Risk Management Proposal:   
 
Citrus  Plants for Planting  
 
 
 
July 2021 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Plant Germplasm Imports  
Animal and Plant Health  Directorate  
Ministry for Primary Industries  
Pastoral House  
25 The Terrace  
PO Box 2526  
Wellington 6140  
New Zealand  
 
Tel: +64 4 894 0100  
 
Email: plantimports@mpi.govt.nz   
i Contents  Page  
Submissions  ................................ ................................ ................................ ................................ ...........  1 
Official Information Act 1982  ................................ ................................ ................................ ................  2 
International context  ................................ ................................ ................................ ..............................  2 
Domestic context  ................................ ................................ ................................ ................................ ... 2 
Overview of the draft import health standard  ................................ ................................ ......................  3 
Objective  ................................ ................................ ................................ ................................ ............  3 
Background inf ormation  ................................ ................................ ................................ ..................  3 
Scope of the draft standard  ................................ ................................ ................................ .............  3 
Format of the draft standard  ................................ ................................ ................................ ............  4 
Nomenclature  ................................ ................................ ................................ ................................ .... 4 
Commodity description  ................................ ................................ ................................ ....................  4 
1. Details of the risk management proposal  ................................ ................................ ..................  5 
1.1 Purpose  ................................ ................................ ................................ ................................ ... 5 
1.2 Source information  ................................ ................................ ................................ .................  5 
1.3 Scope of this risk management proposal  ................................ ................................ .............  5 
1.4 Scope of the import risk analysis ................................ ................................ ..........................  6 
2. Details of the risk management approach  ................................ ................................ .................  7 
2.1 Development of the phytosanitary import requirements  ................................ ....................  7 
2.1.1  Relevant context  7 
2.1.2  Factors considered when developing requirements  8 
2.2 Types of risk management measures that can be applied ................................ ..................  8 
2.2.1  Pre-border measures  9 
2.2.1.1  Production according to an export plan  ................................ ................................ ................................ .... 9 
2.2.1.2  MPI-approved offshore facilities  ................................ ................................ ................................ .............  10 
2.2.2  Border measures  10 
2.2.2.1  Verification activities  ................................ ................................ ................................ ...............................  10 
2.2.2.2  Post-entry quarantine  ................................ ................................ ................................ .............................  11 
Applying temperature regimes in post -entry quarantine  ................................ ................................ ...........................  11 
2.2.2.3  Disease screening methods  ................................ ................................ ................................ ...................  12 
Inspections by the post -entry quarantine facility operator (or n ominated delegate)  ................................ .................  13 
Inspections by the MPI inspector  ................................ ................................ ................................ ..............................  13 
3. Proposed ri sk management measures for Citrus  plants for planting  ................................ ... 14 
3.1 Post -entry quarantine requirements  ................................ ................................ ...................  14 
3.1.1  Quarantine period  14 
3.1.2  Level of quarantine  14 
3.1.3  Temperature requirements in post -entry quarantine  15 
3.1.1.1  Spring -like conditions for three or four months  ................................ ................................ .......................  16 
3.1.1.2  Summer -like conditions for four months  ................................ ................................ ................................ . 16 
3.1.1.3  Autumn-like conditions for two months  ................................ ................................ ................................ ... 17 
4. Priority pests associated with Citrus  plants for planting  ................................ ..................  17  
 ii 4.1 Bacteria  18 
4. 1.1  ‘Candidatus Liberibacter’ spp.  ................................ ................................ ................................ ................  18 
4.1.2 Spiroplasma citri  ................................ ................................ ................................ ................................ ..... 19 
4.1.3 Xanthomonas  spp. ................................ ................................ ................................ ................................ .. 20 
4.1.4 Xylella fastidiosa  ................................ ................................ ................................ ................................ ..... 20 
4.2 Fungi and oomycetes  21 
4.2.1 Ceratocystis  spp. ................................ ................................ ................................ ................................ .... 22 
4.2.2 Diaporthe  spp. ................................ ................................ ................................ ................................ ........  23 
4.2.3 Lasiodiplodia  spp. ................................ ................................ ................................ ................................ ... 23 
4.2.4 Phyllosticta citricarpa  ................................ ................................ ................................ ..............................  24 
4.2.5 Phytophthora  spp. ................................ ................................ ................................ ................................ .. 24 
4.3 Phytoplasmas  25 
4.4 Viruses  25 
4.4.1 Citrus sudden death -associated virus  ................................ ................................ ................................ .... 26 
4.4.2 Indian citrus ringspot virus  ................................ ................................ ................................ ......................  26 
4.4.3 Olive latent virus 1  ................................ ................................ ................................ ................................ .. 27 
4.4.4 Citrus leprosis viruses  ................................ ................................ ................................ ............................  27 
4.5 Viroids  27 
4.5.1 Citrus viroids  ................................ ................................ ................................ ................................ ...........  28 
4.6 Diseases of unknown aetiology  28 
5. Appropriate level of protection proposed for Citrus  plants for planting  ..............................  30 
5.1 Post -entry requirements for plants imported from MPI -approved offshore facilities  ..... 31 
5.1.1  Quaran tine period  31 
5.1.2  Level of quarantine  33 
5.1.3  Transitional arrangement  for plants imported from MPI -approved offshore facilities  34 
Reasons for proposal for a transitional period  ................................ ................................ ................................ ..........  34 
5.2 Import permit  ................................ ................................ ................................ ........................  35 
5.3 Biosecurity clearance ................................ ................................ ................................ ...........  36 
References  ................................ ................................ ................................ ................................ ............  37 
Appendix: Proposed schedule of testing for pests on Citrus  plants for planting  ............................  0  
Ministry for Primary Industries   • 1 Submissions  
The Ministry for Primary Industries (MPI) invites comment from interested parties on the proposed new 
import health standard for Citrus  plants for planting (i.e. nursery stock). The proposed import health 
standard is supported by this risk management propo sal.  
MPI must consult with interested parties in accordance with section 23 of the Act before issuing or 
amending an import health standard under section 24A of the Act. MPI therefore seeks formal comment 
on the proposed import health standard.  
Tips for  preparing comments:  
• Make your comments specific to a section/requirement  of the standard . 
• Provide  reasons, data and supporting published references to support your comments . 
• Use examples to illustrate your points . 
This will help us better understand your comments . 
 
Please send your  comments electronically. Include the following in your submission:  
• The ti tle of the consultation document in the subject line of your email;  
• Your name and title (if applicable);  
• Your organisation’s name (if appli cable);  
• Your address.  
Send submissions to: plantimports@mpi.govt.nz  
 
If you wish to send your submission by post , please send it to the following address : 
 
Plant Germplasm Imports  
Animal and Plant Health  Directorate  
Ministry for Primary Industries  
PO Box 2526  
Wellington 6140  
New Zealand  
 
All submissions must arrive by close of business on 24 May 2021.  Submissions received by the clos ing 
date will be considered during the development of the fi nal standard. Submissions received after the 
closing date may be held on file for consideration when the issued standard is next revised/reviewed.  
 
   
2 • Official Information Act 1982  
Please note that your submission is public information , and it is MPI policy to publish submissions and 
the review of submissions on the MPI website. Submissions may also be the subject of requests for 
information under the Official Information Act 1982 (OIA). The OIA specifies that information is to be 
made a vailable to requesters unless there are sufficient grounds for withholding it, as set out in the OIA. 
Submitters may wish to indicate grounds for withholding specific information contained in their 
submission, such as information being  commercially sensiti ve or personal. Any decision to withhold 
information requested under the OIA is reviewable by the Ombudsman.  
International context  
(1) Where possible, phytosanitary import requirements are aligned with international standards, 
guidelines, and recommendations1 as per New Zealand’s obligations under Article 3.1 of the 
World Trade Organi zation (WTO) Agreement on the Application of Sanitary and Phytosanitary 
Measures  (SPS Agreement) (WTO 1995 ).  
(2) The SPS Agreement sets in place rules that protect each country’s sov ereign right to take the 
measures necessary to protect the life or health of its people, animals and plants , while at the 
same time facilitating trade. It embodies and promotes the use of science -based risk 
assessments to manage the risks associated with t he international movement of goods.  
(3) In keeping  with New Zealand’s obligations under the SPS Agreement and the International Plant 
Protection Convention  (IPPC ), phytosanitary measures must:  
 Be scientifically justified and only for regulated pests (the stren gth of any phytosanitary 
measure will depend on an assessment of risk, with an emphasis on the consequences of the 
pest establishing in New Zealand ); 
 Not discriminate unfairly between countries or between imported and domestically produced 
goods ; 
 Not be mo re trade -restrictive than necessary ; and  
 Be based on international standards wherever possible . WTO members can adopt a measure 
that is more stringent than an international standard, provided the measure is scientifically 
justified.  
Domestic context  
The purpose of an import health standard is defined as follows in section 22(1) of the Biosecurity Act 
1993 (the Act): “An import health standard specifies requirements that must be met to effectively 
manage risks associated with importing risk goods, includin g risks arising because importing the goods 
involves or might involve an incidentally imported new organism”.  
 
  
 
1 Note that international standards, guidelines, or recommendations referred to in the WTO agreement 
are those of Codex, OIE (World Organisation for Animal Health) and the IPPC.  
  
