera, Syrphidae) have already been field released in New Zealand. Releases of the fifth insect, Cheilosia psilophthalma (Diptera, Syrphidae) were also planned. The impact of all released agents is yet to be fully

23

assessed (CABI ISC 2012).

BC recommendable at this point: Yes Currently, P. officinarum is only a problem on one farm (Port Stephens). Eradication is probably still possible but already difficult and would require efforts on an almost industrial scale. Recent trials of chemical control have only been partially successful. In North America, Argentina, and New Zealand it has suddenly spread rapidly after long behaving as an unproblematic “sleeper weed” following introduction as a garden ornamental or contaminant of agricultural seed (Cipriotti et al. 2012). It can be easily transported by machinery. It is undesirable, dangerous, potential invader on account of its vigorous growth due to stolon production, and its wind‐dispersed seeds. P. officinarum displaces the inter‐tussock vegetation leading to loss of forage and biodiversity (CABI ISC 2012). On the Falklands, it is also regarded as problematic within organic farming. Based on multiple factors, therefore, it is highly recommended that the feasibility of future BC of this ‘high risk’ species be assessed in more detail at an early stage. In particular, the possibility of linking efforts (selection and testing of host specificity of suitable agents) with other currently on‐going projects in other countries should be explored. Particular care needs to be taken with host range testing, as two native species of the closely related genus Hieracium (H. patagonicum and H. antarcticum) occur on the Falklands. H. patagonicum is a rare species and listed on the national plants Red List. Cirsium arvense 35 21 69 115.0 Asteraceae

BC feasible: Yes Survey work has identified numerous potential biological control agents for C. arvense (Watson & Keogh 1980; Perju et al. 1995), and such agents for controlling C. arvense have been reviewed more widely (Andres 1980; Peschken et al. 1980; Trumble & Kok 1982; Monnig 1987). Widespread adoption of exotic biological control agents is unlikely because of public concern for native thistles and the lack of effectiveness of a high proportion of currently available biological control agents (Peschken & Beecher 1973). The weevil Ceutorhynchus litura severely reduced overwintering survival of below‐ground adventitious shoots of C. arvense to as little as 3% of that of uninfested shoots in Canada (Peschken & Beecher 1973). In a 3‐year study in Montana, 8 to 12% of weevil‐infested shoots survived from one year to the next compared with 94 to 99% of uninfested shoots (Rees 1990). The insect may have assisted in spreading the rust fungus, Puccinia punctiformis, although this assertion was not substantiated later (Peschken & Beecher 1973; Peschken & Wilkinson 1981). C. litura was released 18 times in the USA in California, Colorado, Idaho, Montana, New Jersey, South Dakota, and Washington between 1971 and 1975. In Montana, C. litura spread 9 km in 10 years and the proportion of infested plants increased from 11 to 29% in 1977 to over 80% after 10 years. In Canada, this insect did not greatly or consistently increase mortality of C. arvense shoots (Peschken & Wilkinson 1981). A weevil, Larinus planus, that feeds on seed heads of C. arvense was accidently introduced into the USA, and may be useful for controlling seed production to prevent large areas of infestation from expanding further (Drlik et al. 2000). However, it has been shown to attack a native thistle, Cirsium undulatum var. tracyi in Colorado (Louda & O'Brien, 2002). Cassida rubiginosa is a fairly effective control agent, and may work well in combination with the effects of competition on C. arvense from plants such as Festuca arundinacea and Coronilla varia (Ang et al. 1995). Fungi and higher plant parasites found on C. arvense have been reviewed (Moore 1975). Drlik et al. (2000) list Pseudomonas syringae pv. tagetis, Puccinia punctiformis, and Sclerotinia scloerotiorum as the three main pathogens under investigation for use against C. arvense in North America. Pseudomonas syringae pv. tagetis showed limited ability to affect Canada thistle survival in one USA study (Gronwald et al. 2002), but in Minnesota it reduced C. arvense biomass significantly in conservation tillage systems (Hoeft et al. 2001). Work in Germany has suggested that control with P. punctiformis could prevent flowering and hinder several years' growth (Kluth et al. 2003), and shows some potential for development into a mycoherbicide (Bond & Turner 2003). The fungus Sclerotinia sclerotiorum applied to C. arvense patches as a biological control agent killed 20 to 80% of shoots in Montana (Brosten & Sands 1986). S. sclerotiorum is an aggressive, persistent pathogen on many broadleaved crop species, limiting its use on commercial farms. A study in the Netherlands showed that the risks associated with S. sclerotinium may be manageable, however (Bourdot et al. 2001). Harvey et al. (1998) investigated using auxotrophic strains of S. sclerotinium to decrease the risk of pathogenic effects on crops, but these strains were less effective against C. arvense. Four insects

24

that feed on C. arvense (Aphis fabae spp. Cirsii acanthoidis, Uroleucon cirsii and the beetle Cassida rubiginosa) were found to transmit the fungal pathogen P. punctiformis (Kluth et al. 2002), indicating the possibility of using synergism in biological control efforts. Furthermore, Bacher et al. (2002) showed that development of the beetle Apion onopordi was improved in plants infested with P. punctiformis, which is in turn is promoted by A. onopordi (Friedli & Bacher 2001). However, Kruess (2002) found that the combination of Cassida rubiginosa and the pathogen Phoma destructiva provided less efficient control of C. arvense. Green et al. (2001) observed high disease ratings for infection by Alternaria cirsinoxia in Saskatchewan, Canada.

BC recommendable at this point: No Eradication still seems possible, and control efforts are being undertaken accordingly. At the moment, only a handful of sites around MPA are affected; these stands are spreading, but eradication appears to be feasible nonetheless. Previously, in some places, local eradication was apparently achieved after 2‐3 years of control. However, a lack of funding (and discontinuation of control) has been followed by the re‐emergence of the weed at these sites in low numbers. C. arvense shows a limited seed set on the Falklands, as mostly only unisexual clones exist in isolated areas.

Cirsium vulgare 40 21 60 114.3 Asteraceae

BC feasible: Yes Biological control programmes have been initiated in North America against C. vulgare as a result of its invasiveness and associated economic losses (CABI ISC 2012). Actions include the release of a gall forming fruit fly, Urophora stylata (Tephritidae), and a thistle head weevil, Rhinocyllus conicus (Curculionidae) (Forcella & Randall 1994). In Canada, U. stylata was released in 1973 and led to a 65% reduction in achene formation in some areas after three years (Parsons & Cuthbertson 1992). This fruit fly is effective in controlling C. vulgare in central and western Europe, but results in North America show that fly dispersal is slow and that the agent only survives in dense stands of C. vulgare (Harris & Wilkinson 1984). Two rosette‐ feeding weevils, Ceutorhynchus trimaculatus and Trichosirocalus horridus, were released in 1974 to control other carduine thistles in North America, and have now spread to C. vulgare (Kok et al. 1979; McAvoy et al. 1987). None of these insects have provided adequate control of C. vulgare (Forcella & Randall 1994). In Czechoslovakia, Terellia serratulae and U. stylata were recommended as biocontrol agents for C. vulgare. U. stylata produces galls in the flowerheads, causing a reduction in the number of cypselas; T. serratulae does not produce galls, but larvae of this species feeding on cypselas decrease seed production of the host plant. Larvae of both species can develop in the same flowerhead. (Kinkorova 1991). The fungus Sclerotinia sclerotiorum has been shown to have potential as a biological herbicide for controlling C. vulgare in pastures (Bourdôt & Harvey 1996; CABI ISC 2012).

BC recommendable at this point: to certain degree only

Although larger stands exist in isolated places (Saunders, Keppell), eradication is still feasible and there are currently on‐going mechanical control efforts. However, during the workshop, BC was seen as an attractive option to underpin other control efforts (i.e. first BC to reduce individuals, then eradication). Also, low populations kept in check by BC may be the most effective protection against future reintroductions, which probably can be expected on a regular basis; this was seen as the best scenario for containing the problem. C. vulgare is certainly a suitable target for biological control in terms of public perception. However, there is currently a lack of suitable control agents with a proven record of persistent high efficacy.

Ammophila arenaria 45 37 79 96.1 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a novel programme is feasible.

25

BC recommendable at this point: No There are some perceived benefits of this species (e.g. as a stabiliser of dunes) and it currently appears to have very limited negative impacts..

Pilosella aurantiaca 25 21 79 94.0 Asteraceae

BC feasible: Yes Since chemical and mechanical control of Pilosella spp. are ineffective and/or not economically viable in New Zealand, a programme to develop biological control was initiated in 1992 (Syrett & Smith 1998). Five insect species of European origin were studied and tested and are approved for release (Syrett et al. 1999; Grosskopf et al. 2002; Klöppel et al. 2003). Four of them have the potential to develop on Pilosella aurantiaca: the plume moth Oxyptilus pilosellae, the larvae of which feed on the above‐ground plant parts; the cynipid Aulacidea subterminalis, which galls the stolon tips of P. officinarum and P. aurantiaca; the syrphid Cheilosia urbana, the larvae of which feed externally on the roots; and Cheilosia psilophthalma, the larvae of which feed in rosette centres, leaf axils and on stolons. P. aurantiaca is not a host plant of the fifth species, the gall midge Macrolabis pilosellae, which galls stolon tips and rosettes (CABI ISC 2012).

BC recommendable at this point: No This species is mainly restricted to the Stanley area. Public perception of it is very positive and the species seems to be integrated in urban habitats rather than becoming dominant over natural vegetation. Currently, existing stands are exempted from mowing during the tourist season. The species needs, however, to be closely monitored. It may be in a lag‐phase and there remains the possibility that it will become a bigger problem in the future.

Berberis microphylla 30 29 79 81.7 Berberidaceae

BC feasible: Yes There is no history of BC against this species. However, calafate B. microphylla was listed among the top twelve invasive alien plants on the Falkland Islands, following an assessment of potential to cause land management problems and economic impact. Additionally, it achieved a top score of 19 in a risk assessment, where non‐native plants that scored above 15 were categorised as potentially invasive species that could out‐ compete local flora and reduce agricultural productivity (Whitehead 2008).

Several management options have been suggested for the control of B. microphylla (Belton 2008a). "Do nothing" has been suggested, as the species currently affects very few landowners, and thus causes very little perceived annoyance. This option will also incur very little economic cost in the short term. However, it will also allow the problem to increase, and is thus not a long term solution. "Containment" has also been suggested. The costs associated with this option are probably very low, but due to the (bird) dispersal mechanism of the plant, it will also be very hard to achieve, and is thus considered inappropriate. "Site‐led management" is another option, which would involve the identification of B. microphylla sites and the prioritization of their treatment (Belton 2008a). Those sites deemed high priority and those where very little effort is required would be treated first, with others treated when resources and funds are available. This approach seems appropriate, as it would treat large sites, hopefully reducing their potency, as well as stopping sites of more limited establishment from becoming more infested. "Eradication" is the final option proposed by Belton (2008a) and would be the largest operation to be undertaken. However, this approach may only be effective in those areas where B. microphylla is in a lag phase, not in other areas where growth has become exponential. This method is not deemed appropriate. The responsibility for control is also an issue raised by Belton (2008a). Affected and concerned landowners, a lead government agency, and a charitable trust have all been suggested as possible groups to take responsibility for B. microphylla control. Only the establishment of a charitable trust is considered as an option in Belton's (2008a) report. Various specific steps were also suggested, as a preliminary plan for the management of this plant: 2008 was to

26

include the mapping and abundance of B. microphylla, the establishment of a Trust of the Falklands and the initiation of control measures on the smallest infected areas; 2009 was to include the acquisition of funding for necessary resources, although the continuation of actual control measures is not mentioned; 2010 was to include further funding acquisition and a review of control techniques to establish best practice. The techniques used for control are "cut and paste treatment", which includes the cutting of all stems as close to the ground as possible, and the application of a herbicide called "Vigilant" which is applied as a paste (Belton 2008a). Manual and mechanical removal are also an option, however, broken roots often re‐sprout, so these methods are not recommended. Foliar spraying of herbicide is another technique which should be successful. It has not been tested on B. microphylla itself; however, it has been proven as an effective technique on other Berberis sp.

BC recommendable at this point: Yes On the Falkland Islands, calafate has been used as an ornamental and for wind shelter for some time. Only after a lag‐phase spanning several decades, during which the species seems not to have behaved invasively, has it started to spread exponentially around Port Sussex on East Falkland and at a few other localities. The rapid spread seems to be facilitated by seed dispersal through birds eating the berries. Calafate has taken over all the valleys in the paddocks around Port Sussex and has spread for seven kilometres along Sussex Mountain. Several other outbreaks have been reported including at Cantera and Island Harbour. Currently, the species is present in seven 10km squares and most populations are still close to settlements. It is feared that further spread, in particular of calafate, may led to a large scale replacement of native flora. Calafate also poses a threat to sheep grazing and in particular to wool quality because of the brittle nature of the shrub’s spiny branches.

Initial trials to control calafate were undertaken by the Department of Agriculture at Island Harbour during 2000 but have not been followed up. Calafate is still subject to control at some locations, in particular at Port Sussex. The ”cut and paste” approach (Belton 2008a) has not been very successful, and according to the farmers at Port Sussex has not led to a marked impact on the calafate population. Only huge on‐going investments in machinery and man‐power may be able to contain the current population at Port Sussex, but even then a complete eradication would be doubtful. Belton (2008a) points out that eradication as a method is not deemed appropriate in areas where growth has become exponential.

Based on the likely failure of other control efforts, BC may be the only viable option to slow down and limit further spread, if severe consequences both for farming and habitat conservation are to be avoided. Although no ‘off the shelf’ solutions are currently readily available, the high risk posed by calafate would justify a pilot study looking for suitable control agents and, at a later stage the development of a full control programme.

Equisetum arvense 25 24 72 75.0 Equisetaceae

BC feasible: Yes There is no history of BC against this species, but the development of a BC programmes is feasible.

BC recommendable at this point: No Because of the limited occurrence of the target species, the possibility of complete eradication, and limited negative impacts of the species at present, BC is not recommended at this stage.

27

Sonchus asper 30 25 55 66.0 Asteraceae

BC feasible: Yes CSIRO (2007, 2011) has recently assessed the possibility of managing S. asper and other Sonchus species through BC in Australia. So far, however, only two widespread species native to Australia, the rust fungus Miyagia pseudosphaeria and an undescribed species of eriophyid mite, have been identified as potentially promising agents. Sonchus species have also previously been the subject of biological control in Canada and surveys for biological control agents have been made in southern France and northern Europe (Scott & Jourdan 2005; Peschken 1984; GISD 2012).

BC recommendable at this point: No The species is very widespread, and occurs in particular on disturbed sites around settlements, along roads, at penguin colonies and in places with high livestock densities (high nitrogen levels). Although S. asper seems to be beyond mechanical or chemical control BC is not recommended at this stage as negative impacts are still very limited and there is no obvious further spread. In addition, no suitable control agents are currently readily available.

Rumex crispus 35 31 54 61.0 Polygonaceae

BC feasible: Yes The possibility of classical biological control of R. crispus and other weedy Rumex spp. has been investigated, based on importing agents from Europe to the USA and Australia (Spencer 1981; Campobasso & Murano 1988; Scott 1990). No introductions are reported for the USA so far, but two sesiid root borers, Bambecia chrysisiformis and Chamaesphecia doryliformis, were imported into Australia and a programme of releases initiated after host specificity studies (Scott & Sagliocco 1991a,b; Fisher 1992). However, there are no published records on the success or otherwise of these programmes. The fungi Uromyces rumicis, investigated by Frank (1973), and Ramularia rubella, investigated by Huber‐Meinicke et al. (1989), which were found to be specific to Rumex spp., have been proposed as potential control agents, but this does not seem to have been followed up (CABI ISC 2012).

BC recommendable at this point: No Only small populations exist in a few places and eradication seems possible.

Rumex obtusifolius 35 31 54 61.0 Polygonaceae

BC feasible: Yes Gastrophysa viridula has been suggested as a possible agent of biological control (Speight & Whittaker 1987). However, although heavy grazing by this beetle reduces leaf area and overall biomass and affects the number and weight of seeds (Bentley & Whittaker 1979; Bentley et al. 1980), it is unlikely that G. viridula, acting alone, could be an effective control agent for the weed (Speight & Whittaker 1987). In Tasmania, the clearwing dock moth Chamaesphecia doryliformis was introduced in 1997 at two sites to control R. obtusifolius. However, there is no further information on the establishment and efficacy of this agent (TAS 2003). Studies involving fungal pathogens have not developed control methods, though the possibilities have been discussed for Uromyces rumicis and Ramularia rubella (Schubiger et al. 1986; Huber‐Meinicke et al. 1989). Hughes et al. (1996) investigated the effects of infection of Armillaria mellea and A. ostoyae, which attack the root system, and reported that the taproots were extensively rotted. Hatcher & Paul (2000) showed that grazing by G. viridula reduces natural infection of R. obtusifolius by fungal pathogens that attack leaves.

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BC recommendable at this point: No Rumex obtusifolius is very widespread and seems to be beyond mechanical or chemical control. However, BC is not recommended at this stage as negative impacts are still very limited and there is no obvious further spread. In addition, no suitable control agents are currently readily available. Hedera helix 25 33 79 59.8 Araliaceae

BC feasible: Yes There has been no attempt to identify and introduce biological control agents and, in view of the species' importance in horticulture in the USA, it is extremely unlikely that any such attempts will be made in that country. In view of the species' near immunity to pests and diseases in its native range, prospects for biological control are limited. Prasad (2002b) has reported that the use of a bioherbicide in the form of the fungus Chondrostereum purpureum has been applied to H. helix but its efficacy has yet to be ascertained.

BC recommendable at this point: No Because of the limited occurrence of the target species, the possibility for complete eradication and currently limited negative impacts, BC is not recommended at this stage.

Lupinus arboreus 30 33 64 58.2 Fabaceae

BC feasible: Yes Lupinus arboreus is an invasive species in New Zealand, where typical habitats invaded are bare ground, riverbeds, coastal areas, short tussock, sandy and well‐drained areas (DoC 2000). The species tolerates wind, salt, temperature extremes, damage, grazing, drought, low fertility and fire (DoC 2000). On the Falklands, it occurs in built up areas and gardens, at altitudes 0‐15m (Broughton & McAdam, 2002). Its potential distribution on the Islands is unknown (Varnham 2009). There is no history of BC against this species.

BC recommendable at this point: No Because of the limited occurrence of the target species, the possibility for complete eradication, and currently limited negative impacts, BC is not recommended at this stage.

Myosotis discolor 20 28 64 45.7 Boraginaceae

BC feasible: No There is no history of BC against this species, and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Sedum acre 25 47 79 42.0 Crassulaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

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Rosa canina 20 38 79 41.6 Rosaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Rosa rugosa 20 38 79 41.6 Rosaceae

BC feasible: No The herbivorous arthropods and pathogenic microorganisms associated with R. rugosa in its native and exotic ranges were reviewed by Bruun (2005) as an initial step towards the identification of potential agents for biological control in Europe and North America. Based on the literature, the most promising candidates seem to be the aphids Myzus japonensis and Amphorophora amurensis, the leaf hopper Empoasca ussurica, the tortricid moth Notocelia longispina, the cynipid gall‐wasp Diplolepis fukudae, and the rust fungi Phragmidium rosae‐rugosae and P. yezoense. A screening programme is suggested, investigating the impact of these organisms on R. rugosa performance, their host specificity and the risk of undesired indirect effects in the ecosystem where agents are released (Bruun 2006; CABI ISC 2012).

Limited current negative impacts and the difficulty in acquiring host‐specific control agents “off the shelf” mean that BC for the target area is probably not feasible at this time.

BC recommendable at this point: No

Plantago lanceolata 30 43 59 41.2 Plantaginaceae

BC feasible: No There is no history of BC against this species, and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Atriplex patula 20 37 64 34.6 Chenopodiaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Taraxacum officinale 25 43 57 33.1 Asteraceae

BC feasible: No Phoma exigua and P. herbarum have been isolated from T. officinale complex in Ontario, Canada, and considered as potential biocontrol agents (Neumann Brebaum 1998; Neumann Brebaum & Boland 1999). Controlled‐environment studies showed that young T. officinale plants were more susceptible to P. herbarum

30

than older plants (Neumann Brebaum & Boland 2002). P. taraxaci was considered as a biocontrol agent for T. officinale complex in Sweden (von Hofsten 1954). P. taraxaci was spread by pycnospores and infected seeds; however, it was extremely variable with respect to its pathogenicity on T. officinale complex and its viability in soil. Von Hofsten (1954) also mentioned an unnamed 'ring‐forming fungus' which released a substance that was highly toxic to T. officinale complex and other plants. Sclerotinia species have also been tested as biological control agents for T. officinale complex in Canada and New Zealand (Riddle et al. 1991; Waipara et al. 1993). Sclerotinia sclerotiorum and S. minor were evaluated in a controlled environment and in turf grass swards for their virulence on T. officinale complex. Isolates of both species reduced the dry weight of plants in a controlled environment and reduced the number of plants in turf grass swards. Heat‐killed seeds of perennial ryegrass were suitable as both a growth substrate for Sclerotinia spp. and a delivery system to T. officinale complex (Riddle et al. 1991). A mycelium‐on‐wheat preparation has been used for S. sclerotiorum, while either a granular sodium alginate formulation or a mycelium‐on‐barley preparation has been employed to deliver S. minor (Ciotola et al. 1991; Brière et al. 1992; Waipara et al. 1993). Sclerotinia sclerotiorum caused localized infection on the leaf laminas and created basal necroses of 1‐2 cm in length on tap roots of T. officinale complex. (Burpee 1992; Waipara et al. 1993). These necroses inhibited leaf regrowth from the root after defoliation (Burpee 1992).

As described above, efficient BC of Taraxacum can be difficult and the occurrence of a native congener mean that BC is not considered feasible for the target area.

BC recommendable at this point: No

Bellis perennis 15 37 79 32.0 Asteraceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Sonchus oleraceus 20 37 55 29.7 Asteraceae

BC feasible: No CSIRO (2007, 2011) has recently assessed the possibility of managing S. asper and other Sonchus species through BC in Australia. So far, however, only two widespread species native to Australia, the rust fungus Miyagia pseudosphaeria and an undescribed species of eriophyid mite, have been identified as potentially promising agents. Sonchus species have also previously been the subject of biological control in Canada and surveys for biological control agents have been made in southern France and northern Europe (Scott & Jourdan 2005; Peschken 1984; GISD 2012).

