Biosecurity – Royal Botanic Gardens Melbourne
Volume 8 Number 2 - July 2011
Biosecurity describes the protection of living plant assets, environmental habitat, and industries from biological threats such as ‘pests’ that may cause damage or disease. The term pest is accepted as a generic definition (IPCC, 2011) for a biological threat that is detrimental to biodiversity, natural habitats, and plant health. Some examples include pathogenic micro-organisms, insects, mites, pest animals, and pest plants.
It is likely that every botanic garden around the world will have serious exotic pests to consider as threats to living plant collections. These risks should also be considered in the context of climate change that has the potential to create conditions suitable for new and emerging exotic pests. Furthermore, globalisation has increased the fluidity of world-wide transport systems, and subsequently, the chances of a serious pest finding purchase in another country, region or garden (Victorian Government, 2009). For example, seeds are often purchased over the internet and readily posted to a customer anywhere in the world, and these packages are not always intercepted by quarantine services. An international traveller with seed or pest-contaminated footwear could easily visit a botanic garden on their first excursion, and walk onto a garden bed to take a photograph.
Over the last decade, a greater emphasis has been placed on the protection of horticultural industries from pest incursions in Australia with Biosecurity Plans developed by Plant Health Australia in association with many agricultural industries and the Nursery and Garden Industry (PHA, 2008). For southern Australian botanic gardens, future serious exotic pests include Asian Gypsy Moth, Dutch Elm Disease (Ulmus spp.), Eucalyptus/Guava Rust, Pine Pitch Canker and Sudden Oak Death. These threats highlight the need to be prepared for potentially devastating pest incursions.
At the Royal Botanic Gardens Melbourne (RBG Melbourne), the high plant diversity of about 10,000 species means that there are a great number of plants suitable for hosting serious exotic pests, especially when combined with close proximity to trade and travel pathways into Victoria.
Currently, biosecurity is included as a matter for attention within the RBG Melbourne Risk Management Plan. Pest incursions that result in significant damage to the living collections are ranked as a high strategic risk to the organisation. While RBG Melbourne has a responsibility to protect its living assets, it also recognises the magnitude of inadvertently spreading pests beyond its managed land that could damage natural biodiversity and plant-based industries.
Early warning – Fireblight strikes!
In 1997, the RBG Melbourne had the unenviable position of Fireblight (Erwinia amylovora) being found on some Cotoneaster spp. (Rosaceae) by a visiting scientist (Jock et al., 2000). This was the first record of this serious exotic pathogen being found in Australia. Fireblight is a devastating disease particularly for the pome fruit industry (mainly apples and pears) and had very significant implications for international trade. The subsequent eradication program that removed the few infected plants, and a large number of potential host species also resulted in the loss of wild-collected plants from Rosaceae with irreplaceable plants from Southern China. Also removed were important landscape specimens including magnificent trees of Pyrus pashia which had been growing in RBG Melbourne for decades. Whilst the eradication program was successful, the importance of active monitoring and surveillance was highlighted and has resulted in heightened awareness, planning and precautionary measures in dealing with biosecurity matters within RBG Melbourne during the past decade. In the interim, hygiene and sanitation practices were implemented and a hygiene protocol document was developed to limit the risk of another undetected incident such as this occurring again or if it was to happen that there would be improved containment measures in place.
Invasive plants management
Prior to 2003, botanical staff had assessed the invasive potential of plants proposed for sale by the Growing Friends. However, there was no formal risk assessment or substantive process to address the weed risk of plants being introduced into RBG Melbourne’s living plant collections. Early in 2003, horticultural coordinators at the Garden initiated a management project to develop a Weed Risk Assessment Process (WRAP). A working group was subsequently formed comprising both horticultural and botanical staff to assist with further development of the WRAP, and to develop a Weed Strategic Plan. RBG Melbourne also worked closely with staff from the Department of Primary Industries Victoria (DPI Victoria) to improve the risk assessment components. Strong interest in the process and valuable observations of plant invasiveness by horticultural staff also helped refine the WRAP. In 2004, the Nursery Coordinator developed an interim WRAP database to improve the processing and recording of weed risk assessment. An information resource ‘Garden plants as environmental and agricultural weeds, resource and information pack’ was developed by botanical staff for botanic gardens and public education and made available as a download from the RBG Melbourne website (RBG Melbourne, 2011a).