Ministry for Primary Industries   • 3 Overview  of the draft import health standard  
Objective  
(4) MPI’s objective in developing a new import health standard for Citrus  plants for planting is to 
ensure that biosecurity risk associated with imported material is managed appropriately to ensure  
ongoing access to new citrus varieties . 
(5) This is an overview of MPI ’s revision to the phytosanitary import requirements for Citrus  plants for 
planting (nursery stock), as identified in the draft Import  Health Standard: Citrus  Plants for 
Planting (hereafter referred to as ‘the draft standard’).  
 The subject of public consultation is the proposed phytosanitary import requirements of the 
draft standard. The draft standard should be read in conjunction with this risk management 
proposal to understand the rationale  behind the proposed import requirements . 
Background  information  
(6) The New Zealand citrus industry is comprised of a mature domesti c market and a niche export 
market, with values reported in 2019 of $59 million and $12 million , respectively  (Plant & Food 
Research 2019) . Access to new citrus varieties is required to expand  the current export portfolio 
and maximise productivity a s well as  domestic and international  profitability . 
(7) Citrus  plants for planting have previously been imported under the Citrus  schedule of the MPI 
Import Heath Standard 155.02.06: Importation of Nurse ry Stock , issued in 2009.  
(8) MPI has reviewed the Citrus  schedule of the above standard because the existing import 
requirements are no longer considered appropriate to manage  biosecurity risk. This can result in 
ineffective risk management  for two reasons:   
 Import requirements are too stringent in relation to the level of risk . 
 Import requirements  do not manage the risk from known regulated pests associated with 
Citrus  in accordance with MPI’s current appropriate level of protection.  
(9) The import requirements f or Citrus were partially reviewed in 2016 , but an updated import health 
standard was not issued. The current review assessed all classes of pest that pose a biosecurity 
risk on Citrus  plants for planting.  The proposed import requirements  align  with the appropriate 
level of protection in place for other high value plants for planting , including Actinidia  and Prunus . 
(10) The proposed import requirements are  based on information in the MPI Import risk analysis: 
budwood/ cuttings of Citrus  spp. The ris k analysis is available on the biosecurity consultations  
page of the MPI website under the heading Draft import health standard for Citrus plants for 
planting . 
Scope of the draft standard  
(11) The draft standard describes the phytosanitary import requirements f or importing varieties of 
Citrus  spp. (including Fortunella  and Poncirus ) into New Zealand for propagation.  This means 
that the existing schedules for Citrus , Fortunella  and Poncirus , in the MPI Standard 155.02.06: 
Importation of Nursery Stock, will be rep laced by the new Citrus  plants for planting import health 
standard once it is issued.   
4 • (12) The draft standard applies to cuttings and plants in vitro  of all species of Citrus , Fortunella  and 
Poncirus  genera that are currently listed in the MPI Plants Biosecurity Index  (PBI) with an import 
specification of “ L2, L3 see 155.02.06 under Citrus , Fortunella  or Poncirus ”.  
(13) Hybrids of Citru s, Fortunella  and Poncirus  will be eligible for impor t provided that the parent 
species are  identified with the full scientific name (genus and species) and listed as eligible in the 
Plant Biosecurity Index.  
Format of the draft standard  
(14) The draft standard has been prepared as a stand -alone document that includes only the 
phytosanitary import requirements for Citrus  plants for planting. This is a similar format to the 
format of the recently issued Import Health Standard for Prunus  Plants for Planting . 
(15) The Introduction to the draft standard, and any information contained in guidance boxes, does not 
form part of the legal requirements and is intended to provide general information about the draft 
standard.  
(16) Parts 1 –3 and the Schedules to the draft standard set out all phytosanitary  requirements for 
importing Citrus  plants for planting.  
Nomenclature  
(17) Instead of  ‘nursery stock’, the commodity type is now referred to as ‘plants for planting’. Thi s 
change has been made to be consistent with the terminology used in the International Standards 
for Phytosanitary Measures (ISPMs) as follows : 
 ‘Plants for planting’ is defined in ISPM 5: Glossary of phytosanitary terms  as “Plants intended 
to remain plante d, to be planted or replanted ”. 
 ‘Planting’ is defined as “Any operation for the placing of plants in a growing medium, or by 
grafting or similar operations, to ensure their subsequent growth, reproduction or 
propagation ”. 
Commodity description  
(18) The followin g plant parts will be eligible for import:  
 Leafless budwood /cuttings  
 Plants in vitro  derived from aerial plant parts  
i. The draft standard defines tissue cultures as “plants in vitro  that have been prepared 
as tissue culture from one parent by asexual reprodu ction (clonal techniques) under 
sterile conditions”.  
ii. “Plants in vitro ” is defined as “a commodity class for plants growing in an aseptic 
medium in a closed container ” (in ISPM 5: Glossary of phytosanitary terms ). 
iii. Plants in vitro  must be derived from aerial plant parts. The standard will not specify the 
type of aerial plant parts that may be used, but this can include plants in vitro  derived 
from stems, shoots, leaves, terminal and axillary buds, flowers, petiole segments, 
anthers, pollen,  seeds, embryos and endosperm . 
iv. Plants in vitro  derived from root or basal stem tissues close to the soil level will not be 
eligible for import. This is because these types of material were excluded from the 
scope of the MPI risk analysis for this commodity .  
Ministry for Primary Industries   • 5 (19) The term ‘ Citrus  plants for planting’ applies only to leafless budwood  and plants in vitro . In the 
context of this document, the phrase does not apply to any other types of Citrus  germplasm (such 
as whole plants, pollen, or seeds).  
1. Details of the risk  management proposal  
1.1 Purpose  
(20) The purpose of this risk management proposal is to:  
 Summarise the biosecurity risks known to  be associated with imported Citrus  plants for 
planting ; 
 Justify  how phytosanitary import requirements  proposed in the draft standard will 
appropriately manage biosecurity risk and how the y are consistent with New Zealand’s 
domestic legislation and international obligations ; and  
 Provide information to support the consultation on the draft standard.  
(21) The ris k management proposal is not itself the subject of consultation. However, MPI will accept 
comments and suggestions on the risk management proposal to improve future consultations on 
import health standards.  
1.2 Source information  
(22) The risk management proposal is based primarily on information from three substantial risk 
assessment documents:  
 MPI Import risk analysis: budwood/ cuttings of Citrus  spp. (2021);  
 MPI Pest Risk Assessments: Citrus  spp. nursery stock (2016);  
 MPI Import risk ana lysis: budwood/ dormant cuttings of Prunus  spp. (2019)   
(23) Where information has been used that is not included in the se risk analys es, citations are given in 
a footnote or in the  reference section of  this risk management proposal.   
1.3 Scope of this risk man agement proposal  
(24) This risk management proposal includes:  
 Background information about MPI ’s approach to managing risk from plants for planting ; 
 A description of generic disease screening measures that will be applied to all Citrus  plants 
for planting impor ted into New Zealand to increase  the likelihood of inducing symptoms of 
infection by known regulated pests and by unknown risk organisms ; 
 A description  of specific testing that is proposed to give assurance that imported material  is 
free from regulated pests that may not display visible disease symptoms in post -entry 
quarantine ; and  
 A proposal to implement a transitional period and details of how this ar rangement will be 
instituted once the new standard is issued.  
(25) This risk management proposal does not:  
 Identify any species of insects  or mites  that may be associated with the commodity.   
6 • i. MPI expects  that insects and mites will be managed by the prescribed insecticide and 
miticide treatments given in Treatment Requirement: Approved Biosecurity Treatments . 
ii. MPI recognises that some of the prescribed insecticide and miticide treatments are not 
always able to be applied prior to export. MPI will assess alternative treatment options or 
allow plants to be treated in New Zealand  by an MPI -approved treatment provider before  
plants enter  post-entry quarantine . 
iii. The requirements for those seeking MPI approval to provide official treatments are given 
in Treatment Requirement: Treatment Supplier Requirements . The application for 
requesting approval to be a treatment provider can be obtained by request to 
standards@mpi.govt.nz . 
 Identify individual species of phytoplasma that may be associated with Citrus  plants for 
planting . 
i. The Plant Health and Environment Laboratory has a generic phytoplasma polymerase 
chain reaction (PCR) assay.  
 Identify all regulated species of fungi and oomycet es. 
i. MPI is confident that anything no t specifically identified  will be managed by  the generic 
measure of growing season inspection during the proposed minimum quarantine period 
of 17 months in a Level 3B quarantine greenhouse (as described in part 3.1 of this risk 
management proposal) . 
1.4 Scope of the import risk analysis  
(26) The import risk analysis for Citrus  plants for planting did not seek to identify all risk pests 
associated with this pathway. The risk management question applied during preparation of the 
risk analysis was , “Which pathogens, nematodes and diseases are associated  with Citrus 
budwood/leafless cuttings  and meet the criteria for requiring additional measures over and above 
the minimum requirements? ”  
 The minimum requirements that served as the baseline for risk reduction were containment in 
a Level 3A post -entry quarantine facility and/or detection during one growing season in Level 
3A post -entry quarantine . 
 Based on the above risk management question and the minimum requirements, the ris k 
analysis should have identified the major  pests that may be associated with Citrus  plants for 
planting from any source and that were considered unlikely to be contained in a Level 3A 
post-entry quarantine facility and which would require specific testing  to reliably detect them.  
 This resulted in a subset of risk pests for which pest risk assessment s were  completed and 
compiled into the import risk analysis . Those  managed by the minimum requirements are 
summarised in the import risk analysis but not discussed in detail.  However they are still 
regulated pests so if found during post -entry quarantine, appropriate actions would be taken  
to identify the pest or disease and prescribe the appropriate management  options (described 
in Part 3.7 of the MPI Guidance Document: Post Entry Quarantine for Plants . 
(27) Each pest risk assessment addresses the following:  
 Likelihood of entry  
i. Strength or frequency of the association with Citrus  budwood;  
ii. The lik elihood of entry given the application of minimum requirements.  
  
Ministry for Primary Industries   • 7 
 Likelihood of establishment  
i. The suitability of the New Zealand environment and the conditions necessary for spread  
 The potential impacts to New Zealand  
i. The economic, environmental, socio -cultural and human health impacts that would result 
from the establishment and spread of the pest.  
(28) MPI undertook a ‘selected hazard identification’ for fungi and oomycetes. The hazard 
identification did not attempt to identify all known fungi and oomycetes that should be regulated 
pests of Citrus  spp. This is because  MPI considers  the generic disease screening measures 
proposed in the draft standard suffi cient to manage risk from many fungi and oomycetes in 
accordance with MPI’s appropriate level of protection, regardless of whether the organism is 
listed in the standard.  
(29) A risk assessment cannot identify all possible pests of concern because  unexpected pe st 
associations occur. This is one of the reasons plants for planting require post -entry quarantine 
screening. Regulated pests that are unlikely to display visible signs or symptoms unless plants 
are screened for disease in post -entry quarantine are not ge nerally listed in the standard but  are 
instead listed in the Official New Zealand Pest Register  .  
 This applies to most species of fungi and oomycetes. These pests will be effectively 
contained within a Level 3B quarantine greenhouse. Similarly, insects  and mites, for which 
official treatment measures2 are applied to manage the risk, are very unlikely to be 
associated with plants for planting and so are also not listed i n the standard but are listed in 
the Official New Zealand Pest Register .  
 
2. Details of the risk management approach  
(30) This part of the risk management proposal includes :  
 A description of the information used to develop the phytosanitary import requirements of the 
draft standard .  
 The types of risk management measures that may be applied to plants for planting that are 
imported into New Zealand.  
2.1 Development of the phytos anitary import requirements  
2.1.1  Relevant context  
(31) Plants for planting are one of the highest risk pathways for the introduction of pests and diseases 
to new areas (ISPM 32: Categorization of commodities according to their pest risk). Part of the 
reason for this is that plant pests can survive in living plant material without showing signs of 
infection/infestation. Because plants imported for planting may be multiplied and/or widely 
distributed throughout the country, including in key areas of comm ercial production, the likelihood 
of pests surviving and being transferred to suitable domestic hosts is higher than for many other 
import pathways. Therefore, if required in an import health standard, plants for planting must be 
screened for regulated pes ts before they are cleared for entry into New Zealand.  
(32) No biosecurity system can reduce risk to zero. This is not feasible and nor is it desirable. The 
objective of New Zealand’s system is to reduce , to an appropriate level , the likelihood of 
 