BC recommendable at this point: No

Senecio squalidus 30 43 42 29.3 Asteraceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

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Poa pratensis 20 43 60 27.9 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Poa trivialis 20 43 60 27.9 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Senecio sylvaticus (misid. S. viscosus) 20 43 49 22.8 Asteraceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Senecio vulgaris 30 43 31 21.6 Asteraceae

BC feasible: No Despite the wide range of natural enemies reported as attacking S. vulgaris, only two fungal species, Erysiphe fischeri and Puccinia lagenophorae, have been tested as biological control agents (CABI ISC 2012). Plants infected with E. fischeri continued growing to set seeds even when 75‐100% of the aerial parts were colonized, but dry matter production of the weed was markedly reduced (Clarke et al. 1979; CABI ISC 2012). Under glasshouse conditions, P. lagenophorae infection reduced weed dry weight both in pure and mixed stands with lettuce. The fungus inhibited leaf expansion and production of capitula, reduced the number of flowering plants and led to more rapid and early senescence of the weed; mature, infected, flowering plants died earlier and more rapidly than healthy plants (Paul & Ayres 1987).The high death rate occurring among autumn‐inoculated plants was due to infection of the hypocotyl which was always killed within 1‐2 weeks. However, heavily‐infected plants were still able to produce some capitula and potentially set seed. Inoculation of plants bearing aecia of P. lagenophorae with an isolate of Puccinia intermedium caused 50% death of hosts 18 days after inoculation and 37 days after inoculation with Gibberella avenacea (Hallett & Ayres 1992).

A lack of successful attempts at BC, in combination with the potential difficulties in identifying suitable agents, means that BC currently not considered feasible for the target area.

BC recommendable at this point: No

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Cerastium fontanum ssp. vulgare 20 47 50 21.3 Caryophyllaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Poa annua 20 43 38 17.7 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

Stellaria media 20 47 31 13.2 Caryophyllaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is not considered realistically feasible.

BC recommendable at this point: No

3.2.2 Falkland Islands - Invertebrates Only four non-native invertebrate species generated an impact score of 20 or above and were evaluated further with the prioritisation tool. Detailed assessments of each species are given in Table 5 below. These suggest that one of the four, the linyphiid spider Tenuiphantes tenuis, is not a suitable target species for biological control. Based on intensive stakeholder consultations on the Falklands, the European earwig Forficula auricularia emerged as a very promising target species. There has been a wide range of reported negative impacts caused by this species, although most of them are not linked to any threats to native species or indigenous habitats. This species has become a major nuisance and has no perceived benefits. As a result, local enthusiasm for any environmentally friendly and safe control options is considerable. As outlined in Table 4, biological control against F. auricularia has already been instigated elsewhere, using tachinid flies. Risk assessments and host-range testing programmes for the introduction of one or both of these tachinid species into the Falklands should be straightforward, as no closely related non-target invertebrates occur on the Falklands or the nearest other islands. Biological control of the two greenbottle flies (Protophormia terraenovae and Lucilia sericata) is also feasible, as numerous releases of parasitoids over many years have shown. Flystrike caused by these species is not currently a substantial problem on the Falklands. Therefore, the impact of these pest species is low, and insufficient to justify biological control efforts at this stage. However, this may change in the future, including in response to climate change. Currently, no dipping (using pesticides, as in Australia) is required on the Falklands, but if the incidence of flystrike were to increase, this control method would be difficult to apply because of the size and layout of farms on the islands.

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Table 5: Assessment of non-native invertebrate species of the Falkland Islands for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol TOTAL EFFORT BIOCONTROL FEASIBILITY x IMPACT Forficula auricularia Dermaptera (Forficulidae) 40 12 86 286.7

BC feasible: Yes Currently, we regard the European earwig Forficula auricularia a very promising target species for BC on the Falkland Islands; particularly as chemical sprays are ineffective because of the insects’ widespread occurrence and great mobility (Santini & Caroli 1992). Off the shelf solutions using parasitoid tachinid flies are readily available. One of these species, Triarthria setipennis, has established successfully in Newfoundland and British Columbia (Morris 1984). Studies on the establishment of T. setipennis in Newfoundland indicated a considerable reduction in earwig numbers, which was most probably due to high levels of parasitism in the mid‐1970s (Morris 1984). However, since 1978, no further evaluation of parasitoid impact has been undertaken. A second species, Ocytata pallipes, was introduced into Canada to control the European earwig during the 1990s (Kuhlman et al. 2001). Maggots were applied singly to about 115 earwigs, and the earwigs and 20 adult flies were later released at one site in Ottawa. Although this ad hoc release programme was useful as a pilot study, the release of such a low number of potentially infected F. auricularia makes success of this introduction unlikely, and no follow up monitoring had been conducted. Ocytata pallipes and Triarthria setipennis have also been introduced into the USA and New Zealand. Introductions into the USA were undertaken as early as the 1920s (Oregon) (Kuhlman et al. 2001). Again, little is known about the success of these releases.

Risk assessments and host‐range testing requirements for the introduction of one or both of these tachinid species into the Falkland Islands could be minimal, as no closely related non‐target invertebrates occur on the Falklands or the nearest other islands. However, the host specificity of both parasitoids is fairly poorly understood and, to date, no laboratory host‐range studies have been conducted. The ecological host‐range of T. setipennis includes at least two other earwig species, Chelidura albipennis Meg. (Thompson) and Forficula decipiens Gené, but the host range of O. pallipes is unknown. To help define the host‐range specificity of both species, a number of closely related Dermaptera and species belonging to other taxonomic orders will need to be tested. In particular, the potential for future accidental introduction of the control agents to the South American mainland will need to be considered. For example, 37 native species of Dermaptera are known from Argentina, just 395km to the west of the Falklands. Tests should be conducted with these native, South American earwigs, particularly those closely related to the target, e.g. the five species within the family Forficulidae: Doru gracilis (Burmeister, 1838), Doru lineare (Eschscholtz, 1822), Doru luteipes (Scudder, 1876), Doru platensis Borelli, 1912, and Doru taeniatum (Dohrn, 1862). As European earwigs also pose a severe problem in southern Chile, it seems feasible that a testing of the species listed above could be undertaken by the Chilean authorities.

BC recommendable at this point: Yes The European Earwig, Forficula auricularia has become locally abundant in the Port Stanley and Mount Pleasant Airport areas. So far, the main outbreaks are restricted to these localities, but individual specimens seem to have been discovered on some of the isolated farmsteads. The earwigs seem to have become a real nuisance over the last four years, but the exact date of introduction is unknown. There seem to be no records or observations away from settlements. Currently, major negative impacts caused by this species include:

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• Earwigs cause huge damage to garden crops (cabbages, broccolis, turnips, beetroot, etc.) including commercially grown crops (damage caused by this species has led to the complete cessation of growing individual crops such as lettuce for commercial purposes); pesticide application in horticulture to control earwigs requires intensive treatment with undesirable products • Earwigs pose certain health hazards (being found behind rubber sealing in oxygen masks at medical facilities; being found in asthma inhalers; children with earwigs in their nose having to be treated in hospital, etc.) • They become a particular nuisance in autumn when retreating into houses (being found in food, toothbrushes, etc.) • Households spend substantial amounts of money to control earwigs with a wide range of methods (spraying with insecticides, use of furniture polish, painting houses from the outside with diluted diesel, sealing cracks with silicone, etc.) with varying success and the need for repeated applications.

The most straightforward approach would be to obtain specimens of both previously used tachinid parasitoids from areas with a climate matching that of the Falklands (the North Sea coast of Germany or in Scotland) and bring these into cultivation at CABI’s facilities in Delemont, Switzerland. Host‐range testing could be highly selective, for the reasons described above, e.g. comprising particular earwig species and representative examples from other orders most closely related to the Dermaptera. We suggest testing selected species from the orders Orthoptera (Crickets, Grasshoppers) and Blattoidea (Cockroaches).

Cultivation of the tachinid agents in laboratory facilities would be required to conduct the host‐specificity tests, but also to obtain sufficient numbers for release. Cultivation over several generations would also eliminate the risk of accidently introducing any hyper‐parasitoids associated with the tachinid flies.

Protophormia terraenovae Diptera (Calliphoridae) 35 12 86 250.8

BC feasible: Yes High priority score, due to the impact on wool quality by this species. Extensive research on the BC of Calliphoridae in general has been conducted in the past; however, despite partial successes, BC does not seem to be a widely applied method for control of this taxonomic group. Alysia manducator (Hym. Braconidae), Brachymeria podagrica (Hym. Chalcididae), Nasonia vitripennis (Hym. Pteromalidae) were introduced in the 1920s to New Zealand to control Calliphoridae (Miller 1922, 1927; Biocat 2010). Previous experiences on islands are mostly related to the control of calliphorid and other flies developing in dung (Ripa 1990). Based on previous programmes, BC seems feasible against this species, at least to some degree. However, the costs and efforts involved in selecting and testing the most suitable control agents are currently unlikely to lead to more effective control than other available methods (Sargison 2008).

BC recommendable at this point: No Flystrike caused by this species is at the moment not a substantial problem on the Falklands. However, this may change in the future, e.g. with the effects of climate change. Currently, no pesticide sheep‐dipping is required on the Falklands, but if the incidence of flystrike increased this could become problematic (as dipping would be difficult to apply because of the size and layout of farms on the islands). In summary, at the workshop in Stanley, BC was not seen as a suitable option at the moment, but one potentially to be revisited in the future.

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Lucilia sericata Diptera (Calliphoridae) 35 12 81 236.3

BC feasible: Yes High priority score, due to the impact on wool quality by this species. Extensive research on the BC of Calliphoridae in general has been conducted in the past; however, despite partial successes, it does not seem to be a widely applied method for the control of this taxonomic group. Alysia manducator (Hym. Braconidae), Brachymeria podagrica (Hym. Chalcididae), Nasonia vitripennis (Hym. Pteromalidae) were introduced in the 1920s to New Zealand to control Calliphoridae (Miller 1922, 1927; Biocat 2010). Previous experiences on islands are mostly related to the control of calliphorid and other flies developing in dung (Ripa 1990). Although BC seems feasible to control this species, at least to some degree, the costs and efforts involved in selecting and testing the most suitable control agents are currently unlikely to lead to more effective control than other available methods (Sargison 2008).

BC recommendable at this point: No Flystrike caused by this species is at the moment not a substantial problem on the Falklands. However, this may change in the future, e.g. with the effects of climate change. Currently, no pesticide sheep‐dipping is required on the Falklands, but if the incidence of flystrike increased this could become problematic (as dipping would be difficult to apply because of the size and layout of farms on the islands). In summary, at the workshop in Stanley, BC was not seen as a suitable option at the moment, but one potentially to be revisited in the future.

Tenuiphantes tenuis Arachnida (Linyphiidae) 20 37 35 18.9

BC feasible: No There is no history of BC against this species (or spiders, in general). Development of biological control programmes would require a large‐scale research effort, and efficacy of this method for this taxonomic group remains speculative. Such efforts would only be justified by substantial negative impacts of the target species on native species and habitats, which have not yet been recorded from the Falklands.

BC recommendable at this point: No

3.2.3 South Georgia- Weeds Eight non-native plant species generated an impact score of 20 or above and were evaluated further with the prioritisation tool. Detailed assessments for each species are given in Table 6. Relatively low overall scores, compared to those for non-native weeds on the Falklands, principally reflect the fact that none of the species listed have been the subject of a successful biological control programme in the past. Of the species in Table 5, Cardamine glacialis presents a rather unusual case. This species is native to the Falkland Islands, and the risk of any biological control agent introduced to South Georgia spreading to the Falklands would therefore need to be taken into consideration. Of course, such risks would be eliminated if surveys revealed the occurrence of suitable control agents on the Falklands themselves. Currently, Cardamine on South Georgia is subject to an eradication programme, and biological control would only become an option to consider should these efforts prove unsuccessful. Grass species are always regarded as potentially difficult from a biological control perspective. As such, there has been little research into the biological control of this group of plant species. Poa annua and Poa pratensis both have an overall score just above the cut-off mark of 50 reflecting the lack of previous research into these species. Due to the invasiveness of Agrostis capillaris syn. tenuis on South Georgia, and in other geographical regions, this species has a high impact score and

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subsequent overall score, putting the species in first position for future priority of CBC. Recent studies looking into the regeneration of native habitats based on grazing exclosures indicate that native plant species may become more competitive after the eradication of reindeers on South Georgia subsequently leading to a decrease of non-native grasses. Although difficult CBC could still become an option for grasses in case their impact on the native ecosystem will continue to be severe even after the cessation of grazing by reindeer. Particularly, in case non-native grasses will hinder the recovery of native vegetation the uptake of CBC would be justified. Herbivores and pathogens specific to the genera Poa and Agrostis do exist and, as there are no native congeners on South Georgia, biological control may well be feasible. Similarly, for Taraxacum officinale the lack of closely related species increases the chance to find suitable control agent. This species has been the subject of classical biological control programmes in North America and Canada and may prove to be a suitable target for South Georgia if the impact of the species warrants further control measures. Again this would need to take the occurrence of native species of the same genus on the Falkland Islands into account. On the basis of intensive stakeholder consultations we don’t regard any of the non-native plant species worthwhile for biological control at this moment. This may change of course in the future in case on-going monitoring activities will record an increase of negative impacts by individual species. In such a case assessments below can provide valuable background information on available options for further steps.

Table 6: Assessment of non-native plant species on South Georgia for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol TOTAL x IMPACT EFFORT BIOCONTROL FEASIBILITY Agrostis capillaris; syn. tenuis 40 33 79 95.8 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, BC of grasses on South Georgia is regarded as unsuitable, in particular, because any introduced agents could spread to the Falkland Islands where target species are beneficial fodder grasses for livestock. The occurrence on the Falklands of native species of target genera is also problematic, as it is notoriously difficult to identify very host‐specific control agents for grasses. In addition, it is expected that the native Acaena on South Georgia will better compete against introduced grasses once reindeers are eradicated.

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Rumex acetosella 35 24 64 93.3 Polygonaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Limited environmental impacts of this species do not justify the uptake of BC at this point.

Taraxacum officinale 30 24 72 90.0 Asteraceae

BC feasible: Yes Phoma exigua and P. herbarum have been isolated from T. officinale complex in Ontario, Canada, and considered as potential biocontrol agents (Neumann Brebaum 1998; Neumann Brebaum & Boland 1999). Controlled‐environment studies showed that young T. officinale plants were more susceptible to P. herbarum than older plants (Neumann Brebaum & Boland 2002). P. taraxaci was considered as a biocontrol agent for T. officinale complex in Sweden (von Hofsten 1954). P. taraxaci was spread by pycnospores and infected seeds; however, it was extremely variable with respect to its pathogenicity on T. officinale complex and its viability in soil. Von Hofsten (1954) also mentioned an unnamed 'ring‐forming fungus' which released a substance that was highly toxic to T. officinale complex and other plants. Sclerotinia species have also been tested as biological control agents for T. officinale complex in Canada and New Zealand (Riddle et al. 1991; Waipara et al. 1993). Sclerotinia sclerotiorum and S. minor were evaluated in a controlled environment and in turf grass swards for their virulence on T. officinale complex. Isolates of both species reduced the dry weight of plants in a controlled environment and reduced the number of plants in turf grass swards. Heat‐killed seeds of perennial ryegrass were suitable as both a growth substrate for Sclerotinia spp. and a delivery system to T. officinale complex (Riddle et al. 1991). A mycelium‐on‐wheat preparation has been used for S. sclerotiorum, while either a granular sodium alginate formulation or a mycelium‐on‐barley preparation has been employed to deliver S. minor (Ciotola et al. 1991; Brière et al. 1992; Waipara et al. 1993). Sclerotinia sclerotiorum caused localized infection on the leaf laminas and created basal necroses of 1‐2 cm in length on tap roots of T. officinale complex. (Burpee 1992; Waipara et al. 1993). These necroses inhibited leaf regrowth from the root after defoliation (Burpee 1992).

BC recommendable at this point: No Taraxacum officinale has become very widespread on South Georgia, and has changed the landscape on this island over the last two decades (possibly promoted by the effects of climate change). It remains, however, mainly restricted to exposed open ground, not outcompeting natural vegetation, although some concerns exist with regards to a diminishing availability of habitats for native invertebrates. BC would be feasible, but is currently not seen as required as the species does not spread into naturally vegetated habitats. Any identified suitable control agents would need to be extremely host specific, as they would otherwise pose a significant risk to native Taraxacum taxa on the neighbouring Falkland Islands. In addition, determination of host specificity would initially require a more detailed identification of the Taraxacum population(s) introduced on South Georgia.

Cardamine glacialis 30 24 62 77.5 Brassicaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No There are good prospects of eradicating this species completely, and control efforts using herbicides are

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underway. The implementation of BC is therefore currently not deemed appropriate. A particular problem would be the risk of spread of any introduced natural enemies to the Falklands, where C. glacialis is a valued native species. However, in case of persistent recurrence of the species on South Georgia, a survey for natural enemies on the Falklands can be highly recommended. Low densities of C. glacialis on the Falklands indicate that is kept in balance by insects or pathogens there. If introduced to South Georgia, after host‐specificity tests, these agents would not pose significant risks for the target species or closely related species on other islands.

Ranunculus repens 35 43 79 64.3 Ranunculaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programmes is feasible.

BC recommendable at this point: No Limited environmental impacts of this species do not justify the uptake of BC at this point.

Poa annua 25 33 79 59.8 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, BC of grasses on South Georgia is regarded as unsuitable, in particular, because any introduced agents could spread to the Falkland Islands where target species are beneficial fodder grasses for livestock. The occurrence on the Falklands of native species of target genera is also problematic, as it is notoriously difficult to identify very host‐specific control agents for grasses. In addition, it is expected that the native Acaena on South Georgia will better compete against introduced grasses once reindeers are eradicated.

Poa pratensis 25 33 79 59.8 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, BC of grasses on South Georgia is regarded as unsuitable, in particular, because any introduced agents could spread to the Falkland Islands where target species are beneficial fodder grasses for livestock. The occurrence on the Falklands of native species of target genera is also problematic, as it is notoriously difficult to identify very host‐specific control agents for grasses. In addition, it is expected that the native Acaena on South Georgia will better compete against introduced grasses once reindeers are eradicated.

Cerastium fontanum 20 33 62 37.6 Caryophyllaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

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3.2.4 South Georgia - Invertebrates Only six non-native invertebrate species generated an impact score of 20 or above. These were evaluated further with the prioritisation tool, and detailed assessments are given in Table 7. Based on these, we currently regard only one invertebrate species, the greenbottle fly Calliphora vicina, as a feasible target for classical biological control. Even so, due to low levels of confirmed negative impacts caused by this species, major control efforts seem currently not to be justified. We believe that none of the other non-native invertebrates is a suitable target for biological control. The main reason for this is the lack of previous biological control programmes against the majority of these species, or even against other members of the families to which these species belong. One exception would be Aptinothrips stylifer, for which we could see the possible development of a biological control programme. However, we regard the current impact of this species on native biodiversity as insufficient to justify the development of such a relatively large programme, which would not be able to draw on ‘off the shelf’ solutions. In summary, we do not regard any of the non-native invertebrate species on South Georgia as appropriate for biological control at this moment. This may change, particularly if on-going monitoring activities record an increase in the negative impacts of individual species. In such a case, the assessments given below can provide valuable background information on available options for further steps.

Table 7: Assessment of non-native invertebrate species on South Georgia for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol TOTAL x IMPACT EFFORT BIOCONTROL FEASIBILITY Calliphora vicina 30 12 34 85.0 Diptera (Calliphoridae)

BC feasible: Yes Extensive research on BC of Calliphoridae in general has been conducted in the past; however, despite partial successes, BC does not seem to be a widely applied method of control for this taxonomic group. Alysia manducator (Hym. Braconidae), Brachymeria podagrica (Hym. Chalcididae), Nasonia vitripennis (Hym. Pteromalidae) were introduced in the 1920s to New Zealand to control Calliphoridae (Miller 1922, 1927; Biocat 2010). Previous experiences on islands are mostly related to the control of calliphorid and other flies developing in dung (Ripa 1990). Based on previous programmes, BC seems feasible against this species, at least to some degree. However, the costs and efforts involved in selecting and testing the most suitable BC agents are currently unlikely to provide more effective control than other applied methods (Sargison 2008).

BC recommendable at this point: No Limited environmental impacts of this species do not justify the uptake of BC at this point.

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Dendrodrilus rubidus 20 28 66 47.1 Oligochaeta (Lumbricoidea)

BC feasible: No There is no history of BC against Lumbricidae (or earthworms, in general). Development of biological control programmes would require a large‐scale research effort, and the efficacy of this method against this taxonomic group remains speculative. Such efforts could only be justified by substantial negative impacts of the target species on native taxa and habitats, which have not yet been recorded from South Georgia.

BC recommendable at this point: No

Trechisibus antarcticus 25 29 34 29.3 Coleoptera (Carabidae)

BC feasible: No There is no history of BC against Carabidae, in contrast with the use of carabid beetles for BC of other pest species. Development of biological control programmes would require a large‐scale research effort, and the efficacy of this method against this taxonomic group remains speculative. Such efforts could only be justified by substantial negative impacts by the target species on native taxa and habitats. However, despite some indications of negative impacts by Carabidae on South Georgia, evidence of long‐term threats to native species and severe habitat alterations has not yet been obtained.

BC recommendable at this point: No

Scatopse notata 20 28 37 26.4 Diptera (Scatopsidae)

BC feasible: No There is no history of BC against Scatopsidae. Development of biological control programmes would require a large‐scale research effort, and the efficacy of this method against this taxonomic group remains speculative. Such efforts could only be justified by substantial negative impacts of the target species on native taxa and habitats, which have not yet been recorded from South Georgia.

BC recommendable at this point: No

Oopterus soledadinus 20 29 34 23.4 Coleoptera (Carabidae)

BC feasible: No There is no history of BC against Carabidae, in contrast with the use of carabid beetles for BC of other pest species. Development of biological control programmes would require a large‐scale research effort, and the efficacy of this method against this taxonomic group remains speculative. Such efforts could only be justified by substantial negative impacts by the target species on native taxa and habitats. However, despite some indications of negative impacts by Carabidae on South Georgia, evidence of long‐term threats to native species and severe habitat alterations has not yet been obtained.