Later in 2004, the then Weeds Cooperative Research Centre (Aust.) provided funding for an Australian Botanic Gardens Weeds Network (ABGWN) workshop which was held in Melbourne and led by RBG Melbourne botanical staff to confirm policy and the WRAP for adoption across Australia. In 2005, the Council of Heads of Australian Botanic Gardens (CHABG) endorsed a common Weed Policy for Australian botanic gardens, and this was followed by the development of a federally funded and customised software version of the WRAP which is a free download available from the Botanic Gardens Australia and New Zealand (BGANZ) website (BGANZ, 2011).
A scientific analysis of the WRAP was published in the journal Plant Protection Quarterly. The paper assessed the discriminatory power and potential cut-off scores for the test (Virtue et al., 2008). The potential for application of the WRAP to industry was noted in the paper and, in April 2011, an industry workshop was held at the Royal Botanic Gardens Sydney to discuss the adoption of the WRAP by the Australian Nursery and Garden Industry and to devise a programme for assessing 1,000 common ornamental plants available in the industry using the WRAP. A researcher has been employed by the industry and the result of the assessment should be known in about a year’s time. (See also RIRDC, 2011).
The WRAP project that was initially derived at RBG Melbourne to reduce the risks of introducing or spreading invasive plants has now developed into a national initiative, receiving funding and being accepted by weed scientists and horticultural industries alike.
Pest Incursions - Case Studies
In September 2000, an undescribed Phytophthora aff. megasperma (Asparagus Phytophthora) was detected on Agavaceae in RBG Melbourne for the first time in Australia, and possibly the world. Within two months, about 70 plants from Agavaceae (particularly Agave spp.) were killed and/or removed due to severe infection. This disease has been a continuing and significant problem to date with devastating impacts primarily on plants from Agavaceae. Over ten irreplaceable, wild-collected Agave spp. were killed outright by this disease. Interestingly, in 2005, this Phytophthora spp. was finally confirmed via DNA analysis as the same organism originally recorded in 1995 damaging culinary asparagus plants being grown over 40 kilometres to the east of the Gardens in Cranbourne (Cunnington et al., 2005). It is possible that the pest originally entered RBG Melbourne via soil supplies as Cranbourne is a common source for sandy loams used in landscapes all over Melbourne. RBG Melbourne had held fears that this disease may also infect Australian plants within natural habitats that had been classified within Agavaceae such as Doryanthes palmeri or D. excelsa. However, these plants appear to not be susceptible.
In October 2010, Phytophthora aff. megasperma was detected damaging Bulbine vagans – not a member of Agavaceae, but related in order through Asparagales. Bulbine vagans is native to northern NSW and Queensland, Australia. This raises the biosecurity issue of the risks for the diseases to spread to natural habitats of B. vagans.
To consider further, what would be the implications of a successful incursion of this pathogen into natural habitats of Agave spp. in Southwest USA?
Diplodia on Pines
In June 2010, unusual symptoms of dieback on Pinus muricata were submitted to Crop Health Services, DPI Victoria. Symptoms identified included stem cankers and dieback, needles dying and resin flow from affected branches. The initial diagnosis was reported as Botryosphaeria sp. This ‘weakly’ pathogenic pest is a common secondary disease in stressed plants and was relatively frequent around the RBG Melbourne due to over a decade of unprecedented drought. However, the RBG Melbourne sought further identification to species level. Further DNA sequence data established the identity of the pathogen as Diplodia africana and this was also later detected from a nearby Pinus patula. D. africana was first described as a new species in South Africa, where it was isolated from shoots of Prunus spp. However, this incursion on Pinus spp. in the RBG Melbourne appears to be the first record described anywhere in the world. Similarly to other Diplodia infections, it was thought that predisposing biotic or abiotic stresses were required to initiate infection. In this case symptoms seemed to be related to previous significant hail damage that occurred to trees in March 2010. The area was barricaded and a ban imposed on movement of Pinus material within and out of RBG Melbourne. From September 2010, further surveillance by Biosecurity Victoria did not detect D. africana in any Pinus spp. within or outside RBG Melbourne. Due to the possible risk to commercial pine plantations and amenity trees in general, it was decided to remove these trees to contain the disease as soon as possible under suitable conditions to reduce risk of spreading fungal spores (low wind speed, dry weather), even though pathogenicity had not yet been fully determined. In October 2010, the two infected trees were removed as a joint operation between Biosecurity Victoria and RBG Melbourne staff under quarantined conditions. Subsequent pathogencity testing of D. africana completed in December 2010 ultimately found it to be less severe than the more common D. pinea. If further incursions of D. africana occur this is now considered to be a local management responsibility for RBG Melbourne.