2 Official treatment measures for insects and mites are prescribed in the MPI Approved Biosecurity Treatments  standard.   
8 • unwanted impa cts occurring. Within this system, the objective of an import health standard is to 
effectively manage the risks associated with imported goods in order to reduce , to an appropriate 
level, the likelihood of introduction (entry and establishment) of regulat ed pests (including pests, 
diseases and weeds).   
(33) An organism is ‘regulated’ quarantine pest by MPI if it could cause unacceptable consequences 
(i.e. unacceptable economic, environmental, sociocultural or human health impacts in New 
Zealand) if it enter ed and establish ed in New Zealand, provided the organism:  
a) Is not present in New Zealand; or  
b) If present in New Zealand , is under official control . 
(34) MPI has developed new proposed phytosanitary import requirements in accordance with:  
 New Zealand’s obliga tions under the World Trade Organization (WTO) Agreement on the 
Application of Sanitary and Phytosanitary Measures;  
 the Biosecurity Act 1993; and  
 the appropriate level of protection that MPI has established for other species of plants for 
planting.  
(35) The app roach used for developing the phytosanitary import requirements for Citrus  plants for 
planting is similar to that applied to other horticultural species under the current import health 
standards Actinidia Plants for Planting  and Prunus  Plants for Planting . 
 One key goal of the above standards, revised in 2018 and 2020, respective ly, was to provide 
an increased level of protection particularly for bacteria, fungi and oomycete pests that were 
not managed to the same level as other classes of pest (e.g. viruses).  
 During consultation on the Prunus  import health standard, most submitte rs agreed that 
New Zealand’s appropriate level of protection should be consistent for organisms that have a 
similar level of risk (regardless of the class of pest).  
2.1.2  Factors considered when developing requirements  
(36) Because plants for planting present a  high biosecurity risk, greater  emphasis is put into measures 
that are applied at the border (including post -entry quarantine) than for other commodity types 
(e.g. fresh produce for consumption). Reasons for this include the following (taken from ISPM 36: 
Integrated measures for plants for planting ): 
 Some pests do not cause distinct visual symptoms, particularly at low pest incidence . 
 Symptoms of infestation may be latent or masked at the time of inspection (e.g. because of 
pesticide use, nutrient imbalances, dormancy of plants at time of dispatch, presence of other 
non-regulated pests or by removal of symptomatic leaves) . 
 Small insects or eggs may be hidden under bark or scales of buds , etc. 
 The type of packaging, size and physical state of the consignment can influence the 
effectiveness of inspection . 
 Detection methods for many pests, particularly pathogens, may not be available.  
2.2 Types of risk management measures that can be applied  
(37) The biosecurity system in New Zealand operates a series of components (pre -border, border  and 
post-border) that together provide a high level of assurance that regulated pests are unlikely to  
Ministry for Primary Industries   • 9 establish in New Zealand. No single part of the system can provide the necessary protection on 
its own.  
2.2.1  Pre-border me asures  
(38) Generic pre-border risk management measures that may be applied include:  
 Commercial production to reduce pest prevalence  
 Treatment for regulated insects  and mites  
 Official pre-export inspection and phytosanitary certification by the national plant p rotection 
organisation ( NPPO ) of the exporting country to verify that pre -export measures have been 
undertaken and were effective and that the consignment is free from visibly detectable 
regulated pests . 
 For any pest observed during inspections by an expor ting country’s NPPO, the pest’s 
regulatory status should be determined by reference to MPI’s Official New Zealand Pest 
Register .  
(39) As well as the generic risk management mea sures, specific measures may be applied offshore , 
to manage risk associated with some or all regulated pests that may be associated with plants for 
planting.  
 When specific measures are applied offshore, the plants for planting are likely to have fewer 
requirements for screening for regulated pests on arrival in New Zealand . 
i. This can be  advantageous to importers , because plants could  be held in a lower level of 
quarantine facility on arrival in New Zealand and/or have a shorter quarantine period (in 
recognit ion of measures that are applied offshore). This may result in lower import costs 
and more rapid clearance of goods . 
ii. The requirements for screening for regulated pests on arrival in New Zealand, along with 
the level of post -entry quarantine and the length of the quarantine period , will depend on 
the number and type of phytosanitary measures that are applied offshore . Any 
phytosanitary measure completed offshore will be in accordance with the agreement 
between MPI and the approved offshore facility.  
2.2.1.1  Production according to an export plan  
(40) An export plan  is an agreement between MPI and the national plant protection organisation 
(NPPO ) of the exporting country that describes all activities that support the effective application 
of phytosanitary m easures that are applied prior to export.  
 An export plan  will not be agreed upon until a chief technical officer  is satisfied that it meets 
New Zealand’s expectations for biosecurity . 
 An export plan  must be agreed on before imports can occur under this arrangement.  
 Any countr y with an export plan for Citrus  plants for planting will be identified in the MPI 
online system . 
 There are no export plans  in place for Citrus  plants for planting at the time of writing this risk 
management proposal.  
(41) A combination of the following measures may be included in an export plan  to manage 
biosecurity risk associated with some, or all, of the regulated pests associated with Citrus  plants 
for planting:  
 Country freedom , where a chief technical officer  is satisfied that a coun try has country 
freedom status in relation to a pest. To ensure country freedom, an exporting country should  
10 • provide evidence of measures described in ISPM 8: Determination of pest status in an area  
and ISPM 4: Requirements for the establishment of pest fr ee areas . 
 Production in a pest -free area , using systems to establish and maintain freedom as described 
in ISPM 4: Requirements for the establishment of pest free areas . 
 Pest-free place of production  under the supervision of the NPPO of the exporting country, as 
described in ISPM 10: Requirements for the establishment of pest free places of production 
and pest free production sites . 
 The use of integrated measures for plants for planting  under the super vision of the NPPO of 
the exporting country, as described in ISPM 36: Integrated measures for plants for planting . 
2.2.1.2  MPI-approved offshore facilities  
(42) MPI can approve an offshore facility to undertake some of the testing for regulated pests that 
would  otherwise be done in post -entry quarantine in New Zealand.  
 Offshore facilities must be approved to the MPI Standard for Offs hore Facilities Holding and 
Testing Plants for Planting .  
 More information about offshore facilities can be found on the MPI website at:  
  https://www.mpi.go vt.nz/news -and-resources/resources/registers -and-lists/offshore/ . 
(43) For plants produced at an MPI -approved offshore facility, some of the risk is managed before 
export. The phytosanitary screening programme of an offshore facility is subject to assessment 
during the MPI -approval process (based on the MPI Standard for Offshore Facilities Holding and 
Testing Plants for Planting ). That process provides insight into the phytosanitary testing, 
treatments and operations applied offshore which indicates the level of risk that is reduced 
through the application of these measures.  
2.2.2  Border measures  
2.2.2.1  Verification activities  
(44) MPI monito rs the pathway performance related to each import health standard to ensure 
biosecurity risks are effectively managed. This is achieved through verification and inspection 
activities at the border and, where necessary, audits of offshore production systems . 
(45) Verification activities undertaken at the border include:  
 Inspecting documents to verify that the phytosanitary certificate and other associated 
documents comply with the requirements of the standard . 
 Inspecting plants at the place of first arrival to verify freedom from visible pests. For 
horticultural crops, it is expected that all plants will be inspected on arrival at the border . 
 Remedial action (for example treatment) if a regulated pest is detected during th e on-arrival 
inspection or if any required treatments were not applied prior to export . 
(46) Verification testing may be required after plants arrive in New Zealand to verify the effective 
application of phytosanitary measures that were applied prior to export.  If audit testing is required, 
plants may need to be held in post -entry quarantine until testing is completed. Any audit testing 
requirements will be identified when MPI agrees on an export plan or approves an offshore  
facility . All testing must be done  in a diagnostic facility accredited to the MPI Facility Standard: 
Standard for Transitional Facilities for the  Identification of Organisms .  
Ministry for Primary Industries   • 11 2.2.2.2  Post -entry quarantine  
(47) When managing biosecurity risks associated with plants for planting, time may be required to 
examine plants for signs and symptoms of regulated pests and/or complete specific testing before 
plants  can be given biosecurity clearance into New Zealand. Therefore, if specified in an import 
health standard, plants for planting must be screened in quarantine to ensure that they are free 
from regulated pests. An import health standard may allow such scree ning to be done either 
offshore or after the plants arrive in New Zealand.  
(48) The purpose for post -entry quarantine  is to ensure that any regulated pests that are imported in 
association with plants  do not escape into the wider environment whil e plants are be ing screened 
for these pests.  The post-entry quarantine greenhouse must be approved  to the MPI Facility 
Standard: Post Entry Quarantine for Plants . 
a) The facility standard sets the operational and structural requirements for post -entry 
quarantine facilities . 
b) All facilities are regularly audited by MPI to ensure ongoing compliance with all relevant 
standards.  
 Level 3B post -entry quarantine greenhouse  
(49) A Level 3B post -entry quarantine greenhouse is the most secure level of quarantine facility under 
the MPI Facility Standard: Post Entr y Quarantine for Plants . This is considered necessary for 
plants for planting from non -approved sources for the following reasons.  
 Basic phytosanitary certification is the only pre -export measure applied, meaning that no 
assurances are given to MPI by the exportin g NPPO that latent and non -visible pests are 
absent from the plant material.  
 High-risk pests that may be present will not be reliably contained in a lower level of 
quarantine (i.e. highly mobile spore -dispersed organisms, as well as mite -vectored 
organisms). A level 3B greenhouse is sufficient to contain these types of pest because:  
i. It operates under negative air pressure.  
ii. Incoming and outgoing air is passed through a HEPA filtration system.  
iii. All wastewater is treated, and there are strict requirements for facility hygiene, 
traceability and record -keeping.  
 Level 3A post -entry quarantine greenhouse  
(50) The main difference between Level 3B and Level 3A greenhouses is that the Level 3A 
greenhouses do not have any air -pressure or air filtration req uirements. All vents in a Level 3A 
greenhouse must be screened with stainless steel insect -proof mesh with a maximum aperture of 
0.2 mm.  
 Level 3A and Level 3B greenhouses have similar operational requirements as described 
above in (46) b) iii.  
(51) Residual ri sk associated with waterborne regulated pests will be effectively managed in a Level 
3A greenhouse, given the requirement for all wastewater to be treated before exiting the facility 
(as specified in the MPI Facility Standard: Post Entry Quarantine for Plants ). 
 Applying temperature regimes in post -entry quarantine  
(52) Under some circumstances, MPI requires plants to be grown in temperatures that are k nown to 
be conducive to disease development. The aim of this is to better manage risk from various  
12 • classes of regulated pest including bacteria, fungi, oomycetes and viroids that may otherwise be 
difficult to detect. This requirement is in place for both Actinidia  (as per the import health standard 
published in 2018) and Prunus  (as per the import health standard published in 2020)  and has 
always been a requirement in place on Citrus  plants for planting.  
 Previously t he risks of some bacteria, fungi and oomyc etes were not being managed to the 
same level as other pests (such as viruses and viroids). A higher level of protection for some 
species of regulated bacteria, fungi, and oomycetes on Actinidia  plants for planting and 
Prunus  plants for planting has been  achieved with the application of specific temperature 
requirements in post -entry quarantine.   
(53) The application of temperature regimes during post -entry quarantine also increases the efficacy 
of growing season  inspection  as a g eneric risk management measures for the following reasons:  
 It increases the likelihood of detecting pests that are not listed in the import health standard 
that are known to be associated with different genera of plants for planting . 
 It increases the likel ihood of detecting unknown or emerging pest risks or unexpected host 
associations, for which specific testing may not be feasible.  
2.2.2.3  Disease screening methods  
(54) The following factors are considered when determining the disease screening measures that w ill 
be applied, the length of the quarantine period, and/or the type of post -entry quarantine facility in 
which the plants must be held:  
 Likelihood of entry of a regulated pest on an import pathway . 
i. Whether a regulated pest is likely to be associated with the plant parts being imported 
(e.g. plants in vitro vs. cuttings vs. whole plants) . 
ii. Whether material is produced under an export plan or at an offshore facility . 
iii. Available treatment methods (for example , insecticide or miticide  before plan ts enter 
quarantine ). 
 The biology of the pest . 
i. Mode of transmission . 
ii. Whether the vectors are present (or likely to be present) in New Zealand . 
iii. Whether vectors are likely to be present near to the quarantine  facility . 
iv. Proximity of hosts: whether the same (o r related) species as the imported plants, or 
other known host species, are likely to be present near  the quarantine facility . 
v. Epidemiological characteristics . 
 Available disease screening methods ( e.g. growing season inspection, biological indexing, 
PCR) . 
 Likelihood of establishment of a regulated pest via an import pathway.  
 Potential environmental, economic, human health and/or sociocultural consequences of 
establishment . 
(55) All plants will require testin g to verify freedom from regulated pests as follows:  
 Diagnostic testing : 
i. Diagnostic testing may be undertaken when disease symptoms become evident on a 
plant in post -entry quarantine to verify the regulatory status of the organism causing the 
symptoms .  
Ministry for Primary Industries   • 13 ii. Depending on the type of symptoms, samples may be tested  for the presence of various 
classes of disease organism s, including bacteria, fungi, oomycetes, phytoplasmas, 
viroids and viruses . 
iii. The exact diagnostic tests that will be done will be decided on by the MPI inspector and 
staff at the diagnostic facility. T his will depend on the type of disease symptoms that are 
present.  
 Mandatory testing : 
i. Mandatory testing is targeted testing that must be done for specified regulated pests 
(identified in Schedules 1 and 2  of the draft standard), regardless of whether the pl ant is 
showing signs or symptoms of pests or disease . 
ii. Mandatory testing is required  to provide additional assurance that a consignment is free 
from particularly  high-risk regulated pests and/or if it is recognised that growing season 
inspection may not eff ectively manage the risk (e.g. when it is known that a particular 
regulated pest has a prolonged latent period , meaning that infected plants may not show 
symptoms in post -entry quarantine ). 
(56) All testing must be done  in a diagnostic facility accredited to th e MPI Facility Standard: Standard 
for Transitional Facilities for the Identification of Organisms . 
 Inspections by the post -entry quarantine facility operator (or nominated delegate)  
(57) The facility operator (or a nominated delegate) must inspect all plants for signs and symptoms of 
pests and diseases two times per week during periods of active growth.  
 The MPI Facility Standard: Post Entry Quarantine for Plants  requires facility  operators to 
keep  accurate records of all inspections (Part 3.6.1).  
i. Part 3.7 of this standard also describes actions that must be taken following the 
detection of a pest or disease in post -entry quarantine.  This standard can be read in 
conjunction with the MPI Guidance Document: Post Entry Quarantine for Plants . 
 Inspections by the MPI inspector  
(58) The MPI inspector must inspect all plants in the post -entry quarantine greenhouse for signs and 
symptoms of regulated pests and disease at regular intervals throughout the quarantine period.  
There is i nformation about inspections by the MPI inspector in Part 3.6.2 of the MPI Facility 
Standard: Post Entry Quarantine for Plants  and in the Guidanc e Document: Post Entry 
Quarantine for Plants  
 
