Tasmanian Plant Biosecurity Routine Import Risk Analysis (IRA) for Potato Spindle Tuber Viroid (PSTVd)
Plant Biosecurity & Diagnostics Branch BIOSECURITY TASMANIA
DEPARTMENT OF PRIMARY INDUSTRIES, PARKS, WATER AND ENVIRONMENT
Version 2.6
Controlled Copy
Published by: © Biosecurity Tasmania, Department of Primary Industries, Parks, Water and Environment, Hobart, Tasmania.
Online publication ISBN: 978-1-74380-069-0 Printed publication ISBN: 978-1-74380-068-3
Cite as: Cross, P. (2020) Routine Import Risk Analysis for Potato Spindle Tuber Viroid (PSTVd). Biosecurity Tasmania, DPIPWE, Hobart, 34PP. URL: https://dpipwe.tas.gov.au/biosecurity-tasmania/plant-biosecurity/biosecurity-tasmania-import- risk-analysis-assessment-processes/finalised-import-risk-analyses
COVER PHOTOGRAPHY Left: Potatoes – Lynn Broos, DPIPWE. Middle - PSTVd-infected tomato plant (on left compared to a healthy tomato plant on right) – image courtesy of Department of Primary Industries and Regional Development website, Western Australia. Right – Potato plants – Lynn Broos, DPIPWE.
INSIDE COVER PHOTOGRAPHY (from left to right) PSTVd-infected potatoes (on right compared to a healthy tuber on left) – image courtesy of National Plant Protection Organization, The Netherlands, Bugwood.org PSTVd-infected tomato plant (on left compared to a healthy tomato plant on right) – image courtesy of Department of Primary Industries and Regional Development website, Western Australia Tomato seed – image courtesy of Gardening Australia website
ACKNOWLEDGEMENTS This template has drawn upon elements of methodology first presented in Standard Operating Procedure No.10 – Routine IRA Methodology (DPIPWE 2014), other Plant Biosecurity & Diagnostics Branch (PBDB) IRA reviews, and the Tasmanian Risk Analysis Framework (DPIPWE 2010). Review of this (single) Pest IRA Template by PBDB colleagues is appreciated.
Further information:
Plant Biosecurity and Diagnostics Branch Biosecurity Tasmania, DPIPWE PO Box 303 Devonport TAS 7310 Phone: 1300 368 550 Email: [email protected]
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DOCUMENT RELEASE NOTICE
This is Version 2.6 of this Routine Import Risk Analysis (IRA) for Potato spindle tuber viroid.
This Report is a managed document controlled and issued by the Plant Biosecurity & Diagnostics Branch (PBDB), Biosecurity Tasmania (BT) Division, Department of Primary Industries, Parks Water and Environment (DPIPWE). Recipients should remove superseded versions from circulation. Recipients are responsible for accurate citation when referring to this Report. This document is authorised for release.
PREPARED by: Peter Cross, Team Leader – Plant Pathology, BT DATE: 4/05/2021
REVIEWED by: PBDB Policy Group, BT
ACCEPTED: Andrew Bishop, Chief Plant Health Manager, BT DATE: 05/05/2021
1. BUILD STATUS:
Version Date Author Reason Focus
1.0 17/04/2020 Peter Cross, PBDB, BT Draft review Internal
2.0 11/05/2020 Peter Cross, PBDB, BT Draft for peer review Internal
2.1 14/05/2020 Peter Cross, PBDB, BT Draft for peer review Internal
2.2 15/05/2020 Peter Cross, PBDB, BT Draft for peer review Internal
2.3 28/05/2020 Peter Cross, PBDB, BT Modified draft for public comment External
2.4 7/10/2020 Peter Cross, PBDB, BT Further modifications Internal
2.5 19/10/2020 Peter Cross, PBDB, BT Modified draft for public comment (2nd round) External
2.6 4/05/2021 Peter Cross, PBDB, BT Final draft incorporating public feedback External
2. DISTRIBUTION:
Copy No Version Issue Date Issued To
Controlled 1.0 17/04/2020 Chief Plant Health Manager and Plant Biosecurity & Diagnostics Branch policy team in Biosecurity Tasmania
Controlled 2.0 11/05/2020 Chief Plant Health Manager and Plant Biosecurity & Diagnostics Branch policy team in Biosecurity Tasmania
Controlled 2.1 14/05/2020 Chief Plant Health Manager and Plant Biosecurity & Diagnostics Branch policy team in Biosecurity Tasmania
Controlled 2.2 15/05/2020 Public release draft consultation round
Controlled 2.5 19/10/2020 Public release draft consultation round (2nd round)
Uncontrolled 2.6 4/05/2021 Public Release final IRA
Disclaimer The information provided in this document is provided in good faith. The Crown, its officers, employees and agents do not accept liability however arising, including liability for negligence, for any loss resulting from the use of or reliance upon the information in this document and/or reliance on its availability at any time.
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TABLE OF CONTENTS GLOSSARY and Acronyms v EXECUTIVE SUMMARY 1 RECOMMENDATIONS 2 1. Introduction 3 1.1 BACKGROUND 3 1.2 PURPOSE 3 1.3 SCOPE 4 1.4 INDUSTRY PROFILE 5 2. Method 7 2.1 RISK ASSESSMENT 8 2.1.1 Pest Categorisation 8 2.1.2 Estimation of Unrestricted Risk 9 2.2 RISK MANAGEMENT 10 3. Risk Assessment Results 12 3.1 PEST CATEGORISATION PRELIMINARY SCREENING 12 3.2 PEST PROFILE 14 Species: Potato spindle tuber viroid (PSTVd) 14 Distribution 14 Host Range 14 Biology 16 Control 17 Invasive Capacity 17 3.3 RISK ASSESSMENT 19 3.3.1 Potato spindle tuber viroid (PSTVd) 19 3.3.1.1 Likelihood of Entry, Establishment & Spread 20 3.3.1.2 Consequence Estimations 24 3.3.1.3 Overall Magnitude of Consequence: 25 3.3.1.4 ALOP Statement: 26 3.3.1.5 Level of Pest Quarantine Status for Potato spindle tuber viroid 27 4. Risk Management 28 4.1 IDENTIFICATION AND ASSESSMENT OF RISK MANAGEMENT OPTIONS 28 4.1.1 Potatoes for propagation, processing or consumption 29 4.1.2 Ornamental hosts including seed 30 4.1.3 Further Considerations 31 4.2 STAKEHOLDER COMMUNICATIONS 32 4.3 IRA Review Timelines 32 5. Conclusions 32 6. References 33 7. Appendices 35 APPENDIX 1 – FLOWCHART OF KEY DECISION STEPS OF THE TASMANIAN PLANT BIOSECURITY IRA REVIEW PROCESS 35 APPENDIX 2 - REVISED IMPORT REQUIREMENT 9: POTATOES - IMPORT CONDITIONS 36 APPENDIX 3 - SCIENTIFIC ISSUES RAISED IN STAKEHOLDER COMMENTS 39
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 iv Controlled Copy GLOSSARY AND ACRONYMS
ALOP Appropriate Level of Protection: For Tasmania, this is defined as a high or very conservative level of protection that does not demand zero risk, but only accepts risk at or below a ‘very low’ level. APPD Australian Plant Pest Database AQP Approved Quarantine Place (as per Plant Quarantine Act 1997 (Tasmania)) AuSPICA Australian Seed Potato Independent Certification Authority DAWE / DAWR Commonwealth Department of Agriculture, Water and Environment (Australia) / Commonwealth Department of Agriculture and Water Resources (Australia) DPIPWE Department of Primary Industries, Parks, Water, and Environment (Tasmania) SDQMA Subcommittee on Domestic Quarantine and Market Access (Australia) FAO Food and Agriculture Organization of the United Nations ICA Interstate Certification Assurance (agreement) IPPC International Plant Protection Convention IRA Import Risk Analysis IR Import Requirement (for plant and plant products specified in the Plant Biosecurity Manual Tasmania) ISPM 10 International Standard for Phytosanitary Measures: Pest Free Place of Production ISPM 11 International Standard for Phytosanitary Measures: Pest Risk Analysis List A disease A declared disease (Regulated Quarantine Pest) that is not present in Tasmania List B disease A declared disease (Regulated Quarantine Pest) that is present in Tasmania but under official control NQP Non-Quarantine Pest PBDB Plant Biosecurity & Diagnostics Branch, Biosecurity Tasmania, DPIPWE PBMTas Plant Biosecurity Manual Tasmania PCN Potato Cyst Nematode PFPP Pest Free Place of Production PQA 1997 Plant Quarantine Act 1997 (Tasmania) PQP Potential Quarantine Pest PRA Pest Risk Analysis PSTVd Potato spindle tuber viroid RAF Risk Analysis Framework (Tasmania) Risk Analysis Risk assessment, risk management and risk communication RQP Regulated Quarantine Pest SOP Standard Operating Procedure SPS Agreement WTO Agreement on the application of Sanitary and Phytosanitary Measures TBIMS Tasmanian (Plant) Biosecurity Information Management System UQP Unwanted Quarantine Pest URE Unrestricted Risk Estimate WTO World Trade Organisation
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EXECUTIVE SUMMARY Potato spindle tuber viroid (PSTVd) was determined as being established on mainland Australia and not eradicable in 2015 by the National Management Group (NMG). This change of status nationally meant that Tasmania needed to risk assess this pest and determine if it required reclassification as a List A disease Regulated Quarantine Pest (RQP) and thus regulate for it. Whilst there have been a number of successful eradication programs in glasshouse / polyhouse tomatoes for PSTVd, establishment in field grown tomato crops in Carnarvon, Western Australia (including weeds), plus the distribution of infected potato vine via nursery supply chains means that the viroid is likely widespread. Further to this, the viroid is asymptomatic in potato vine and its other ornamental hosts meaning that its potential spread has gone unnoticed. A key issue is assessing the risk of movement from these ornamentals in established residential gardens to potato and tomato crops in Tasmania. A pest profile was conducted to determine the potential impact to Tasmanian agricultural industries and the potential pest status including inherent challenges in regulating. The resulting unrestricted risk estimate (URE) was ‘Low’ which does not meet Tasmania’s ALOP of ‘very low’ risk. Therefore a full import risk analysis was required. Four major commodity import pathways were considered:
• Tomato / capsicum seed lots
• Fruit and vegetables (tomato, capsicum, avocado, pepino excluding potato)
• Potatoes for propagation, processing or consumption
• Ornamental hosts including seed
This IRA has evaluated the URE for each pathway with the following results:
PATHWAY URE Tomato / capsicum seed lots Very Low Fruit and vegetables (tomato, capsicum, avocado, pepino excluding Very Low potato) Potatoes for propagation, processing or consumption Low Ornamental hosts including seed Low
Potatoes for propagation, processing and consumption, and ornamental hosts including seed, do not meet Tasmania’s ALOP of ‘very low’ risk. Therefore, consideration of risk management options is required for these pathways.
Area freedom was the only risk management option identified for potatoes.
The risk management options presented for ornamentals including seed were not considered acceptable due to the impracticalities in regulating symptomless ornamental hosts within the nursery trade as discussed in section 4.1. This has resulted in the following recommendations.
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 1 Controlled Copy RECOMMENDATIONS
In this IRA PSTVd, the following recommendations are made: Recommendation 1: A specific IR for PSTVd should not be introduced because the potato pathway can be addressed with additions to IR9 (Import Requirement 9: Potatoes – Import Conditions), and the ornamental host pathway does not present a direct risk of transmission of the disease to the primary ‘at risk’ cropping sectors, and is therefore not considered to meet the SPS regulatory principle of ‘least trade restrictive wherever possible’. Recommendation 2: PSTVd should remain a List A disease and be regulated through additions to IR9. Recommendation 3: Surveillance of ornamental hosts should be undertaken to determine the status of PSTVd in Tasmania outside of cropping sectors. Recommendation 4: If PSTVd is found to be widespread via surveys of ornamental hosts, then it should be relisted as a List B disease.