BC recommendable at this point: No

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Aptinothrips stylifer 20 47 48 20.4 Thysanoptera (Thripidae)

BC feasible: No There exist numerous examples of biological control against species in the same family; however, these programmes are concerned exclusively with horticultural pests, and regard predominantly augmentative BC in greenhouses (mostly without the need to conduct specific host‐range testing). Development of a biological control programme for Aptinothrips stylifer seems feasible, but would still require considerable research efforts. Such efforts could only be justified by substantial negative impacts by the target species on native taxa and habitats, which have not yet been recorded from South Georgia.

BC recommendable at this point: No

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3.2.5 Ascension Island - Weeds

Forty-one non-native plant species generated an impact score of 20 or above and were further evaluated with the prioritisation tool. The results of these assessments are outlined in Table 8. Initially, Opuntia stricta generated an extremely high overall score. However, site visits on Ascension revealed that satisfactory control had been achieved by previous biological control efforts. Consequently, this species has been eliminated from the list of species considered for further interventions using this method. Classical biological control has already been implemented against Mexican Thorn Prosopis juliflora on Ascension. Two species of host-specific, seed-feeding bruchid beetles, Algarobius prosopis and Neltumius arizonensis (see Figure 3) were introduced to the island in the 1990s, and have resulted in some success, probably slowing down the still on-going spread of the plant (Fowler 1998, 2011; Jewsbury 2001; Cheesman 2006; White 2009). Nonetheless, it emerged during on-site stakeholder consultations that P. juliflora still poses the biggest threat to indigenous biodiversity and landscape features of any introduced plant species. Consequently, further efforts can be regarded as a high priority, particularly as a new, highly effective and safe agent has become available. For biological control of P. juliflora, the currently most promising agent is a small gelechiid moth, Evippe sp., which has caused spectacular damage to Prosopis spp. in dry tropical parts of Australia (van Klinken et al. 2009; Fowler 2011).

Figure 3: Stamps issued in 1998 on CBC on Ascension Island.

Because it has never been a target for biological control in the past, Wild Tobacco Nicotiana glauca did not score highly under the modified Paynter assessment. However, it emerged during extensive stakeholder consultations on Ascension in March 2012 that classical biological control was a potential way forward against this species, which (aside from Mexican Thorn) probably poses the greatest threat of all non-native weeds to endangered native species on the island. In cases like Nicotiana glauca, without a history of biological control programmes elsewhere, a full project would be more costly compared with species where successfully tested host-specific agents are readily available. However, the severity of the invasion of wild tobacco justifies an initial exploration of the potential for

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classical biological control, including a survey for suitable control agents in the area of origin of Nicotiana glauca. Another species achieving a very high overall score but initially thought to be an unlikely candidate for further biological control because of successful previous attempts was Lantana camara. Here, stakeholder consultations and field site visits revealed that the introduced control agents have only been fully effective against L. camara where it occurs at relatively low altitude on the island. As the species still poses a severe threat to the indigenous fauna and flora in higher parts of Ascension, it remains a promising target for improved biological control through additional effective and tested agents. During the first initial assessment Rubbervine Cryptostegia grandiflora achieved a very high overall score, partly due to the extremely damaging effects it has had on native ecosystems globally and partly due to the availability of tested and effective control agents. However, as C. grandiflora seems to be a rather recent introduction to Ascension, complete eradication may still be feasible (resulting in an exclusion from further assessments in this study), and attempts at this should take priority over other options. However, biological control could provide a readily available ‘off the shelf’ solution should C. grandiflora spread more widely. (We suspect that this could occur in a relatively short period of time, given that habitat conditions on Ascension are similar to those in parts of the plant’s area of origin in Madagascar).

Biological control using the thrips Liothrips urichi could be very successful for Clidemia hirta. However, this will depend on how much of the population of C. hirta occurs in open areas with direct sunlight as the control agent is only effective under such conditions (see Table 7). For some species, no readily available biological control agents have been tested and proven to be effective, but research efforts are on-going as these species cause severe problems in other geographical regions. This group includes Leucaena leucocephala, Tecoma stans, Casuarina equisetifolia, Argemone mexicana, Sonchus asper, S. oleraceus and Cynodon dactylon. For these species, suitable agents may become available in the future. Alternatively, independently funded scoping studies and host-range testing could be initiated. Such larger scale projects need, of course, to be considered in relation to the current or imminent threats these species pose to indigenous species and habitats. Although they achieved relatively low overall scores, it may be worth considering in more detail the potential of biological control against Alpinia zerumbet, Buddleja madagascariensis and Rubus pinnatus, as other species within these genera are currently the subjects of biological control programmes. The lack of closely related species on Ascension could make them suitable targets, based on the results of these on-going projects. In particular, complementary initial scoping studies looking for suitable biological control agents can be highly recommended. Psidium guajava, Juniperus bermudiana, Heliotropium curassavicum, Begonia hirtella, Commelina diffusa, Chenopodium murale, Adiantum raddianum, A. capillus-veneris, Paspalum scrobiculatum and Borreria verticillata belong to a group of plants that have received no (or insufficient) attention from biological control programmes historically. Initiating new control projects would be costly, compared to situations where ‘off the shelf’ solutions are available, and would need to be justified on a case-by- case basis according to the scale of current and expected impacts. We currently regard the impact of these species on the indigenous biodiversity to be too low to recommend the implementation of full scale biological control projects. However, this preliminary judgement may turn out to be unjustified for some of these species in the future, and remains open for reassessment at any time. The feasibility of BC of all species with a high impact factor is described in Table 7, with the species arranged in order of their overall assessment score. As noted above, however, this does not necessarily reflect the actual priority order of species for biological control. Taking stakeholder consultations and all other available information into account, the implementation of biological control efforts can currently be strongly recommended for the following four species (in order of priority):

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1. Mexican Thorn (Prosopis juliflora) 2. Wild Tobacco (Nicotiana glauca) 3. Mexican Poppy (Argemone mexicana) 4. Spanish Flag (Lantana camara)

Table 8: Assessment of non-native plant species of Ascension Island for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol TOTAL x EFFORT BIOCONTROL FEASIBILITY IMPACT Lantana camara 45 4 100 1125.0 Verbenaceae

BC feasible: Yes Worldwide, well over 200 releases have been made (of 39 different natural enemies, in 29 countries); however, in the majority of cases, the control agent either failed to become established or became established without achieving control. Despite this limited success, classical biological control is still considered to be the only viable, long‐term control option, since it offers a safe, economic and environmentally benign method of suppressing the weed. Most previous releases have been carried out in the Pacific, South Africa and Australia (for historical details see Taylor 1989; Cilliers & Neser 1991; Davis et al. 1992; Denton et al. 1991; Swarbrick et al. 1995). The most widely established species include Ophiomyia lantanae, Uroplata girardi and Octoma scabripennis. Day et al. (2003) have produced a detailed review of 48 control agents (CABI ISC 2012). Teleonemia scrupulosa has been used to control L. camara on St Helena (Ashmole & Ashmole 2000).

BC recommendable at this point: limited Lantana camara appears to be under successful biological control on Ascension Island, arising from attack by the deliberately released tingid bug Teleonemia scrupulosa, the hispid beetle Uroplata girardi, and the accidentally introduced ‘Jacaranda bug’. The infamous ‘Jacaranda bug’, Orthezia insignis, nearly caused the demise of the endemic gumwood trees on St Helena before its successful biological control in 1993‐4. However, it does not appear to attack any other plant species on Ascension Island to any great extent, so its present role seems beneficial (Fowler 2011). Interestingly, BC of L. camara on Ascension seem to be mostly restricted to lower altitudes; at higher levels, large stands of Lantana still thrive. The introduction of other readily available and tested control agents, in particular the leaf rust Prospodium tuberculatum, may be able to reduce Lantana more widely on Ascension, and more detailed assessments of this potential are recommended.

Prosopis juliflora 55 13 80 338.5 Mimosaceae

BC feasible: Yes Several biological control programmes using species of seed‐feeding bruchid beetles have been developed and implemented worldwide. The advantage with bruchids is their observed host specificity, with many species found to feed only on Prosopis, and some only on a single species. Other insect species known to have a deleterious effect on native and exotic Prosopis in the Americas, mainly twig girdlers and psyllids, have also been suggested as possible biological control agents. The twig girdler Oncideres limpida attacks P. pallida in

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Brazil (Lima 1994), whereas Oncideres rhodostricta is seen as a serious pest of P. glandulosa in the USA (Polk & Ueckert 1973). Psyllids are known to severely affect the growth of Prosopis (Hodkinson 1991) and have been suggested for use in controlling invasions. Two bruchid species were introduced to Ascension Island in an attempt to control P. juliflora, which is present on 80% of the island, often in dense thickets. Two other species, one a psyllid and the other a mirid, were identified as attacking P. juliflora on Ascension Island and were thought to have been introduced accidentally from the Caribbean. The mirid Rhinocloa sp. causes widespread damage and is thought to lead to substantial mortality of trees (Fowler 1998; CABI ISC 2012). White (2009) recorded stunting from these insects on 98% of the Mexican thorn trees she sampled, with 30% showing heavy dieback. High levels of damage from these insects was not apparent in visits to the island in 1993 and 1995, however, but were very obvious in 1997 (Fowler 1998, 2011).

BC recommendable at this point: Yes Currently, the general opinion is that the introduced herbivores noted above, by causing substantial damage to the plant, have brought down levels of recruitment of new seedlings considerably. However, Mexican thorn is still expanding its range on Ascension, albeit at a slower pace than might have been the case otherwise.

During extensive stakeholder consultations on Ascension in March 2012, the prospect of enhancing on‐going biological control of Mexican thorn through the introduction of additional agents was discussed. Synergistic effects of a whole suite of agents, including new introductions, have a high potential to finally reduce overall population densities, size of individual plants and area of invaded habitat. This would provide substantial support to other (mechanical and chemical) management efforts, and could eventually allow the species to be driven back or eradicated from vulnerable sites such as turtle nesting beaches or other valuable and threatened locations. During the stakeholder consultations, it was seen as worthwhile in particular to consider introduction of additional species that have already been tested for host specificity and used successfully in other parts of the world. Such ‘off the shelf' solutions are very cost effective and would require only limited additional host‐range testing with native or valued plant species. This approach is also in line with Fowler (2011), who recommends targeting of limited resources on integrated management of Mexican thorn, through continuation of existing site‐specific efforts and the release of further biocontrol agents with a proven track record if these are readily available.

One candidate seems to be particular well suited for a release on Ascension. This agent is a tiny (as yet undescribed) gelechiid moth, Evippe sp. from Argentina, which has caused spectacular damage to Prosopis spp. in dry tropical parts of Australia (Fowler 2011; van Klinken et al. 2009). It has been introduced throughout Australia, but performs best where conditions are warm to hot all year round, very similar to the climate on Ascension (van Klinken et al. 2009). Where it has become established, it maintains high densities, resulting in greatly reduced growth rates and seed production. However, tree mortality remains limited even after prolonged defoliation (van Klinken et al. 2009). This means that rapid die‐back of Mexican thorn is unlikely; instead, further spread should be curtailed, followed by a slow decrease of the population over time. This would be very helpful as part of an integrated control approach at localities of high conservation value (including avoiding re‐colonisation after clearance), but should also be compatible with the perceived beneficial impacts of Mexican thorn discussed above.

Leucaena leucocephala 25 15 91 151.7 Mimosaceae

BC feasible: Yes BC was first contemplated in Hawaii (Smith 1985) and South Africa (Neser 1994), but has been frustrated by the economic importance of L. leucocephala. Nonetheless, proposals to release the seed‐eating bruchid Acanthoscelides macrophthalmus in South Africa were pursued (Neser 1994; Henderson 2001), and the species has also been accidentally introduced into Australia (CABI ISC 2012). The psyllid Heteropsylla cubana (accidentally spread in the mid‐1980s) can cause cyclical defoliation, but does not kill trees; the psyllid itself appears to have been brought under control by a number of generalist local (and in some cases introduced)

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psyllid predators and parasites (GISD 2012).

BC recommendable at this point: No On Ascension, there is currently some damage reported by the beetle Acanthoscelides suramerica, which probably arrived accidentally from the Caribbean in 1997 (Fowler 2011). Because of the currently relatively limited negative impacts of the plant, BC of this species is not a priority at this stage. However, close monitoring of the population is recommended.

Tecoma stans 30 15 69 138.0 Bignoniaceae

BC feasible: Yes Host specificity tests on two rust fungus species, namely, the microcyclic Prospodium transformans and the macrocyclic P. appendiculatum from Mexico, are in progress in South Africa. P. appendiculatum is already present in Brazil and Argentina, but is not contributing much to the suppression of populations. Further surveys for additional host‐specific natural enemies are planned. A raceme‐feeding membracid and the pyralid pod‐feeding moth Clydenopteron sp. are to be introduced into quarantine in South Africa for possible biological control (CABI ISC 2012).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant on Ascension, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Clidemia hirta 20 15 101 134.7 Melastomataceae

BC feasible: Yes Biological control using the thrips Liothrips urichi was initiated in Fiji in the early 1930s, and two decades later in Hawaii (Mune & Parham 1967; Wester & Wood 1977). L. urichi seriously affects the growth of C. hirta in open, sunny areas, whereas in shaded areas (forest or frequent cloud cover) it is not effective. The thrips failed to establish following their introduction to the Solomon Islands (Julien 1987). Over the past four decades, extensive searches for biological agents to control C. hirta in Hawaiian forests have been made (Nakahara et al. 1992). A pyralid moth, Blepharomastix ebulealis [Ategumia ebulealis], released in 1970, has been heavily parasitized and has been ineffective in controlling C. hirta. Several of 14 species of insects recently evaluated in Trinidad can be considered for introduction into Hawaii, and the release of four pathogens is envisaged. A leaf spot fungus, Colletotrichum gloeosporioides f.sp. clidemiae, introduced from Panama to Hawaii for host‐range studies, shows promise as a biocontrol agent. The introduction of effective biological control agents into Hawaii must be considered with care; the potential sudden death of large monotypic stands of C. hirta, found on steep mountain sides, could result in either severe soil erosion or the establishment of other invasive species such as Psidium cattleianum (Smith 1992; CABI ISC 2012).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant on Ascension, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

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Casuarina equisetifolia 25 12 61 127.1 Casuarinaceae

BC feasible: Yes USDA Agricultural Research Service (ARS) scientists have been searching in Australia's outback and coastlines for insects that could provide biological control of C. equisetifolia (Flores 2008). From 300 species, including wasps, weevils, stem‐borers, sap‐suckers and seed‐eaters, about 12 candidates have been identified. Not only do these agents attack C. equisetifolia, but many also attack the related invasive C. glauca and C. cunninghamiana. The most promising potential agents include the seed‐feeding wasp Bootanelleus orientalis, which is host‐specific to Australian pine, and the defoliator moth Zauclophora pelodes. These insects are still undergoing testing to determine their suitability for use as biocontrol agents in the United States (GISD 2012).

BC recommendable at this point: No There is a high likelihood of competition with the endemic Ascension spurge. On the other hand, the species has some value as an ornamental tree (Ashmole & Ashmole 2000). It is generally considered on Ascension that mechanical control (felling of timer) would be a straightforward option, should further spread threaten native species; therefore we do not regard BC as the preferred option for control of this species at this point.

Alpinia zerumbet 35 29 100 120.7 Zingiberaceae

BC feasible: Yes Alpinia zerumbet is invading suitable habitats of native endemic ferns (Lambdon et al. 2009). Mechanical control is difficult, as small fragments of rhizome quickly lead to recolonization of cleared areas. Biological control is feasible, particularly as no other members of this plant family are commercially used on the island. Currently, a number of insects are being tested to control Wild Ginger (Hedychium) on Hawaii, in South Africa and New Zealand. Some of these species are feeding on several genera within the Zingiberaceae, and their potential for the control of Alpinia could easily be tested.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant on Ascension, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Argemone mexicana 30 15 53 106.0 Papaveraceae

BC feasible: Yes This native of Mexico is naturalized in most warm countries of the world, in sub‐humid as well as semiarid regions. A bacterial wilt, Xanthomonas papavericola [X. campestris pv. papavericola], periodically checks the growth of A. mexicana in some areas (Holm et al. 1977), but there is a dearth of information on natural enemies of this weed. A biological control programme against A. mexicana and the closely related A. ochroleuca has been initiated in Australia. This project sought natural enemies in Mexico and identified several predatory insects including an extremely damaging species of root‐breeding and leaf‐feeding weevil (CSIRO 1999; Julien 2002; CABI ISC 2012).

BC recommendable at this point: Yes Similar to tree tobacco, this species poses a serious threat to the biological diversity of the Ascension and is threatening nesting sites of marine turtles by colonising beaches. As Ascension harbours the second largest breeding ground for the green turtle in the South Atlantic, any efforts to control the spread of Argemone mexicana should be explored.

Although BC would not lead to a complete eradication of Argemone mexicana on Ascension, it may have the

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potential to reduce its overall population densities, size of individual plants and area of invaded habitat. In doing so, it would provide substantial support to other (mechanical and chemical) control efforts. This may eventually allow the plant to be driven back or eradicating from vulnerable sites such as turtle nesting beaches. The severity of the invasion justifies further exploration of the potential for BC, initially through exploration of insects identified by Australian workers and/or additional surveys for suitable control agents in the area of origin.

Psidium guajava 40 31 76 98.1 Myrtaceae

BC feasible: Yes Biological control is invariably problematic for this species, because there are direct conflicts of interest with fruit growers (Smith 1998); consequently, and no programmes have been implemented (CABI ISC 2012).

BC recommendable at this point: No Ineffective attempts to control Psidium guajava on Ascension were made around 1900 (Ashmole & Ashmole 2000). Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Heliotropium curassavicum 40 31 69 89.0 Boraginaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant on Ascension, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Nicotiana glauca 50 38 64 84.2 Solanaceae

BC feasible: Yes Nicotiana glauca has been reported to be invasive in a number of countries but there has never been a full attempt to control this species by biological means. The only existing reference in the literature, mentioning the successful use of a beetle (Malabris aculeata) in combination with an herbicide (Cronk & Fuller 2001), which is widely cited on factsheets and in databases is often misquoted. It remains doubtful whether this refers to biological control at all. So far, Nicotiana glauca has not been regarded as a priority target species for BC in other countries, because of a generally limited impact on agriculture and the environment in combination with the economic importance of closely related commercially used members of the same plant family, in particular of tobacco (Nicotiana tabaccum) itself. The Management Plan developed for Ascension (Pickup 1999) recommends attempting to push invasion fronts back and control seed spread. However, for St Helena, Ashmole & Ashmole (2004) observe that the complete removal of wild tobacco is probably impracticable (GISD 2012).

BC recommendable at this point: Yes Tree tobacco poses a serious threat to the biological diversity of Ascension Island, where it is invading lowland areas. The species has spread rapidly over the last 20 years (Ashmole & Ashmole 2000), and is now threatening biodiversity within the Hummock Point nature reserve and nesting sites of marine turtles. The species has also been reported to cause damage to roads by its expansive root system. Opinions over possible beneficial effects (diminishing soil erosion) are currently divided. The colonisation of beach nesting sites of the green turtle Chelonia mydas, an internationally protected species, in recent years is particularly alarming from a conservation perspective. The Management Plan (Pickup 1999) recommends removing this species

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from all beaches. However, so far, attempts to control Nicotiana glauca mechanically have been only partially successful and seem not to have been able to stop its continuing spread, even locally on such critically important sites. It seems to be likely that, as on St Helena, a complete removal of wild tobacco on Ascension using conventional methods is currently impracticable (Ashmole & Ashmole 2004). Without management, however, tree tobacco has the potential to further colonise habitats on Ascension Island, to the detriment of native (including endemic) biodiversity. An invasion by this species could, for example, reduce niche availability and thereby displace invertebrate species.

During extensive stakeholder consultations on Ascension in March 2012, classical biological control was discussed as a potential way to advance control of wild tobacco. Although it will not lead to a complete eradication of Nicotiana glauca on Ascension, BC may have the potential to reduce population densities, size of individual plants and area of invaded habitat, supporting other (mechanical and chemical) management efforts. This may eventually allow the plant to be driven back or eradicated from vulnerable sites. In cases like Nicotiana glauca, without a history of biological control, implementation of a full project would be more costly compared with species where successfully tested host‐specific agents are readily available. However, the severity of the invasion by wild tobacco justifies an initial exploration of the potential for BC, e.g. through surveys for suitable control agents in the area of origin of Nicotiana glauca.

Pennisetum clandestinum 35 28 65 81.3 Poaceae

BC feasible: Yes The rust fungus Phakopsora apoda has been released in South Africa and has become established. This agent decreases the photosynthetic capacity of the leaves, but does not kill the plant (Haubensak & Smyth 1999). Pennisetum clandestinum is also affected by the fungus Pyricularia grisea, which can kill seedlings (FAO 2003; GISD 2012). Two insects, Sphenophorus ventus vestitus and Herpetogramma licarsicalis, damage kikuyu grass in Hawaii, but it is not known if these are native natural enemies (Cronk & Fuller 2001).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Piper aduncum 30 29 76 78.6 Piperaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Begonia hirtella 30 31 79 76.5 Begoniaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

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Commelina diffusa 30 31 69 66.8 Commelinaceae

BC feasible: Yes There have not been any attempts to use biological control against Commelina spp. and the possibilities have not been explored. However, Waterhouse (1994) notes that, although Commelina spp. are believed to be of Old World origin, it is curious that there are no records of agromyzid leaf miners, except from the Americas, and therefore tropical and subtropical areas of the Americas may be promising sources of candidate biological control agents (CABI ISC 2012).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Rubus rosifolius/nanus 35 38 71 65.4 Rosaceae

BC feasible: Yes Rubus rosifolius is susceptible to strawberry mild yellow edge‐associated potexvirus, transmitted (in a non‐ persistent manner) by the insect vector Chaetosiphon fragaraefolii (Aphididae). The virus possibly requires, for vector transmission, a helper virus (strawberry mild yellow edge luteovirus) transmitted by mechanical inoculation and by grafting (Brunt et al. 1996; GISD 2012).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Sonchus asper 25 21 51 60.7 Asteraceae

BC feasible: Yes CSIRO (2007, 2011) has recently assessed prospects for managing S. asper and other Sonchus species through BC in Australia but, so far, only two widespread species native to Australia, the rust fungus Miyagia pseudosphaeria and an undescribed species of eriophyid mite, have been identified as potential agents. Sonchus species have also been the subject of biological control in Canada, and surveys for biological control agents have been made in southern France and northern Europe (Scott & Jourdan 2005; Peschken 1984; GISD 2012).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Pennisetum macrourum 35 38 65 59.9 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

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Plantago lanceolata 25 28 65 58.0 Plantaginaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Juniperus bermudiana 25 28 64 57.1 Cupressaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended. It should also be noted that Juniperus bermudiana is a threatened species in its area of origin (GISD 2012).