 
 
   
14 • 3. Proposed risk management measures for Citrus  plants for 
planting  
(59) This section of the risk management proposal includes the following:  
 A description of the proposed requirements for post -entry quarantine including the length of 
the quarantine period and the level of post -entry quarantine greenhouse required for Citrus  
plants for planting . 
 A summary of all regulated pests for which specific phytosanitary measures are proposed 
and a description of the diseas e screening measure(s) that are proposed for each pest  (See 
Appendix for proposed schedule of testing for pests of Citrus  plants for planting) . 
(60) All phytosanitary measures described in this section must be applied in New Zealand unless 
plants are produced under an export plan or at an MPI-approved offshore facility. Plants that are 
produced using one of these options will have fewer requirements on arr ival in New Zealand 
because some or all the required measures will have been applied prior to export.  
 For Citrus  plants for planting from an MPI-approved offshore facility , proposed post-entry 
quarantine requirements are given in part 5.1 of this risk mana gement proposal.  
(61) For each consignment of Citrus  plants for planting, the phytosanitary measures that need to be 
applied in New Zealand will be identified on the import permit, as discussed in part 5. 2 of this risk 
management proposal.  
3.1 Post -entry quarantine requirements  
3.1.1  Quarantine period  
(62) For Citrus  plants for planting  from non-approved sources , MPI propose  that plants complete a 
minimum quarantine period of 17 months  (two growing seasons)  before they can become eligible 
for biosecurity clearance . 
 The proposed quarantine period is slightly longer  than the previous requirement (which was 
for a minimum 16-month  period  of active growth ) and has been extended to capture the 
physiological growth flushes for two concurrent growth se asons (Silveira et al. 2020) . A 
slightly longer growing season inspection provides a higher level of management for pests 
which are known to have prolonged periods of latency, (e.g. Phyllosticta citricarpa ).  
 Mandatory testing over two growing seasons is c onsidered necessary to manage risk from 
certain high -risk pests, as identified in part 4 of this risk management proposal.  
 As well as managing known risk, post -entry quarantine is an important measure by which 
new risk organisms or new host associations could be identified  on the plants for planting 
pathway.  
 The quarantine period must be long enough to ensure that, when combined with other risk 
management measures, risk will be appropriately managed before  biosecurity clearance is 
given . 
3.1.2 Level of quar antine  
(63) For Citrus  plants for planting from non-approved  sources, MPI propose to maintain the existing 
requirement for plants to be held in a Level 3B quarantine greenhouse  for growing season 
inspection and disease screening .   
Ministry for Primary Industries   • 15 
 The level of quarantine is determined by the pests of concern identified for any given plant 
genus and the specific containment features required to contain these pests.  
 For material  with no measures applied offshore, Level 3B has served as  the baseline 
measure and the  current risk analysis  supports a continuation of this level of quarantine . 
(64) MPI are proposing  that if the mandatory tests completed in the first growing season return 
negative results for the regulated pests being screened for in those tests, importers will be 
allowed to transfer plants to a Level 3A greenhouse for the remainder of the quarantine period.  
 The first growing season in Level 3B is necessary for verifying freedom from the highest risk 
regulated pests. These types of organisms require containment  in a Level 3B greenhouse 
because of their means of dispersal and transmission and/or because of their potential high 
impacts.  
 Transfer to a Level 3A greenhouse can occur after the plants are grown in autumn -like 
conditions.  
(65) MPI regards quarantine in a Lev el 3A greenhouse for the second growing season as being in line 
with the level of residual risk associated with Citrus  plants for planting for the following reasons:  
a) Screening for highly mobile and particularly high -risk regulated pests, along with mandato ry 
testing for other regulated pests, will have been done in the first growing season, so the 
plants will no longer be of unknown phytosanitary status.  
b) Plants will have been regularly inspected for disease symptoms over the previous 10 months, 
with remedia l action (e.g. treatment) taken if any regulated pests are identified.  
(66) Although risk will be lower in the second growing season, sporulating organisms which may not 
be contained within a Level 3A greenhouse based solely on the physical requirements for thi s 
level of facility , could still be present in the imported plants. However, the following operational 
measures are considered sufficient to manage this risk during the second season:  
 Regular plant health inspections must be completed by the post -entry quarantine facility 
operator to detect any disease symptoms as soon as practical . 
 Contingency plans must be developed to describe actions that will be taken to contain any 
spore -borne disease organisms within the facility if disease symptoms are obse rved. 
 Operational restrictions must be applied to minimise the likelihood of spores being dispersed 
outside the post-entry quarantine  facility. Overhead irrigation is prohibited to minimise the 
chances of fungi , which are aerially dispersed (e.g. by rain splash) , escaping from the facility.  
3.1.3 Temperature requirements  in post -entry quarantine  
(67) It is important to note that while the application of temperature regimes during post -entry 
quarantine was a new requir ement on Actinidia  and Prunus  plants for planting, this has always 
been a requirement in place on Citrus  plants for planting, to favour disease expression and/or 
increase pathogen titre, particularly for ‘ Candidatus ’ Liberibacter spp.  
 Even if symptoms do not become visible, growing plants under conditions conducive to 
disease development is likely to increase the pathogen titre and hence increase the likelihood 
of detection by other methods such as PCR.  
(68) On Actinidia  and Prunus  plants for planting, examples  of high impact pests that are being more 
effectively managed by growing plants under defined temperature regimes include Ceratocystis  
spp., Phytophthora  spp., Spiroplasma citri  and Xylella fastidiosa . All these pests are associated 
with Citrus  plants for planting and the proposal to maintain temperature requirements ensures 
that a similar level of protection is provided across different genera of plants for planting.   
16 • (69) MPI propose s exposing  Citrus  plants imported into New Zealand to temperatures , in post -entry 
quarantine,  that will increase the likelihood of detecting regulated pests either directly (by 
inducing expression of visible disease symptoms) or indirectly (by increasing the titre of an 
organism before samples are taken for pre -determined testing).   
a) The temperatures will imitate spring -like, summer -like and autumn -like conditions as outlined 
below in parts 3.1.1.1 -3.1.1.3.   
b) The two-growing -season period , combined with the application of  temperature requirements  
and mandatory testing for specified regulated pests , is intended to maximise the likelihood of 
detecting pests identified in the draft standard and hence minimise biosecurity risk associated 
with these pests . 
3.1.1.1  Spring -like conditions for three or four months  
(70) Spring is the optimal time for viral replication  (MPI, 2016) . Growing plants in spring -like 
temperatures is  conducive to the detection of viral diseases  either directly through symptom 
expression  or indirectly with testing . 
 By way of providing context, t he spring -like conditions required for Actinidia  and Prunus  
plants for planting in post -entry quarantine include daytime temperature s between 16°C and 
22°C and night -time temperatures  between 14°C and 2 0°C. 
(71) For Citrus  plants for planting, MPI propo se that for  the start of the first growing season3, plants 
are held for a minimum of four months at daytime temperature s between 1 6°C and 2 0°C and 
night -time temperatures between 1 4°C and 18°C. 
 Four months under spring -like conditions in the first  growing season is to ensure sufficient 
plant growth to enable leaf samples to be taken for mandatory virus testing  (outlined in 
Schedule 1 and 2 of the draft standard) .  
 This is reduced to three months in the second growing season which  is considered long 
enough for sufficient quantities of leaf material to be available (taking into consideration the 
evergreen nature of citrus therefore reduced leaf -drop compared to deciduous plants)  for 
testing and visu al detection of viral diseases (the latter being important for those viruses for 
which MPI are proposing to manage with growing season inspection only).  
3.1.1.2  Summer -like conditions for four months  
(72) Summer -like conditions are expected to be broadly conduc ive to symptom development of certain 
fungal, oomycete and bacterial diseases. Furthermore, these types of conditions will also provide 
conditions suitable for maximising the likelihood of detecting phytoplasmas and viroids.  
 This is consistent with New Zea land’s appropriate level of protection for these classes of pest 
on other plant genera (i.e. Actinidia  and Prunus ). 
 By way of providing context, t he summer -like conditions required for Actinidia  and Prunus  
plants for planting in post -entry quarantine include daytime temperatures between 20 °C and 
26°C and night -time temperatures  between 17°C and 2 3°C. 
(73) Following the spring -like conditions, MPI propose that Citrus  plants are held for four months at 
daytime tem perature s between 23 °C and 2 7°C and night -time temperatures between 1 8°C and 
22°C. This temperature range also applie s to plants being held for a second growing season.  
(74) For the last month of the summer -like growth period , MPI propose that plants are  expose d to 
higher daytime temperatures  between 27 °C and 31°C and night -time temperatures  between 
 
3 A “growing season” is defined as a period during which plants are exposed to spring -, summer - and autumn -like conditions.   
Ministry for Primary Industries   • 17 21°C and 2 5°C to maximise the likelihood for detecting high impact bacteria  such as Spiroplasm a 
citri and Xylella fastidiosa .   
3.1.1.3  Autumn -like conditions for two months  
(75) Following the summer -like conditions, MPI propose that Citrus  plants are  held for two months at 
temperature s between 15°C and 19°C. Citrus are evergreen plants and do not enter a dormant 
phase marked by leaf drop. The autumn -like conditions are to provide an environment conducive 
to the vegetative growth phase that would normally occur for citrus in the field  and when some 
regulated pests may induce disease symptoms . Growing season inspections will be required in 
autumn to identify  any regulated pests that may induce symptoms under these conditions.  
 