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 2 Controlled Copy 1. INTRODUCTION
1.1 BACKGROUND PSTVd has become established on mainland Australia and is considered not eradicable. This change of status nationally means that Tasmania needs to risk assess this pest and determine if it requires reclassification as a Regulated Quarantine Pest (RQP) and thus regulate for it. Whilst there have been a number of successful eradication programs in glasshouse / polyhouse tomatoes for PSTVd, establishment in field grown tomato crops in Carnarvon, Western Australia (including weeds), plus the distribution of infected potato vine via nursery supply chains means that the viroid is likely widespread. Further to this, the viroid is asymptomatic in potato vine and its other ornamental hosts meaning that its potential spread has gone unnoticed. A key issue is assessing the risk of movement from these ornamentals in established residential gardens to potato and tomato crops in Tasmania. PSTVd has not been detected in Tasmania. Seed potato crops under Tasmania’s seed potato certification scheme include health inspections that effectively monitor for any signs of disease caused by PSTVd and other pathogens. Testing is done routinely for export certification purposes. However this viroid has not been detected in potatoes in Australia since 1984 after a successful eradication campaign. Similarly a 2012 national PSTVd survey indicated that the viroid is not present in Tasmania’s main tomato growing operations. Ornamental hosts in the retail nursery chain were also included with no detections. PSTVd is highly infectious, stable and transmitted mechanically. It readily infects host crops causing serious disease. It is known to be transmitted in sap on contaminated machinery and implements, by contact between plants and probably also by horticultural workers as they handle plants (Verhoeven 2010; Mackie 2010). The viroid is also transmitted in potato tubers, through pollen and true seed of potato and tomato. Whilst under certain conditions it can be transmitted by aphids and by other insects1, these are considered rare and won’t be addressed in this document. Recent unpublished research by the Queensland Department of Employment, Economic Development and Innovation (DEEDI) shows that PSTVd is also readily mechanically transmitted from tomato fruit. Jurisdictions generally maintain PSTVd as a notifiable pest and have import conditions in place for seed potatoes requiring area freedom or seed certification / testing. This is also the case in Tasmania where the viroid is currently a List A disease. However, whilst Tasmania does have import conditions for potatoes (IR9) that mitigate the risks posed by PSTVd (incidentally through requirements for PCN and bacterial wilt), it does not have an IR dedicated to it (part of the rationale for this IRA). The unrestricted risk estimate component of this IRA is done independently of IR9 i.e. assumes it does not exist.
1.2 PURPOSE This Import Risk Analysis evaluates any requirement for further regulation of PSTVd pathways by assessing the risks and consequences of the pathogen entering, establishing and spreading in Tasmania from mainland Australia in interstate trade. Current import requirements both nationally and at state
1 PSTVd is not usually spread by insect vectors (Schumann et al., 1980; Querci et al., 1997; Verhoeven, 2010), however, PSTVd transmission by aphids (Myzus persicae) has been confirmed from plants co-infected with Potato leaf roll virus (PLRV; Querci et al., 1997; Syller et al., 1997; Verhoeven, 2010). PLRV is well managed in the seed potato certification scheme but its status outside that is unknown. Also unknown is if ornamental hosts discussed here are also hosts of PLRV.
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 3 Controlled Copy level already mitigate some of the risks however PSTVd is not regulated for in its own right as a List A disease.
1.3 SCOPE Target pest: Potato spindle tuber viroid (PSTVd) Pest class: Viroid, family Pospiviroidae, genus Pospiviroid Pest(s) known to be vectored: None Commodity type: Hosts of PSTVd are listed in Tables 6 and 7 below, and include solanaceous crops (potato, tomato) and various ornamental species Commodity condition: Living, unprocessed plants and seed Commodity origin: Australian mainland Commodity end-use: Planting and human consumption Commodity distribution: Unrestricted, general distribution in Tasmania Area for which risk is assessed: Whole of Tasmania
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1.4 INDUSTRY PROFILE The three main industries most likely to be affected by PSTVd are: potato, tomato/capsicum, and nursery plant industries. Data in this section is taken from the Tasmanian Agri-Food Scorecard 2017- 2018 (DPIPWE 2019a) unless otherwise stated.
Tasmania’s potato industry has a farm gate value of approximately $123 million (the second largest producer in the country) with a processed value of $435 million. This makes up about 9% of the state’s total agricultural and seafood production. Net interstate sales of potatoes is $333 million, much of which is processed / frozen as food products (e.g. chips, fries, hash browns). Processing ends the viroid pathway however a significant outbreak of PSTVd in Tasmania might see seed and ware markets close overnight or be highly regulated. Tasmania’s international exports were <1% of the total potato production which might not be significant when considering a loss of international export markets due to an outbreak of PSTVd.
The industry has over 300 commercial growers (D. Clark 2020, pers. comm., 1 May). Most of these (223) are contracted by Simplot and McCain Foods for processing whilst 55 grow certified seed. An estimated 35 grow for local fresh markets. Many of these employ staff and contractors. The processing sector (especially the processing plants located at Simplot, Ulverstone and McCain Foods, Smithton) employ around 500 people (PotatoPRO 2019a, 2019b). Any industry downturn would see flow-on effects on jobs with fertiliser and machinery suppliers, irrigation, agribusinesses, cartage, storage, agronomists, and researchers, among others. These employment figures are estimates only but would be significant when considering Tasmania’s relatively small population.
Importation of potato propagation material into both Australia and Tasmania is highly regulated. At the national level, material must be in the form of tissue culture, true seed or microtubers/minitubers; inspected on arrival with some treatments; grown out in a post-entry quarantine (PEQ) facility for 6 months; and tested free from a suite of pathogens (including PSTVd) before release. Equivalent regulations apply for any propagation material sourced from interstate as outlined in IR 9: Potatoes – Import Conditions (DPIPWE 2019b). Tasmania only accepts material for propagation in the form of tissue culture or minitubers that meet these national requirements. Imported tubers for processing or consumption from interstate must satisfy strict PCN and bacterial wilt requirements.
Protected environments (e.g. greenhouses) for tomato and capsicum production are not a large-scale contributor to Tasmania’s overall farm gate value. Based on 2017-18 data, there were 3 major greenhouse producers in Tasmania and a number of smaller producers. Together they generate 1.2 million kilograms combined of capsicums and tomatoes with an annual farm gate value of around $4.91 million 2(AgriGrowth, DPIPWE 2020, pers. comm. 22 April). These enterprises combined employ an estimated 70-100 full time staff. Whilst there is some interstate export of both fruit and processed product, it is quite low and considered negligible for this analysis. There are no international exports of fresh Tasmanian tomatoes and capsicums. Consequently, almost all fruit grown in Tasmania is consumed here.
2 Whilst capsicums appear to be unaffected by the viroid (Lebas et al 2005), any regulatory action on a detection could have an impact on production, especially where planted with tomatoes. For this reason, the combined industry value is retained.
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Importation of tomato and capsicum seed into Australia is regulated through mandatory pathogen testing requirements for Pepino mosaic virus and a suite of pospiviroids (since 2013). Whilst there is no longer a requirement for PSTVd certification at the national level from a biosecurity perspective, it is nevertheless tested for (as part of the generic pospiviroid test) with any positive results resulting in rejection.
The nursery trade of ornamental hosts of PSTVd include seedlings of Brugmansia, Calibrachoa, Cestrum, Petunia, and Solanum (potato vine) which are imported from interstate (although Tasmanian wholesale nurseries also bulk up material from existing mother stock). Whilst import requirements for nursery stock do exist (IR38), none of the treatments specified are effective against PSTVd. Ornamental host plants enter Tasmania in small numbers on a regular basis however the economic value of this trade is considered low in comparison to the other affected industries.
Whilst ornamental hosts in the nursery trade are key to this risk analysis as a pathway, any impact on this industry is more likely to come from an introduction of restrictive regulations rather than from a plant health perspective, as the viroid does not appear to impact on the health of nursery plant hosts (asymptomatic).
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 6 Controlled Copy 2. METHOD
The method used to evaluate biosecurity risk posed to Tasmania by trade in plants and plant products is based upon pest risk analysis guided by the International Standard for Phytosanitary Measures (ISPM) No.2: Framework for pest risk analysis (FAO 2007); ISPM No.11: Pest risk analysis for quarantine pests including analysis of environmental risks and living modified organisms (FAO 2004); and Tasmania’s import risk analysis framework (DPIPWE 2010). Terms used are in accord with ISPM No.5: Glossary of phytosanitary terms (FAO 2012).
The Tasmanian Import Risk Analysis Framework (DPIPWE 2010) is given practical effect, when undertaking more ‘routine’ IRA assessments and day-to-day pest risk enquiry, through the use of an internal Departmental Standard Operating Procedure (SOP); SOP No.10 – Routine IRA Methodology (DPIPWE 2014).
ISPM 11 describes a three-stage approach to pest risk analysis comprising: • Initiation • Pest risk assessment • Pest risk management
Stage 1 The initiation stage involves identifying the trigger and scope of the analysis, including the organisms(s) and potential pathways of interest. Initiation of the pest risk analysis for PSTVd is described in the introduction section of this report.
Stage 2 Risk assessment comprises pest categorisation, assessment of the likelihood of entry, establishment and spread, and assessment of potential economic, environmental and social consequences if the pest(s) were to establish, in the absence of specific risk mitigation measures. Overall likelihood and consequence estimates are combined to give a risk estimate that is judged against Tasmania’s Appropriate Level of Protection (ALOP) of ‘very low’ risk. Tasmania’s biosecurity policy (DPIW 2006) provides the rationale for ALOP.
Stage 3 Risk management comprises evaluation and selection of options to reduce the risk of introduction and spread of a pest, as necessary. It also involves considering verification activities and stakeholder communication pertinent to ensuring decisions to impose or not impose measures, remain robust over time.
The key decision steps undertaken with each pest risk analysis are summarised in a flowchart (Appendix 1).
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2.1 RISK ASSESSMENT 2.1.1 PEST CATEGORISATION Pest categorisation, based upon the IPPC definition of a Quarantine Pest, is undertaken in the context of five key selection criteria: − presence or absence in Tasmania − regulatory status in Tasmania − association with the import pathway(s) under consideration − potential for establishment and spread in Tasmania − potential for consequences in Tasmania.
Categorisation is undertaken in a two stage evaluation process. The first phase of analysis utilises a preliminary screening mechanism to test whether the potential quarantine pest(s) of interest: 1. require(s) further risk assessment; or 2. is of no quarantine concern, therefore not requiring any further risk assessment. The second phase of analysis, requires a risk assessment be undertaken for every pest arising from first phase preliminary screening. The purpose of pest risk assessment is to determine the target pests Unrestricted Risk Estimate (URE) in relation to Tasmania’s Appropriate Level of Protection (ALOP), which is set at a ‘Very Low’ level of risk.
Biosecurity Tasmania plant biosecurity, uses a three tier pest categorisation system, when classifying the level of risk a given pest presents to the State. A target pest will be recommended as being either: 1. A Regulated Quarantine Pest (RQP); or 2. An Unwanted Quarantine Pest (UQP); or 3. A Non-Quarantine Pest (NQP). The selection criteria for each category of pest are fully described in SOP No. 10 – Routine IRA Methodology (DPIPWE 2014).