Rubus pinnatus 30 40 76 57.0 Rosaceae

BC feasible: Yes Nothing is known about BC of this species, but other Rubus species (such as R. niveus and R. ellipticus) are currently subject to research in this respect. It seems likely that BC of R. pinnatus is feasible, at least in the absence of any commercially valuable, closely related species.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended. Rubus pinnatus rapidly grows to a much larger size than the common bramble of Europe (Rubus fruticosus agg.). Early attempts to eradicate this species on St. Helena have failed, as the plants regrows from any root fragments left in the soil (Jackson 1905; GISD 2012).

Melinis minutiflora 30 40 74 55.5 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Chenopodium murale 25 24 51 53.1 Chenopodiaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

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BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Vitex trifolia 20 29 76 52.4 Verbenaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Cynodon dactylon 30 40 68 51.0 Poaceae

BC feasible: Yes Drechslera cynodontis, Ustilago cynodontis, Puccinia cynodontis, and Fusarium poae as fungal pathogens and a specimen belonging to the Thripidae family have been identified on C. dactylon and are being studied for potential use in biological control (Uygur 2000; CABI ISC 2012).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Adiantum raddianum and A. capillus‐veneris 30 38 64 50.5 Adiantaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Paspalum scrobiculatum 30 40 67 50.3 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Borreria (Spermacoce) verticillata 30 40 67 50.3 Rubiaceae

BC feasible: No No information on BC of this species is available. There is also a theoretical risk that any BC agent could endanger the endemic Oldenlandia adscensionis. Although this is now believed to be extinct, it is closely related to S. verticillata.

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BC recommendable at this point: No

Buddleja madagascariensis 20 31 76 49.0 Buddlejaceae

BC feasible: Yes Nothing is known about BC of this species, but other species within this genus are currently subject to research. It seems possible that biological control of Buddleja may be feasible in the future. In 2006, Cleopus japonicus was introduced and released as a potential biocontrol agent for B. davidii in New Zealand (Zhang et al. 1993; Kriticos et al. 2006; Watson 2007). Further releases were made in 2007 and 2008, following careful monitoring of weevil behaviour and establishment (Watson 2008). As of 2009, it was still considered too early to judge the field effectiveness of C. japonicus. A second species under consideration for biological control of B. davidii in New Zealand is the stem weevil, Mecysolobus erro. The adults feed on the tender terminal shoots causing tips to wither and die. Host‐range testing of this species is still underway (Kay 2002; CABI ISC 2012).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Waltheria indica 20 31 76 49.0 Sterculiaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Sonchus oleraceus 20 21 51 48.6 Asteraceae

BC feasible: Yes CSIRO (2007, 2011) has recently assessed prospects for managing S. asper and other Sonchus species through BC in Australia but, so far, only two widespread species native to Australia, the rust fungus Miyagia pseudosphaeria and an undescribed species of eriophyid mite, have been identified as potential agents. Sonchus species have also been the subject of biological control in Canada, and surveys for biological control agents have been made in southern France and northern Europe (Scott & Jourdan 2005; Peschken 1984; GISD 2012).

BC recommendable at this point: No Because of the currently relatively limited negative impacts of this plant, BC of the species is not a priority at this stage. However, close monitoring of the population is recommended.

Acacia farnesiana 20 29 67 46.2 Mimosaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

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Ricinus communis 25 38 61 40.1 Euphorbiaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Ageratum conyzoides 30 38 50 39.5 Asteraceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Digitaria ciliaris/D. sanguinalis 25 38 53 34.9 Poaceae

BC feasible: No There are no reports of serious interest in, or attempts at BC against this species (CABI ISC 2012).

BC recommendable at this point: No

Setaria verticillata 25 40 55 34.4 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Conyza bonariensis 25 38 48 31.6 Asteraceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Eleusine indica 20 40 50 25.0 Poaceae

BC feasible: No Biological control of Eleusine indica has been considered in great detail in Australia, where the related finger millet (E. coracana) does not occur (e.g. Wapshere 1990a, b; Waterhouse 1993, 1994). For classical biocontrol, potential organisms include the smut fungus Melanopsichium eleusinis, the nematode Heterodera delvii, and certain cecidomyiid gall midges (Contarinia sp.) but all require further study before they could be

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used. Fungi which might be developed as mycoherbicides include Bipolaris [Cochliobolus] setariae and Pyricularia [Magnaporthe] grisea (Figliola et al. 1988) but no active programme of development of these has yet been reported (CABI ISC 2012).

BC recommendable at this point: No

Euphorbia hirta 30 50 36 21.6 Euphorbiaceae

BC feasible: No Jeritta & David (1986) reported that Haplothrips euphorbiae was specific to E. hirta; however no information on BC is currently available (CABI ISC 2012).

BC recommendable at this point: No

Solanum nigrum 30 50 35 21.0 Solanaceae

BC feasible: No No natural enemies have been recorded for S. nigrum, although it has been shown to be a host for many nematode and virus pests, and the thrip pest Frankliniella occidentalis (Lacasa et al. 1996; CABI ISC 2012).

BC recommendable at this point: No

Cryptostegia grandiflora 0 0 0 0 Asclepiadaceae

BC feasible: Yes The leaf‐feeding caterpillar Euclasta whalleyi, from Madagascar, was released in Queensland, Australia in 1988‐1991 (McFadyen & Harvey 1990; McFadyen & Marohasy 1990), despite the fact that it is not specific to the target genus Cryptostegia but only within the sub‐family Periplocoidae. However, its impact on the weed has been insignificant (Tomley 1995), probably due to parasitism, although more recent reports indicate that permanent populations may be establishing (Mo et al. 2000). Assessments of the Madagascan rust fungus Maravalia cryptostegiae showed that this pathogen had the highest biocontrol potential of the natural enemies surveyed, being highly damaging, specific at the genus level, and climatically adapted to Queensland conditions (Evans 1993; Evans & Fleureau 1993; Evans & Tomley 1994). This potential has now been proven, and a strain of the rust from south‐west Madagascar, introduced in 1995, has had an enormous impact on the weed throughout its invasive range following a mass production and release programme (Evans 2002; Tomley & Evans 2004). Rust‐induced defoliation has resulted in a significant reduction in weed biomass leading to almost complete loss of fecundity, as well as to widespread plant death (Tomley & Evans 2004; CABI ISC 2012). The population currently recorded on Ascension still seems to be small. However, considering the high risk that this species poses to indigenous habitats, and the ready availability of tested and effective control agents, this species should certainly be considered for CBC should eradication efforts fail.

BC recommendable at this point: No Complete eradication of this high risk invasive species is currently still possible, as only a limited number of ornamental plants have been recorded. However, because effective BC agents are readily available, it is retained on the list of plants with a high potential for application of this method on Ascension. It is certainly recommended that the status of this species is monitored very closely; should eradication fail, fall‐back to CBC is certainly feasible.

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3.2.6 Ascension - Invertebrates Only nine non-native invertebrate species achieved an impact score of 20 or above and were further evaluated with the prioritisation tool. Individual assessments for each species are given in Table 9. Currently, we regard only one invertebrate species, the hemipteran Icerya purchasi, to be a worthwhile target for classical biological control. However, this species has been the subject of at least partially successful biological control on Ascension in the past. Renewed efforts should only be taken up if current control levels by Rodiola cardinalis, particularly where the pest is impacting on the endemic spurge Euphorbia origanoides, are not sufficient. In addition, augmentative control of Periplaneta americana is feasible; particularly as there are no native or endemic cockroach species known from Ascension. Again, however, low recorded impact levels do not justify extensive biological control efforts against this species at this moment. For other species, where biological control is potentially feasible but no effective biological control agents have already been identified, we currently regard the impact these species have on indigenous biodiversity to be too low to recommend the implementation of full scale biological control projects. However, this situation could change for some of these species, and our preliminary conclusion remains open for reassessment at any time. Species belonging to this group are Musca domestica and Cryptophlebia leucotreta. Despite an overall score of above 50, we do not regard biological control against the termite Cryptotermes brevis to be feasible at this time. Many attempts have been made over a long period to find suitable biological control options for termites, but so far no effective agents have been identified, despite considerable effort.

Table 9: Assessment of non-native invertebrate species on Ascension for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol TOTAL x IMPACT EFFORT BIOCONTROL FEASIBILITY Icerya purchasi 35 4 123 1076.3 Hemiptera (Coccoidea; Margarodidae[Monophlebidae])

BC feasible: Yes Rodolia cardinalis was released on Ascension Island in 1976 to control cottony cushion scale on ornamental plants (Cronk 1980; Pickup 1999). The beetle also provided protection for the endemic spurge Euphorbia origanoides, which was suffering decline due to scale attack (Cronk 1980; Fowler 2004). By 1995, scale density on the island was low, and the scale was completely absent on sampled E. origanoides populations (Cronk 1980). Icerya purchasi was also absent on E. origanoides when the plant was surveyed in 1997 (Ashmole & Ashmole 1997; van Driesche et al. 2010). Rodolia cardinalis was also introduced in 1896 and 1898 to control this pest on citrus on St. Helena (Greathead 1971).

BC recommendable at this point: No Previous BC seems to have been successful, but proper monitoring arrangements should be put in place, given the potential risks from any resurgent population of this damaging pest. Should resurgence occur, additional agents (as released on Sao Tome, before 1960) are readily available for the control of I. purchasi (Cryptochaetum iceryae; Cryptochetidae, Diptera) (Greathead 1971). Multiple introductions of Rodolia plus Cryptochaetum may also be effective, should further action be required (CABI ISC 2012).

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Periplaneta americana 30 12 63 157.5 Blattodea (Blattidae)

BC feasible: Yes Little information is available regarding classical BC of cockroaches, but there are numerous cases of augmentative BC for this group. Dolichurus stantoni (Hym. Ampulicidae), Rhinopsis caniculatus (Hym. Ampulicidae), Sceliphron haematogastrum (Hym. Sphecidae) have been introduced against cockroaches in general in Hawaii (Lai & Funasaki 1983; Biocat 2010). Ampulex compressa (Hym. Sphecidae) was introduced into Guam and Hawaii specifically to control this species (Lai & Funasaki 1983; Rao et al. 1971; Biocat 2010).

BC recommendable at this point: No Development of classical biological control programmes would require a large‐scale research effort, and efficacy of the method for this taxonomic group remains speculative. Such efforts can only be justified by substantial negative impacts of the species on native taxa and habitats, which have not yet been recorded on Ascension.

Musca domestica 20 14 81 115.7 Diptera (Muscidae)

BC feasible: Yes There is a long history of BC of Musca domestica and Muscidae in general. Consequently, a number of suitable, host‐specific control agents are readily available (Biocat 2010). However, even the relatively minor costs of 'off the shelf' solutions would need be weighed against impacts on native species and habitats (or as a nuisance pest), which appear to be very limited on Ascension at this time.

BC recommendable at this point: No Limited environmental impacts of this species do not justify the uptake of BC at this point.

Cryptophlebia leucotreta 25 22 69 78.4 Lepidoptera (Tortricidae)

BC feasible: Yes BC of this species has been undertaken in the past but is currently not deemed to be cost effective (Newton & Odendaal 1990). CBC would however be feasible, should impacts justify the start‐up of a BC programme.

BC recommendable at this point: No Development of a biological control programme against this species on Ascension would require significant research efforts, which would only be justified by substantial impacts of the species. Such impacts have not been recorded from Ascension as yet.

Cryptotermes brevis 20 25 66 52.8 Isoptera (Calotermitidae)

BC feasible: No Despite long‐running attempts to find suitable BC agents, no sufficiently effective control has yet been achieved with this method against Isoptera (Chouvenca et al. 2011).

BC recommendable at this point: No

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Scolopendra morsitans 25 29 37 31.9 Chilopoda (Scolopendromorpha; Scolopendridae)

BC feasible: No There is no history of BC against Chilopoda in general. Development of novel biological control programmes would require a large‐scale research effort, and the efficacy of this method for this taxonomic group remains speculative. Such efforts can only be justified by substantial negative impacts of the target species on native species and habitats, which have not yet been recorded from Ascension.

BC recommendable at this point: No

Paratrechina longicornis 25 31 32 25.8 Hymenoptera (Formicidae)

BC feasible: No Biological control agents exist for ants, such as phorid flies (Vazquez et al. 2006). However, the influence of such agents in regulating any ant population is still to be demonstrated; generally, CBC for ants has not been developed to a level where it can yet be successfully applied (CABI ISC 2012; Rabitsch 2011).

BC recommendable at this point: No

Pheidole megacephala 30 31 25 24.2 Hymenoptera (Formicidae)

BC feasible: No Biological control agents exist for ants, such as phorid flies (Vazquez et al. 2006). However, the influence of such agents in regulating any ant population is still to be demonstrated; generally, CBC for ants has not been developed to a level where it can yet be successfully applied (CABI ISC 2012; Rabitsch 2011).

BC recommendable at this point: No

Erechthias minuscula 20 48 11 4.6 Lepidoptera (Tineidae)

BC feasible: No There is no history of BC against this species. However, given the success of biological control against many other Lepidoptera, the potential of this method is clear. Nonetheless, development of a new programme would still require a substantial research effort, which could only be justified by greater impacts of the target species than have yet been recorded on Ascension.

BC recommendable at this point: No

3.2.7 St. Helena - Weeds With 61 non-native plant species generating an impact score of 20 or above, St. Helena appears to be substantially negatively affected by more alien weeds than any of the other UKOTs investigated. All 61 species were evaluated further with the prioritisation tool, and the results of these assessments are summarised in Table 10. It should be noted at the outset that the species achieving highest overall scores according to the prioritisation tool are not necessarily those for which biological control is the highest priority on St.

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Helena; for a number of them, this method probably does not provide the most suitable approach at this stage. Therefore, the results presented for St. Helena have a more preliminary character compared to those for the Falkland Islands, South Georgia and Ascension Island, where assessment results were reinforced or refined by direct stakeholder consultations and/or ground truthing. The three species achieving the highest overall scores (Opuntia stricta, O. ficus-indica, Lantana camara) have all been subject to biological control on St. Helena in the past. However, there are indications that all three species are still extremely widespread and continue to impact heavily on native flora and fauna. If this can be verified through more detailed assessments on the ground, all three species would become highly suitable and recommendable targets, as more effective, well- tested biological control agents have become available since the last programmes conducted on St. Helena. Ulex europaeus has been the subject of biological control programmes in other geographical regions. Consequently, ‘off-the-shelf’ biocontrol agents are available, significantly reducing the costs of implementing programmes against this species on St. Helena. However, the species provides some benefits, such nitrogen-fixing, and is seen as a good pollen source for bees. It has also been seen as providing good quality forage for livestock, but is no longer favoured due the ready availability of alternatives. With regards to the control of this species, a detailed cost-benefit analysis, including intensive stakeholder consultations, is required to determine the relationship between the perceived/actual value of the plant and any negative impacts it has on the local community and biodiversity. For a number of species, no readily available biological control agents have been tested and proven to be effective, but research efforts are still on-going as these species cause severe problems in other geographical regions. This group includes Asparagus asparagoides, A. densiflorus, Tecoma stans, Schinus terebinthifolius, Leucaena leucocephala, Carpobrotus edulis, Chrysanthemoides monilifera and Hedychium coronarium. For these species, suitable agents may become available in the near future. Alternatively, independently funded scoping studies and host-range testing could be initiated, if these are justified by the current or imminent threats that these plants pose to indigenous species and habitats. Furcraea foetida and Nicotiana glauca belong to a group where no or insufficient biological control projects have been conducted in the past. As in similar cases elsewhere, new control projects would be costly compared to ‘off the shelf’ solutions, and would need to be considered carefully considered. However, we currently regard the impact that these species have on indigenous habitats as sufficiently severe to recommend more detailed assessments, including stakeholder consultation, to analyse available options for future control efforts. In particular, N. glauca may turn out to be a species for which biological control measures could be combined with efforts on Ascension, where this species has been reported to impact heavily on endangered native wildlife. The feasibility of biological control against all species with a high impact score is outlined in Table 9, where species are arranged in order of their overall assessment score. As in other cases, this does not necessarily reflect the likely order of priority of species for biological control. Based on the available information, we tentatively recommend the uptake of biological control options for the following species (in order of priority):

1. Opuntia stricta 2. Opuntia ficus-indica 3. Lantana camara 4. Ulex europaeus 5. Asparagus asparagoides 6. Asparagus densiflorus 7. Tecoma stans 8. Schinus terebinthifolius 9. Leucaena leucocephala 10. Carpobrotus edulis

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11. Chrysanthemoides monilifera 12. Hedychium coronarium 13. Furcraea foetida 14. Nicotiana glauca

However, this preliminary evaluation of priorities is made without the benefit of field site visits and detailed stakeholder consultations, and is consequently subject to revision. Equally a number of species currently not listed here may be considered suitable for biological control on St. Helena after a more detailed assessment.

Table 10: Assessment of non-native plant species of St Helena for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol TOTAL x FEASIBILITY BIOCONTROL EFFORT IMPACT Opuntia stricta var. dillenii (Opuntia vulgaris) 35 4 100 875.0 Cactaceae

BC feasible: Yes The release of the cactus moth Cactoblastis cactorum in Australia in 1926, against O. stricta that had invaded about 24 million ha in Queensland and New South Wales, resulted in spectacular control of the weed. Today, remnant infestations of O. stricta are limited to regions where C. cactorum is less effective (Hosking et al. 1993). The cochineal Dactylopious opuntiae was first released in Australia in 1921, and provided excellent control of dense stands, but by 1928 there was a rapid decrease in cochineal populations following the major destruction of the weed by C. cactorum. Cochineal is still widely used as an effective biocontrol agent in areas where C. cactorum is less effective, such as high‐lying areas. The insects have limited dispersal abilities in low host‐plant density situations, and manual dispersal of infested cladodes to uninfested plants is necessary to ensure that maximum benefits are derived from this insect (Mann 1969; Hosking et al. 1993). Fifty years later, the biological control of prickly pears in Australia has continued to be satisfactory (CABI ISC 2012). In South Africa, serious infestations of O. stricta var. stricta only became apparent in the 1970s, with large infestations reported from the Krüger National Park. After the release of C. cactorum to these remote infestations, the insect became well established and had a striking effect on both the density and average size of the cactus plants in both dense and sparse infestations. However, C. cactorum mainly caused fragmentation of large plants, resulting in small fragments taking root and producing many new plants, increasing the density of small plants. Overall, C. cactorum has not reached levels required for satisfactory control, and excessive ant predation of eggs along with baboon predation of larvae may contribute to this (Hoffmann et al. 1998). Early attempts to establish the cochineal D. opuntiae, which was so effective on O. ficus‐indica, failed. In 1997, however, a new biotype was introduced from Australia which showed a strong preference for O. stricta and closely related species (Githure et al. 1999; Volchansky et al. 1999). After its release in the large infestations in the Krüger National Park, the increase in cochineal was dramatic, and stands of the cacti have totally succumbed to insect attack. Control is now aimed at manually spreading the insect to all clumps and large plants as a substitute for chemical control (Hoffmann et al. 1999). Few options for control remain other than mechanical and chemical control, which have been shown to be impractical and uneconomic (CABI ISC 2012).

BC recommendable at this point: Yes

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Opuntia stricta is extremely common over much of the lowlands, where it is one of the main colonist species. A very pernicious weed, it sometimes forms dense thickets which can be impenetrable by humans. The abundant fallen pads easily regenerate to give rise to new plants, making this species very difficult to manage (SAISP 2010). There are some perceived benefits of the plant, including that the undergrowth provides cover for rabbits. It is also a good colonist of bare ground, which helps to prevent erosion and provides a shaded microhabitat to encourage the establishment of herbs. It is therefore a useful plant at facilitating succession. The invaded habitats are often not greatly used by humans, and large stands may develop where land has been neglected. On‐going management is necessary to prevent populations from fouling‐up valleys and hillsides entirely (SAISP 2010). The moth Cactoblastis cactorum, which feeds on tungy pads, has already been introduced to St Helena in 1971 (Simmonds 1973; Ashmole & Ashmole 2000; SAISP 2010) but there are no detailed records of its impact. All indications are that enhanced CBC would promise a substantial and sustainable control comparable with Ascension. Initial cost/benefit analysis, in particular, in combination with consideration of the related Opuntia ficus‐indica, should be a first step before starting on a control programme based on agents with a proven safety and efficiency record.

Opuntia ficus‐indica (cochenillifera?) 25 4 100 625.0 Cactaceae

BC feasible: Yes Several countries opted for biological control after other methods were shown to be ineffective (Julien & Griffiths 1998). However, other countries do not consider biological control as a solution because a large proportion of the population depends on the plant as a source of food and fodder. Hawaii, Australia and South Africa have used biological control to reduce O. ficus‐indica infestations along with other Opuntia species. Mainly, control has been achieved using four insects introduced from Argentina, Mexico and the USA, namely, the cactus moth Cactoblastis cactorum, the cochineal Dactylopius opuntia, the long‐horn stem borer Archlagocheirus funestus and the stem‐boring weevil Metamasius (Cactophagus) spinolae (Dodd 1940; Pettey 1948; Mann 1970; Annecke & Moran 1978; Moran & Zimmermann 1984). The control achieved has been satisfactory, with the cochineal D. opuntiae achieving best results in South Africa where infested plants are felled and stacked. The cactus moth C. cactorum was not able to kill large plants but is an excellent biological control agent of smaller plants with less than 10 cladodes (Zimmermann & Malan 1981). The cactus weevil M. spinolae, released in South Africa in 1948, gives total control of large plants but dispersal is very slow from the point of release (Zimmermann & Moran 1991). Overall, the biological control of O. ficus‐indica in South Africa was satisfactory to the point where the remaining populations are not a threat and are now being utilized fully with no risk of continued invasions (CABI ISC 2012).