Table 1. Summary of proposed temperature requirements in post -entry quarantine . 
 Duration  Temperature (day)  Temperature (night)  
Spring  4 months (season 1)  18°C (± 2°C) 16°C (± 2°C) 3 months (season 2)  
Summer  3 months (both seasons)  25°C (± 2°C) 20°C (± 2°C) 
1 month (both seasons)  29°C (± 2°C) 23°C (± 2°C) 
Autumn  2 months  17°C (± 2°C) 17°C (± 2°C) 
 
4. Priority pests associated with Citrus  plants for planting  
(76) This part of the risk management proposal identifies all priority pests associated with Citrus  plants 
for planting that could have a significant adverse impact on citrus, other crops and/or the New 
Zealand environment.  
(77) Pests identified in this section are those that  the MPI risk analysis assessed as meeting the 
criteria for additional measures bas ed on evidence that they potentially could not be contained in 
a Level 3A post -entry quarantine  and/or be detected in one growing season  and/or have 
unacceptable impacts.  
 Growing season inspection is a general requirement that must be applied to help manag e risk 
from all regulated pests that may be associated with plants for planting imported into New 
Zealand.  
i. As illustrated in the following sections, MPI consider s growing season inspection  
sufficient to appropriately manage risk from some regulated pests,  for example , where 
there is evidence  that disease symptoms will be expressed in the post -entry quarantine 
greenhouse and/or where pests are likely to have a limited impact  (meaning that 
additional measures, such as mandatory testing, are not commensurate with the risk) .  
 For other pests, where there is greater risk and/or evidence that symptoms will not be seen in 
quarantine, additional measures (for example , specific testing using PCR) may be required. 
The combination of measures proposed to manage each r egulated pest are identified in this 
section.  
(78) All reasoning and evidence given below has been taken from the MPI risk analysis, unless 
otherwise cited.  
   
18 • 4.1 Bacteria  
(79) Six species of bacteria , currently regulated in the existing citrus standard,  were identi fied as 
requiring specific phytosanitary measures in post -entry quarantine, in addition to growing season 
inspection, as discussed below.  
4. 1.1 ‘Candidatus Liberibacter ’ spp.4 
(80) Growing plants in temperatures optimal for ‘Candidatus  Liberibacter ’ spp. and PCR testing , are 
justified and sufficient to manage the risk from ‘Candidatus  Liberibacter africanus’, ‘ Candidatus  
Liberibacter americanus’ and ‘ Candidatus  Liberibacter asiaticus ’ on Citrus  plants for planting for 
the following reasons:  
 ‘Candidatus  Liberibacter ’ spp. ha ve the potential to cause economic impacts if introduced into 
New Zealand.  
i. ‘Candidatus  Liberibacter ’ spp. are associated with the citrus disease huanglongbing 
(HLB), also known as citrus greening. This is a high -impact disease , for which the only 
effective means of treatment is removal of infected trees.  
 ‘Candidatus  Liberibacter ’ spp. may not be detected by visual inspection of Citrus  plants for 
planting.  
i. Asymptomatic infections can occur, and the length of incubation is influe nced by plant 
age and health.  
 ‘Candidatus  Liberibacter ’ spp. are likely to be able to establish in New Zealand.  
i. ‘Candidatus Liberibacter ’ spp. can be spread by propagatin g infected planting material . 
- Diaphorina citri  is the only recorded vector of ‘ Candida tus Liberibacter ’ spp. and is 
not known to be present in New Zealand.  
ii. The New Zealand climate is likely to be suitable for establishment . 
iii. ‘Candidatus  Liberibacter ’ spp. can remain systemically in the plant for the lifetime of the 
plant.  
 PCR is likely to de tect ‘Candidatus  Liberibacter ’ spp. in Citrus  plants for planting.  
i. PCR has been able to detect ‘Candidatus  Liberibacter ’ spp. in asymptomatic trees.  
ii. MPI consider s it important to grow plants under conditions likely to be conducive to the 
disease , as the risk analysis has identified that ‘Candidatus  Liberibacter ’ spp. may be 
unevenly distributed and present at very low levels which may produce false negative 
results (T immer, 2000) . Because of this variable distribution, MPI are proposing to 
conduct  mandatory testing for ‘ Candidatus  Liberibacter ’ spp. in both growing seasons.  
(81) MPI propose that samples for PCR are collected  following plant growth at 23–27°C for a 
minimum o f three  months for the following reasons:  
 There are specific PCR assays for ‘Candidatus  Liberibacter africanus ’, ‘Candidatus  
Liberibacter americanus ’ and ‘Candidatus  Liberibacter asiaticus ’. 
i. ‘Candidatus  Liberibacter’ spp. have been detected by PCR in symptomatic and 
asymptomatic citrus plants at least three months after inoculation (Folimonova et al. 
2009).  
 
4 Information taken from Pest Risk Assessments: Citrus  spp. nursery stock (MPI, 2016)   
Ministry for Primary Industries   • 19 
 The optimal temperature range for ‘Candidatus  Liberibacter africanus ’ and ‘Candidatus  
Liberibacter  americanus ’ to multiply and produce symptoms is between 18 –25°C. These 
species are heat sensitive and may not produce symptoms above 27°C. The optimal 
temperature range for ‘Candidatus  Liberibacter asiaticus ’ to multiply and produce symptoms 
is between 17 –32°C. Due to some ‘ Candidatus  Liberibacter’ species having optimum 
temperatures up to 27°C, MPI propose that samples for PCR are collected before  plants are 
exposed to the higher temperature range conducive for Spiroplasm a citri and Xylella 
fastidiosa  (which is 27-31°C, refer to next section) .  
4.1.2  Spiroplasma citri5 
(82) Growing plants in temperatures optimal for Spiroplasma  citri and PCR testing ar e justified and 
sufficient to manage the risk from Spiroplasma  citri on Citrus  plants for planting for the following 
reasons:  
 Spiroplasma  citri has the potential to cause economic impacts if introduced into New 
Zealand.  
i. Spiroplasma  citri causes stubborn disease of citrus, a high -impact disease that can be a 
significant restraint on citrus production . 
ii. Spiroplasma  citri causes disease on other hosts  that are economically important to New 
Zealand , including Prunus  spp. 
 Spiroplasma  citri may not be detected by visual inspection of Citrus  plants  for planting . 
i. There are reports that Spiroplasma  citri is associated with Citrus  spp. that do not display 
any symptoms of infection.  
 Spiroplasma  citri is likely to be able to establish in New Zealand.  
i. The bacterium may be spread by the propagation of infected planting material.  
- Spiroplasma citri  is transmitted by phloem -feeding leaf hoppers in the genera 
Circulifer , Scaphytopius  and Neoaliturus . 
- Although these genera are not present in New Zealand, they are  in the family 
Cicadellidae, subfamily Deltocephaline, which is well represented in New Zealand.  
- Another species in the same subfamily, Macrosteles fascifrons , is an experimental 
vector. One member of this genus is present in New Zealand, so may be able to  act 
as a vector.  
ii. The New Zealand climate is likely to be suitable for establishment . 
iii. There are known host plants present in New Zealand.  
 PCR is likely to detect Spiroplasma  citri in Citrus plants for planting.  
i. Detection by PCR is very sensitive  and fast and is more reliable than woody indexing 
and culturing  (Yokomi 2008) . 
ii. It is considered important to grow plants under conditions likely to be conducive to the 
disease, even when using PCR for detection, based on information that, in Citrus , 
Spiroplasma  citri may be unevenly distributed and present at very low levels  (Shi et al. 
2014) .  
(83) The optimal temperature range for Spiroplasma  citri to multiply and produce symptoms is  
between 29°C and 32°C (Markham 1983) . As such , MPI propose that samples for PCR testing 
are collected within 14 days of completing growth  between 27°C and 31°C. Because of v ariation 
 
5 Information taken from Import risk analysis: budwood/ dormant cuttings of Prunus spp. (MPI, 2019), unless cited.   
20 • observed between seasons, MPI are proposing to conduct mandatory PCR testing for 
Spiroplasma  citri in both growing seasons.  
4.1.3 Xanthomonas  spp. 
(84) Xanthomonas alfalfae  subspecies citrumelonis  (formerly X. campestris  pv. citrumelo ), 
Xanthomonas citri  subspecies citri (X. axonopodis  pv. citri) and Xanthomonas fuscans  
subspecies aurantifolii  (formerly X. campestris  pv. aurantifolii ), listed in the existing import health 
standard , are associated with Citrus  plants for planting and contin ue to meet the criteria to be 
regulated pests for New Zealand. These species were not considered further as part of the risk 
analysis. MPI propose s manag ing these pests as follows:  
 MPI will  retain  PCR  as a specific measure for managing Xanthomonas citri  subspecies citri.  
i. Xanthomonas citri  subspecies citri is the causative agent of citrus canker disease , with 
widespread global distribution (Ference et al. 2018).  It is reported to cause latent 
infections and may not be detected during growing season inspe ction (EFSA, 2014).  
 Xanthomonas alfalfae  subspecies citrumelonis  and Xanthomonas fuscans  subspecies 
aurantifolii  have previously  been  managed with specific measures  (i.e. grafting and PCR ). 
During the 2016 consultation for the revised citrus import require ments at that time, it was 
proposed to remove specific measures and manage  these two bacterial pests  with growing 
season inspection  in post -entry quarantine  only. This is because they are likely to display 
symptoms during the growing season. For the latest  review, there was no evidence found to 
suggest a change to that proposal.  
i. This aligns with other plants for planting species for which Xanthomonas  spp. are 
managed with growing season inspection and are expected to show symptoms after 
plants have been grown in summer -like conditions.  
4.1.4 Xylella fastidiosa6 
(85) Growing plants in temperatures optimal for Xylella fastidiosa  and PCR testing are justified and 
sufficient to manage the risk from Xylella fas tidiosa  on Citrus  plants for planting for the following 
reasons:  
 Xylella  fastidiosa  has the potential to cause economic, environmental and social impacts if 
introduced into New Zealand.  
i. Xylella  fastidiosa  causes devastating diseases in crops that are impor tant to the 
New Zealand economy, including grapes and stone fruit . 
ii. Xylella  fastidiosa  causes citrus variegated chlorosis disease, which has been a major 
factor limiting citrus production around the world . 
iii. Xylella  fastidiosa is known to be capable of infecting native New Zealand plant genera , 
including iconic trees  such as pōhutukawa and kauri.  
iv. Xylella  fastidiosa is a high-risk regulated pest on other plants for planting species such 
as Prunus . 
 Xylella fastidiosa  may not be detected by visual inspection of Citrus plants for planting.  
i. Asymptomatic infections frequently occur in many hosts, often for a long time after 
inoculation (Bragard et al. 2019).  
 Xylella  fastidiosa  is likely to be able to establish in New Zeal and. 
i. There are known hosts plants present in New Zealand . 
 