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2.1.2 ESTIMATION OF UNRESTRICTED RISK Unrestricted risk is risk posed by an organism that passes categorisation, in the absence of specific risk mitigation measures. Unrestricted risk is estimated by combining estimated likelihoods of entry, establishment and spread or L(EES), with estimated magnitude of consequence. If unrestricted risk is at or above Tasmania’s ALOP of ‘very low’ risk, risk mitigation measures are then evaluated. If unrestricted risk rests below ‘very low’ risk, specific risk management measures are not normally warranted. Unrestricted risk estimation is informed by assembling a pest data sheet that presents biological, ecological, invasive and economic impact data relevant to evaluating L(EES) and consequences. For those pests which pass categorisation as being of quarantine concern, a pest profile is formed from both the pest data sheet, and its risk assessment. Likelihood estimation Likelihoods for entry, establishment or spread are estimated taking into account relevant biological and ecological factors, and described according to a descriptive scale in Table 1.
Table 1. Nomenclature for Descriptive Likelihoods
Likelihood (L) Description Indicative Probability (P) Range
High The event would be very likely to occur 0.7 < P ≤ 1.0 (probability between 70% - 100%)
Moderate The event would occur with an even 0.3 < P ≤ 0.7 (probability between 30% - 70%) possibility
Low The event would be unlikely to occur 0.05 < P ≤ 0.3 (probability between 5% - 30% )
Very Low The event would be very unlikely to occur 0.001 < P ≤ 0.05 (probability between 0.1% - 5% i.e. between one in a thousand and one in twenty)
Extremely Low The event would be extremely unlikely to 0.000001 < P ≤ 0.001 (probability between 0.0001% - 0.1%, i.e. occur between one in a million and one in a thousand)
Negligible The event would almost certainly not occur 0 ≤ P ≤ 0.000001 (probability less than one in a million)
The individual estimates for each likelihood are combined to give an overall estimate of likelihood of entry, establishment and spread or L(EES). The rules for combining descriptive likelihoods are described in Table 2.
Table 2. Rules for Combining Descriptive Likelihoods
High Moderate Low Very low Extremely Low Negligible
High High Moderate Low Very Low Extremely Low Negligible
Moderate Low Low Very Low Extremely Low Negligible
Low Very Low Very Low Extremely Low Negligible
Very Low Extremely Low Extremely Low Negligible
Extremely Low Negligible Negligible
Negligible Negligible
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Consequence estimation Consequences are estimated by identifying direct and indirect economic, environmental and social impacts and estimating the magnitude of each type of impact at an appropriate scale and describing it as: • indiscernible - impact is not usually distinguishable from normal day-to-day variation in the criterion, or unlikely to be noticeable; • minor significance - impact not expected to threaten economic viability, but would lead to a minor increase in mortality/morbidity or a minor decrease in production. For environmental or social amenity criterion, the impact is not expected to threaten the intrinsic value, though the value of the criterion would be considered ‘disturbed’. Effects generally expected to be reversible; • significant - impact would threaten economic viability through a moderate increase in mortality/morbidity, or a moderate decrease in production. For environmental or social amenity criteria, intrinsic value could be expected to be significantly diminished or threatened. Effects may not be reversible; • highly significant - impact would threaten economic viability through a large increase in mortality/morbidity, or a large decrease in production. For environmental or social amenity criteria, intrinsic value could be expected to be severely or irreversibly damaged. The descriptions are translated using the schema outlined in Table 3. In this risk assessment, magnitude of consequence corresponds with the highest level of significance for any single type of impact.
Table 3. Magnitude of Local, District, Regional and State Consequences
Extreme Highly significant Highly significant Highly significant Highly significant
High Highly significant Highly significant Highly significant Significant
Moderate Highly significant Highly significant Significant Minor significance
Low Highly significant Significant Minor significance Indiscernible
Consequence Very Low Significant Minor significance Indiscernible Indiscernible
Negligible Minor significance Indiscernible Indiscernible Indiscernible Local District Regional State
Unrestricted Risk Estimate (URE) The unrestricted risk estimation is made by combining the overall estimate for L(EES), with the overall estimate for consequences, according to the matrix in Table 4. If unrestricted risk exceeds Tasmania’s ALOP of ‘very low’ risk, specific risk mitigation measures are evaluated. If unrestricted risk falls at or below ‘very low’, specific risk mitigation measures are not warranted and hence are not evaluated.
2.2 RISK MANAGEMENT Risk mitigation Risk management includes identifying, evaluating and making recommendations about risk mitigation options for reducing unrestricted risk, where necessary, to “Very Low”. In addition, options are selected which are least trade restrictive, and most cost-effective, consistent with ISPM 11.
Table 4. Risk Estimation Matrix
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High Negligible Very low Low risk Moderate High risk Extreme
likelihood risk risk risk risk
Moderate Negligible Very low Low risk Moderate High risk Extreme risk risk risk risk
Low Negligible Negligible Very low Low risk Moderate High risk risk risk risk risk
Very low Negligible Negligible Negligible Very low Low risk Moderate risk risk risk risk risk
Extremely Negligible Negligible Negligible Negligible Very low risk Low risk low risk risk risk risk
Negligible Negligible Negligible Negligible Negligible Negligible Very low Likelihood of Establishment Entry, and Spread (L)EES likelihood risk risk risk risk risk risk
Negligible Very low Low Moderate High Extreme impact impact
Consequences of Entry, Establishment and Spread
Recommendations about risk mitigation measures are typically formulated as a draft Import Requirement (IR). A Departmental internal SOP, SOP No7 – (Tasmanian Plant Biosecurity) IR Formulation in Tasmania (DPIPWE 2012), provides guidance on regulatory governance clauses for differing levels of pest area freedom, whether it be regional, property or consignment freedom. Any new IR is normally subject to a 30 day public consultation period pre-finalisation. After final sign-off, the Import Requirement is given effect under the Plant Quarantine Act 1997 by public notification, and subsequent publication in Tasmania’s Plant Biosecurity Manual, usually with a sixty day pre- notification phase-in period.
Verification activities Since risk changes, verification of risk management effectiveness and appropriateness over time is prudent. Verification of risk management can occur whether or not measures have been recommended.
If measures are imposed, monitoring strategies to test their effectiveness are considered, with major regulatory measures subject to review every 5 years. Monitoring can also be considered if measures have not been imposed, to ensure risks do not increase to unacceptable levels.
Stakeholder communication Risk management is a shared responsibility, including in the context of import regulation. The effectiveness of measures depends significantly on suitable levels of stakeholder awareness and understanding. As necessary, means for notifying specific stakeholders and the community at large, about risk management decisions, are considered. Once a draft IRA is completed, a 30 day external public consultation with relevant stakeholders will normally be sought, before finalisation of the report (see Appendix 1).
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3.1 PEST CATEGORISATION PRELIMINARY SCREENING
Data presented in Table 5 demonstrates that Potato spindle tuber viroid is a pest of potential quarantine concern which requires further pest risk assessment with respect to importation of host material.
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TABLE 5. PEST CATEGORISATION PRELIMINARY SCREENING RESULTS A preliminary screen is undertaken of the pest, as measured against the IPPC’s definition of a quarantine pest, to determine whether or not further pest risk assessment is required.
Pest Regulatory Pathway Association Pest Presence Potential for Establishment Potential for Consequence Risk Comments (scientific & Status in assessment common Tasmania required? name) Known Commodity Interstate * Tas concerned? Potato List A Disease True seed Tomato, capsicum, WA, (other None Yes; hosts of PSTVd are Yes; introduction of the Yes A key challenge spindle tuber since 2016 states abundant across Tasmania. disease will have an impact with regulation is viroid Potato Potato tissue sporadically but Solanaceous weeds, particularly on cropping (seed potatoes managing the (PSTVd) No specific IR propagation culture and eradicated). rejected, yield losses in asymptomatic blackberry nightshade, are material minitubers Other records processing and ware nursery plant common in Tasmanian exist outside of potatoes, losses due to (ornamentals) Living plants Nursery plant hosts cropping agricultural areas and tomatoes, rogueing of glasshouse pathway. (nursery stock (see Table 7) sectors i.e. potatoes, capsicum, eggplant tomatoes and capsicums). If Managing this hosts including appear to be ornamentals and other Solanaceae are regulated, there may be pathway may not seed) unaffected and are common garden plants or crops. further losses due to be cost-effective, asymptomatic PSTVd is a temperate / biosecurity eradication feasible, and is activities. Exports would be trade restrictive. subtropical pathogen and the Fruit and Tomato, capsicum, impacted. There would be The consequences vegetables potatoes for Tasmanian climate is likely to be some damage to Tasmania’s of not managing processing or suitable for the establishment ‘clean-green’ pest and this pathway could consumption and persistence of the pathogen disease free reputation, and undermine the if not managed. Brand Tasmania image in veracity of any Mechanical Potential transfer It is possible (but not proven) selected industry sectors. restrictions. transfer from infected that the viroid is established in However there would be no (personnel and garden plants into impact on nursery plants as random perennial ornamental equipment) cropping areas by their health does not appear growers hosts in residential gardens but to be affected not in crops. (asymptomatic).
* Pest distribution data for Australia is outlined in more detail in the accompanying Pest Profile
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3.2 PEST PROFILE
The pest profile below draws upon the pest data sheet held in Appendix 2.
SPECIES: POTATO SPINDLE TUBER VIROID (PSTVD)
Synonyms: potato gothic virus, potato spindle viroid, spindle tuber viroid, tomato bunchy top viroid
Common Names: Potato spindle tuber viroid (PSTVd)
Taxonomic Confusion: none (although numerous isolates exist which vary in pathogenicity3).
Type of Pest: viroid
DISTRIBUTION State: Absent in Tasmania – No pest records
Interstate: There have been around 12 incursions of PSTVd into Australia since 1996. The viroid has been detected in tomato crops in NSW, Qld, WA and SA, and in chilli and capsicum crops in WA. Most detections of PSTVd in Australia have been in commercial greenhouse tomato crops and the contained nature of this cropping has resulted in successful eradications in these cases. However, the viroid (Chittering strain) is present and established in field tomato crops in the Carnarvon area of WA. PSTVd has not been reported in Australia in potato since the early 1980s. More recently potato vine (Solanum laxum) stock has tested positive in Queensland but only after being distributed around the country.
International: The disease is reported to occur in Asia, Africa, North America, Central America, South America, Europe, China, and New Zealand (although there are many reports of successful eradications).
Potential Distribution: PSTVd occurs or has occurred in many countries across the world representing a large climate range. Whilst protected cropping might be responsible for detections in some colder climates, the viroid infects field-grown potatoes in Northern China, Russia and Poland (and others) (CABI 2019). Tasmania falls well within this range and is therefore considered suitable for the establishment and persistence of PSTVd. Similarly hosts are widely grown and flourish across populated areas of the state.
HOST RANGE Primary: Plants in the family Solanaceae as listed in both tables 6 and 7.
Table 6: Summary of reports of PSTVd in crop species in other countries (DAWR, 2011)
Natural Host Family Symptoms Incident total Persea americana Mill. Lauraceae Symptomless unless in dual infection with 1 (avocado) Avocado sunblotch avsunviroid (ASBVd)
3 This analysis does not distinguish between PSTVd isolates but considers a highly pathogenic strain (such as the Chittering strain present in Western Australia).
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Capsicum annuum L. Solanaceae Symptomless to mild leaf wavy margins to 1 (capsicum) delayed fruit setting and small fruit
Solanum lycopersicum L. Solanaceae Growth reduction to stunting, distortion and 20 (tomato) chlorosis of young leaves.
Solanum muricatum Ait. Solanaceae 1 (pepino) Solanum tuberosum L. Solanaceae No leaf symptoms and tubers are smaller, 3 (potato) malformed and spindly with reduced yields.