BC recommendable at this point: Yes Opuntia ficus‐indica is widespread across the barren parts of the island, though less so than O. stricta. There is little general distinction between the habitats of the two species, but O. ficus‐indica tends to occupy slightly higher, less arid ground (SAISP 2010). O. ficus‐indica is probably a little less invasive than O. stricta, forming less dense stands. However, in parts it is still very common and therefore can become a nuisance. In places, the species performs a useful role in helping to stabilize eroded dryland areas, and the fruit is good to eat and widely harvested (SAISP 2010). In contrast to O. stricta, action seems to be less urgently needed. However, all indications are that CBC would promise a substantial and sustainable control, comparable with the control of O. stricta on Ascension. Initial cost/benefit analysis should be a first step, before starting on a control programme based on agents with a proven safety and efficiency record for a combined control of both Opuntia species.

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Lantana camara 35 11 80 254.5 Verbenaceae

BC feasible: Yes Worldwide, well over 200 releases have been made (of 39 different natural enemies, in 29 countries); however, in the majority of cases, the control agent either failed to become established or became established without achieving control. Despite this limited success, classical biological control is still considered to be the only viable, long‐term control option, since it offers a safe, economic and environmentally benign method of suppressing the weed. Most previous releases have been carried out in the Pacific, South Africa and Australia (for historical details see Taylor 1989; Cilliers & Neser 1991; Davis et al. 1992; Denton et al. 1991; Swarbrick et al. 1995). The most widely established species include Ophiomyia lantanae, Uroplata girardi and Octoma scabripennis. Day et al. (2003) have produced a detailed review of 48 control agents (CABI ISC 2012).

BC recommendable at this point: Yes The Lantana lacebug Teleonemia scrupulosa, which causes severe leaf damage to Lantana on St Helena (Lambdon & Darlow 2008) was deliberately introduced in the 1970s and provided some control in parts of the island (Ashmole & Ashmole 2000). Still, the SAISP (2010) reported Lantana as the most widespread plant species on the Island, occurring in large stands at high densities. This indicates that currently, control is limited at best. Further BC using additional agents with a proven safety and impact record is highly feasible and recommended.

Asparagus asparagoides 40 11 60 218.2 Asparagaceae

BC feasible: Yes Three biological control agents for A. asparagoides, all of South African origin, have been released in Australia: an undescribed Erythroneurini leaf hopper in 1999, the rust fungus Puccinia myrsiphylli in 2000 and a Crioceris sp. leaf beetle in 2002 (Witt & Edwards 2000, 2002; Kleinjan et al. 2004a,b; Morin & Edwards 2006; Morin et al. 2006b). A Eurytoma sp. seed wasp was also considered a promising candidate agent, but host‐ specificity testing could not be performed due to rearing difficulties and concerns raised about the conflict of interest with producers of cultivated asparagus seeds. Large‐scale releases of the leaf hopper and rust fungus were carried out in partnership with community groups, land managers and schools (Kwong 2002; Batchelor et al. 2004; Overton & Overton 2006). Impact of the agents on A. asparagoides has been assessed in a series of glasshouse and field experiments (Batchelor & Woodburn 2002; Morin et al. 2002, 2006b; Kleinjan et al. 2004a; Jacob et al. 2007; Turner et al. 2008). The rust fungus has had a major impact in reducing A. asparagoides populations, particularly in moist coastal areas of Australia where climatic conditions are conducive to epidemics. The leaf hopper has also adversely affected A. asparagoides at some sites, but its populations have a tendency to fluctuate from year to year, limiting its impact. Establishment of the leaf beetle has been extremely poor despite considerable release efforts and therefore this agent is not currently contributing to control. Puccinia myrsiphylli was found in New Zealand in November 2005 near Auckland, probably as a result of an accidental introduction or natural dissemination of spores from Australia on wind currents (Waipara et al. 2006). Subsequent surveys and field assessments revealed that it was widespread throughout the range of A. asparagoides in northern New Zealand, often causing severe damage and premature defoliation (Harman et al. 2008; CABI ISC 2012).

BC recommendable at this point: Possibly yes Little detailed, up to date information is available on the status of this species on St Helena. Within the SAISP, it is described as a currently quite localised, high risk invasive weed, which is challenging to control. Indications are that BC would be a feasible option, but a more in depth assessment of the current situation would be required.

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Ulex europaeus 35 13 60 161.5 Fabaceae BC feasible: Yes Ulex europaeus has a long history of classical biological control, mainly from programmes conducted in New Zealand and Australia (CABI ISC 2012). The gorse seed weevil Exapion ulicis was the first biological control agent used against U. europaeus. Introduced to New Zealand in 1931, it was widely established by 1935 and has destroyed approximately 35% of the seed crop annually since then (Miller 1970; Cowley 1983). A further six control agents have been introduced to New Zealand (Hill et al. 2000). The gorse spider mite Tetranychus lintearius was introduced in 1989, and has become widely established (Hill et al. 1993). The thrips Sericothrips staphylinus was released in New Zealand in 1990 and is spreading slowly (Hill et al. 2001). Three foliage‐ feeding Lepidoptera have been introduced. Agonopterix ulicetella was released in 1990 (Hill et al. 1995) and, although firmly established, no populations have yet reached damaging proportions. Scythris grandipennis was released in 1993 but did not establish, and Pempelia genistella was released in 1995 but has established at only two sites to date (Hill et al. 2000). The bivoltine seed‐feeding moth Cydia succedana was introduced in 1992 to augment the seed predation provided by Exapion ulicis and it has spread rapidly and become abundant in New Zealand (Hill & Gourlay 2002). Seed losses to predation by both insects exceed those from E. ulicis alone, but the effect on the annual seed crop has yet to be assessed (Hill et al. 2000). Exapion ulicis was introduced to the island of Maui, Hawaii, in 1956 and was established on the island of Hawaii in 1984, attacking 78% of seed pods by 1994. The gall‐forming weevil Perapion scutellare was released in 1961, and again from 1989, but has not established. Agonopterix ulicetella was released in 1988 and, unlike in New Zealand, this moth has become abundant on the island of Hawaii and larvae destroy a high proportion of growing tips. The rust fungus Uromyces pisi f.sp. europaei was released in Hawaii (Markin et al. 2002) but has been recovered only once. Tetranychus lintearius was released on St Helena in 1995, but again appears to be regulated by predatory mites (Julien & Griffiths 1998). Exapion ulicis was released in Tasmania, Australia, in 1939, but has not prevented the spread of U. europaeus (Julien & Griffiths 1998). Tetranychus lintearius and Sericothrips staphylinus have also been released there (Ireson et al. 2003). E. ulicis, T. lintearius, and Agonopterix ulicetella have been released in Chile (Norambuena et al. 2001). The fungus Fusarium tumidum (Gibberella tumidum) is being developed as a bioherbicide for use against U. europaeus worldwide (Fröhlich & Gianotti 2000; CABI ISC 2012).

BC recommendable at this point: Yes On St Helena, gorse is one of the major invasive species of pasture and scrubland at middle altitudes, often forming dense monocultural thickets (SAISP 2010). It is pernicious on pastureland and little grazed, especially by cattle. Once it becomes well‐established in an open area, gorse is capable of outcompeting most other species and therefore forms extensive monocultures, being difficult to access and to control. It is difficult to cut or spray, and can resprout from stumps (SAISP 2010). The species has, on the other hand, some benefits. It is a nitrogen‐fixing species, and a good pollen source for bees. Formerly, it was used as an effective hedging plant and a source of fodder for livestock. It makes good quality, nutrient‐rich forage but is no longer favoured due to its spikiness, and the availability of alternatives which are easier to manage (SAISP 2010). The SAIS project concluded that on‐going management is necessary to keep pastureland clean. More coordinated efforts, including the widespread enforcement of control measures on pasture and removal from nearby waste ground, may help to prevent sources of recolonization. Experimentation with less labour‐intensive weed suppression measures may also be beneficial (e.g. mechanization, or the use of grazing animals such as goats to provide targeted control).

All currently applied or suggested control methods require on‐going and probably costly efforts. Therefore, BC seems well suited to provide a more practical long‐term solution. BC is likely to enhance the efficacy of other control methods and make them more cost effective. Tetranychus lintearius was released on St Helena in 1995, but appears not to be very effective due to the impact of predatory mites. However, other tested ‘off the shelf’ solutions are available (see above) and several options exist for the introduction of additional control agents.

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Tecoma stans 30 15 76 152.0 Bignoniaceae BC feasible: Yes Host specificity tests on two rust fungus species, namely, the microcyclic Prospodium transformans and the macrocyclic P. appendiculatum from Mexico, are in progress in South Africa. P. appendiculatum is already present in Brazil and Argentina, but is not contributing much to the suppression of populations. Further surveys for additional host‐specific natural enemies are planned. A raceme‐feeding membracid and the pyralid pod‐feeding moth Clydenopteron sp. are to be introduced into quarantine in South Africa for possible biological control (CABI ISC 2012).

BC recommendable at this point: potentially yes Tecoma stans is currently not particularly widespread on St. Helena, but is expected to spread, possibly rapidly (SAISP 2010). Dry, eroded hillsides which cover much of the lower altitudes are ideally‐suited, and a number of areas could eventually become infested with dense populations (SAISP 2010). The SAIS project saw Tecoma stans as one of the species most likely to become important new invaders in the coming years, and the fast rate of spread makes it a particularly difficult issue to address. Longer‐term eradication would be expensive, but is seen as desirable to limit on‐going management costs (SAISP 2010). There are indications that BC may become a recommendable option for St Helena in the near future; depending on the further spread and negative impact of this species.

Schinus terebinthifolius 25 19 106 139.5 Anacardiaceae

BC feasible: Yes Cronk & Fuller (1995) report that biological control has been attempted on Hawaii, but has so far been ineffective. Elfers (1988) records that Bruchus atronotatus, Crasimorpha infuscata and Episimus utilis were introduced, but none is believed to have effected significant control. A fruit‐eating wasp, Megastigmus transvaalensis, has also been trialled in Florida (Randall 2003), but Luken & Thieret (1997) consider that other insects native to Brazil may hold greater potential. Pedrosa‐Macedo et al. (2006) studied means of multiplying the sawfly Heteroperreyia hubrichi (Hymenoptera: Pergidae), as a potential biocontrol agent for Florida and Hawaii. However, further work on biological control in Hawaii may be unlikely since S. terebinthifolius is an important nectar source for the bee‐keeping industry there (Elfers 1988; CABI ISC 2012).

BC recommendable at this point: Yes, but limited This is an extremely invasive species in certain parts of the world, notably in Florida, but possibly nowhere more so than on St. Helena (SAISP 2010). It covers large tracts of dryland with sparse scrub, making recolonization by other vegetation unlikely and therefore presenting a substantial barrier to native replanting schemes. The dense riverine populations probably intercept large amounts of water and outcompete native wetland flora, rendering the habitats species‐poor and of little utilizable or amenity value (SAISP 2010). Management of S. terebinthifolius is one of the most pressing invasive species issues on the island. The priority lies in tackling the infestations on wetland, where it is particularly damaging. However, the difficulty in removing many large trees, which are capable of rapid regrowth, presents a considerable problem and is a highly costly process (SAISP 2010). This indicates that research into suitable biological control agents may well be worthwhile. However, as no effective agents are currently readily available this but would require significant investment.

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Leucaena leucocephala 45 20 61 137.3 Mimosaceae BC feasible: Yes BC was first contemplated in Hawaii (Smith 1985) and South Africa (Neser 1994), but has been frustrated by the economic importance of L. leucocephala. Nonetheless, proposals to release the seed‐eating bruchid Acanthoscelides macrophthalmus in South Africa were pursued (Neser 1994;Henderson 2001), and the species has also been accidentally introduced into Australia (CABI ISC 2012). The psyllid Heteropsylla cubana (accidentally spread in the mid‐1980s) can cause cyclical defoliation, but does not kill trees; the psyllid itself appears to have been brought under control by a number of generalist local (and in some cases introduced) psyllid predators and parasites (GISD 2012). On Ascension there is currently some damage reported by the beetle Acanthoscelides suramerica. This beetle probably arrived accidentally on Ascension Island from the Caribbean in 1997 (Fowler 2011).

BC recommendable at this point: Yes Dramatic expansion of this species, which now forms very extensive stands, was recorded during the SAIS project. Leucaena forest areas have clearly spread very rapidly in recent years, the seeds being produced in abundance and germinating in large quantities. They are perhaps dispersed by sheep, which often shelter under the canopy at night or in wet conditions (SAISP 2010). This indicates that research into suitable biological control agents may well be worthwhile. However, as no effective agents are currently readily available this would require significant initial investment.

Sporobolus africanus 40 26 80 123.1 Poaceae

BC feasible: No Biological control of Sporobolus africanus has been investigated using the stem wasp Tetramesa sp. and the smut fungus Ustilago sporoboli‐indici. Both were unsuccessful, however, and future efforts are concentrated on the development as a mycoherbicide of a pathogen already present in Australia (Palmer 2008; Palmer et al. 2008; Palmer et al. 2010; GISD 2012). BC of grasses is notoriously difficult and, despite the relatively high overall score generated for this species, based on the failure of previous attempts we consider that BC against S. africanus is probably not feasible at this stage.

BC recommendable at this point: No In the SAISP this species was among the ‘top 12’ invasive species on St. Helena, when ranked according to their summed abundance scores. Nonetheless, as BC does not appear to be feasible, it cannot currently be recommended.

Arundo donax 40 26 76 116.9 Poaceae

BC feasible: Yes Natural enemy surveys and assessments have been initiated for the biological control of Arundo donax, but no biological control agents have yet been released. A number of invertebrates are known to feed on the grass in Eurasia and Africa (El‐Enany 1985; Hoshovsky 1987). Caterpillars reported feeding on A. donax include those of Phothedes dulcis in France (Dufay 1979), Zyginidia guyumi in Pakistan (Ahmed et al. 1977) and Diatraea saccharalis in Barbados (Tucker 1940). A review of the CABI Bioscience herbarium suggests that there are obligate biotrophic fungi associated with A. donax in China, but not India or Pakistan, lending weight to the theory that China may in fact be a truer centre of origin for the species (CABI ISC 2012). As with invertebrates, a number of pathogens are also associated with A. donax in its naturalized range. Given the commercial value of A. donax, the use of insects and/or pathogens would undoubtedly engender conflicts of interest. However, biological control is thought to offer one of the best options for long‐term, affordable and environmentally friendly management of A. donax. The ARS European Biological Control Laboratory

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(Montpellier, France), in cooperation with a USDA‐ARS laboratory, initiated a foreign exploration programme in 1999, which has already located potential agents in the Mediterranean Basin, India and Sri Lanka (Kirk et al. 2003). A. donax stems and leaves contain a wide array of noxious chemicals, including silica (Jackson and Nunez 1964), tri‐terpines and sterols (Chandhuri and Ghosal 1970), cardiac glycosides, curare‐mimicking indoles (Ghosal et al., 1972), hydroxamic acid (Zuñiga et al., 1983) and numerous other alkaloids which probably protect it from most native insects and other grazers (Zuñiga et al. 1983; Miles et al. 1993; CABI ISC 2012). An unidentified stem‐boring sawfly that appears similar to Tetramesa romana has been demonstrated to cause significant damage to A. donax, and it is being tested in quarantine as a candidate biocontrol agent (McWilliams 2004; Dudley et al. 2006; GISD 2012).

BC recommendable at this point: No Invasive species are a major cause of deterioration of wetlands on St Helena, and Arundo donax is among the species which can form large, dense stands along waterways, reducing the flow of water, causing stagnation and increasing evaporation (SAISP 2010). However, little more is known about the negative impacts of this species, and only further detailed assessments would allow the potential benefits of BC to be determined.

Schinus molle 25 19 76 100.0 Anacardiaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programmes is feasible.

BC recommendable at this point: No According to the SAISP, this species is much less common than Schinus terebithifolius and spreading less aggressively. However, this is a well‐established species, which is capable of becoming invasive and currently forms dense stands in similar habitat in upper James Valley. If not for the dominance of S. terebinthifolius in many of the other valleys, it may have become more of a problem on St. Helena (SAISP 2010). The SAISP recommended some level of control in James Valley and, in the long term, in Rupert's Valley. However, owing to its relatively limited distribution, this species presents less urgent problems than a number of other species. In the light of this, BC is probably not a suitable option in the current situation.

Sonchus oleraceus 30 21 68 97.1 Asteraceae

BC feasible: Yes Biological control agents are currently being researched for the management of S. asper and other Sonchus species in Australia (CSIRO 2007). Sonchus species have previously been the target of biological control in Canada (Peschken 1984). Preliminary surveys for biological control agents have been undertaken in southern France and northern Europe (Scott & Jourdan 2005; Peschken 1984). Currently, the rust fungus Miyagia pseudosphaeria and an unidentified eriophyid mite species are two widespread organisms in Australia with potential as control agents (GISD 2012).

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

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Acacia melanoxylon 25 23 80 87.0 Mimosaceae

BC feasible: Yes A seed‐feeding weevil Melanterius acaciae was tested for host‐specificity in South Africa (Neser & Kluge 1986) and subsequently released in 1985. Levels of seed‐damage may reach 100%, thus reducing the number of seeds that accumulate in the soil (ARC 2012). Tunison (1991) comments that biological control is not yet required and would not be a viable control approach on Hawaii (CABI ISC 2012).

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Carpobrotus edulis 40 29 61 84.1 Aizoaceae

BC feasible: Yes Carpobrotus edulis may be damaged by Verticillium wilt but this can also harm many other crop species. The scale insects Pulvinariella mesembryanthemi and Pulvinaria delottoi, believed to have been introduced from South Africa, were noted to be causing serious damage to the plant in California (Dahlsten & Hall 1999), but this was regarded as undesirable as the plant was being used as a roadside ground‐cover. In Australia, P. mesembryanthemi is said to be host specific to C. edulis (Collins & Scott 1982; CABI ISC 2012; GISD 2012).

BC recommendable at this point: Yes One of the commonest plants across the dryland areas, covering large tracts of land and excluding most other species, this species was seen as one of the major threats to biodiversity on St Helena during the SAIS project. SAISP (2010) reported that: “The leaves accumulate salt, which is concentrated on the surface when the plant dies and this may make the ground less hospitable for other colonists. Although often considered to be a good plant at preventing erosion, the failure of other species to establish in creeper wastes mean that processes of natural succession, to more valuable vegetation types, are almost halted. This is a particular problem as C. edulis competes with native plants. Fortunately, so far, it has not become established on the major sea cliff areas, which remain extremely important as refuges for several endemics, but elsewhere in the world, introduced populations of creeper have become spectacularly dominant in these habitats and are the cause of considerable conservation concern. In addition, interactions with animals are important. The fruits provide food for rats and rabbits, and the dense mats are likely to exclude endemic invertebrates, especially on Prosperous Bay Plain. Certainly an excellent colonist of bare ground and currently the only means of preventing erosion over much of the very barren wastes. Due to its extreme dominance, extensive control is impractical, but management programmes are urgently needed to reduce the impacts in key areas like Prosperous Bay Plain, and any plants establishing in sensitive cliff areas should be removed as priority. Longer term land management decisions should consider ways of replacing the creeper wastes with more valuable types of ground cover.”

There are strong indications that BC may be able to provide a long‐term solution to the threats caused by this species, in particular because other control options are not feasible on the required scale. A more detailed analysis of the potential for BC, conducted in collaboration with relevant stakeholders is highly recommended.

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Juncus tenuis 30 28 77 82.5 Juncaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No The plant appears to have negative impacts on Wirebird nesting habitat and to spread slowly (McCulloch & Norris, in prep.). However, the current limited distribution, and potential for chemical control (as with J. capillaceus) do not justify the uptake of BC measures for this species at this point.

Chrysanthemoides monilifera 30 22 60 81.8 Asteraceae

BC feasible: Yes Noble & Weiss (1989) measured the movement of buried Chrysanthemoides monilifera (subsp. rotundata) seed in the soil. From their research, a mathematical model was developed, which predicted that pre‐ dispersed seed predation by a biological control agent would have to reduce the potentially germinable seed population by more than 95% to provide satisfactory control. A number of biological control agents have been released within C. monilifera populations in Australia. The host preferences of the biological control agents vary between subsp. monilifera and rotundata. Of the biological control agents released in Australia, three have established and caused damage: Comostolopsis germana, a tip moth released in 1989 (Adair & Scott 1991); Mesoclanis polana, a seed‐predating fly released in 1996; and Tortrix sp., a leafroller released in 2000 (Kriticos & Groves 2000). As well as the insects already released, a fungus and an eriophyiid mite are under consideration for release. An assessment of three species of Mesoclanis spp. seed flies present in South Africa as potential biological control agents against the two subspecies of the weed in Australia is provided by Edwards (1998). An evaluation of the likely impact of the rust fungus Endophyllum osteospermi as a biological control agent is provided by Wood (2002). Stuart et al. (2002) modelled the population dynamics of subsp. rotundata. The results of this research emphasised that effective biological control of C. monilifera may require multiple agents that each influence different aspects of the plant's life cycle (CABI ISC 2012).

BC recommendable at this point: Yes SAISP (2010) gave for the following assessment of Chrysanthemoides monilifera on St. Helena: “A very common species, forming large populations across parts of the upper dryland zone. Often intermixed with other species but sometimes forming dense stands. Also and occasional pasture weed at lower altitudes, e.g. at Deadwood. May have some negative effects on the endemic Commidendrum rugosum, although is more likely to impede the re‐establishment of this species as it rarely competes directly with it at present (except possibly near Flagstaff). Probably not a serious ecological problem as the stands are seldom dense enough to prevent other species establishing, although often a community dominant, so clearly has an important ecological influence. The species is undesirable in pastures and requires some control effort. Aside from routine weeding of pastures, there is probably little management necessity. Structured grazing is one possibility to help reduce the manual effort involved in this task.”

CBC may well provide a suitable control option on St. Helena and could also help the re‐establishment of Commidendrum rugosum. However, further and more detailed assessments in collaboration with relevant stakeholders are required before deciding on the introduction of possible control agents.

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Pennisetum clandestinum 35 28 65 81.3 Poaceae

BC feasible: Yes The rust fungus Phakopsora apoda has become established in South Africa, but appears only to decrease the photosynthetic capacity of the leaves and does not kill the plant (Haubensak & Smyth 1999). Two insects, Sphenophorus ventus vestitus and Herpetogramma licarsicalis, damage kikuyu grass in Hawaii (Cronk & Fuller 2001). Plants are also affected by a fungus disease caused by Pyricularia grisea, which kills seedlings (FAO 2003; GISD 2012).

BC recommendable at this point: No As no severe threats to biodiversity have been reported arising from the presence of this species in St. Helena, and given the difficulties associated with BC of grasses in general, this approach is not recommended at this point.