6 Information taken from Impo rt risk analysis: budwood/ dormant cuttings of Prunus  spp. (MPI, 2019), unless cited.   
Ministry for Primary Industries   • 21 ii. The New Zealand climate is likely to be suitable for establishment.  
iii. There is the potential for Xylella fastidiosa  to be transmitted to other hosts if it arrive s in 
New Zealand.  
- At least one known vector of Xylella fastidiosa  is present in New Zealand. Many 
other insect species in the same family as the known vector are present in New 
Zealand and are potential vectors of Xylella fastidiosa . 
 PCR is likely to detect Xylella fastidiosa  in Citrus plants for planting.  MPI propose that 
samples for PCR testing are  collected within 14 days of completing growth  between 27°C 
and 31°C to maximise the likelihood of detecting Xylella fastidiosa , for the following reasons:  
i. Plant tissue samples collected in spring are known to have lower amounts of Xylella 
fastidiosa  bacteria, which could lead to false negative test results (Francis et al. 2006), 
therefore testing of plant samples collected in summer conditions is considered more 
reliable.  
ii. High populations of Xylella fastidiosa  have been detected in symptomatic and 
asymptomatic plants exposed to temperatures within this range (Almeida et al. 2001; 
Ribeiro et al. 2004).  
iii. Because Xylella fastidiosa  can have a variable distributio n, MPI are proposing to 
conduct  mandatory PCR testing for Xylella fastidiosa  spp. in both growing seasons.  
4.2 Fungi and oomycetes  
(86) Eighteen  species  of fungi and oomycetes meet the criteria to be  regulated pests on Citrus  plants 
for planting . 
 Only a limited  number of fungi, identified using major literature sources, have been  
considered as part of the hazard identification and risk assessment.  This means that species 
of regulated fungi and/or oomycetes considered managed by growing season inspection may 
not be listed in the standard.  
 If such species are identified on Citrus  plants for planting  during post -entry quarantine , MPI 
will assess their regulatory status by referring  to MPI ’s online pest database.  
(87) The risk analysis showed that risk from some fungi considered regulated pests would be 
appropriately managed with growing season inspection  by growing  plants in summer -like 
temperatures to encourage disease expression. For some pests,  visible symptoms are expected 
to become evident over the proposed 17-month period of post -entry quarantine . This applies to 
the following species:  
 
 Colletotrichum abscissum  and Colletotrichum  limetticola   
i. Disease s ymptoms  are expected to be observed within the first growing se ason in post -
entry quarantine.  
 Elsinoe australis  
i. Disease symptoms are expected to be observed within the first growing season in post -
entry quarantine.  
 Erysiphe quercicola   
i. Disease symptoms are expected  to be observed  within the first  growing season  in post -
entry quarantine .   
22 • ii. There was no evidence found of E. quercicola causing  asymptomatic infections in Citrus  
spp.  
iii. Temperature requirements in post -entry quarantine are likely to be conducive to 
symptom expression,  because the optimal conditions for conidial germination are 20 –
25°C.  
 Fibroidium tingitaninum   
i. Disease symptoms are expected to be observed within the first growing season in post -
entry quarantine.   
ii. There was no evidence found of F. tingitaninum  causing  asymptomatic infections in 
Citrus  spp.  
iii. Temperature requirements in post -entry quarantine are likely to be conducive to 
symptom expression, because the optimal conditions for conidial germination are 20 –
25°C.  
 Plenodomus tracheiphilus  
i. Disease symptoms are expected to be observed within  the first growing season in post -
entry quarantine.   
ii. Temperature requirements in post -entry quarantine are likely to be conducive to 
symptom expression, because the optimal conditions for mycelium growth are 20 –25°C. 
4.2.1  Ceratocystis  spp.7 
(88) Growing plants in temperatures optimal  for Ceratocystis  spp. and PCR are justified and sufficient 
to manage the risk from members of the Ceratocystis  genus on Citrus  plants for planting for the 
following reasons:  
 Ceratocystis  spp. has the potential to cause economic impacts if introduced into New 
Zealand.  
i. Ceratocystis spp. causes serious cankers on many plants, including fruit trees. I n citrus , 
it causes fruit rot, w hich could severely impact production (Mirzaee et al. 2009).  
ii. The proposed measures are consistent with those previously consulted on to manage 
risk from Ceratocystis spp. on Actinidia and Prunus  plants for planting . 
- Ceratocystis  spp. are a high -risk regulated pest on other plants for planting species 
such as Actinidia and Prunus . 
 Ceratocystis spp. may not be detected by visual inspection of Citrus  plants for planting.  
 PCR is likely to detect Ceratocystis  spp. in Citrus plants for planting.  
i. Ceratocystis  spp. is managed with PCR (and growing plants in temperatures optimal for 
Ceratocystis  spp.) on other plants for planting species such as Actinidia and Prunus .  
ii. MPI considers that testing on arrival and again  at the end of the first summer growth 
period will increase  the likelihood of detecting latent infections . This testing regime is 
necessary  to achieve a  very high degree of certainty that members of the Ceratocystis  
genus are not present in imported plant material.  
 
7 Information taken from Import risk analysis: budwood/ dormant cuttings of Prunus spp. (MPI, 2019), unless cited.   
Ministry for Primary Industries   • 23 4.2.2  Diaporthe  spp. 
(89) Three species of Diaporthe  (D. baccae , D. hongkongensis  and D. novem ) meet the criteria to be 
regulated pests for New Zealand for the following reasons:  
 These Diaporthe  species have been isolated from symptomatic ( D. baccae  and D. novem ) 
and asymptomatic ( D. hongkongensis ) twigs and branches of citrus. However, because these 
species are only recently described, it is still unclear how often they are found associated with 
citrus and whether all species can be latent and asymptomatic in citrus  plants.  
i. Diaporthe hongkongensis  has been isolated from asymptomatic twigs of several citrus 
spp. in a field survey.  
ii. No reports were found of D. baccae  and D. novem  being isolated from asymptomatic 
citrus twigs or branches.  
 These Diaporthe  species have been reported from geographical locations that have a very 
similar climate to New Zealand.  
 Diaporthe  species are recorded as causing disease on economically significant crops in New 
Zealand , including blueberry, grapevine and kiwifruit, and o n ornamentals such as camellia, 
sunflower and hydrangea.  
 Several other Diaporthe  species have recently been isolated from citrus plants. However, 
there is insufficient information to assess them beyond the category of emerging risk at this 
time.  
(90) Additiona l measures other than growing season inspection in post -entry quarantine are not 
justified  to manage risk from the named Diaporthe  spp. on Citrus  plants for planting  at this time 
for the following reasons:  
 These Diaporthe  species have only been described r ecently (i.e. since 2015), and there is 
limited information on impact and optimum environmental conditions for disease 
development.  
 There are other species of Diaporthe  known to be present in New Zealand that are closely 
related to D. baccae , D. hongkongen sis and D. novem  and have a similar host range. There 
were no records found on the impacts of these Diaporthe  on crops of significant economic 
value in New Zealand such as blueberry, citrus, grapevine, and kiwifruit. There is uncertainty 
about whether D. baccae , D. hongkongensis  and D. novem would have impacts beyond what 
is caused by the Diaporthe  known to be present in New Zealand.  
 This aligns with the level of protection offered for Diaporthe  on Actinidia  and Prunus , for 
which there is also limited info rmation on impact and optimum environmental conditions.  
4.2.3 Lasiodiplodia  spp. 
(91) Eight species of Lasiodiplodia  (L. brasiliensis , L. citricola , L. hormozganensis , L. iraniensis , 
L. mediterranea , L. mitidjana , L. pseudotheobromae  and L. subglobosa ) meet the criteria to be 
regulated pests for New Zealand for the following reasons:  
 These Lasiodiplodia  species have all been identified in association with diseases of Citrus  
spp., including cankers and dieback.  
 Lasiodiplodia  spp. are members of the Botryosphae riaceae, which have an endophytic 
phase, and therefore, these fungi may be associated with material used for budwood without 
causing symptoms.  
 These Lasiodiplodia  species are recorded as causing disease on economically significant 
crops in New Zealand , which include Vitis, Malus , Prunus  and Vaccinium .    
24 • (92) Additional measures other than growing season inspection in post -entry quarantine are not 
justified to manage risk from the named Lasiodiplodia  spp. on Citrus  plants for planting at this 
time for the followi ng reasons:  
 Much of the evidence assessed for Lasiodiplodia  spp. reported that they occurred in hosts as 
mixed infections (often with other species of Lasiodiplodia ). The impact of Lasiodiplodia  spp. 
in single infections is not currently known, but disease  severity may be reduced.  
i. A related species, L. theobromae , is present in New Zealand but has not thrived. There 
are no reports of this species causing serious disease in New Zealand.  
 There were no reports found of Lasiodiplodia  spp. being isolated from asymptomatic material. 
While this does not rule out the possibility that Lasiodiplodia  spp. can be latent in Citrus  spp., 
it is considered unlikely that diseased trees will be a source of budwood for propagation.  
 These are emerging pat hogens, and so there is currently limited information available on the 
impacts of Lasiodiplodia  spp. on citrus.  
4.2.4  Phyllosticta citricarpa  
(93) Growing plants in temperatures optimal  for Phyllosticta citricarpa  and PCR , on arrival and again 
during the first growing season,  are justified and sufficient to manage the risk from Phyllosticta 
citricarpa  on Citrus  plants for planting for the following reasons:  
 Phyllosticta  citricarpa  has been detected by PCR in citrus twigs and branches that did not 
exhibit symptoms.  
 Phyllosticta  citricarpa can be latent in citrus budwood  therefore symptoms may not develop 
during one season in post -entry quarantine.  
 Phyllosticta  citricarpa  can cause significant impacts  to yield because of premature fruit drop 
and lesions in f ruit. 
i. There are historical records of yield losses of more than 90%. While crop losses of this 
magnitude are not likely to occur in today’s commercial orchards, the application of 
fungicides during fruit development to prevent high levels of infection and damage are 
likely to increase costs and cause environmental impact.  
- Disease caused by Phyllosticta citricarpa  is estimated to cost Australian citrus 
growers approximately AU$80 million per year through export restrictions, 
fungicide applicati ons and fruit damage (Hort Innovation 2018)8. 
 Phyllosticta citricarpa  is known to be present in Australia  (confirmed by the Australian 
Department of Agriculture, Water and the Environment  (DAWE) ). While material from 
Australia is likely to be sourced from an MPI -approved offshore facility in New South Wales,  
there is no specific testing conducted for this pest  at the facility . Therefore, an on-arrival test 
will provide a greater level  of certainty of pest freedom before the material enters post -entry 
quarantine.   
4.2.5 Phytophthora  spp. 
(94) Growing plants in temperatures optimal  for Phytophthora spp. and PCR  or plating , on arrival and 
again during the first growing season,  are justified and sufficient to manage the risk from 
Phytophthora spp. on Citrus plants for planting for the following reasons:  
 