Table 7: Summary of reports of PSTVd in ornamental species in other countries (DAWR, 2011)
Natural Host Family Symptoms Incident total
Brugmansia ×candida Pers. Solanaceae None 1 Brugmansia cordata Solanaceae None 2 Brugmansia suaveolens (Willd.) Bercht. & Solanaceae None 3 C.Presl Brugmansia variegata Solanaceae None 2 Brugmansia spp. Solanaceae None 5 Calibrachoa sp. Solanaceae 2 Cestrum aurantiacum Lindl. Solanaceae None 1 Cestrum auriculatum L’Her. Solanaceae None 1 Cestrum endlicheri Miers. Solanaceae None 1 Cestrum nocturnum L. Solanaceae None 1 Cestrum rubrum Hort. ex Francey Solanaceae None 2 Cestrum × cultum Solanaceae None 1 Cestrum spp. 3 Datura sp. Solanaceae 2 Lycianthes rantonnetii (Carrière) Bitter Solanaceae None 9 (Solanum rantonnetii Carr. ex Lescuyer)
Physalis peruviana L. (P. edulis Sims) Solanaceae None to 3 severe leaf distortion etiolation Petunia ×hybrida Hort. ex. Vilm. Solanaceae None 8 Solanum laxum Spreng. (S. jasminoides Solanaceae None 33 Paxton) Streptosolen jamesonii Miers. Solanaceae None 1
Weeds: Solanum nigrum (black nightshade), Datura leichhardtii (thornapple) and Nicandra physalodes (apple-of-Peru) (Solanaceae), and Conyza bonariensis (flaxleaf fleabane) (Asteraceae); are known hosts and present in Australia (Mackie 2016).
Australian native species: Atriplex semilunaris (annual saltbush), Rhagodia eremaea (thorny saltbush) (Chenopodiaceae), and Streptoglossa sp. (Asteraceae) (Mackie 2016).
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There is no shortage of PSTVd hosts across Tasmania. Solanaceous weeds, particularly blackberry nightshade, are abundant in Tasmanian agricultural areas and tomatoes, potatoes, capsicum, eggplant and other Solanaceae are common garden plants or crops.
Plant Parts Affected: generally all parts.
Plant Stage Affected: most prevalent during flowering, fruiting, and vegetative growth stages.
BIOLOGY General: PSTVd is in the family Pospiviroidae, genus Pospiviroid. This family of viroids include a number of important plant pathogens.
Detection & Identification: can be detected on symptomatic plant tissue using PCR (polymerase chain reaction) or kits from manufacturers utilising nucleic acid hybridisation platforms.
Habitat: within host cells but can survive for long periods in plant sap as a result of cultivation practices.
Climate suitability: PSTVd is a temperate/subtropical pathogen and the Tasmanian climate is likely to be suitable for the establishment and persistence of the pathogen if not managed. A warming climate due to climate change forecasting is unlikely to have any impact on the risk of this pest establishing, however a gradual increase in temperatures might be more favourable to both the pest and symptom expression (i.e. closer to the middle of the temperate/subtropical range). Life Cycle: viroids are low molecular weight infectious nucleic acids. They replicate autonomously in susceptible plant hosts (Diener, 1987). Pospiviroids are predominantly located in the nuclei of infected cells and they replicate via a rolling circle mechanism (Diener, 1987).
Pest Vectoring: no specific relationships are known although there are reports that aphids can transmit PSTVd in the presence of Potato leaf roll virus via encapsidation. Transmission: via propagules (infected tubers, cuttings, micro-plants, seed) and cultivation practices including grafting and mechanical inoculation due to poor hygiene.
Host Symptoms: variable amongst different hosts
Whole plant
In tomato, growth reduction and chlorosis occurs in the top of the plant. Subsequently, this growth reduction may develop into stunting, and the chlorosis may become more severe, turning into reddening and/or purpling. In this stage, leaves may become brittle. Generally, this stunting is permanent; occasionally, however, plants may either die or partially recover. As stunting begins, flower and fruit initiation stop. (Mackie et al., 2002; Owens and Verhoeven, 2009).
In potato, PSTVd can induce severe growth reduction; however, reduction may also be hardly visible. Vines of infected plants may be smaller, more upright, and produce smaller leaves than their healthy counterparts. Infected tubers may be small, elongated (from which the disease derives its name), misshapen and cracked. Their eyes may be more pronounced than normal and may be borne on knob- like protuberances that may even develop into small tubers. Symptom expression is influenced by the potato cultivar, strain of PSTVd, environmental conditions and method of inoculation (Pfannenstiel and Slack, 1980; Diener, 1987; Owens and Verhoeven, 2009).
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Capsicums display only very mild symptoms in response to PSTVd infection. The only visible symptom is a certain 'waviness' or distortion of the leaf margins near the top of infected plants (Lebas et al., 2005).
Ornamentals: infections of solanaceous ornamentals are usually symptomless (Verhoeven et al., 2008a, b, 2010b; Luigi et al., 2011).
Yield Loss:
In potato there are reports of yield losses varying from 1% up to 64% depending on viroid strains, potato varieties, and incidence of infection within the crop.
In tomatoes, plants infected from seed and where conditions are conducive to disease will not produce fruit once chlorosis and stunting set in. Transmission rates in infected seed lots range from 2-11% and so a yield loss commensurate with these figures is typical.
Additionally, a 2019 Australian research study on the effects of PSTVd (Chittering strain) sourced from the Carnarvon area has concluded that this tomato strain poses a threat to both tomato and potato industries worldwide. Significantly this strain was found to be highly pathogenic to tomato cultivars Rutgers, Petula and Swanson; and potato cultivars Russet Burbank, Nadine and Atlantic causing serious yield losses of 50-90% in both fruit and tubers.
CONTROL
Physical & cultural: plant certified seed, practice strict hygiene, rogue infected plants
Chemical: none
Biological: none
Mechanical: strict hygiene
Regulatory: certification schemes for quality propagules, import restrictions, post-entry quarantine.
Potential for Eradication: Possible for closed cropping systems (tomatoes), but unlikely for field crops.
Costs: variable – see yield loss section.
INVASIVE CAPACITY
Dispersal Mechanisms:
Trade Assisted: via seed and whole plants (long distance)
Natural: mechanical via contact (passive) through wounds or natural openings (short distance)
Invasion History (including known Quarantine Interceptions/Detections):
International: Since the 1960s and 1970s, PSTVd has spread rapidly throughout the world and become an important pest on solanaceous crops. However eradication has been successful in many countries – especially where certification schemes exist.
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National: First reported in Australia in 1983 in potatoes but eradicated. There have been around 12 incursions of PSTVd into Australia since 1996. The viroid has been detected in tomato crops in NSW, Qld, WA and SA, and in chilli and capsicum crops in WA – most likely via infected seed lots. Most detections of PSTVd in Australia have been in commercial greenhouse tomato crops. The viroid is present and established in field tomato crops in the Carnarvon area of WA.
Target State or Territory: No interceptions or detections are known to have occurred in Tasmania.
Evidence of ornamentals in PSTVd epidemiology:
In 2009, scientists from the Netherlands published evidence that PSTVd occurred frequently in nurseries in the Netherlands infecting potato vine (Solanum jasminoides), cape gooseberry (Physalis peruviana) and several Brugmansia species (Verhoeven et al. 2010a). The infected plants were symptomless. PSTVd was also reported in ornamental plants (Solanum spp.) in Israel, Kenya and Italy.
Analysis of PSTVd RNA sequences indicated close relationships between strains isolated from ornamental plants and tomato plants (Verhoeven et al. 2010a). From this and other observations4, the scientists concluded that infected ornamental plants are the source of PSTVd outbreaks in tomato crops. Sequences from Australian isolates were included in the analysis and the scientists suggested that outbreaks in tomato in Australia may have originated from infected P. peruviana. Links were also inferred between Australian isolates of PSTVd and S. jasminoides.
In 2010, scientists from the Netherlands and Slovenia reported transmission of PSTVd from researcher’s fingertips, contaminated by rubbing infected ornamental plants, to tomato and potato plants (Verhoeven 2010b). Research by WA scientists showed the viroid can survive on surfaces for at least 24 hours (Mackie 2010).
A European Research Area report, co-authored by Dr Verhoeven of the Netherlands, concluded that “Many ornamental plant species are hosts of pospiviroids and they can be successfully transmitted within ornamentals and from ornamentals to potato and tomato by contact and crop handling... Seed transmission in tomato is a fact…” (Verhoeven 2010). At the 9th Australasian Plant Virology Workshop held in October 2010, Dr Verhoeven stated that traded tomato seed may be another source of PSTVd, but presented data suggesting tomato seed may not be as important a source as ornamental plants.
Pathways: Identified import pathways for risk assessment are:
1. Tomato / capsicum seed lots
2. Fruit and vegetables (tomato, capsicum, avocado, pepino excluding potato)
3. Potatoes for propagation, processing or consumption
4. Ornamental hosts including seeds
NB: whilst not an import pathway, PSTVd can be vectored mechanically via infected plant sap which increases the likelihood of spread – potentially from residential to cropping areas.
4 based on four observations: (i) the previously performed back‐tracing of pospiviroid infections in tomato, (ii) the high PSTVd infection rates found in Brugmansia spp. and S. jasminoides, (iii) the phylogenetic grouping of PSTVd genotypes from tomato with those from vegetatively propagated plant species, and (iv) the results of ‘natural’ and experimental transmissions of specific PSTVd genotypes (Verhoeven 2010)
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3.3 RISK ASSESSMENT
3.3.1 POTATO SPINDLE TUBER VIROID (PSTVD)
Pathways:
Pathway 1 – Tomato / capsicum seed lots
Of the cropping hosts listed in Table 6, tomato and capsicum are the only ones cultivated from true seed and thus addressed in this pathway. Most tomato and capsicum fruit production crops in Australia are grown from imported seed with 760 kilograms of seed imported into the country annually resulting in an estimated 200 million plants.
Major wholesalers and retailers regularly import seed into Tasmania to supply commercial growers and home gardeners. At a national level, and in response to PSTVd and other seed-borne solanaceous pathogens, seed lots imported from other countries are screened (certified free) before release into Australia (since 2013). This mandatory testing has detected PSTVd often (20 seed lots in 2013 alone) resulting in rejection of those infected lots.
Pathway 2 – Fruit and vegetables (tomato, capsicum, avocado, pepino excluding potato)
Of the cropping hosts listed in Table 6, (tomato, capsicum, pepino, avocado and potato) all but potato are imported by major wholesalers and retailers on a daily basis, from several key suppliers at major produce markets interstate. Imported material is subject to mandatory inspection on arrival at the biosecurity barrier in Tasmania, though not all consignments are inspected. Other import regulations apply (for example, fumigation for Queensland fruit fly hosts) however these treatments are not effective against PSTVd. Being a consumable product item, product is distributed both rapidly and repeatedly on a daily or weekly basis all over the State in an unrestricted manner.
Pathway 3 – Potatoes for propagation, processing or consumption
Potatoes imported for propagation can be in the form of tissue culture plantlets or tubers, including minitubers in accordance with IR9. Those for processing or consumption must be produced from certified seed, free from soil, grown in states/regions where freedom from bacterial wilt and potato cyst nematode can be demonstrated, transported in clean packaging, and without contact from potentially contaminated agricultural equipment (also in accordance with IR9). Given this and the state’s self-sufficiency, recent data reveals that tuber imports for this purpose are not received except under exemption5. These requirements are in place because there is always the risk that potatoes intended for consumption will be sown in backyard veggie gardens, an issue commonly referred to as ‘diversion of use’. Whilst processing and consumption sees an end to the pest pathway, this scenario extends the pathway, and it is not possible to control any such behaviour. Hence the pest free status of the material must be verified prior to import. As previously stated, the following unrestricted risk estimate component of this IRA is done independently of IR9. Whilst it is acknowledged that the three different end-uses in this pathway represent different levels of risk, the highest risk option of sowing is the main consideration throughout the assessment process.
Pathway 4 – Ornamental hosts including seed
5 At the time of writing, one business has an exemption to supply tubers to Tasmania under strict conditions that have equivalence to IR9. Other businesses use exemptions to move Tasmanian potatoes interstate and back as part of food kits.