Olea europaea ssp. africana 35 29 64 77.2 Oleaceae

BC feasible: Yes The Australian native Olive Lace Bug Froggatia olivinia is known to attack Olea e. europaea but not O. e. cuspidata (Cuneo et al. 2006; GISD 2012).

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Kalanchoe pinnata 30 31 79 76.5 Crassulaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Hedychium coronarium 25 26 79 76.0 Zingiberaceae

BC feasible: Yes A research project has been on‐going since 2008 to investigate the potential for BC of invasive Hedychium species for a consortium of sponsors from New Zealand and Hawaii. Surveys of the native range in 2008‐2010 revealed a large suite of natural enemies associated with H. coronarium, but the focus of the research will be on H. gardnerianum, which is the most pernicious of the invasive Hedychium complex (Djeddour, CABI, personal communication 2011; CABI ISC 2012).

BC recommendable at this point: Yes The SAIS project reported that this species can form dense cover, inhibiting succession. BC may well be the most suitable method to inhibit further spread and break up existing dense stands. Therefore, it is recommended that this species be assessed for potential future BC in more detail.

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Anredera cordifolia 25 28 79 70.5 Basselaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Lonicera japonica 25 28 79 70.5 Caprifoliaceae

BC feasible: Yes A review of the potential for biocontrol in New Zealand (Standish 2002) shows that no programmes are currently operative anywhere in the world. There are no obvious insect agents, but there are 14 fungal pathogens of L. japonica with potential (Standish 2002). In particular, two fungal pathogens recently found attacking L. japonica in its native range may be promising biocontrol agents: Appendiculella lonicerae (Song et al. 2002) and Cladosporium lonicericola (He & Zhang 2001; CABI ISC 2012).

BC recommendable at this point: No Infestations seem localised and could be controlled fairly easily by spraying, or cutting and stump swabbing, with glyphosate (SAISP 2010). In addition, limited environmental impacts of this species do not currently justify the uptake of BC measures, but close monitoring of the situation has been recommended by the SAIS project.

Asparagus densiflorus 30 31 72 69.7 Asparagaceae BC feasible: Yes Some potential biological control agents have been identified in South Africa but none has so far been developed for biological control (CABI ISC 2012).Preliminary surveys of natural enemies of Asparagus spp. in South Africa have suggested a chalcid wasp, a moth larva and a rust to be of potential interest. There is also galling by the chalcids Asparagobius braunsii and a Eurytoma sp. (Parsons & Cuthbertson 1992). Greenhouse‐ grown A. densiflorus in Poland is attacked by the spiral nematode Scutellonema brachyurum (Wojtowicz & Szczygiel 1990). In France, it is a host to Corynebacterium fascians (Faivre‐Amiot 1967), and in Germany to Pseudomonas tumefaciens (Stapp 1940) and Phytomonas fascians [Rhodococcus fascians] (Pape 1938). In the USA, it is believed to have been infected by Agrobacterium tumefaciens (Brown & Weiss 1937; CABI ISC 2012).

BC recommendable at this point: Yes Asparagus densiflorus is likely to be a relatively recent arrival on St. Helena, but is already spreading fast (SAISP 2010). Patches can be difficult to walk through, due to the thorns, and it is an extremely difficult species to eradicate owing to the persistent bulbs. SAISP (2010) reported that: ”Asparagus densiflorus represents a significant impending threat to St. Helena’s environment, and the worst‐case scenario is extremely serious, and at best, they are almost certain to incur substantial investment in control, over a prolonged time period. As the bulbs are not easily removed, eradication is likely to be a difficult and time‐ consuming process, especially because many of the affected areas are difficult to access due to the density of vegetation. However, unless controlled while the distribution is still relatively narrow, this species is likely to spread across densely‐vegetated habitats over much of the island and could develop into a serious ecological problem. Greater public awareness of the threat is needed”. This assessment indicates that BC may turn out to be a feasible and cost effective control method for this species, and its potential should be analysed in more detail with relevant stakeholders.

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Populus alba 25 28 76 67.9 Salicaceae

BC feasible: No No effective biological control agents are known that are suitable for use in natural areas (CABI ISC 2012).

BC recommendable at this point: No

Acacia longifolia 25 23 60 65.2 Mimosaceae

BC feasible: Yes Biological control agents previously used are the gall wasp Trichilogaster acaciaelongifoliae and the seed‐ feeding weevil Melanterius ventralis (Dennill & Donnelly 1991). Both of these insects control A. longifolia at seed level. T. acaciaelongifoliae affects floral buds and occasionally vegetative buds, causing gall formation that halts normal development of buds, while M. ventralis attacks seeds that are unaffected by T. acaciaelongifoliae (Dennill & Donnelly 1991). Together, these two organisms have decreased A. longifolia reproductive potential by >90% in South Africa (Dennill et al. 1993). Similar biological control agents are being investigated for New Zealand and Portugal (Hill 2005; Marchante et al. 2005; GISD 2012).

BC recommendable at this point: No Because this species is useful at preventing erosion and provides a useful source of fodder for livestock it has been extremely widely planted in dry areas for erosion control, sometimes forming dense forests (SAISP 2010). However, it has a rather invasive character and forms large monoclonal stands. The leaf litter is dry and poorly‐decayed, and is only slowly colonised by other species, generally with an almost bare understorey (SAISP 2010). The SAISP recommended a better habitat management to establish more valuable communities faster by more intensive harvesting for forage. This indicates that BC is currently not of high priority as control methods may be preferable. Sonchus asper 20 21 68 64.8 Asteraceae

BC feasible: No Biological control agents are currently being researched for possible management of S. asper and other Sonchus species in Australia (CSIRO 2007). Sonchus species have previously been the target of biological control in Canada (Peschken 1984). Preliminary surveys for biological control agents have been made in southern France and northern Europe (Scott & Jourdan 2005; Peschken 1984). Currently, the rust fungus Miyagia pseudosphaeria and an unidentified eriophyid mite species are two widespread organisms in Australia with potential as control agents (GISD 2012).

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Phormium tenax 30 37 79 64.1 Agavaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

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Kalanchoe delagoensis 25 31 79 63.7 Crassulaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No Kalanchoe delagoensis is clearly spreading and can be extremely abundant in certain places (SAISP 2010). Although rarely considered to be a threat, its ability to spread through clonal budding offers the possibility that it could expand rapidly. It probably remains local through a lack of efficient long‐distance dispersal mechanisms, but as plants are accidentally introduced to new valleys by human movements, there may be continued expansion (SAISP 2010). The limited environmental impacts associated with this species do not justify the uptake of BC measures at this point, but close monitoring of the situation has been recommended by the SAIS project and BC could become a recommended option in the future.

Solanum mauritianum 25 36 91 63.2 Solanaceae

BC feasible: Yes Biological control has only been attempted in South Africa, where the sap‐sucking lace bug Gargaphia decoris (Tingidae), released in 1999, is so far the only agent that has been used (Olckers 1999, 2000). However, this insect has proved ineffective to date, largely because of its failure to establish at many release sites and its inability to sustain high population densities throughout the year. Permission for the release of a second agent, the flower bud‐feeding weevil Anthonomus santacruzi (Curculionidae) that prevents fruiting, is currently being sought in South Africa (Olckers 2003). Besides South Africa, only New Zealand has considered biological control of S. mauritianum (Withers et al. 2002). This plant has proved to be a difficult target for biological control because of closely related cultivated and native plants in the genus Solanum, which have made it difficult to obtain clearance for the release of biological control agents (CABI ISC 2012).

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Eleusine indica 30 22 45 61.4 Poaceae

BC feasible: No Biological control of Eleusine indica has been considered in great detail in Australia, where the related finger millet (E. coracana) does not occur (e.g. Wapshere 1990a,b; Waterhouse 1993). For classical biocontrol, potential organisms include the smut fungus Melanopsichium eleusinis, the nematode Heterodera delvii, and certain cecidomyiid gall midges (Contarinia sp.), but all require further study before they could be used. Fungi which might be developed as mycoherbicides include Bipolaris [Cochliobolus] setariae and Pyricularia [Magnaporthe] grisea (Figliola et al. 1988) but no active programme for the development of these has yet been reported (CABI ISC 2012).

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

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Pennisetum macrourum 35 38 65 59.9 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Psidium guajava 30 40 76 57.0 Myrtaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Furcraea foetida 20 28 79 56.4 Agavaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: Yes Furcraea foetida is a very common invasive species on St. Helena, dominating large patches of hillsides (SAISP 2010). Locally, dense populations may be problematic, impeding access and outcompeting other vegetation. F. foetida could potentially suppress some dryland native species, although there is rarely a conflict at present as it seldom grows in the same areas, and seems to be partly outcompeted by vigorous species in less arid habitats (SAISP 2010). The species also has some benefits, as it plays a useful role in preventing erosion on the steep, barren valley slopes along the north side of the island, where it is one of the first species to colonize (SAISP 2010). Due to the high costs of control, management is currently a low priority. However, it is likely to spread at a reasonably high rate, and future assessment will be necessary to determine the threat posed by expansion (SAISP 2010). The assessment provided in the SAIS project indicates that BC may turn out to be a feasible and cost‐effective control method for this species; its potential should be analysed in more detail with relevant stakeholders.

Juncus capillaceus 20 29 79 54.5 Juncaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible; in particular, because closely related species on St. Helena are all non‐native.

BC recommendable at this point: No The species is densely invading pasture and Wirebird habitats and, may be effecting invertebrate populations. A control trial is underway using 2,4‐D herbicide (SAISP 2010). At this stage, there are no indications that negative impacts are sufficient to justify the development of a BC programme. However, a more detailed assessment through field site visits and stakeholder consultations is recommended.

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Cynodon dactylon 30 38 67 52.9 Poaceae

BC feasible: Yes Drechslera cynodontis, Ustilago cynodontis, Puccinia cynodontis and Fusarium poae as fungal pathogens and a specimen belonging to the Thripidae family have been identified on C. dactylon and are being studied for potential use in biological control (Uygur 2000; CABI ISC 2012).

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Watsonia borbonica 20 29 76 52.4 Iridaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Alpinia zerumbet 25 38 79 52.0 Zingiberaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is still feasible.

BC recommendable at this point: No The uptake of CBC measures is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Argemone mexicana 25 31 64 51.6 Papaveraceae

BC feasible: Yes This native of Mexico is naturalized in most warm countries of the world, in sub‐humid as well as semiarid regions. A bacterial wilt, Xanthomonas papavericola [X. campestris pv. papavericola], periodically checks the growth of A. mexicana in some areas (Holm et al. 1977) but there is a dearth of information on natural enemies of this weed. A biological control programme against A. mexicana and the closely related A. ochroleuca has been initiated in Australia. This project has sought natural enemies in Mexico and identified several predatory insects, including an extremely damaging species of root‐breeding and leaf‐feeding weevil (CSIRO 1999; Julien 2002; CABI ISC 2012).

BC recommendable at this point: No At this stage there are no indications that negative impacts are sufficient to justify the development of a BC programme. However, more detailed assessment through field site visits and stakeholder consultations is recommended; in particular, as this species is already of major concern on Ascension.

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Rubus rosifolius 25 38 74 48.7 Rosaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible. However, Rubus rosifolius is susceptible to strawberry mild yellow edge‐associated potexvirus it is transmitted by a vector; an insect; Chaetosiphon fragaraefolii belonging to family Aphididae. It is transmitted in a non‐persistent manner. The virus possibly requires, for vector transmission, a helper virus (strawberry mild yellow edge luteovirus); transmitted by mechanical inoculation and by grafting (Brunt et al. 1996; GISD 2012).

BC recommendable at this point: No

Oxalis pes‐caprae 25 29 55 47.4 Oxalidaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Rubus pinnatus 25 40 74 46.3 Rosaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Austroeupatorium inulaefolium 30 40 60 45.0 Asteraceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Pennisetum setaceum 25 38 65 42.8 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

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Digitaria ciliaris 30 37 52 42.2 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Ipomoea indica? (blue flowers) 30 48 64 40.0 Convolvulaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Panicum maximum 30 40 52 39.0 Poaceae

BC feasible: No Drechslera gigantea, Exserohilum rostratum, and E. longirostratum have been highly effective in controlling P. maximum. A 'cocktail' of these fungi, applied in an emulsion, was the most effective treatment compared to each pathogen alone or all pathogens applied with water or Metamucil as carriers (Chandramohan et al. 1999; CABI ISC 2012). Despite these results, the development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Cyperus rotundus 30 31 40 38.7 Cyperaceae

BC feasible: No It is questionable whether a cosmopolitan weed like C. rotundus with a huge regenerative capacity would be a good target for biological control, but Evans (1991) claims that several fungi are promising candidates for classical biocontrol, including Puccinia conclusa, P. philippinensis and Phytophthora cyperi. Evans (1991) also notes that several pathogens are damaging to C. rotundus and warrant evaluation as possible mycoherbicides. The fungal pathogen Dactylaria higginsii, has shown promise as a bioherbicide for the control of C. rotundus; three applications of 10 million conidia/ml gave >90% control (Kadir et al. 2000). Invertebrate herbivores of C. rotundus that have been investigated as biological control agents include Athesapeuta cyperi, Chaetococcus australis, Bactra minima, B. venosana and B. verutana (Julien 1998). Bactra spp. have been widely tested but natural enemies have restricted their impact (CABI ISC 2012). Despite these results, the development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

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Nicotiana glauca 20 40 76 38.0 Solanaceae

BC feasible: Yes Nicotiana glauca has been reported to be invasive in a number of countries but there has never been a full attempt to control this species by biological means. The only existing reference in the literature, mentioning the successful use of a beetle (Malabris aculeata) in combination with an herbicide (Cronk & Fuller 2001), which is widely cited on factsheets and in databases is often misquoted. It remains doubtful whether this refers to biological control at all. So far, Nicotiana glauca has not been regarded as a priority target species for BC in other countries, because of a generally limited impact on agriculture and the environment in combination with the economic importance of closely related commercially used members of the same plant family, in particular of tobacco (Nicotiana tabaccum) itself. The Management Plan developed for Ascension (Pickup 1999) recommends attempting to push invasion fronts back and control seed spread. However, for St Helena, Ashmole & Ashmole (2004) observe that the complete removal of wild tobacco is probably impracticable (GISD 2012). The development of a BC programme for the target area would probably only be realistically feasible if combined with efforts on Ascension, where much more severe impacts of this species are reported.

BC recommendable at this point: Yes In cases like Nicotiana glauca, without a history of biological control, a full project would be costly compared with species where successfully tested host‐specific agents are readily available. In combination with the limited negative impacts reported from St. Helena, such efforts would not generally be justified (as is reflected by the rather low overall assessment score here). However, the severity of the invasion of wild tobacco on Ascension would justify a joint exploration of the potential for BC, initially through surveys for suitable control agents in the area of origin of Nicotiana glauca.

Acacia mearnsii 25 31 46 37.1 Mimosaceae

BC feasible: No Henderson (2001) reports that both seed feeders and a mycoherbicide are used to control A. mearnsii. Dennill et al (1999) name two agents that it supplies for the purpose of biological control in South Africa; the seed weevil Melenterius maculatus and the native South African fungus Cylindrobasidium laeve, which attacks stumps and is applied after felling to prevent resprouting. More recently, the cecidomyiid midge Dasineura rubiformis, which forms galls in the flowers and prevents pod development, was released (Impson et al. 2008; CABI ISC 2012). Despite these results, the development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Ageratum conyzoides 25 38 52 34.2 Asteraceae

BC feasible: No Following a review of natural enemies for Ageratum conyzoides, Waterhouse (1994) provided a long list of insects and pathogens. However, almost all were polyphagous and many were pests of useful plants. Holm et al. (1977) list a number of pathogens and nematodes that have been isolated from A. conyzoides. There is no evidence that these cause significant damage, unlike virus infections, particularly Bidens mottle virus (Logan & Zettler 1984), which can be a problem where A. conyzoides is used for garden bedding (CABI ISC 2012). Despite these results, the development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

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Paspalum scrobiculatum 25 40 52 32.5 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Buddleja madagascariensis 20 29 46 31.7 Buddlejaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Physalis peruviana 20 38 52 27.4 Solanaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Tagetes minuta 20 38 50 26.3 Asteraceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Acacia cyclops 20 35 46 26.3 Mimosaceae

BC feasible: No Biological control of Acacia cyclops using three Melantarius species is currently under investigation (Working for Water 2003), and Impson et al. (2000) reported that adult and larval seed‐feeding weevils Melanterius ?servulus destroyed up to 95% of A. cyclops seeds at release sites in Western Cape Province. Continued research into the effectiveness of Melantarius servulus as a biocontrol agent is focusing on weevil dispersal, interference by birds, a native alydid bug and rodents, and asynchrony in the phenologies of the weevils and A. cyclops (Impson et al. 2000; CABI ISC 2012). Despite these results, the development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

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Poa annua 20 37 48 25.9 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Poa pratensis 20 37 48 25.9 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Setaria verticillata 20 38 48 25.3 Poaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Bidens pilosa 25 38 38 25.0 Asteraceae

BC feasible: No The natural enemies of Bidens pilosa have not been investigated in detail as potential biological control agents. However, Waterhouse (1994) considers agromyzid flies as the most promising agents. Some fungal pathogens associated with B. pilosa are likely to be host specific, and so they are also potential biological control agents (CABI ISC 2012). Despite these results, is the development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Pinus pinaster 20 43 44 20.5 Pinaceae

BC feasible: No Cronk & Fuller (2001) note that any biological control should not interfere with intended commercial plantations and that the choice of agent is therefore restricted to seed predators. However, Henderson (2001) reports that research for a suitable biological control agent for use in South Africa is on‐going, with ARC investigations currently focussing on Pissodes validirostris only, with a view to establishing the host specificity of various biotypes of this promising agent (CABI ISC 2012). Despite these results, the development of CBC for the target area is currently not realistically feasible.

BC recommendable at this point: No

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Plantago major 20 43 35 16.3 Plantaginaceae

BC feasible: No There is no history of BC against this species and development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

3.2.8 St. Helena - Invertebrates Twenty-six non-native invertebrate species achieved an impact score of 20 or above and were evaluated further with the prioritisation tool. Individual assessments of each species are given in Table 11. Of these, we regard only the hemipteran Pseudococcus viburni as a highly recommendable target for classical biological control. The Gumwoods on St. Helena are reported to be infested by P. viburni, and the infestation appears to weaken the trees (Mendel et al. 2008). Classical biological control will probably provide the only practical and sustainable control of this pest in response to the severe threat that it poses to the Gumwoods, and tested and effective control agents are already available ‘off the shelf’. As the species has been recorded to be a major pest on St Helena, biological control of the fly Stomoxys calcitrans may also be justified. However, a more detailed feasibility assessment through field site visits and on-the-ground stakeholder consultations is necessary. Equally, it is important to monitor the spread of Vespula vulgaris very closely. So far, biological control of wasps in other countries has led only to limited success, despite intensive, long-term efforts. However, considering the severe potential threat posed by this species to the environment and quality of life on St Helena, further more detailed assessments of the feasibility of biological control of this species should be pursued. For other species listed in Table 10, biological control is feasible in principle, but no effective biological control agents have been identified to date. We currently regard the impact of these species on indigenous biodiversity in St Helena to be too low to justify the implementation of full scale biological control projects. However, this preliminary judgement may need to be reassessed as the situation on the ground changes, or as new information comes to light.

Table 11: Assessment of non-native invertebrate species on St. Helena for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol x TOTAL BIOCONTROL FEASIBILITY EFFORT IMPACT Plutella xylostella 20 4 124 620.0 Lepidoptera (Plutellidae)

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BC feasible: Yes Bacillus thuringiensis and the two parasitic wasps Cotesia plutellae and Diadromus collaris have recently been introduced for BC of this species on St Helena (Ashmole & Ashmole 2000; Neuenschwander et al. 2003). There are also numerous examples of successful BC in other countries (Biocat 2010; CABI CPC 2012).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species. However, an assessment about the efficacy of the more recent introductions is recommended.

Trioza erytreae 20 4 84 420.0 Hemiptera (Psyllidae)

BC feasible: Yes On La Reunion, T. erytreae has been successfully controlled by the introduction of a parasite, Tamarixia dryi, from South Africa (Aubert et al. 1980). Research on biological control has also been carried out on Mauritius and Reunion where Psyllaephagus pulvinatus (Hym. Encyrtidae) and, Tamarixia dryi (Hym. Eulophidae) have been introduced (Aubert 1987; Van den Berg 1990; Biocat 2010). In South Africa, numerous predators occur but have not been found to reduce populations to economically acceptable levels (Van den Berg et al. 1987; CABI ISC 2012).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Phthorimaea operculella 20 6 124 413.3 Lepidoptera (Gelechiidae)

BC feasible: Yes An assessment has been conducted, although it is possible that this species arrived on St. Helena as a result of natural dispersal (Ashmole & Ashmole 2000). Many BC agents against this pest have been introduced to various countries around the globe including into St. Helena itself (Biocat 2010). There are records for the introductions of the following parasitoids to control P. operculella (Biocat 2010): Chelonus curvimaculatus, Diadegma mollipla, Orgilus parcus, Eriborus trochanteratus, Apanteles scutellaris, Bracon gelechiae, Copidosoma koehleri, Agathis unicolorata, Apanteles subandinus, Campoplex haywardi, Orgilus lepidus, Temelucha sp., Diadegma turcator.

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species. This may be the results of previous introductions of parasitoids into St. Helena. Stomoxys calcitrans 30 14 81 173.6 Diptera (Muscidae)

BC feasible: Yes There is a long history of BC of Muscidae in general. Consequently, a number of suitable host‐specific control agents are available (Biocat 2010). On Mauritius, for example, Muscidifurax uniraptor, Pachycrepoideus vindemmiae, Spalangia endius, Spalangia nigra, Sphegigaster sp. (all Hym. Pteromalidae); Tachinaephagus zealandicus (Hym. Encyrtidae); Pachylister chinensis (Col. Histeridae) have all been previously been released (Biocat 2010).

BC recommendable at this point: Yes As the species has been recorded to be a major pest on St Helena, BC may well be justified. However, a more detailed assessment through field site visits and stakeholder consultations is recommended.