This incident highlights the importance of avoiding assumptions about disease symptoms and / or being satisfied with identifications to genus level (which is often influenced by testing costs). If the scenario had involved a more serious pathogen, and RBG Melbourne had not requested further identification, it is conceivable that an epidemic on Pinus spp. may have ensued, damaged commercial interests and opened RBG Melbourne to scrutiny and loss of reputation in the community.
Relationships with Plant Health Agencies
RBG Melbourne has fostered highly collaborative relationships with plant health agencies both within and outside Australia. In particular, Plant Standards, Biosecurity Victoria has recognised the sentinel value of the diversity of RBG Melbourne’s plant collections and are very responsive to notifications of unusual pest symptoms. Personnel will often make the effort to visit and take specimens for analysis at no cost. In 2006, Plant Standards undertook a Hazard Site Surveillance program that operated for two years to inspect large gardens and urban landscapes for serious exotic pests which included RBG Melbourne due to its proximity to the city. There have also been other collaborative projects with Biosecurity Australia in screening for particular exotic pests. Being able to provide current plant records and/or horticultural staff assistance to locate host plants improves the efficiency of the site surveillance, and is noted and welcomed by the personnel involved.
In 2007, RBG Melbourne began assisting with the New Zealand (NZ) Expat Plants Project (Biosecurity New Zealand, 2011) which was a component of the Better Border Biosecurity (B3) program. The intent of this forward thinking project was to identify NZ plant collections growing overseas that could then be used as international sentinels of emerging pests that may threaten NZ flora. Some pest affected specimens from RBG Melbourne were collected by NZ researchers under phytosanitary conditions to consider for pest risk to NZ’s natural resources. Communication has continued with the B3 program when pests on NZ flora are identified. It is also understood that other BGANZ member Australian botanic gardens have assisted with this project.
In 2006, conceptual planning began for developing a system that would integrate recording, education and management of pest problems in RBG Melbourne. In 2008, a pest database was completed as a component of the RBG Melbourne’s living plant collections database. It is now possible to produce comprehensive reports of particular hosts, known distribution, treatment history, images of symptoms, etc. This has become a valuable management tool toward improving pest management within RBG Melbourne. Being linked to the plant collections database also means that changes in plant nomenclature or location names are also readily updated.
Professional and Public Education
In March 2010, BGCI and BGANZ delivered the International Certificate in Botanic Gardens Management course in Singapore (BGCI, 2011) to range of participants generally from SE Asia. Two of the modules under horticulture led by RBG Melbourne addressed biosecurity through management of invasive plants and pests.
A range of training is regularly delivered by horticultural staff and external experts for employees, friends and volunteers. Information relating to biosecurity and pest management has also been provided via the website (RBG Melbourne, 2011b).
Policy and Procedures
In 2010, RBG Melbourne improved its biosecurity strategy in completing an organisational Biosecurity Policy and is currently reviewing the associated procedures. Within the policy, RBG Melbourne acknowledges the importance of the stewardship of its living assets to protect them from exotic pest threats, and also its responsibility to prevent pest threats to others. The organisation has adopted the philosophy that effective biosecurity includes the implementation of both border quarantine and internal pest management practices such as Integrated Pest Management (IPM).
Underpinning the RBG Melbourne Biosecurity Policy are eight principles:
- Seek to prevent pest excursion, incursion and further spread.
- Manage risk of transport of landscape materials across management boundaries.
- Conduct regular surveillance.
- Promote plant health according to the prevailing environmental and climatic conditions, and available resources.
- Implement effective hygiene and sanitation practices.
- Conduct regular employee training and visitor education programs.
- Maintain and develop effective relationships with plant health agencies.
- Continue to develop and improve procedures for effective monitoring, recording and managing pests.
There is an increasingly vital role for botanic gardens to fulfil in protecting the biosecurity of natural environments, cultural landscapes and industries. Whilst the high plant diversity intrinsic to botanic gardens may be seen as a risk to biosecurity, it can actually provide an ‘early warning’ mechansim through sentinel plants to herald the incursion of a new invasive species. This early identification of pests provides greater opportunity for the success of containment and eradiction programs. World-wide, botanic gardens can readily share their expertise and observations from practitioner to scientist, to work with plant health agencies and produce a more robust surveillance network. Increasing globalisation also means that botanic gardens must set a priority agenda to develop biosecurity management, policy and practices to reduce the risk of introducing or spreading invasive species. Botanic gardens have readily demonstrated leadership through dedicated personnel in reducing the risk and impacts from invasive species upon biodiversity.
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Curator, Environmental Horticulture
Royal Botanic Gardens Melbourne
(Private Bag 2000)