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The ornamental hosts listed in Table 7 enter via wholesale and retail nursery supply chains on a regular basis. Nursery stock is regulated under an import requirement as are seeds for sowing however the requirements and treatments are not effective against PSTVd. Further to this, virtually all recorded infections have been asymptomatic meaning visual inspections are not effective.
Similarly to pathway 2, there are no direct issues identified with this pathway regarding commercial production.
3.3.1.1 LIKELIHOOD OF ENTRY, ESTABLISHMENT & SPREAD
Likelihood of Entry: Likelihood of Entry: Pathway 1 – Tomato / capsicum seed lots There have been numerous outbreaks in glasshouse tomatoes over the years (especially prior to 2013) with successful eradication responses – mainly because of the containment nature of glasshouses. Infected tomato seed has been considered the likely source of these outbreaks, and is supported by statistics on seed lot testing at the national border. This pathway has been largely addressed by mandatory seed certification testing at the national border for new seed lots introduced in 2013 however the status of older potentially infected seed stocks is not known (though viability diminishes with each passing year and may no longer be an issue). There is also the risk that some infected seed slips through the certification testing. If mandatory seed testing was to be stopped, the likelihood estimate would change to high however this is unlikely6. Additionally there is a suite of other pospiviroids (exotic) that do require testing which also detects PSTVd as the test is group specific. Likelihood estimate: Low
Likelihood of Entry: Pathway 2 – Fruit and vegetables (tomato, capsicum, avocado, pepino excluding potato) Fruit and vegetables (tomatoes and capsicums) entering the state as produce could also carry the viroid. In many cases, produce from PSTVd-infected plants would not meet quality standards and in some cases would not bear fruit at all. However field grown tomatoes in the Carnarvon region of WA have demonstrated that infected tomato plants and fruit can also be asymptomatic. This pathway ends with the cooking / consumption of produce with scraps going to residential garbage or compost bins. There is a low risk of the viroid surviving poor composting conditions. Likelihood estimate: Low
Likelihood of Entry: Pathway 3 – Potatoes for propagation, processing or consumption Unregulated movement of potato material into Tasmania is a risk of PSTVd entry. Whilst the viroid has not formally been detected in potatoes since the early 1980s, this provides confidence with the managed cropping sector only. Material grown outside of certification schemes is capable of harbouring all sorts of diseases. Heirloom potatoes and material used in veggie gardens, for example, are not strictly assessed for disease so they go undiagnosed, with poor quality tubers discarded rather than sent off for testing at cost. Less virulent strains of PSTVd could be present in such material across many generations and remain unnoticed due to a lack of symptoms. Similarly, tolerant potato varieties might harbour virulent strains without symptoms. With no evidence to the contrary regarding the
6 “The presence of PSTVd in Australia and repeated introductions of the viroid have the potential to affect the Australian avocado, potato and tomato industries. While the department evaluates the status and impacts of PSTVd, the emergency measures for tomato seed importation requiring testing for PSTVd will be maintained to protect these Australian industries.” (DAWR, 2018b)
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 20 Controlled Copy status of PSTVd in potatoes outside of the highly managed cropping sector, the risk of entry is considered significant in an unregulated environment. Likelihood estimate: Moderate
Likelihood of Entry: Pathway 4 – Ornamental hosts including seed Findings associated with a 2012 national PSTVd survey revealed that infected stocks of symptomless Solanum laxum (potato vine and ornamental host) vegetatively propagated in Queensland have been widely distributed around the country. These are essentially nursery plants for residential and public space (amenity) plantings. The logical assumption is that PSTVd could be present in Tasmania as a latent pathogen in these ornamental hosts in residential and amenity environments, but not in crops. If it is not present currently then the risk of entry via symptomless nursery stock is high. A number of the ornamental hosts are perennial so sources of inoculum are ever present and will only increase (i.e. not purged as with an annual cropping cycle of tomatoes). Likelihood estimate: High
Likelihood of Establishment: Likelihood of Establishment: Pathway 1 – Tomato / capsicum seed lots
PSTVd transmission rates through seed are high but must be considered against the percentage of infected seeds within a seed lot. For infected seed to get through mandatory testing, the percentage of infected seeds is likely to be very low.
In the case of tomato / capsicum sown seeds, cropping is of annuals so the establishment is likely to be limited by the length of the season. However, there is plenty of opportunity in cropping scenarios for spread to occur (pruning tools, physical handling, proximity on bench), which is enough for the notion of establishment to be met.
Likelihood estimate: Moderate
Likelihood of Establishment: Pathway 2 – Fruit and vegetables (tomato, capsicum, avocado, pepino excluding potato) For establishment to occur, the viroid must re-infect new host material via mechanical inoculation through contact from infected plant debris, or where infected material is used as a propagation source e.g. heirloom tomato seed.
In a residential backyard scenario, the risk of re-infecting new host material is very low because the viroid has to survive decaying infected material (discarded fruit or fruit scraps in a compost pile), be transferred to the soil (soil bed), come into contact with new host material through wounds or natural openings (via passive entry), and replicate successfully inside the new host (under ideal conditions). Whilst each of these are possible, the chances of them all aligning is very low. Even then, in a veggie garden context, infected plants (annuals) are likely to perform poorly and not prosper resulting in a limited chance of survival.
It is possible that a resident might attempt to propagate from uneaten infected fruit and vegetables – for example by removing seed from tomatoes for planting. Even though the plants may not perform well, there is a low chance that the infection cycle could persist.
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Another scenario is if seed from infected fruit is displaced from the rotting material and, under the right conditions, fall or get carried to soil where they germinate. However, it is unlikely that the new plant will survive as it is unlikely to be cared for since it was not intentionally grown.
Fruit and vegetable remains that are discarded in garbage end up at urban tip sites which are hostile environments for establishment due to deep burial practices by heavy machinery, and/or local government green waste composting streams for use in council ornamental displays and parks. Likelihood estimate: Very low
Likelihood of Establishment: Pathway 3 – Potatoes for propagation, processing or consumption Once in Tasmania, infected tubers vary in risk depending on their end use. Those for processing and consumption are very low risk despite spilt product and factory waste being potential sources of inoculum. As discussed previously, some tubers for consumption will inevitably be sown in backyards. Potatoes for propagation are a much higher risk with translocation to seedlings/growing plants highly likely – resulting in a new generation of infected potato plants and thus establishment. Despite the risk being assessed outside of current regulations, it is unlikely that anything other than certified seed will be sown in the managed cropping sector. This means that whilst establishment of PSTVd is a real possibility, it is most likely to occur outside of industry via community exchange points of product sale and/or exchange of home-grown product. Volunteer potatoes arising from either private (home-grown) and/or commercial industry operations is always problematic in serving as an ongoing source of inoculum for any potato pests (and diseases) present in crops in Tasmania. The removal of such material in field is a constant challenge for the commercial cropping sector. It is highly possible that if PSTVd were introduced into the commercial cropping sector, it could persist year-to-year in volunteer potatoes, thus increasing the risk of establishment. Likelihood estimate: Moderate
Likelihood of Establishment: Pathway 4 – Ornamentals including seed In this case, for establishment to occur, the viroid does not have to re-infect new host material as many of the ornamental hosts, including Solanum laxum, are perennial and persist for years in residential backyards across the state. They tolerate PSTVd infection (remaining asymptomatic) and where infected, PSTVd would be considered established. In this case the likelihood of establishment equates to the likelihood of entry. Likelihood estimate: High
Likelihood of Spread:
Likelihood of Spread: Pathway 1 – Tomato / capsicum seed lots Where the viroid has established by successful germination and growth of tomato and capsicum seeds/plants, spread is possible via distribution of seedlings between growers through informal sharing of material. For example, potted seedlings could be sent around the state via family connections or a network of commercial growers. Further spread can then occur mechanically through poor hygiene practices to other plants where present. Again, infected plants are unlikely to perform well and the pathway is unlikely to perpetuate.
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Likelihood estimate: Low
Likelihood of Spread: Pathway 2 – Fruit and vegetables (tomato, capsicum, avocado, pepino excluding potato) For this pathway, scenarios have been considered whereby PSTVd might survive in residential veggie gardens. Without an insect vector, the most likely means of spread to other areas is by human mediated dispersal. Examples include the sharing of fruit and vegetables within communities combined with propagating from that material. The result is that the viroid manages to persist across increased numbers of backyard gardens albeit with various levels of success. This scenario is considered low risk.
The likelihood of spread from backyards to cropping sectors is very low but possible especially where farm hygiene is not practised. For example, a resident could be growing select varieties of tomatoes in their veggie garden and then work as an employee on a farm crop nearby, potentially infecting that crop mechanically via infected sap on their hands – as a result of poor hygiene awareness. Despite this the risk remains very low for this scenario. When combining the scenarios, the highest risk potential is taken, which in this case is low. Likelihood estimate: Low
Likelihood of Spread: Pathway 3 – Potatoes for propagation, processing or consumption
As mentioned previously, PSTVd can be vectored mechanically via infected plant sap which increases the likelihood of spread – potentially from residential to cropping areas. In the absence of an insect vector, PSTVd in an infected potato crop in a backyard could also spread to another backyard by the informal sharing of infected tuber propagules and/or harvesting tools and equipment. Community gardens and allotment growing systems can also present a risk with a pool of tools being shared amongst individual gardeners to save costs amongst growers. This is most likely in situations where the viroid is a less virulent strain, or the potato varieties are tolerant, or both. Hence, the risk of PSTVd spreading around the state and enduring into the future is possible.
Similarly, for pathway 2 above, the likelihood of spread from backyards to cropping sectors is low but also possible especially where farm hygiene is not practised. It is anticipated there would be a higher chance of such an event occurring if a commercial grower of potato, also had their own domestic garden production on site and as a lover of heritage, unusual or heirloom varieties were to introduce such non-certified propagative plant material onto their properties without due diligence in regard to such materials provenance. Though it is highly unlikely to occur, if it were to occur then it would be a significant risk. In addition, a resident could tend to their veggie garden and then work as an employee on a farm crop nearby, potentially infecting that crop mechanically via infected sap on their hands – as a result of poor hygiene awareness. The chances of such events occurring increase when considering long timeframes which in this risk analysis seems the appropriate cautionary response. As mentioned previously for this pathway, controlling volunteer potatoes is problematic. If PSTVd was present in uncontrolled volunteer potatoes, it could persist year-to-year and thus increase the risk of spread. Likelihood estimate: Moderate
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Likelihood of Spread: Pathway 4 – Ornamentals including seed
Effective spread within Tasmania is likely to be ad hoc and hard to predict although probably limited despite the viroid being very contagious (mechanically). In the absence of an insect vector, spread will be via mechanical means, and will need to be from one host to another. For example, there is the slight risk of a farmer handling infected potato vine in his garden and then going out to a potato crop and handling potato plants thus potentially transmitting the viroid. Similarly, the chances of gardeners getting infected plant sap on their hands and tools is high, however transmitting that infected sap to crops outside their yard would be considered low. Likelihood estimate: Low
Likelihood of Entry, Establishment and Spread (L(EES)):
Pathway 1: Low x Moderate x Low = Very Low
Pathway 2: Low x Very Low x Low = Very Low
Pathway 3: Moderate x Moderate x Moderate = Low
Pathway 4: High x High x Low = Low
3.3.1.2 CONSEQUENCE ESTIMATIONS
Economic Consequences Economic consequence is estimated in terms of field cropping environments and protected cropping environments.
Field crop environments:
Tasmania’s potato industry has a farm gate value of approximately $123 million which is 26% of total Australian production (Agri-Food Scorecard 2017-18). This makes up about 9% of the state’s total agricultural and seafood production. Australia’s international exports are currently about 4% of the total potato production (Tasmanian amount unknown) which might not be significant at this time.