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Lucilia sericata 20 12 81 135.0 Diptera (Calliphoridae)

BC feasible: Yes Extensive research on BC of Calliphoridae in general has been conducted but, despite partial successes, this method does not seem to have been widely applied for the control of this taxonomic group. Alysia manducator (Hym. Braconidae), Brachymeria podagrica (Hym. Chalcididae), Nasonia vitripennis (Hym. Pteromalidae) were introduced in the 1920s to New Zealand to control Calliphoridae (Miller 1922, 1927; Biocat 2010). Previous experiences on islands are mostly related to the control of calliphorid and other flies developing in dung (Ripa 1990). Although BC seems feasible to control this species, at least to some degree, the costs and efforts involved in selecting and testing the most suitable agents are currently unlikely to lead to more effective control than can be achieved by other available methods (Sargison 2008).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Musca domestica 20 14 81 115.7 Diptera (Muscidae)

BC feasible: Yes There is a long history of BC of Musca domestica, and Muscidae in general. Consequently, a number of suitable host‐specific control agents are readily available (Biocat 2010). For example, Muscidifurax raptor (Hym. Pteromalid) has been introduced to Canada, Ecuador and the Seychelles; Spalangia endius (Hym. Pteromalid) to Chile, Guam and the Seychelles; Spalangia sp. (Hym. Pteromalid) to Ecuador; Dirhinus sp. (Hym. Chalcidid) to Fiji; Mesembrina meridian (Diptera, Muscidae) to Fiji; Spalangia cameroni (Hym. Pteromalid) to Guam, the Soloman Islands and Hawaii; Pachylister chinensis (Col. Histeridae) to Palau and Samoa; Pachycrepoideus vindemmiae (Hym. Pteromalid) to the Seychelles; Sphegigaster sp. (Hym. Pteromalidae) to Hawaii; and Muscidifurax uniraptor, M. zaraptor and Spalangia nigra (Hym. Pteromalid) to Hawaii.

BC recommendable at this point: No The limited environmental impacts associated with this species do not appear to justify the uptake of BC at this point. However, more a more detailed assessment through field site visits and stakeholder consultations is recommended.

Helix aspersa 30 12 44 110.0 Mollusca (Helicidae)

BC feasible: Yes Most promising BC efforts against this species are based on indigenous predators. The scope for the usage of parasitoids is yet unknown.

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

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Pseudococcus viburni 35 22 68 108.2 Hemiptera (Pseudococcidae)

BC feasible: Yes As part of IPM programmes, in particular, mealybugs have been successfully brought under control using CBC (Charles 1993, 2011; Laudonia & Viggiani 1986; Moore 1988). For example, biological control of P. calceolariae was successfully achieved as early as 1928, in California, by the Australian parasitoids Tetracnemoidea brevicornis (as Tetracnemus pretiosus) and Coccophagus gurneyi (Compere & Smith 1932; CABI CPC 2012). Pseudaphycus maculipennis (Hym. Encyrtidae) was introduced into Australia in 1997 to control Pseudococcus viburni and has successfully established (Biocat 2010). In addition, a number of predators and parasitoids have been used to control this species in various other countries (CABI CPC 2012).

BC recommendable at this point: Yes The endemic gumwoods on St. Helena are currently infested by Pseudococcus viburni, which is attacking the roots. The infestation appears to weaken the trees (Mendel et al. 2008). CBC is probably the only possible sustainable method of control of this species; in particular, because tested and effective control agents are already available ‘off the shelf’. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Acanthoscelides obtectus 20 12 64 106.7 Coleoptera (Bruchidae)

BC feasible: Yes So far, only limited control through BC has been achieved (Schmale 2001; Schmale et al. 2006).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Heterotermes perfidus 40 25 66 105.6 Isoptera (Rhinotermitidae)

BC feasible: Yes Despite long‐running attempts to find suitable BC agents, no sufficiently effective control has yet been achieved with this method against Isoptera (Chouvenca et al. 2011).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Vespula vulgaris 35 19 48 88.4 Hymenoptera (Vespidae)

BC feasible: Yes Over a number of years, biological control has been used in attempts to achieve widespread control of wasps. For example, the icheumonid parasitoids Sphecophaga vesparum vesparum, S. v. burra and Sphecophaga orientalis have been utilised as biological control agents against V. germanica (Donovan et al. 1987, 1989, 2002; Beggs & Harris 2000, 2002; Beggs et al. 2002; CABI ISC 2012). Despite intensive, long‐term efforts, however, such programmes have achieved only limited success.

BC recommendable at this point: Yes Despite limited success elsewhere, given the severe threat posed by this species to the environment and

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public health on St Helena, further and more detailed assessments of the potential for BC of this species should be pursued.

Galleria mellonella 25 21 64 76.2 Lepidoptera (Pyralidae)

BC feasible: Yes Despite the fact that this species is widely used for research on entomophathogenic organisms, relatively little work has been directed at BC of G. mellonella itself (Sharaf‐El‐Din & Kolaib 1991; Tawfik et al. 1985; Dridah et al. 2009).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Ceratitis capitata 30 22 54 73.6 Diptera (Tephritidae)

BC feasible: Yes CBC has been tried against C. capitata in various countries, and establishment of introduced parasitoids and partial success of control has been reported in some cases (Wharton 1989; Biocat 2010).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Brevicoryne brassicae 25 28 64 57.1 Hemiptera (Aphididae)

BC feasible: Yes Early biological control attempts made in Australia were all unsuccessful (Wilson 1960). Habitat manipulation to enhance biological control of brassica pests by hoverflies (syrphid larvae) has been carried out in New Zealand (White et al. 1995). The predacious midge Aphidoletes aphidimyza has shown potential as a biological control agent of B. brassicae in greenhouses. Pfrommer & Mendgen (1992) described control attempts with the fungal pathogen Verticillium lecanii against B. brassicae, in which they mixed a water suspension of spores with polysaccharides and detergents to produce an effective spray (CABI CPC 2012). A number of BC agents, particularly various coccinellid species have been introduced into Australia (Biocat 2010).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

Cryptotermes brevis 20 25 66 52.8 Isoptera (Calotermitidae)

BC feasible: Yes Despite long‐running attempts to find suitable BC agents, no sufficiently effective control has yet been achieved with this method against Isoptera (Chouvenca et al. 2011).

BC recommendable at this point: No The uptake of BC is not justified at this point, as there are no (or only limited) environmental impacts associated with this species.

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Adoretus versutus 30 29 46 47.6 Coleoptera (Scarabaeidae)

BC feasible: No Campsomeris marginella (Hym. Scoliidae) has been introduced into Fiji, Western Samoa, the Soloman Islands, and Vanuatu (Biocat database 2010), but CBC against this species has not been successful so far (Waterhouse & Norris 1987).

BC recommendable at this point: No

Herpetogramma licarsisalis 30 40 62 46.5 Lepidoptera (Crambidae)

BC feasible: No Granulosis and nucleopolyhedrosis viruses, and the parasite Stomatomyia tricholygoides, are known as natural enemies (CABI CPC 2012). There is a history of successful biological control of other Crambidae, although the focus seems to be on augmentative control.

BC recommendable at this point: No

Heteronychus arator (syn. H. sanctaehelenae) 30 31 44 42.6 Coleoptera (Scarabaeidae)

BC feasible: No While a range of natural enemies and pathogens infecting H. arator have been identified, attempts at applying them in CBC have been unsuccessful (Cameron et al. 1989). For example, Microphthalma europaea (Dip. Tachinidae) and Scarites spp. (Col. Carabidae) have been introduced to New Zealand to control this species (Biocat 2010). Most of the organisms were general predators or pathogens with unpredictable or unclear effects on the population dynamics of H. arator. The extremely low economic threshold population density for H. arator in most crops means that it is extremely unlikely that biological control agents will deliver sufficient suppression of numbers at an economic cost to offer adequate reduction in the risk of damage (CABI CPC 2012).

BC recommendable at this point: No

Cosmopolites sordidus 20 22 44 40.0 Coleoptera (Curculionidae)

BC feasible: No Many attempts at CBC were conducted in the first half of the 20th century, with introductions into a number of countries, but often with only partial success; however, there is potential for the trial and introduction of newly discovered parasitoids (CABI CPC 2012). Possibilities and considerations for classical biological control of banana weevil have been reviewed by Greathead (1986), Greathead et al. (1986), Waterhouse and Norris (1987), Neuenschwander (1988), Kermarrec et al. (1993) and Koppenhöfer (1993a,b,c); Schmitt (1993) provides a partial list of arthropod natural enemies. Based on the weevil's biology, Greathead et al. (1986) gave a ca. 30% chance for complete success in biological control programmes.

BC recommendable at this point: No

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Dysdera crocota 30 28 37 39.6 Arachnida (Dysderidae)

BC feasible: No This species would be a good target in principle, as it is one of the introduced invertebrate species most likely to cause severe damage to native biodiversity on St. Helena; but there is no history of biological control against spiders in general.

BC recommendable at this point: No

Scolopendra morsitans 25 29 37 31.9 Chilopoda (Scolopendridae)

BC feasible: No There is no history of BC against Chilopoda in general.

BC recommendable at this point: No

Stegobium paniceum 20 21 27 25.7 Coleoptera (Anobiidae)

BC feasible: No Although subject to successful augmentative BC (as part of IPM programmes), no information on classical BC against this species is available.

BC recommendable at this point: No

Pheidole megacephala 30 31 25 24.2 Hymenoptera (Formicidae)

BC feasible: No Biological control agents exist for ants, such as phorid flies (Vazquez et al. 2006). However, the influence of such agents in regulating any ant population is still to be demonstrated; generally, CBC for ants has not been developed to a level where it can yet be successfully applied (CABI ISC 2012; Rabitsch 2011).

BC recommendable at this point: No

Linepithema humile 20 31 25 16.1 Hymenoptera (Formicidae)

BC feasible: No CBC of L. humile is hampered by a lack of known, host‐specific natural enemies (Orr et al. 2001). However, it has been suggested that its unicoloniality could be disrupted by increasing intra‐specific aggression through the alteration of hydrocarbon‐based recognition cues (Silverman & Liang 2001) or as a result of an increase in its genetic diversity through the introduction of males from genetically diverse populations (Suarez et al. 1999).

BC recommendable at this point: No

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3.2.9 Tristan da Cunha - Weeds Forty-seven non-native plant species generated an impact score of 20 or above and were evaluated further with the prioritisation tool. Assessments of individual species are given in Table 12. As in other cases, the species achieving the highest overall scores may not always be the ones for which biological control is the highest priority on Tristan. For a number of the higher scoring species, biological control may not provide the most suitable method at this stage. This is largely because the results presented here lack the benefit of refinement through direct stakeholder consultations and field visits, as conducted for the Falklands, South Georgia and Ascension Island. There is no history of biological control against non-native plant species on Tristan da Cunha. Almost all species recorded from the islands generated relatively low overall scores from the prioritisation tool, principally because none had been the subject of successful biological control programmes in other geographical areas. For some, however, promising biological control agents have been identified, and research efforts are still on-going, as these species cause severe problems in other countries. For these species, suitable agents may become available in the near future. Alternatively, independently funded scoping studies and host-range testing targeted for Tristan da Cunha could be initiated, where this is justified by the current or imminent threats these species pose to indigenous species and habitats. In summary, we believe that for a number of non-native weeds on Tristan biological control would be feasible and can cautiously be recommended. For these species, a significant negative impact on the environment and/or agriculture has already been recorded, but in most cases it is difficult to judge with confidence whether this is sufficient to justify investment in biological control at this stage. Only stakeholder consultations on site would allow better informed recommendations to be made. Potentially suitable candidates for biological control on Tristan da Cunha are currently: • Pennisetum clandestinum • Sonchus asper • Sagina procumbens • Taraxacum officinale • Rumex obtusifolius • Sonchus oleraceus • Juncus effusus • Polycarpon tetraphyllum • Rumex acetosella • Mariscus congestus • Agrostis stolonifera • Agrostis tenuis

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Table 12: Assessment of non-native plant species on Tristan da Cunha for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol TOTAL x EFFORT BIOCONTROL FEASIBILITY IMPACT Pennisetum clandestinum 40 28 65 92.9 Poaceae

BC feasible: Yes The rust fungus Phakopsora apoda has become established in South Africa, but appears only to decrease the photosynthetic capacity of the leaves and does not kill the plant (Haubensak & Smyth 1999). Two insects, Sphenophorus ventus vestitus and Herpetogramma licarsicalis, damage kikuyu grass in Hawaii (Cronk & Fuller 2001), and Mootooka et. al. (2002) states that it is also susceptible to the yellow sugarcane aphid (Sipha sp.). Plants are also affected by a fungal disease caused by Pyricularia grisea, which kills seedlings (FAO 2003; GISD 2012).

BC recommendable at this point: Yes There are negative impacts on biodiversity reported from Tristan, but control of this species is not considered practical by existing means (SAISP 2010). This suggests that BC could well be appropriate, to provide a long‐ term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Sonchus asper 40 21 48 91.4 Asteraceae

BC feasible: Yes Biological control agents are currently being researched for possible management S. asper and other Sonchus species in Australia (CSIRO 2007). Sonchus species have previously been the target of CBC in Canada (Peschken 1984). Preliminary surveys for biological control agents have been undertaken in southern France and northern Europe (Scott & Jourdan 2005; Peschken 1984). Currently, the rust fungus Miyagia pseudosphaeria and an unidentified eriophyid mite species are two widespread organisms in Australia with potential as control agents. The CSIRO project has focused on determining the impact of these potential control agents on related native Australian species (CSIRO 2007; GISD 2012).

BC recommendable at this point: Yes There are negative impacts on biodiversity reported from Tristan, but control of this species is not considered practical by existing means (SAISP 2010). This suggests that BC could well be appropriate, to provide a long‐ term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

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Sagina procumbens 35 28 72 90.0 Caryophyllaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: Yes It is feared that the negative impacts of this species will increase in the future (SAISP 2010). An eradication programme for Sagina procumbens from Gough Island is underway, but control of this species on Tristan is not considered practical by existing means (SAISP 2010). This suggests that BC could well be appropriate, to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Juncus tenuis 35 28 69 86.3 Juncaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, there are no indications that negative impacts of this species are sufficient to justify the development of a BC programme. However, a more detailed assessment through field site visits and stakeholder consultations is recommended.

Taraxacum officinale 35 33 67 71.1 Asteraceae

BC feasible: Yes Phoma exigua and P. herbarum have been isolated from T. officinale complex in Ontario, Canada, and considered as potential biocontrol agents (Neumann Brebaum 1998; Neumann Brebaum & Boland 1999). Controlled‐environment studies showed that young T. officinale plants were more susceptible to P. herbarum than older plants (Neumann & Boland 2002). P. taraxaci was considered as a biocontrol agent for T. officinale complex in Sweden (von Hofsten 1954). P. taraxaci was spread by pycnospores and infected seeds; however, it was extremely variable with respect to its pathogenicity on T. officinale complex and its viability in soil. Von Hofsten (1954) also mentioned an unnamed 'ring‐forming fungus' which released a substance that was highly toxic to T. officinale complex and other plants. Sclerotinia species have also been tested as biological control agents for T. officinale complex in Canada and New Zealand (Riddle et al. 1991; Waipara et al. 1993). Sclerotinia sclerotiorum and S. minor were evaluated in a controlled environment and in turf grass swards for their virulence on T. officinale complex. Isolates of both species reduced the dry weight of plants in a controlled environment and reduced the number of plants in turf grass swards. Heat‐killed seeds of perennial ryegrass were suitable as both a growth substrate for Sclerotinia spp. and a delivery system to T. officinale complex (Riddle et al. 1991). A mycelium‐on‐wheat preparation has been used for S. sclerotiorum, while either a granular sodium alginate formulation or a mycelium‐on‐barley preparation has been employed to deliver S. minor (Ciotola et al. 1991; Brière et al. 1992; Waipara et al. 1993). Sclerotinia sclerotiorum caused localized infection on the leaf laminas and created basal necroses of 1‐2 cm in length on tap roots of T. officinale complex. (Burpee 1992; Waipara et al. 1993). These necroses inhibited leaf regrowth from the root after defoliation (Burpee 1992).

BC recommendable at this point: Yes It is feared that the negative impacts of this species will increase in the future, and control of this species on

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Tristan is not considered practical by existing means (SAISP 2010). This suggests that BC could well be appropriate, to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Rumex obtusifolius subsp. obtusifolius 40 29 50 69.0 Polygonaceae

BC feasible: Yes Gastrophysa viridula has been suggested as a possible agent of biological control. However, although heavy grazing by this beetle reduces leaf area and overall biomass and affects the number and weight of seeds (Bentley et al. 1979, 1980), it is unlikely that G. viridula, acting alone, could be an effective control agent for the weed. In Tasmania, the clearwing dock moth Chamaesphecia doryliformis was introduced in 1997 at two sites to control of R. obtusifolius. However, there is no further information on the establishment and efficacy of this agent. Studies involving fungal pathogens have not developed control methods, though the possibilities have been discussed for Uromyces rumicis and Ramularia rubella. Hughes et al. (1996) investigated the effects of infection of Armillaria mellea and A. ostoyae, which attack the root system, and reported that the taproots were extensively rotted.

BC recommendable at this point: Yes The impact of this species on native biodiversity is quite serious (SAISP 2010). This suggests that BC could well be appropriate to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Sonchus oleraceus 30 21 48 68.6 Asteraceae

BC feasible: Yes Biological agents are currently being researched as for possible management of S. oleraceus and other Sonchus species in Australia (CSIRO 2007). Sonchus species have previously been the target of biological control in Canada (Peschken 1984). Preliminary surveys for biological control agents have been undertaken in southern France and northern Europe (Scott & Jourdan 2005; Peschken 1984). Currently, the rust fungus Miyagia pseudosphaeria and an unidentified eriophyid mite species are two widespread organisms in Australia with potential as control agents (CSIRO 2007; GISD 2012).

BC recommendable at this point: Yes S. oleraceus affects native biodiversity, invading native plant communities, resulting in the vegetation becoming dominated by alien species (SAISP 2010). This suggests that BC could well be appropriate to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Cyperus esculentus 40 40 65 65.0 Cyperaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, there are no indications that the negative impacts of this species are sufficient to justify the development of a BC programme. However, more a more detailed assessment through field site visits and stakeholder consultations is recommended.

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Juncus effusus 20 28 90 64.3 Juncaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: Yes At present, the impact of J. effusus on agriculture as well as on native biodiversity is small, due to its limited distribution. There is no reason to expect the distribution of this species to remain as restricted as it is at present, and future impacts are expected to be very serious (SAISP 2010). This suggests that BC could well be appropriate to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Centella asiatica 35 38 65 59.9 Apiaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, there are no indications that the negative impacts of this species are sufficient to justify the development of a BC programme. However, more a more detailed assessment through field site visits and stakeholder consultations is recommended.

Polycarpon tetraphyllum 30 28 55 58.9 Caryophyllaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: Yes The species has a clear negative impact on efficient food production. It also is one of the species invading native habitats, contributing to the transformation of these plant communities to alien‐dominated vegetation. Other forms of control of this species on Tristan are not considered practical (SAISP 2010). This suggests that BC could well be appropriate to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Rumex acetosella 40 47 67 57.0 Polygonaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: Yes This species has a serious negative impact on local food production, as well as on native biodiversity. Other means of control of this species on Tristan are not deemed practical (SAISP 2010), so BC could well be appropriate to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

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Mariscus congestus 35 40 65 56.9 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: Yes This species has a serious negative impact on local food production, as well as on native biodiversity. Other means of control of this species on Tristan are not deemed practical (SAISP 2010), so BC could well be appropriate to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Agrostis stolonifera 40 47 65 55.3 Poaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: Yes Agrostis stolonifera has a very large negative impact on native biodiversity on Tristan, but conventional control of this species is not considered feasible here (SAISP 2010). This suggests that BC could well be appropriate to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Agrostis tenuis 40 47 65 55.3 Poaceae

BC feasible: Yes There is no history of BC of this species, but development of a BC programme is feasible.

BC recommendable at this point: Yes Agrostis tenuis has a very large negative impact on native biodiversity on Tristan, but conventional control of this species is not considered practical here (SAISP 2010). This suggests that BC could well be appropriate to provide a long‐term solution where eradication is no longer possible. A more detailed assessment through field site visits and stakeholder consultations is highly recommended.

Oenothera glazioviana 25 28 61 54.5 Onagraceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, there are no indications that the negative impacts of this species are sufficient to justify the development of a BC programme. However, a more detailed assessment through field site visits and stakeholder consultations is recommended.

Plantago lanceolata 30 37 65 52.7

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Plantaginaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, there are no indications that the negative impacts of this species are sufficient to justify the development of a BC programme. However, a more detailed assessment through field site visits and stakeholder consultations is recommended.

Euphorbia peplus 30 28 48 51.4 Euphorbiaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, there are no indications that the negative impacts of this species are sufficient to justify the development of a BC programme. However, a more detailed assessment through field site visits and stakeholder consultations is recommended.

Prunella vulgaris 20 28 72 51.4 Lamiaceae

BC feasible: Yes There is no history of BC against this species, but development of a BC programme is feasible.

BC recommendable at this point: No At this stage, there are no indications that the negative impacts of this species are sufficient to justify the development of a BC programme. However, a more detailed assessment through field site visits and stakeholder consultations is recommended.

Sporobolus africanus 30 40 65 48.8 Poaceae

BC feasible: No Biological control of Sporobolus africanus has been investigated using the stem wasp Tetramesa sp. and the smut fungus Ustilago sporoboli‐indici. Both were unsuccessful, however, and future efforts are concentrated on the development as a mycoherbicide of a pathogen already present in Australia (Palmer 2008; Palmer et al. 2008; Palmer et al. 2010; GISD 2012). BC of grasses is notoriously difficult and, despite the relatively high overall score generated for this species, based on the failure of previous attempts we consider that BC against S. africanus is probably not feasible at this stage.

BC recommendable at this point: No

Poa pratensis 25 37 72 48.6 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

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BC recommendable at this point: No

Senecio pterophorus 30 38 61 48.2 Asteraceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Oxalis corniculata 20 29 67 46.2 Oxalidaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Conyza sumatrensis 35 38 50 46.1 Asteraceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Poa annua 35 37 48 45.4 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Holcus lanatus 25 37 67 45.3 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Leucanthemum vulgare 20 37 76 41.1 Asteraceae

BC feasible: No

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Currently, CABI is involved in programmes to control this invasive species in North America. However, no tested control agents are available yet, and the development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

Rubus loganobaccus 20 37 76 41.1 Rosaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Cynodon dactylon 25 40 65 40.6 Poaceae

BC feasible: No The Inaccessible Island Management Plan recommends that this species should be eradicated where possible, to avoid potential future problems (Ryan & Glass 2001). Drechslera cynodontis, Ustilago cynodontis, Puccinia cynodontis, and Fusarium poae as fungal pathogens and a specimen belonging to the Thripidae family have been identified on C. dactylon and are being studied for potential use in biological control (Uygur 2000; CABI ISC 2012). Development of CBC for the target area is, however, currently not realistically feasible.