8 Joint Florida and Australian Citrus Black Spot Research Initiative   
Ministry for Primary Industries   • 25 
 Phytophthora spp. on Citrus  (and other recently reviewed plants species such as Actinidia  
and Prunus ) has previously been managed with growing season inspection in post -entry 
quarantine.  However, because there is  evidence that some regulated Phytophthora  spp. may 
not induce visible disease symptoms in post -entry quarantine , relying on this measure  is not 
appropriate as a sole method of diagnosis . Therefore, PCR or plating is also proposed as a 
requirement.  
 Phytophthora  spp. is managed on Actinidia  and Prunus  with specific measures in post -entry 
quarantine, namely PCR or culture -based identification after plants have been grown in 
summer -like conditions. The same level of protection to manage Phytoph thora  spp. on Citrus  
is appropriate , particularly because at least one species, P. palmivora , is a regulated pest on 
Actinidia , Citrus  and Prunus . 
 Some species of Phytophthora  are known to be present in Australia (confirmed by DAWE ). 
While material from Australia is likely to be sourced from an MPI -approved offshore facility in 
New South Wales, there is no specific testing conducted for this pest  at the facility . Therefore, 
an on -arrival test will provide a greater level of certainty of pest freedom before the material 
enters post -entry quarantine.  
4.3 Phytoplasmas  
(95) MPI propose s removing  citrus rubbery wood as a phytoplasma on Citrus  plants for planting for 
the following reasons:  
 Citrus rubbery wood has not been reported on since 1985 (Frison and Taher 1991; Timmer et 
al. 2000) . 
 There are no records indicating that phytoplasmas are the causal agent for citrus rubbery 
wood.  
(96) Please note that MPI will manage  Phytoplasma s with PCR using un iversal phytoplasma primers . 
The proposal  in (92)  is simply to remove citrus rubbery wood as a regulated phytoplasma 
because there is inconclusive evidence that this disease is a phytoplasma.   
4.4 Viruses  
(97) MPI is aware that sometimes there is a preference for PCR over biological indexing  methods . 
Where that has been  supporting evidence to replace biological indexing with PCR, MPI have 
implemented those changes ( e.g. the removal of woody indicator testing as a method to detect 
viruses on Prunus  plants for planting). However,  biological indexing is still considered a valuable 
diagnostic tool around the world for the detection and biological characterisation of citrus viruses 
(and viroids). Citrus indicator plants serve as bio -amplification hosts tha t can increase the ability 
to detect viroids and viruses that may be present at a low titre in the original sample (Donovan, 
2018). In this section, MPI are proposing the manage some viruses with biological indexing 
and/or PCR to ensure a greater level of assurance that imported plants are free from these 
regulated pests.  
(98) Previously, to manage risk from  some viruses , MPI has required a combination of growing 
season inspection and biological indexing  on susceptible Citrus  cultivars . PCR tests are available 
for some viruses and would be sufficient to manage the risk of these viruses on Citrus  plants for 
planting. MPI propose  to replace  biological indexing  with PCR tests for the following species of 
virus:  
 Apple stem grooving virus  [citrus strain]  
 Citrus leaf rugose virus  
 Citrus variegation virus   
26 • 
 Citrus yellow mosaic virus  
 Citrus yellow vein clearing virus  
(99) Viruses that will continue to be managed by growing season inspection and PCR or biological 
indexing  on susceptible Citrus  cultivars  include:  
 Citrus chlorotic dwarf -associated virus  
 Citrus psorosis virus  [strains not in New Zealand]  
 Satsuma dwarf virus  
(100) The development of PCR assays for these viruses is still in progress , and  therefore , biological 
indexing  on susceptible Citru s cultivars  will be required to manage the risk of these viruses until 
such time as validated PCR assays are available.  
(101) In addition to the viruses listed above, there are n ine new viruses that meet the criteria to be 
regulated pests and have been included in the revised standard9. The risk management proposal 
for those nine new viruses is provided in sections 4.4.1 to 4.4.5.  
4.4.1  Citrus sudden death -associated virus  
(102) MPI propose to manage Citrus sudden death -associated virus  on Citrus  plants for p lanting with 
specific phytosanitary requirements in post -entry quarantine, namely biological indexing or PCR, 
the following reasons:  
 Citrus sudden death -associated virus  can have an impact on the citrus industry in 
New Zealand.  
i. This is considered the causa l agent of the disease citrus sudden death.  
ii. This virus has been found to produce symptoms  of greater severity  when co -infected 
with Citrus tristeza virus , some  strains of which are present in New Zealand . 
 Citrus sudden death -associated virus  may not be det ected by visual inspection alone . 
i. This virus can exist in plants asymptomatically.  
 Citrus  sudden death -associated virus can be detected using an appropriate PCR assay.  
i. Citrus sudden death -associated virus  has been detected by PCR in all plant parts  of 
trees infected with citrus sudden death . 
ii. MPI are in the process of developing a PCR assay for Citrus sudden death -associated 
virus and will manage the risk of this virus with  biological indexing until this ass ay is 
available.  
4.4.2  Indian citrus ringspot virus  
(103) MPI propose to manage Indian citrus ringspot virus on Citrus  plants for planting with specific 
phytosanitary requirements in post -entry quarantine, namely PCR, for the following reasons:  
 Indian citrus rin gspot virus  can have an impact on the citrus industry in New Zealand.  
i. Fruit yield is heavily reduced, with disease progression causing dieback symptoms.  
 Indian citrus ringspot virus may not be detected by visual inspection alone . 
i. This virus can exist in pl ants asymptomatically.  
 Indian citrus ringspot virus  can be detected by PCR.  
 
9 Information taken from Pest Risk Assessments: Citrus  spp. nursery stock (MPI, 2016)   
Ministry for Primary Industries   • 27 i. MPI have  developed a PCR assay to detect Indian citrus ringspot virus . 
4.4.3  Olive latent virus 1  
(104) MPI propose to manage Olive latent virus 1  on Citrus  plants for planting with specific 
phytosanitary requirements in post -entry quarantine, namely PCR, the following reasons:  
 Olive latent virus 1 can impact several crops of economic importance to New Zealand.  
i. Citrus  spp.,  Liliaceae  spp. (tulip), Olea  spp. (olive) and Solanum lycopersicum  (tomato)  
are known to be hosts of Olive latent virus 1 . 
 Olive latent virus 1 may not be detected by visual inspection alone . 
i. This virus can exist in plants asymptomatically.  
 Olive latent virus 1 can be detected by PCR.  
i. MPI have developed a PCR assay to detect Olive latent virus 1 . 
4.4.4  Citrus leprosis viruses  
(105) There are six citrus leprosis viruses that meet the criteria to be regulated  pests on Citrus  plants 
for planting.  
 MPI propose to manage Citrus leprosis virus C  and Citrus leprosis virus C2  with specific 
phytosanitary requirements in post -entry quarantine, namely PCR , the following reasons:  
i. Citrus leprosis virus C  and Citrus leprosis virus C2  are the most widespread of the citrus 
leprosis viruses and are quaranti ne pests in countries that are export markets for 
New Zealand . 
- The geographic distribution of citrus leprosis disease includes regions that have a 
similar climate  to New Zealand . 
- Citrus sinensis , an important commercial crop for New Zealand, is the primary  
species affected by citrus leprosis disease.  
ii. MPI have developed PCR assays  to detect  Citrus leprosis virus C  and Citrus leprosis 
virus C2 . 
- Citrus leprosis induces symptoms of localised lesions on foliage, stems and fruit and 
severe disease can result in extensive crop loss and tree debilitation . PCR offers a 
higher degree of assurance commensurate with this impact .  
b) Citrus chlorotic spot virus , Citrus leprosis virus N dichorhavirus , Hibiscus green spot virus 2  
and Orchid fleck dichorhavirus  would be appropriately managed in post -entry quarantine 
without any risk management measures other than growing season inspection.  
i. Disease symptoms are expected to be observed within the first growing season in post -
entry quarantine.  
4.5 Viroids  
(106) Previously,  to manage the risk of some viroids, MPI has required return -polyacrylamide gel 
electrophoresis  (R-PAGE) , PCR and biological indexing . This applies to the following species of 
viroids : 
 Citrus bent leaf viroid  (synonym: Citrus viroid I ) 
 Hop stunt viroid  [citrus strain] (synonyms:  Citrus viroid II , Citrus cachexia viroid ) 
 Citrus bark cracking viroid  (synonym: Citrus viroid IV )  
28 • (107) MPI proposes remov ing the requirement for S-PAGE and manag ing these viroids by growing 
plants in temperatures optimal for vi roid replication , and PCR  AND  biological indexing . 
 Viroid replication and symptom development is enhanced as temperature increases above 
20°C to at least 35°C (MPI, 2016).  
i. MPI propose that samples for PCR are collected after plants are exposed to summer -
like conditions (i.e. 23°C - 27°C) for three months.  
 MPI previously consulted on the removal of S -PAGE during the 2016 consultation for the 
revised citrus import requirements. This is because PCR assays for the above viroids offer 
greater sensitivity than S -PAGE. For the latest review, there was no evidence found to 
suggest a change to that proposal.  
(108) Two additional viroids meet the criteria for regulated pests and have been included in the revised 
standard  and are described below10. 
4.5.1  Citrus viroids  
(109) MPI propose to manage Citrus viroid V  and Citrus viroid VI  on Citrus plants for planting by 
growing plants in summer -like conditions and with specific phytosanitary requirements in post -
entry quarantine, namely biological indexing and PCR, for the following reasons:  
 Citrus viroid V  and Citrus viroid VI  can infect plants asymptomatically and  may not be 
detected during growing season inspecti on in post -entry quarantine . 
i. Citrus viroid V  and Citrus viroid VI  are members of the genus Apscaviroids , whose 
presence in citrus orchards is reported to go  unknown unless active surveys are 
conducted.  
- A field survey in Pakistan found that 93% of plants s amples were infected with Citrus 
viroid V , indicating that it could be more widespread tha n first anticipated . 
 Citrus viroids in mixed infections can lead to more severe  symptom expression , which would 
have a greater impact on citrus production , and therefore reliable detection is necessary . 
i. Citrus viroid V  and Citrus viroid VI  have been found in mixed infections  with other viroids 
(including Citrus dwarfing viroid  which is present in New Ze aland) in which the disease 
symptoms were more pronounced . 
ii. Citrus viroids in general are known to infect most citrus species . 
 MPI have developed PCR assays to detect Citrus viroid V  and Citrus viroid VI . 
i. MPI propose that samples for PCR are collected after plants are exposed to summer -
like conditions (i.e. 23°C - 27°C) for three months.  
4.6 Diseases of unknown aetiology  
(110) Australian citrus dieback, citrus  blight and concave gum blind pocket continue to meet the criteria 
for regulated pests on Citrus  plants for planting.  The existing standard manages  these diseases 
with either country freedom or biological indexing  on Citrus  cultivars.  MPI propose s manag ing 
them with growing season inspection for the following reasons:  
 There is significant uncertainty around biology , given that the causal agents have not been 
identified . 
i. Australian citrus dieback is believed to be associated with phytoplasma -like organisms . 
However , this is not  confirmed (Donovan et al. 2018 ). 
 
10 Information taken from Pest Risk Assessments: Citrus  spp. nursery stock (MPI, 2016)   
Ministry for Primary Industries   • 29 ii. Citrus blight and blight -like diseases have similar symptomatology . However , in the 
absence of a known causal agent, there is currently no method available to identify 
diseased trees in the absence of s ymptoms . 
iii. Concave gum blind pocket  symptoms were recently reported in citrus trees , and a 
putative causal agent, tentatively named Citrus concave gum associated virus, has been 
identified . However , this is not  confirmed (Navarro et al. 2018a ; 2018b) . 
(111) MPI propose s remov ing the following diseases of unknown aetiology as regulated diseases on 
Citrus  plants for planting:  
 Bud union  
 Citrus fatal yellows  
 Citrus impietratura  
 Citrus sunken vein  
 Cristacortis  
 Gummy bark  
 Gum pocket  
 Kassala  
 Lemon sieve tube necrosis  
 Shell bark  
 Zonate chlorosis  
(112) Each of the above diseases is highlighted for removal for one or more  of the following reasons.   
 There were no records found of the occurrence of some disease agents for at least the last 
20 years.  
i. The use of virus and viroid -free nucellar or shoot -tip grafted material has likely led to the 
disappearance of some of these historical diseases of unknown  aetiology ( Roistacher 
1991) . 
ii. Although no causal agents have been definitively identified for these diseases, 
progressive research that has identified  and characterised  viruses and viroids isolated 
from symptomatic plants have informed phytosanitary screen ing programmes common 
for citrus source material . Propagation of material that has been screened for commonly 
known viruses and viroids may also contribute to the low incidence of these diseases 
and therefore lack of reports of their occurrence . 
 The disease has  been determined to be a  non-transmissible genetic disorder that is 
overcome with compatible scion/rootstock combinations.  
i. Lemon sieve tube necrosis is a typical bud union incompatibility of lemon  shown to be 
overcome with grapefruit rootstock ( Roistacher 2012).  
 The causal agents for the disease are known and are managed on Citrus  plants for planting.  
i. Apple stem grooving virus , Citrus tristeza virus  and Citrus sudden death -associated 
virus  are known to be associated with bud union disease and wil l be managed by the 
new standard.  
   