The proportion of crop losses attributed to a PSTVd outbreak is difficult to estimate. Infected crops might be effectively ‘written off’ due to biosecurity containment requirements despite a relatively low incidence of infected plants. Only a small percentage of crops are likely to be infected in the early stages of an outbreak, and seed certification scheme practices in place (along with PSTVd epidemiology) will mitigate large numbers of crops being infected and hence quarantined. This greatly reduces the potential negative impacts.
A PSTVd outbreak, however, is likely to impact dramatically on trade. A worst-case scenario would be a total prohibition by mainland states on Tasmanian potato exports due to the loss of pest free area status with significant ramifications. This is a possibility given that most jurisdictions retain PSTVd as a quarantine pest and that seed certification schemes have a zero tolerance for it. The impacts could be short-term or long-term depending on the success of any biosecurity response and if pest free status can be reclaimed. Additionally, current international market access negotiations could be
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 24 Controlled Copy jeopardised. Therefore, the likelihood of negative impacts on potentially susceptible solanaceous field crops (e.g. potatoes) in Tasmania (considered in a regional context) is Significant.
Protected crop environments: Susceptible solanaceous crops such as tomatoes are grown in protected environments (e.g. greenhouses) in Tasmania and these conditions are likely to be suitable for the development of disease caused by PSTVd.
Protected environments (e.g. greenhouses) for tomato and capsicum production are not a large-scale contributor to Tasmania’s overall farm gate value. Based on 2017-18 data, there were three major greenhouse producers in Tasmania and a number of smaller producers. Together they generate 1.2 million kilograms combined of capsicums and tomatoes with an annual farm gate value of around $4.91 million (AgriGrowth, DPIPWE). These enterprises combined employ an estimated 70-100 full time staff.
The proportion of crop losses attributed to a PSTVd outbreak is difficult to estimate. An infected glasshouse crop might be effectively ‘written off’ due to biosecurity containment requirements and eradication attempts, despite a relatively low incidence of infected plants. Whilst this might have an extreme impact for that season, eradication attempts in glasshouse environments are often successful and the glasshouse could return to production after a few weeks. Unlike potatoes, there are only a small number of major glasshouse producers so one producer equates to a significant percentage of total production to be affected in the early stages of an outbreak. Even so, the likelihood of negative impacts on susceptible protected crops (tomatoes only) from a State level is of Minor significance.
Due to the significance of the potato industry, economic consequences for Tasmania (potatoes and tomatoes combined), are estimated at the State level as Significant.
Social Consequences: PSTVd would have a negative impact on susceptible crops in both field and protected cultivation, as well as market access. This could impact on these businesses, related businesses and employees. Solanaceous crops are a major component of Tasmania’s agricultural economy and the losses over time would be reasonable in percentage terms, hence the social consequences of PSTVd for Tasmania in a regional context is estimated as Significant.
Environmental Consequences: It is possible that PSTVd could infect native Solanaceae, however this is not considered significant as these hosts are likely to be asymptomatic and are not important to the environment. Therefore the likelihood of significant environmental consequences in a State context is estimated as Indiscernible.
3.3.1.3 OVERALL MAGNITUDE OF CONSEQUENCE: At the state and regional level, economic, environmental and social consequences of PSTVd are likely to be Moderate (based on the highest level of significance for any single type of impact being ‘Significant’).
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Table 8: Unrestricted Risk Estimate (URE):
PATHWAY PEST RISK ASSESSMENT L(En) L(Es) L(S) L(EES) Magnitude of URE Consequence
Tomato / capsicum Low Moderate Low Very Low Moderate Very Low seed lots Fruit and vegetables Low Very Low Very Low Very Low Moderate Very Low (tomato, capsicum, avocado, pepino, excluding potato) Potatoes for Moderate Moderate Moderate Low Moderate Low propagation, processing or consumption
Ornamental hosts High High Low Low Moderate Low including seed
3.3.1.4 ALOP STATEMENT: An unrestricted risk estimate of Low does not meet Tasmania’s ALOP of ‘very low’ risk. Therefore, consideration of risk management options is required for both potatoes (for propagation, processing or consumption) and ornamental hosts.
Very low and negligible unrestricted risk estimates meet or are below Tasmania’s ALOP of ‘very low’ risk. Therefore the tomato/capsicum seed lots and fruit and vegetables do not have to be considered further in this risk analysis.
GENERAL COMMENT: As stated previously, one critical issue is the chance event/s for PSTVd to transmit from backyard potatoes or asymptomatic ornamental hosts in residential and amenity areas to potato crops and tomato/capsicum glasshouses. In the case of ornamental hosts, the risk pathway across host types once in Tasmania (post-border) is arguably not addressed appropriately within the IRA structure. In other words, regulating an import commodity type (ornamental hosts in the nursery trade) to protect unrelated industries (potato and tomato) is an uncommon scenario and very difficult to gain any meaningful measure of risk. The question of diverted end-use is highly problematic and something which must be acknowledged as an ongoing background risk or potentiality. It is BT policy to follow a precautionary biosecurity risk position when dealing with uncertainties that cannot be quantified. The precautionary approach is supported in the relevant international pest risk analysis standards when dealing with ‘hard-to-quantify’ and/or unknown risk factors such as this.
Messaging to counteract the risk from ‘diverted end-use’ by members of the community is likely to be cost prohibitive with only moderate success in outcome at best in changed behaviour - as the desire to ‘plant on’ favoured lines of plant stock can also be strongly driven by cultural norms and familial
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 26 Controlled Copy connections. The federal government does devote community education resource expenditure to programs designed to combat these behaviours through its “Plate It - Don’t Plant It” initiative (see https://www.agriculture.gov.au/pests-diseases-weeds/protect-animal-plant/dont-plant-it ). However, such messaging can also be at risk of being counter-productive because it may draw unintended attention to the potential for the very activity you are seeking to discourage – making it a difficult line to tread.
3.3.1.5 LEVEL OF PEST QUARANTINE STATUS FOR POTATO SPINDLE TUBER VIROID
Existing: Potato spindle tuber viroid is a List A Regulated Quarantine Pest (RQP) Recommended: That Potato spindle tuber viroid remains a List A Regulated Quarantine Pest (RQP) and either a specific import requirement or addition to the existing potato import requirement be considered to address the recommendations from this IRA, pending the outcome of the next section Risk Management.
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4.1 IDENTIFICATION AND ASSESSMENT OF RISK MANAGEMENT OPTIONS
As the unrestricted risk estimates for potatoes (for propagation, processing or consumption) and ornamental hosts exceeds ALOP, it is necessary to identify any risk management regulatory measures that hold the capacity to reduce the risk of introduction of the pest to the level which meets Biosecurity Tasmania’s ALOP. This includes any significant uncertainties in the risk analysis and how it is proposed to best manage them.
It has already been assessed that the risk of PSTVd establishment is negligible for tomato/capsicum seed lots and very low for imported fruit and vegetables (excluding potatoes) for consumption including any waste material. Hence only potatoes and ornamental hosts need to be considered further in this section.
Identified import pathways for risk management are:
• Potatoes for propagation, processing or consumption
• Ornamental hosts including seed
Risk management options:
• Area freedom, region freedom, pest free place of production
• Seed treatments
• Plant testing (including seeds)
• Barrier inspections of seedlings / mature plants
• Period of time spent in an Approved Quarantine Place (AQP) including inspections/testing
• Post-border risk management including early warnings from seed potato certification scheme
or glasshouse environment monitoring and surveillance
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Table 9: Risk management options against commodity pathways and suitability – Yes, No, Possible, Unlikely
Pathway Area Freedom, Seed Plant Testing Barrier AQP Period Post-border Region Freedom Treatments* (including Inspections including Risk and/or Pest Free seeds) inspections Management Place of / testing Production (PFPP) Potatoes for Yes for area No Yes for tissue No (tubers Possible No propagation, freedom. culture plantlets symptoms processing or Unlikely for region and mini tubers are not clear) consumption freedom and for propagation. PFPP. No for potato tubers for processing or consumption. Ornamental Not reliable for No Possible (but No (plants Possible No hosts via ornamentals as likely to be don’t display (only nursery states are unlikely impracticable symptoms) practical for trade to know if they due to costs of perennials, (including have infected destructive not for seed seed, plants as they are testing and or seedlings) seedlings asymptomatic. laboratory fees) and mature Possible** for plants) known status in tomatoes. PFPP arrangements are unlikely to be economically viable for businesses due to the cost burden associated with administrative aspects and certifying PSTVd- free stocks versus the value of the traded commodity.
* PSTVd is carried within the seed (including tubers) so seed treatments are not effective. ** Freedom types should be assessed with regard to ornamental hosts as well as vegetable hosts
4.1.1 POTATOES FOR PROPAGATION, PROCESSING OR CONSUMPTION Area Freedom (AF) is a sound way of mitigating risk and would be acceptable for commercial potato lines produced from certified seed given the amount of health scrutiny given to this commodity. Mainland certified seed potato lines have a number of certification label ratings (e.g. black, red, blue) which all have a 0% tolerance for PSTVd as per the AuSPICA Conditions for the AuSPICA Seed Potato Certification Scheme.
Import Requirement 9: Potatoes – Import Conditions currently has AF requirements for bacterial wilt and PCN; and requires a Black Certification Label for minitubers for propagation, and a Red Certification Label for processing or consumption. Adding PSTVd AF to IR9 is recommended - keeping
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 29 Controlled Copy in mind that AF status of individual states may change in an ad hoc manner with ongoing incursions and eradications in tomato glasshouses. Regional freedom is often difficult to administer (e.g. PCN in Victoria) however it could be considered as a way of managing these transient AF situations.
Pest Free Place of Production (PFPP) is another way of mitigating risk (outlined in ISPM 10) and the requirements are well suited to enable high value trade. PFPP arrangements are unlikely for the potato industry as potatoes are not a high value commodity (per tonne) and seed certification schemes are already in place to provide levels of pest freedom.
Seed treatments are not considered adequate as the viroid is present internally within infected potato tubers. Tuber infection normally results in transmission of viroids from the tuber to the emerging plant.
Potato material for propagation (tissue culture plantlets and minitubers) currently require PSTVd testing as part of their accreditation status, whether it is via an AuSPICA accredited tissue culture laboratory, a post-entry quarantine facility, or an approved minituber facility. IR9 does not require further testing for this material but relies on the accreditation status. Similarly, it does not specify testing requirements for potato tubers for processing or consumption – which would be expensive, difficult to justify given the proposed end-use, and yet still retain some risk.
Barrier inspections are not a viable risk management option as infected potato tubers or tissue culture plantlets won’t display clear signs. PSTVd-infected plants will not be identifiable during inspections and will remain on the import pathway.
Similarly, the limitations of inspections and plant testing will be the same if plants are grown out post- border in an Approved Quarantine Place (AQP) but exacerbated with additional costs. Industry would not see this as a viable option and there don’t appear to be the mechanisms to make it happen.
To summarise, the identified risk management option for potato imports to reduce the risk of introduction of PSTVd to an acceptable level of ALOP (in addition to those existing in IR9) is area freedom.
It is recommended that the following regulatory controls be introduced to IR9, as illustrated in Appendix 2 (as per yellow highlighted text).
4.1.2 ORNAMENTAL HOSTS INCLUDING SEED Reliable AF status for PSTVd in asymptomatic ornamental hosts across states is not currently available, both in nursery production and residential/amenity areas as there are no ongoing surveillance programs. The viroid was widely distributed across Australia through infected potato vine via the nursery trade some years ago and similar scenarios are likely to have occurred. PSTVd is known to be established in field tomatoes in the Carnarvon area of Western Australia but nowhere else at the time of writing. Sporadic outbreaks in glasshouse tomatoes across states/regions are likely to continue and complicate area freedom status.