BC recommendable at this point: No

Paspalum dilatatum 30 50 67 40.2 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Veronica serpyllifolia 20 37 74 40.0 Scrophulariaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Poa humilis 20 37 72 38.9 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

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BC recommendable at this point: No

Poa trivialis 20 37 72 38.9 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Solanum nigrum 30 38 48 37.9 Solanaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Paspalum notatum 25 50 67 33.5 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Coronopus didymus 25 38 50 32.9 Brassicaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Vellereophyton dealbatum 20 38 59 31.1 Asteraceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Vulpia bromoides 20 37 57 30.8 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is

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currently not realistically feasible.

BC recommendable at this point: No

Senecio vulgaris 20 34 48 28.2 Asteraceae

BC feasible: No Despite the wide range of natural enemies reported as attacking S. vulgaris, only the two fungal species Erysiphe fischeri and Puccinia lagenophorae have been tested as biological control agents (CABI ISC 2012). Plants infected with E. fischeri continued growing to set seeds even when 75‐100% of the aerial parts were colonized, but dry matter production of the weed was markedly reduced (Clarke et al. 1979). Under glasshouse conditions, P. lagenophorae infection reduced weed dry weight both in pure and mixed stands with lettuce. The fungus inhibited leaf expansion and production of capitula, reduced the number of flowering plants, and led to more rapid and early senescence of the weed, whereas mature, infected, flowering plants died earlier and more rapidly than healthy plants (Paul and Ayres 1987).The high death rate occurring among autumn‐inoculated plants was due to infection of the hypocotyl which was always killed within 1‐2 weeks. However, heavily‐infected plants were still able to produce some capitula and potentially set seed. Inoculation of plants bearing aecia of P. lagenophorae with an isolate of Puccinia intermedium caused 50% death of hosts 18 days after inoculation and 37 days after inoculation with Gibberella avenacea (Hallett & Ayres 1992). The lack of success with attempted BC, in combination with difficulties in identifying suitable control agents, means that application of this method is not currently feasible in the target area.

BC recommendable at this point: No

Agrostis castellana 20 47 65 27.7 Poaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Crepis capillaris 20 37 48 25.9 Asteraceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Gnaphalium luteo‐ album 25 57 48 21.1 Asteraceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

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Gnaphalium purpureum 25 58 48 20.7 Asteraceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Trifolium dubium 20 57 57 20.0 Fabaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No Trifolium glomeratum 20 57 57 20.0 Fabaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Trifolium micranthum 20 57 57 20.0 Fabaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Trifolium cernuum 20 58 57 19.7 Fabaceae

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

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3.2.10 Tristan da Cunha - Invertebrates Only six non-native invertebrate species achieved an impact score of 20 or above and were further evaluated with the prioritisation tool. Detailed assessments for these species are given in Table 13. We believe that none of these non-native invertebrates currently represent suitable targets for biological control. This is largely because biological control has not previously been attempted elsewhere against the majority of these species, or against any other species belonging to the same families. This conclusion may change, should on-going monitoring activities record increasing negative impacts from particular species. In such cases, the assessments below can provide valuable background information on available options for further steps. Equally, the evaluation presented here can only be considered preliminary, until supported or refined by on-site assessments and stakeholder consultations.

Table 13: Assessment of non-native invertebrate species on Tristan da Cunha for their potential biological control

1/Effort) (IMPACT

x SCORE

SCORE SCORE

SCORE

Biocontrol TOTAL x EFFORT BIOCONTROL FEASIBILITY IMPACT Lumbricus rubellus 20 28 66 47.1 Annelida; Oligochaeta (Lumbricidae)

BC feasible: No There is no history of BC against Lumbricidae, or earthworms in general. Development of biological control programmes would require a large‐scale research effort, and the efficacy of this method for this taxonomic group remains speculative. Such efforts could only be justified by substantial negative impacts on native species and habitats, which have not yet been recorded from Tristan da Cunha.

BC recommendable at this point: No

Lehmannia valentiana 30 28 28 30.0 Mollusca (Limacidae)

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Porcellio scaber 25 37 37 25.0 Isopoda (Porcellionidae)

BC feasible: No Introduced detritivores on Gough Island, like P. scaber, lumbricid worms and the millipede Cylindroiulus latestriatus, could have long‐term effects on nutrient cycles of its peaty soils, which lack such species and have formed in the absence of rapid organic breakdown. Long‐term effects could include changes in floral and faunal communities (Jones et al. 2003a). Rikettsiae of the genus Wolbachia may, in the future, provide

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suitable control agents for Isopoda (Hawkins & Cornell 1999). However, there is no history BC against this species, and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Milax gagetes 25 28 26 23.2 Mollusca (Milacidae)

BC feasible: No There is no history of BC against this species and development of a BC programme for the target area is currently not realistically feasible.

BC recommendable at this point: No

Deroceras reticulatum 20 24 26 21.7 Mollusca (Limacidae)

BC feasible: No There is no information on classical biological control against this species (Howlett 2012; CABI ISC 2012), although some integrated pest management is possible through augmentative releases of the nematode Phasmarhabditis hermaphrodita (Speiser et al. 2001; Rae et al. 2008). Development of BC for the target area is currently not realistically feasible.

BC recommendable at this point: No

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4. Project conclusions The assessment tool adapted for this study, and modified to cover not only weeds but also invertebrate species, turned out to be a very valuable instrument with which to compile information on individual species and estimate the feasibility of biological control in each case. Paynter et al. (2009) designed it for use in relation to large geographical units, rather than the more confined environments of islands. Nonetheless, it provided a very useful basis by which to generate an initial ranking of priority of individual species for biological control. Stakeholder consultations, in combination with on- site visits, revealed that the ranking based on this strictly numerical assessment may not be entirely consistent with priority needs. However, this is likely to be the case wherever such analytical tools are applied and limitations of purely numerical evaluations are well known (Maczey 1991; Garshelis 2000; Morrison et al. 2006). Further consultations are therefore essential to develop definitive, evidence- based, economically viable recommendations for future action (see case study below). Consequently, any ranking given in this report for St. Helena and Tristan da Cunha can only be regarded as preliminary, as the scope of the project did not allow for ”ground truthing” of the numerical assessments through on-site stakeholder consultations and field site visits.

Casy study: Gorse (Ulex europaeus) in the Falkland Islands

With an overall score of 900 Ulex europaeus, achieved one of the highest feasibility values of all species assessed during this study, suggesting that this species is a very suitable candidates for classical biological control. Indeed, gorse has been the subject of extensive biological control programmes in other geographical regions. Hence, ‘off- the-shelf’ biocontrol agents would be available, significantly reducing the costs of implementing programmes against these species on the Falkland Islands. However, during stakeholder consultation in Port Stanley it became obvious that Ulex europaeus is regarded as having substantial benefits to the Falklands, going beyond what was previously published. Although some information on benefits, for example that it provides shelter for farming purposes, is available and could therefore be included into the initial assessement of the species, it turned out that the species has also acquired over a long period significant cultural and ornamental value. In addition, gorse provides shelter for native animals and is used as nesting habitats by birds in particular by barn owls. This benefit is however questionable and subject to on-going debate, as native wildlife would still be able to survive in the original habitat without gorse and this aspect is mainly a question of scale to preserve diversity on large scale instead of small scale very localised diversity. In summary, with regards to the potential control of this species, a detailed cost-benefit analysis and careful stakeholder consultations are required to determine the balance between perceived value and any negative impacts this species has. It was therefore agreed on during the stakeholder consultation in Port Stanley that gorse was probably not suitable as first choice for CBC project on the Falklands due to positive public perception of the species with in the public. However, there is a worrying increasing spread of it in particular on smaller island after reduction or cessation of grazing. Given the perceived and real benefits of gorse biological control efforts need to be well targeted and require initial education for higher acceptance levels. During the workshop consultations it was pointed out that under the given circumstances the release of host specific seed eating agents maybe a viable option. This would preserve existing stands but result in a slowdown of spread and diminished germination of seedlings would also underpin other integrated control efforts.

Despite significant previous and on-going efforts, invasive species (in particular non-native weeds) continue to pose a severe threat to native species and habitats on all of the UKOTs considered under this project. With the exception of South Georgia, where it currently does not appear to be appropriate for any of the non-native plants and invertebrates assessed, all of the South Atlantic UKOTs support invasive species against which biological control is a feasible and recommended option for cost effective, long-term management. In a number of cases, the Territories concerned could benefit from previous successes against the same invasive species in other geographical areas. Furthermore, the often limited number of native species (or at least the lack of closely related non-target taxa) will make testing for host-specificity prior to the release of any agents straightforward and highly cost efficient. We have also identified and described a number of species where no biological control programmes have been developed so far, but where the chances that investment in this method will eventually pay off and lead to satisfactory long-term control are high. Of course, starting new programmes from scratch requires a large commitment both in terms of time and costs. The absence of previous programmes need not indicate that biological control is not a suitable approach for the target species,

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it may simply be that programmes in other geographical areas have not been pursued due to the occurrence there of highly valued, closely related non-target species. Equally, however, a number of potential target species in the South Atlantic UKOTs, some impacting seriously on native ecosystems, have turned out in this study to be unsuitable for biological control for various reasons. One important aspect of future CBC on the SAUKOTs is to integrate this method into other control efforts for example to underpin on-going mechanical measures or the application of herbicides. During this study we identified in particular that this is likely to be beneficial in the case of thistle control on the Falkland Islands and possible also with regards to future control of Gorse (Ulex europaeus) and Calafate (Berberis microphylla) on this island. Currently there is no acute demand to accompany any future CBC on South Georgia or the Falkland with programs for soil remediation to support a more rapid regeneration of native vegetation and prevent undesired ‘side-effects’ after successful control such as soil erosion due to delayed re-colonisation by native plants. Whereas currently on South Georgia no suitable candidates have been identified for CBC at all, on the Falkland Islands infestations of species suitable for CBC are still on a scale where the re-establishment of native vegetation after successful control is not expected to be problematic. Finally, we hope that the data compiled during this project will provide a source of valuable background information for decision makers, particularly should more severe threats arise in the future from any of the assessed species. In such situations, this report should provide a useful starting point and a guide for assessing available biological control options, even if the current situation does not justify its use.

5. Recommendations In a number of cases, we would like to urge a rapid uptake of biological control, in particular where an accelerated spread of species has recently been recorded. We would make the same recommendation where a recently reported immediate threat to native species could be relatively quickly counteracted by the introduction of readily available, efficient and safe control agents. On the Falkland Islands only few species can currently be recommended for the uptake of CBC efforts. Gorse (Ulex europaeus) is regarded as having substantial benefits, therefore, detailed cost- benefit analysis and careful stakeholder consultations would be required to determine the balance between perceived value and any negative impacts this species has. One possible way forward may be the introduction of seed-feeding control agents, which have the ability to slow down further spread and support mechanical control efforts but do not impact on existing stands. The implementation CBC against P. officinarum may be able slow down further spread and contain negative impacts caused by this species and assessments building on ongoing research are highly recommended. Berberis microphylla (Calafate) is a weed of great concern in the Falklands, due to a recently substantially increased rate of spread, potentially substantial threats to the environment and wool production, and the difficulty of control by chemical or mechanical means. Based on this, we highly recommend the initiation of scoping studies, surveying suitable CBC agents for Calafate as soon as possible. In addition, current control efforts against Cirsium vulgare are likely to benefit from reinforcement by additional CBC measures. The European earwig Forficula auricularia emerged as a very promising target species. As this species has become a major nuisance and has no perceived benefits. CBC against F. auricularia has already been instigated elsewhere, and risk assessments and host-range testing programmes should be straightforward, as no closely related non-target invertebrates occur on the Falklands. On the basis of intensive stakeholder consultations we don’t regard any of the non-native plant species or terrestrial invertebrates occurring on South Georgia worthwhile for CBC at this moment. However, it is recommended to pursue the control of earwigs (Forficula auricularia) on the Falklands rapidly as this would significantly reduce the risk of this species spreading also into South Georgia. On Ascension, Mexican Thorn (Prosopis juliflora) still poses the biggest threat to indigenous biodiversity and landscape features of any introduced plant species. Consequently, further efforts can be regarded as a high priority, particularly as a new, highly effective and safe agent has become

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available. Equally, the severity of the invasion of Wild Tobacco (Nicotiana glauca) and Mexican Poppy (Argemone mexicana) justifies an initial exploration of the potential for CBC, including a survey for suitable control agents in the area of origin of these species. As it still poses a severe threat to the indigenous fauna and flora in higher parts of Ascension, Lantana camara also remains a promising target for improved CBC through additional effective and tested agents. For St. Helena and Tristan da Cunha, a preliminary evaluation of priorities for both non-native plants and terrestrial invertebrates was made without the benefit of field site visits and detailed stakeholder consultations. Consequently, species for which CBC is feasible and recommended are subject to further consideration. Nonetheless, the uptake of CBC measures is provisionally highly recommended for the fast spreading Asparagus densiflorus on St. Helena and the scale insect Pseudococcus viburni currently threatening the endemic gumwood trees on St. Helena. Opuntia stricta, O. ficus- indica and Lantana camara have all been subject to CBC on St. Helena in the past. However, there are indications that all three species are still extremely widespread and continue to impact heavily on native flora and fauna. If this can be verified through more detailed assessments on the ground, all three species would become highly suitable and recommendable targets, as more effective, well- tested CBC agents have become available since the last programmes conducted on St. Helena. The results presented for St. Helena and Tristan da Cunha in this study have a more preliminary character compared to those for the Falkland Islands, South Georgia and Ascension Island, where assessment results were reinforced or refined by direct stakeholder consultations and/or ground truthing. We therefore recommend extending the detailed assessments by using the template provided by this study to St. Helena and Tristan. Equally, we believe that this study has provided a template, which can be successfully applied to other overseas territories and islands where ecosystems are facing similar threats through invasive weeds and terrestrial arthropods. On Ascension and St. Helena, where the number of invasive non-native species surpasses the number of indigenous taxa, any future CBC needs to consider the impact of successful control of individual weeds on other invasive species. There is a real risk that the overall impact on native habitats can become worse if some invasive weeds can take advantage of the control of another one. This is particular feared for the area of ‘Green Mountain’ on Ascension where numerous invasive species are highly dominant, but where also the majority of endemic plants still survive. A similar situation can be anticipated for St. Helena where there are already cases known, where the control (in this case not CBC) of one species has led to the advance of a second non-native weed increasing the overall impact on native habitats (Colin Clubbe pers. comment 2012).

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Annexes

Annex 1: Evaluation tool (adjusted from Paynter et al. 2009)

SPECIES IMPORTANCE & DESIRABILITY OF OUTCOME Prosopis juliflora BIOCONTROL 1. Is the species native or at least possibly native? a. Yes and in its natural range Biological control is undesirable Biological control may be ecologically feasible, go b. Yes, but occurring outside its natural range to question 2.

c. No, but possibly colonised island(s) naturally Biological control is undesirable

d. No Go to question 2. Y 2. Is opposition to biocontrol likely? Does the species have socioeconomic value a. Yes and value of species demonstrably >cost of control/detrimental impacts Biological control is undesirable i. species valuable as control agent of introduced other non-native species Biological control is undesirable Cost-benefit data is likely to be required for biocontrol to proceed, delaying biocontrol, adding b. Yes, but cost-benefit analysis data does not exist to cost & uncertainty of success c. Yes and value of species demonstrably

island? a. No, only records of single specimen(s) or doubtful records Biological control is unfeasible

b. No, no recent records Biological control is unfeasible

c. Establishment unknown Biological control is unfeasible

d. Yes Go to question 4. Y 4. Has the species already been subject of biological control on the island(s) a. Yes, successful control achieved Further biological control is of low priority b. Yes, but control insufficient or success not sufficiently monitored Go to question 5. Y

c. No Go to question 5. 5. Has eradication recently recommended as suitable control method a. Eradication has been recommended and only small populations locally restricted exist Biological control is undesirable b. Eradication has not been recommended but the occurrence and life history of the species does not warrant biological control measures Biological control is undesirable c. Eradication has been suggested as control method but species is already widespread Go to question 6. d. Eradication has not been recommended as suitable control method Go to question 6. Y

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6. Is the species sufficiently widespread/intractable/important to justify Question investment in biocontrol? Is the species only recently introduced/recorded on the island(s)?

(0-no, or no data available; 5-yes) 0 Does the species currently have a widespread recorded distribution on the island(s)?

(0-no, or no data available; 5-yes) 5 Is the species currently expanding its range on the island(s)?

(0-no, or no data available; 5-yes) 5 Is the species known to be invasive in other geographical regions?

(0-no, or no data available; 5-yes) 5 Is the species known to have negative impacts on biodiversity in other geographical regions?

(0-no, or no data available; 5-yes) 5 Is the species known to cause economic damage in other geographical regions?

(0-no, or no data available; 5-yes) 5 Is the species known to cause threats to human or animal health in other geographical regions?

(0-no, or no data available; 5-yes) 0 Are habitats on the island(s) which can potentially be invaded of conservation importance?

(0-no, or no data available; 5-yes) 5 Does the SAIS assessment suggest a likely negative impact on biodiversity, agriculture or health

(0-no; 5-yes) 5 Have ecological impacts been recorded on the island(s) for this species?

(0-no; 10-yes) 10 Have economic impacts (agriculture and others) been recorded on the island(s) for this species?

(0-no; 10-yes) 10 Have impacts on human or animal health recorded on the island(s) for this species?

(0-no; 10-yes) 0 species IMPACT SCORE 55 Ashmole & Ashmole 2000; Belton 2008; Lambdon et al. References records, impact and 2009; Varnham 2009; CABI invasiveness in other geographical regions ISC 2011, GISD 2011

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7. Is impact score equal or above 20 if yes, go to next question a. No Biological control is undesirable b. Yes Go to next set of questions Y EFFORT REQUIRED TO OBTAIN & HOST-RANGE TEST BIOCONTROL AGENTS 8. Has the species been/is it a subject of adequately resourced biocontrol program elsewhere? If specific agents are already known & host-range testing has already been conducted overseas, then programme is a. Yes, successful program likely to be cheaper 1 1 Law of diminishing returns - if current known suite of agents is ineffective, finding b. Yes, unsuccessful program new ones will be harder 15 c. Current target/too early/insufficient data to assess Potential for cost savings, but uncertainty success elsewhere or variable success elsewhere factored into score 8 d No, never 20 9. Accessibility and ease of working in native range a. Difficult 5 b. Moderate 3 c. Easy 2 d. Not applicable (if repeat programme) 1 1 10. Literature regarding natural enemies well known/accessible a. Yes 1 1 Formal identification of candidate agents (required for import/release permits) may b. No be time consuming, delaying a program 5 11. Phylogeny: How closely related to indigenous/valued species is the target species? Cheaper no-choice tests may be sufficient, a. None in same family larger pool of candidate agents 1 b. Same Family 10 10 More extensive host-range testing may be required, more species may require testing before a sufficiently specific species is c. Same Genus identified 20

EFFORT SCORE 13

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PREDICTING THE POTENTIAL IMPACT OF BIOCONTROL

12. Has the species been a subject of adequately resourced biocontrol programme overseas? a. Yes, successful target overseas 1 or more Maximum score: do not go to next set of occasions questions 100 b. Yes, only one example or with varying degrees of success or partial success i. Reason for variable success known (e.g. agent only attacks certain forms of species, or is restricted to certain habitats/climates) and considered unlikely to be a problem Do not go to next set of questions 80 80 ii. Reason for variable success unknown Do not go to next set of questions 60 iii. Reason for variable success known and considered likely to be a problem Do not go to next set of questions 40 c. Unsuccessful target overseas only once 30 d. Unsuccessful target overseas more than once 20 e. Not a target elsewhere or too early to assess success of overseas program Go to next set of questions 1 13. Habitat

Aquatic/wetland Higher probability of success 35

Terrestrial Lower probability of success 14 14. Life cycle Predominantly temperate annual 3 Predominantly tropical/sub-tropical annual 5 Biennial/perennial 5 15. Reproduction Vegetative (+/- seed/spore) 25 Seed/spore only 10

16. Weed in native range a. Yes Lower probability of success 3 b. No Higher probability of success 10 17. Difficulty targeting multiple forms of weed, or probability of replacement of the weed by forms or congeners of the target following successful biological control thereby negating benefits a. Likely Lower probability of success 0 b. Unlikely Higher probability of success 5 c. Unknown 2

18. Occurring in competitive environment (agricultural vs. environmental) a. Predominantly agricultural Lower probability of success 1 b. Predominantly environmental Higher probability of success 5 c. Unknown/both equally 3 19. Native/valued exotic congener a. Yes 0 b. No 15 References for efforts, potential impact and on Belton 2008; CABI ISC BC in other geographical areas 2011, GISD 2011

BIOCONTROL FEASIBILITY SCORE 80 TOTAL SCORE (species IMPACT x Biocontrol x 1/Effort) 338.46

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Comments Several biological control programmes using species of seed-feeding bruchid beetles have been developed and implemented. The advantage with bruchids is their observed host specificity, with many species found to feed only on Prosopis, and some only on a single species. Other insect species known to have a deleterious effect on native and exotic Prosopis in the Americas, mainly twig girdlers and psyllids, have also been suggested as possible biological control agents. The twig girdler Oncideres limpida attacks P. pallida in Brazil (Lima, 1994), whereas Oncideres rhodostricta is seen as a serious pest of P. glandulosa in the USA (Polk and Ueckert, 1973). Psyllids are known to severely affect the growth of Prosopis (Hodkinson, 1991) and have been suggested for use in controlling invasions. The same two bruchid species were also introduced to Ascension Island in an attempt to control P. juliflora which is present on 80% of the island, often in dense thickets. Two other species, one a psyllid and the other a mirid, were identified as attacking P. juliflora on Ascension Island and were thought to have been introduced accidentally from the Caribbean. The mirid Rhinocloa sp. causes widespread damage and is thought to lead to substantial mortality of trees (Fowler, 1998) [extract from CABI ISC 2011].

Annex 2 Assessment tables weeds

Annex 3 Assessment tables invertebrates

Annex 4 Project reference list

Annex 5 Questionnaire

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