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Similarly, PFPP arrangements are unlikely to be economically viable for mainland nurseries due to the cost burden associated with administrative aspects and certifying PSTVd-free stock versus the value of the traded commodity of host ornamentals into Tasmania.
Seed treatments are not considered adequate as the viroid is present internally within infected ornamental seed i.e. embryo and endosperm. Embryo infection ensures efficient seed transmission of viroids generally.
Ornamental plant testing including seed could be considered however it is likely to be impracticable. For example, asymptomatic plants would mean that representative samples would be required for destructive analysis at cost. Given the relative small numbers of ornamental hosts coming into Tasmania at any one time, the numbers of plants lost to destructive testing (statistically valid) combined with the cost of analysis would not be economically feasible in most cases (notwithstanding very large shipments). Seed testing might be more plausible but becomes redundant unless grown plants are also tested.
Barrier inspections are not a viable risk management option as infected ornamental hosts are asymptomatic. PSTVd-infected plants will not be identifiable during inspections and will remain on the import pathway.
Similarly, the limitations of inspections and plant testing will be the same if plants are grown out in an Approved Quarantine Place (AQP) but exacerbated with additional costs. Post-border risk management options don’t exist for nursery plants destined for residential gardens and amenity areas.
To summarise, there are no identified risk management options for ornamental hosts including seed that can be applied in a practical sense that are least trade restrictive and manageable from a regulatory standpoint.
4.1.3 FURTHER CONSIDERATIONS Whilst post-border risk management does not have to be considered for the negligible and very low risk pathways, it is worth noting that post-border risk management practices remain in place as part of normal biosecurity business. For example, in 2019 Biosecurity Tasmania seized tomato seeds and seedlings at a commercial glasshouse facility that were from an alleged PSTVd-infected imported seed lot after notification was received from NSW authorities with trace forward information. Further actions followed including destruction of nearby hosts, sanitisation of the glasshouse, and testing of the material.
When considering what an Import Requirement for PSTVd would need to address, as discussed, Solanaceous fruit, vegetable (excluding potatoes) and seed lot pathways meet ALOP so it would only include potatoes (for propagation, processing or consumption) and ornamental hosts in the nursery trade. However, this section sets out the difficulties in regulating ornamentals and these combined would be very trade restrictive and a challenge to justify given the across-industry predicament (one industry suffers at the benefit of another). This leaves potatoes as the only pathway with risk management options which can be managed with additions to IR9.
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On the basis of this Pest IRA, it is recommended that a specific IR for PSTVd should not be introduced, that PSTVd remains on the List A disease list and is regulated via additions to IR9 (see Section 5 - Conclusions). If any surveillance of ornamental hosts determine that the viroid is widespread then it would most likely become a List B disease.
4.2 STAKEHOLDER COMMUNICATIONS Communication with stakeholders is a vital component of any Biosecurity Tasmania plant biosecurity IRA review process. Communication processes used in this review include: 1. A 30 day public consultation period; 2. Review and integration of public critique supported by evidentiary material not necessarily considered in this review; 3. A 60 day phase-in period for the introduction of any new IR, from the date specified on the IR’s public declaration notice; 4. biosecurity e-Advisories; 5. publication of both the final draft IRA as an online PDF downloadable file, and/or any related new information on the DPIPWE’s Biosecurity Tasmania website and Facebook page; and 6. direct contact with leading Tasmanian CEA producers holding an interest in this issue.
Stakeholder comment received in relation to this draft IRA review, and how that comment was addressed in the final draft IRA, are cited in Appendix 3.
4.3 IRA REVIEW TIMELINES Existing IRA’s may be reviewed on a standing 5 year cycle, and/or adapted at any time to address differing import pathway requests for the same commodity, host plant in question.
5. CONCLUSIONS In this IRA PSTVd, the following recommendations are made: Recommendation 1: A specific IR for PSTVd should not be introduced because the potato pathway can be addressed with additions to IR9 (Import Requirement 9: Potatoes – Import Conditions), and the ornamental host pathway does not present a direct risk of transmission of the disease to the primary ‘at risk’ cropping sectors, and is therefore not considered to meet the SPS regulatory principle of ‘least trade restrictive wherever possible’. Recommendation 2: PSTVd should remain a List A disease and be regulated through additions to IR9. Recommendation 3: Surveillance of ornamental hosts should be undertaken to determine the status of PSTVd in Tasmania outside of cropping sectors. Recommendation 4: If PSTVd is found to be widespread via surveys of ornamental hosts, then it should be relisted as a List B disease.
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 32 Controlled Copy 6. REFERENCES
AuSPICA – Australian Seed Potato Industry Certification Authority (2015) Conditions for the AuSPICA Seed Potato Certification Scheme https://www.auspica.org.au/wp-content/uploads/2020/02/AuSPICA- Scheme-condition-2019.pdf
CABI – Centre for Agriculture and Bioscience International Invasive Species Compendium (2019) Potato spindle tuber viroid Pest Datasheet. Wallingford, UK. https://www.cabi.org/isc/datasheet/43659
DAWE - Department of Agriculture and Water Resources BICON (accessed 1/05/2020) Australian Biosecurity Import Conditions https://bicon.agriculture.gov.au/BiconWeb4.0/ImportConditions/Questions/EvaluateCase?elementID=0 000137325&elementVersionID=291
DAWR - Department of Agriculture and Water Resources (2018a) Biosecurity Fact Sheet: Pepino mosaic virus and Pospiviroids Associated with Tomato Seed. Department of Agriculture and Water Resources, Canberra https://www.agriculture.gov.au/biosecurity/risk-analysis/plant/pepino-mosaic-virus- pospiviroids-tomato-seed/factsheet
DAWR - Department of Agriculture and Water Resources (2018b) Draft Pest Risk Analysis for Pepino mosaic virus and Pospiviroids Associated with Tomato Seed. Department of Agriculture and Water Resources, Canberra https://www.agriculture.gov.au/biosecurity/risk-analysis/plant/pepino-mosaic-virus- pospiviroids-tomato-seed
DAWR - Department of Agriculture and Water Resources (2011) PSTVd National Surveillance Strategy (unpublished)
DPIPWE - Department of Primary Industries, Parks, Water and Environment (2019a) Tasmanian Agri-Food Scorecard 2017-18, AgriGrowth Tasmania DPIPWE – Department of Primary Industries, Parks, Water and Environment (2019b). Plant Biosecurity Manual Tasmania 2020 Edition. Hobart
DPIPWE – Department of Primary Industries, Parks, Water and Environment (2015) Pest Incident Reporting in Tasmania – A Generic Guidelines & Discussion Paper. Version 1.0, Biosecurity Tasmania, DPIPWE, Hobart DPIPWE – Department of Primary Industries, Parks, Water and Environment (2014) Standard Operating Procedure No.10 – (Tasmanian Plant Biosecurity) Routine Import Risk Analysis (IRA) Methodology. Version 5.0, Biosecurity Tasmania, DPIPWE, Hobart, 51 pp DPIPWE – Department of Primary Industries, Parks, Water and Environment (2012) Standard Operating Procedure No.7– (Tasmanian Plant Biosecurity) Import Requirement (IR) Formulation in Tasmania. Version 2.0, Biosecurity Tasmania, DPIPWE, Hobart, 10 pp DPIPWE – Department of Primary Industries, Parks, Water and Environment (2010) Import Risk Analysis: A Framework of Context, Concepts, Methods and Administrative Procedures –Version 1, 212 pp.
ISPM 10 – International Standard for Phytosanitary Measures, Requirements for the establishment of pest free places of production and pest free production sites. International Plant Protection Convention (2016) https://www.ippc.int/static/media/files/publication/en/2017/03/ISPM_10_1999_En_2015-12- 22_PostCPM10_InkAmReformatted.pdf Lebas B. S. M., Clover G. R. G., Ochoa-Corona F. M., Elliott D. R., Tang Z., Alexander B. J. R. (2005) Distribution of Potato spindle tuber viroid in New Zealand glasshouse crops of capsicum and tomato. Australasian Plant Pathology 34: 129-133. Mackie, A.E. et al (2019) Effects of a Potato spindle tuber viroid Tomato Strain on the Symptoms, Biomass, and Yields of Classical Indicator and Currently Grown Potato and Tomato Cultivars. Published Online: https://apsjournals.apsnet.org/doi/10.1094/PDIS-02-19-0312-RE Mackie, A.E. et al (2016) Potato spindle tuber viroid: alternative host reservoirs and strain found in a remote subtropical irrigation area. European Journal of Plant Pathology 145 No.2: 433-446.
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Mackie, A. E., McKirdy, S. J, Rodoni, B and Kumar, S. (2002) Potato spindle tuber viroid eradicated in Western Australia. Australasian Plant Pathology 31: 311-312.
Matsushita, Y. et al (2018) Vertical and Horizontal Transmission of Pospiviroids. Published Online: Dec 12 2018 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6315636/
Matsushita, Y. et al (2014) Distribution of Potato spindle tuber viroid in reproductive organs of petunia during its developmental stages. Published Online: 12 Aug 2014 https://apsjournals.apsnet.org/doi/10.1094/PHYTO-10-13-0294-R
Plant Viruses Online – Descriptions and Lists from the VIDE Database. http://bio-mirror.im.ac.cn/mirrors/pvo/vide/famly124.htm
PotatoPro.com (2019a) https://www.potatopro.com/news/2019/mccain-foods-upgrade-its-smithton-french- fry-plant PotatoPro.com (2019b) https://www.potatopro.com/companies/simplot-australia-ulverstone Verhoeven, J. T. J., Jansen, C. C. C., Botermans, M. and Roenhorst, J. W. (2010). Epidemiological evidence that vegetatively propagated, solanaceous plant species act as sources of Potato spindle tuber viroid inoculum for tomato. Plant Pathology 59: 3-12.
Verhoeven J. T. J., Jansen, C. C. C., Roenhorst, J.W., (2008b). Streptosolen jamesonii ‘Yellow’, A new host plant of Potato spindle tuber viroid. Plant Pathology 57: 399.
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APPENDIX 1 – FLOWCHART OF KEY DECISION STEPS OF THE TASMANIAN PLANT BIOSECURITY IRA REVIEW PROCESS
IRA Trigger STAGE 1 - INITIATION
Project Background Project Brief Project Scoping & Data Gathering Sign -off Stakeholder Identification
Pest Categorisation Pest Categorisation STAGE 2 - RISK ASSESSMENT Phase 1 Analysis Phase 2 Analysis
Potential Quarantine Pest Quarantine Pest (QP) Profiling (PQP) Preliminary Screening
Pest Data Sheet Risk Assessment Non-QPs & some Unwanted QPs Likelihood of Entry, Establishment & Spread = L (EES)
Magnitude of Consequences
Decision on QP Status Unrestricted Risk Estimate
Regulated Quarantine Pest Unwanted Quarantine Pest Non-quarantine Pest (> ALOP) (≤ ALOP) (< ALOP)
Degree of Risk Measures STAGE 3 - RISK MANAGEMENT
Specific Measures = General Measures = No Measures = Regulated QPs Unwanted QPs Non-QPs (> ALOP) (= ALOP) (< ALOP)
Stakeholder Input IRA External Review & Sign-off
IR Fit-for-Purpose IR & IRA Monitoring & Periodic Review
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APPENDIX 2 - REVISED IMPORT REQUIREMENT 9: POTATOES - IMPORT CONDITIONS
IMPORT REQUIREMENT 9
Prior to import, a “Notice of Intention to Import’ prescribed matter must be submitted to the relevant Biosecurity Tasmania Operations Centre (see Section 2.2 of this Manual). Importation must occur in compliance with general Conditions and Restrictions for Prescribed Matter in Part 2 of the Plant Biosecurity Manual Tasmania.
9 Potatoes – Import Conditions
A person must not import, or cause to be imported, any potatoes, except in accordance with the following:
I. Imported potatoes or parts of potatoes intended for propagation must be in the form of tissue culture plantlets or minitubers and meet the requirements detailed in Explanatory Note 1.
II. Potato tubers intended for processing or consumption must be free of all other potato plant parts and washed completely free from soil and other extraneous matter. The potato tubers will be subject to a barrier inspection by Biosecurity Tasmania at the port of entry and must be accompanied by a Plant Health Certificate or Plant Health Assurance Certificate signed by an approved person stating that:
(a) The potato tubers were grown in a State or Territory that can demonstrate freedom from Potato Cyst Nematode (PCN) (Globodera rostochiensis (Wollenweber) Behrens). [Validation of State or Territory freedom will be on provision of survey data, the requirements of which are outlined in Explanatory Note 2. Where such freedom cannot be demonstrated, potatoes may be imported under the Area Freedom conditions outlined in Clause IV (a) and (b); and
(b) The potato tubers were grown in a State or Territory that can demonstrate freedom from Bacterial Wilt (Ralstonia solanacearum (Smith) Yabuuchi et al. (syn. Pseudomonas solanacearum (Smith)). [Validation of State or Territory freedom will be on the provision of survey data, the requirements of which are outlined in Explanatory Note 3. Where such freedom cannot be demonstrated, potatoes can be imported under the Area Freedom conditions outlined in Clause V (a) and (b)]; and
(c) The potato tubers were grown in a State or Territory that can demonstrate freedom from Potato spindle tuber viroid (PSTVd); and
(d) The potatoes were produced from certified seed (to be accompanied by a Red Certification Label and PCN Soil Test Certificate if grown in Victoria) which was grown in a region where PCN and Bacterial Wilt have not been recorded; and
(e) The potatoes were produced on a property that does not share agricultural equipment with any properties in another State, Territory or area unless that State, Territory or area meets all the conditions of this Import Requirement for freedom from PCN and Bacterial Wilt; and
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(f) The potatoes have been packed in clean (free from soil, extraneous matter or other residues) containers (bags, bins etc).
III. The consignment must be accompanied by a statutory declaration signed by the grower stating that he/she complies with Clause II (d) above.
IV. Where State or Territory freedom from PCN cannot be demonstrated as outlined in Explanatory Note 2, in addition to complying with Clauses II (b) to (e) the following documentation must be supplied to validate Area Freedom from PCN:
(a) Complete survey data for PCN from all the potato crops within a defined growing Area plus a 20 km buffer zone surrounding the Area, covering the 3 years prior to the proposed potato tuber importation. Survey requirements are outlined in Explanatory Note 2; and
(b) A PCN soil test from the paddock in which the potatoes were grown, conducted either pre-planting, during the growing season, or post-harvest (Explanatory Note 2).
V. Where State or Territory freedom from Bacterial Wilt cannot be demonstrated as outlined in Explanatory Note 3, in addition to complying with Clauses II (a) and (c) to (e), the following documentation must be supplied to validate Area Freedom from Bacterial Wilt:
(a) Complete survey data for Bacterial Wilt from all the solanaceous crops within a defined growing Area plus a 20 km buffer zone surrounding the Area, covering the 3 years prior to the proposed potato tuber importation. Survey requirements are outlined in Explanatory Note 3; and
(b) A soil test for Bacterial Wilt from the paddock in which the potatoes were grown, conducted either pre-planting, during the growing season, or post-harvest.
EXPLANATORY NOTE 1: Importation of potatoes for propagation
• Tissue culture: Sterile potato plantlets produced at a ViCSPA accredited tissue culture laboratory and accompanied by a copy of the Certificate of Accreditation; or as released from a Post-entry Quarantine facility.
• Minitubers: ‘Generation 0’ material (minitubers, microtubers etc) produced at a ViCSPA accredited facility and accompanied by a Black Certification Label indicating material variety and generation and a copy of the Certificate of Accreditation of the minituber facility that produced it; or as released from a Post-entry Quarantine facility.
EXPLANATORY NOTE 2: Survey requirements for PCN.
In order to demonstrate State or Territory Area Freedom from PCN, the following information is required:
(a) A survey of all of the potato crops in the defined Area for which freedom from PCN is being claimed must have been completed over the 3-year period prior to the proposed importation. The survey should also encompass a 20km buffer surrounding the Area. One third or greater of the crops in the Area must be surveyed each year. Survey
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 37 Controlled Copy information must be accompanied by a map detailing the Area for which freedom from PCN is being claimed. If freedom from PCN is to be claimed, survey data must indicate no cases of PCN within the Area or the buffer zone over the 3-year period.
(b) The National protocol for soil sampling and testing for PCN must be followed (Hinch, 1991. National sampling strategies and standards for detection of potato cyst nematode. In: Potato Cyst Nematode- Impact on Australian Horticulture and a Proposed National Strategy). Horticultural Policy Council Industry Report No 6, 1993, pp 127-131).
The minimum acceptable sampling intensity under this protocol is deemed to be the collection of 200 x 10cm3 samples on a 10 x 10m grid pattern for every 2 hectares, providing a combined 2kg field sample from which a 500g sub sample of dried soil is processed.
In order to declare freedom from PCN, no cysts will have been found in any of the samples over the entire three-year period of testing.
EXPLANATORY NOTE 3: Survey requirements for Bacterial Wilt.
In order to demonstrate State or Territory Area Freedom from Bacterial Wilt, the following information is required:
(a) A visual survey of all solanaceous crops within the defined Area for which freedom from Bacterial Wilt is being claimed will have been completed over the 3-year period prior to the proposed importation. The visual survey should also encompass a 20km buffer surrounding the Area. One third or greater of the crops in the Area must be surveyed each year. Any suspect plants will have been serologically tested for Bacterial Wilt. Survey information must be accompanied by a map detailing the Area for which freedom from Bacterial Wilt is being claimed. If freedom from Bacterial Wilt is to be claimed, survey data must indicate no cases of Bacterial Wilt within the Area or the buffer zone over the 3-year period. Specimens suspected of infection with R. solanacearum must be laboratory tested for the presence of the bacterium.
PROOF: Consignments must be accompanied by a Plant Health Certificate
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APPENDIX 3 - SCIENTIFIC ISSUES RAISED IN STAKEHOLDER COMMENTS
A summary of stakeholder feedback on major issues of concern, and how they have been considered in this review follow.
Summary of feedback received Description on addressing feedback Relevant section and page number Please consider the issue of potato volunteers in your risk Whilst potato volunteers are not directly related to imports, they do Section 3.3.1.1 Likelihood of Establishment: Pathway assessments. increase risk by being potentially an ongoing source of inoculum for 3, page 22 establishment and spread, particularly as they are challenging to control. Likelihood of Spread: Pathway 3, page 23 Text has been added to address this issue.
The pathways do not separate the different end uses for The approach taken was to consider the worst-case scenario of potatoes Section 3.3.1 Risk Assessment PSTVd Pathway 3, potatoes which represent varied levels of risk. End use for potentially being sown (which includes elements of diverted end-use) and page 19 potatoes impacts on the probability of entry in terms of the this is clear in the discussions made in the risk assessment section. probability of transfer to a suitable host. The probability that However to clarify this approach, the following statement has been PSTVd will transfer to a suitable host from processing potatoes added to the Pathway 3 description – “Whilst it is acknowledged that the either before of after processing would be extremely low or three different end-uses in this pathway represent different levels of risk, negligible. The risk from potatoes for consumption would be the highest risk option of sowing is the main consideration throughout higher than for processing potatoes due to the diverted end the assessment process.” use, where the tubers are planted by householders. The probability for entry (spread to suitable hosts) would be greater with potatoes for seed, however mitigation measures such as testing have been proposed and are currently adopted by the industry.
Inaccurate information claiming potato vine mother stock Changed to “potato vine stock has tested positive in Queensland…”. Section 3.2 Pest Profile, page 14 tested positive in NSW. Preliminary screening Table 5 (pg 13) Potential for Changed to “It is possible (but not proven) that the viroid is established in Section 3.1 Pest Categorisation Preliminary Establishment column: “It is likely (but not proven) that the random perennial ornamental hosts in residential gardens but not in Screening, Table 5, Page 13 viroid is established in random perennial ornamental hosts in crops”. A key recommendation of the IRA is to survey to confirm the area residential gardens but not in crops”. If this statement has freedom status for PSTVd in Tasmania. been made in regard to the situation in Tasmania then, how does this speculation affect the area freedom status for Tasmania?
Preliminary screening Table 5 (pg 13) Potential for This section is referring to consequences (impact) on hosts. In the case of Section 3.1 Pest Categorisation Preliminary Consequence column: “However nursery plant hosts would nursery plants there would be no impact which was described originally Screening, Table 5, Page 13 as ‘remain unaffected’. To avoid ambiguity this has been changed to
Routine IRA for Potato spindle tuber viroid, Ver 2.6, PBDB, DPIPWE, May 2021 39 Controlled Copy
remain unaffected”. Rather, nursery plant host could be “However there would be no impact on nursery plants as their health affected but remain symptomless does not appear to be affected (asymptomatic)”.
pg 18 “From this and other observations, the scientists Additional information added as a footnote. “Based on four Section 3.2 Pest Profile, page 18 concluded that infected ornamental plants are the source of observations: (i) the previously performed back‐tracing of pospiviroid PSTVd outbreaks in tomato crops." Would it be possible to find infections in tomato, (ii) the high PSTVd infection rates found out what the other observations are reported in, and to get in Brugmansia spp. and S. jasminoides, (iii) the phylogenetic grouping of copies? PSTVd genotypes from tomato with those from vegetatively propagated plant species, and (iv) the results of ‘natural’ and experimental transmissions of specific PSTVd genotypes (Verhoeven 2010)”. Footnote 5 (pg20) the risk assessment relies upon the It has been suggested that Commonwealth testing will stop when PSTVd Section 3.3.1.1 Likelihood of Entry, Establishment & Commonwealth continuing to regulate the risk of PSTVd is no longer regulated for. It is our understanding that generic pospiviroid Spread, page 20 introduction at the border through mandated testing of testing will continue as other exotic viroids fall into this category, and any tomato seed (see also Likelihood of Establishment Pathway 1 positive result will be rejected. If a positive pospiviroid result is tested (pg21)). This is likely to be tenuous due to Commonwealth further to ID it with a PSTVd positive result then rejection is still likely proposals to remove this entry requirement. from a health perspective, though not mandated. No change to the document.
Pg 22, “Likelihood of Spread: Pathway 2 – Fruit and vegetables Numerous scenarios are considered in this section, some considered ‘low’ Section 3.3.1.1 Likelihood of Entry, Establishment & (tomato, capsicum, avocado, pepino excluding potato)”, the and some considered ‘very low’. When combining the scenarios, the Spread, page 23 likelihood is stated as Very low in the text but given as Low in highest risk potential is taken, which in this case is low. This later statement the likelihood estimate. This discrepancy needs to be has been added to address the issue. No change to the provided estimate. explained. Should the estimate be adjusted to Very low?
Question the impact estimates, regional impacts (pg 24) are as Most of the potato crops are grown in regional areas away from the main Section 3.3.1.2 Consequence Estimations, Page 25 this would suggest the entire state would be impacted, and not population centres of Hobart and Launceston, e.g. the North-west coast. just potato growing areas? It is these regional areas that are most likely to be impacted. No change to the document. Question the estimate of “moderate” for spread for the Whilst the terms ‘low’ and ‘possible’ are mentioned in part of the Section 3.3.1.1 Likelihood of Entry, Establishment & ‘potatoes’ pathway. discussion, the risk estimate increases to ‘moderate’ when considered over Spread, page 23 long timeframes. No change to the provided estimate.
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