30 • 5. Appropriate level of protection  proposed for Citrus  plants for 
planting  
(113) The revision s of phytosanitary import requirements for  Actinidia  and Prunus  have indicated a 
change in the appropriate level of protection to en sure that all classes of pest are managed 
consistently. During the consultation  for both standards , it was identified from the submissions 
received from stakeholders and interested parties that even for a single pathway, a diverse range 
of risk tolerance  can exist  (i.e. submissions ranged from requests for a higher level of protection 
than the level  MPI w as proposing , to requests for a continuation of the previous level of 
protection ). MPI regards the  appropriate level of protection in place on b oth Actinidia  and Prunus  
as a balance between th ose viewpoints.  
(114) The best guide for gauging the appropriate level of protection is previous decisions made, as 
represented in recent import health standards that have been subject to consultation (i.e. 
Actinid ia and Prunus ). To demonstrate how the measures proposed in the draft Citrus  import 
health standard are consistent with the appropriate level of protection on other pathways, pests 
common on all  three pathways , and their measures,  are laid out in Table 1.  
 
Table 1. Pests in common on Actinidia , Prunus  and Citrus  material, from non -approved sources,  with instituted and 
proposed measures.   
Pests  Generic and/or specific r isk management measures in 
place * Propose d measures  
Actinidia  Prunus  Citrus  
Ceratocystis spp. Growing season in 
temperature and 
humidity -controlled 
environment  AND PCR  Growing season in 
temperature -controlled  
environment AND PCR  Growing season in 
temperature -controlled  
environment AND PCR  
Colletotrichum  spp. Growing season in 
temperature and 
humidity -controlled 
environment   Growing season in 
temperature -controlled  
environment  
Diaporthe  spp. Growing season in 
temperature and 
humidity -controlled 
environment  Growing season in 
temperature -controlled  
environment  Growing season in 
temperature -controlled  
environment  
Phytophthora  spp. Growing season in 
temperature -controlled  
environment AND PCR 
or plating  Growing season in 
temperature -controlled  
environment AND PCR 
or plating  Growing season in 
temperature -controlled  
environment AND PCR 
or plating  
Phytoplasmas  PCR  PCR  PCR  
Spiroplasma citri   Growing season in 
temperature -controlled  
environment AND 2x 
PCR  Growing season in 
temperature -controlled  
environment AND 2x 
PCR  
Xylella fastidiosa   Growing season in 
temperature -controlled  
environment AND 2x 
PCR  Growing season in 
temperature -controlled  
environment AND 2x 
PCR  
* Material from non -approved sources must go into Level 3B post -entry quarantine.   
Ministry for Primary Industries   • 31  
(115) Table 1 shows that growing plants in tempera ture and or humidity -controlled  environments has 
been implemented  to better manage risk from various classes of regulated pest including 
bacteria, fungi  and oomycetes . As mentioned previously in paragraphs (49), (50) and (64), 
applying environmental contro ls to favour disease expression and/or increase pathogen titre  
increases the effectiveness of growing season as well as the likelihood of detection by other 
methods such as PCR. MPI ha s long recognised the se advantages to growing plants in at least a 
temperature -controlled  environment as this  has been a long -standing requirement in the Citrus  
schedule  (namely for ‘ Candidatus ’ Liberibacter spp.).   
(116) Table 1 demonstrates that applying the same level of risk management to other classes of pest 
provides a co nsistent level of protection across other horticultural crop species.  
5.1 Post -entry requirements for plants imported from MPI -approved 
offshore facilities  
(117) The post -entry requirements for plants imported from MPI -approved offshore facilities will apply to 
leafless budwood/cuttings that have been sourced f rom mother plants kept in insect proof plant 
houses.  MPI will no longer allow citrus material to be sourced from plants in an open field for the 
following reasons:  
a) A core requirement of MPI’s Administrative Standard for Offshore Facilities Holding and 
Testing Plants for Planting  is as foll ows (as per Part 3.1 of the standard):  
The offshore facility holding plants for planting must be designed, constructed,  and maintained to 
ensure effective prevention of infestation, infection or contamination of pests and their vectors on 
plants for planti ng destined for export to New Zealand.  
b) Although not implicitly stated in the offshore standard, the reference to “design, construction 
and maintenance” of the facility that holds plants for planting prior to export implies an 
intention for the facility to  be a physical structure, rather than an open field.  
c) Keeping plants in an enclosed structure such as a screenhouse makes it much easier to 
manage the risk of re -infection from insect -vectored pests, and from water - or soil -borne 
pests (for example includin g some bacteria and fungi). It also reduces the likelihood of 
infection by rain or wind -borne pests.  
(118) The proposed post-entry quarantine requirements have been considered  in the context of the 
phytosanitary screening programme applied at the Elizabeth Macar thur Agricultural Institute  
(EMAI), in Australia. This is because this facility has been the only MPI -approved offshore facility 
for citrus material since 2001 . The recent re -approval of this facility against the MPI Standard for 
Offshore Facilities Holding and Testing Plants for Planting  means that the most current practices 
at EMAI have been  considered in this proposal.  
5.1.1  Quarantine period  
(119) MPI propose  that Citrus  plants for planting from MPI -approved offshore facilities complete a  
minimum of eight months quarantine , rather than 17 months,  in New Zealand , provided the 
residual risk is similar to plants provided for export to New Zealand by EMAI in Australia.    The 
reduced quarantine period in New Zealand is proposed for the following reasons:  
 This will give sufficient time for samples to be collected at appropriate times of the year for all 
residual testing  to be completed.   
32 • i. The risks associated with high impa ct pests that MPI are proposing to specifically 
manage across two growing seasons - ‘Candidatus  Liberibacter’ spp., Spiroplasma citri  
and Xylella fastidiosa - are likely to be managed on material from EMAI.  
- Citrus material at EMAI that is of Australian origi n is likely to be free from ‘Candidatus  
Liberibacter’ spp., Spiroplasma citri  and Xylella fastidiosa  because there is no 
evidence of their presence in Australia  (confirmed by DAWE ). 
- Citrus material at EMAI that has been i mported into Australia is likely to  be free from 
‘Candidatus  Liberibacter’ spp., Spiroplasma citri  and Xylella fastidiosa  because there 
are specific measures in place to manage the risk of these pests on imported material 
coming into Australia.   
 Australia has robust entry requirements to prevent pests of citrus entering  Australia . This 
contributes to MPI’s confidence that pl ants imported into Australia, and maintained at EMAI, 
are of high health status, and free from the citrus pests not known to be present in  Australia.  
i. DAWE’s import requirements for Citrus plants for planting into Australia, that contribute 
to these new pes ts not entering  Australia, include:  
- Mandatory disease elimination treatments, namely shoot -tip grafting, are to be 
completed and only shoot -tip grafted plants are considered for biosecurity clearance 
(BICON - import requirements for Rutaceae as nursery stoc k).  
- Shoot -tip grafting is a technique where shoot tips of a citrus variety are aseptically 
grafted onto disease -free citrus rootstock seedlings that have been grown in vitro. 
The technique is used to eliminate graft -transmissible pathogens, such as viruse s 
and viroids, from citrus germplasm.  
- Plants are required to be grown in specific temperatures to induce symptom 
expression and/or increase disease titre (for specific testing) for certain classes of 
pest (e.g. ‘Candidatus  Liberibacter ’ species).  
- Plants are inspected and tested for a minimum o f 24 months in post entry quarantine.  
- A series of biological and molecular diagnostic tests are performed to screen for high 
impact bacteria, fungi, phytoplasma, viruses and viroids that are regulated in Australia  
and New Zealand .  
- Regulated citrus pests t hat might be present on imported material are likely to be 
contained within DAWE’s post entry quarantine facility, Mickleham, and not escape 
into the wider environment . 
- The facility’s construction and operation are designed primarily to prevent pests and 
diseases from escaping into Australia’s environment and equally, to prevent insect 
vectors from entering and accessing quarantine plants that are of unknown 
phytosanitary status.  
 The proposed 8 month minimum  quarantine period  will allow mandatory plant heal th 
inspections to be completed over one complete growing season (by both the facility operator 
and the MPI inspector) for those pests for which MPI are not proposing to manage with 
specific testing but rather through growing season inspections.  
i. This is pre dominantly for fungi that are expected to exhibit symptoms within the first 
growing season, when plants are exposed to temperatures conducive to symptom 
expression.    
Ministry for Primary Industries   • 33 5.1.2  Level of quarantine  
(120) MPI propose that Citrus  plants  for planting  from MPI -approved offshore facilities complete post -
entry quarantine in a Level 3A greenhouse  (rather than 3B, as required for plants from non -
approved sources in the first growing season within PEQ; and rather than level 2, as was 
previously allowed for plants from approved sources) , provided  the residual risk is similar to 
plants provided for export to New Zealand by EMAI in Australia.   Level 3A PEQ is proposed for 
the following reasons:  
a) Based on measures applied at EMAI, a  Level 3A quarantine greenh ouse will appropriately 
manage the risk from residual pests where risk is not managed, or only partially managed, at 
an MPI -approved offshore facility . 
i. In the Citrus  import risk analysis, pests that met the criteria for additional 
measures are those that c annot be contained in a Level 3A post -entry 
quarantine facility and/or cannot be detected during one growing season in a 
Level 3A post -entry quarantine facility . 
- Some h igh impact pests of citrus  that meet the above criteria , namely Ceratocystis  
spp., Phyll osticta citricarpa  and Phytophthora  spp., are present in Australia 
(confirmed by DAWE ) and are only managed with regular plant inspections at EMAI . 
MPI consider Level 3A to be appropriate (rather than Level 3B) because the risk of 
these pests has been part ially managed with plants being contained in screenhouses 
as opposed to open fields.  
- MPI require s a higher level of certainty of pest freedom than is provided at  EMAI. 
Onshore testing, and observation of plants during post entry quarantine would 
provide th e level of certainty required that plants sourced from EMAI are free from 
these high impact pests.   
ii. There are some fungi that were not assessed past the hazard identification 
stage (of the import risk analysis process) because MPI determined that they 
were managed by the minimum requirements (i.e. containment in a Level 3A 
post-entry quarantine facility and/or detection during one growing season in 
Level 3A post -entry quarantine)11. Two high risk fungi that met these criteria  and 
which are unlikely to be appropriately managed in a Level 2 facility if they were 
present in imported material  include:  
-  Rhizoctonia noxia  (synonym Corticium koleroga ), which has a large host range, 
attacks t wigs, fruit and leaves of Citrus  trees . The spread of this  fungus  is assisted 
by wind, water and insects  (Dechassa, 2019) . The infrastructure and operations of a 
Level 2 facility may not appropriately contain the risk of this pest.  
- Pseudocercospora angolensis  is reported to cause spots and lesions on leaves, 
fruit, and stems of all citrus species, including grapefruit, lemon, orange, lime and 
tangerine. Pseudocercospora angolensis  is considered a quarantine pest for 
Europe. The sprea d of this fungus is assisted by wind and water (Ahmed  et al., 
2019).  The infrastructure and operations of a Level 2 facility may not appropriately 
contain the risk of this pest.  
b) Level 3A  PEQ  has the infrastructure to support the application of temperature regimes  which 
are an existing measure which MPI is proposing to retain and expand.  Level 2 PEQ does not 
have that infrastructure.  
 
11 Appendix 1: Summary of taxa excluded at hazard identification in the Citrus import risk analysis   
34 • i. Growing plants under temperature regimes  conducive to diseas e development is likely 
to provide the necessary  level of protection for various species of regulated bacteria, 
fungi and oomycetes . 
- This is particularly important for pests for which MPI are not proposing to manage 
with any specific measures which  include s Erysiphe quercicola , Fibroidium 
tingitaninum  and Plenodomus tracheiphilus . This is because the import risk analysis 
provided evidence to suggest that these pathogens are likely to exhibit disease 
symptoms if plants are exposed to specific temperatures.  Growing plants in a level 
of containment that relies on ambient temperature r educe s the level of confidence 
that plants are free from these pathogens .  
ii. There will be a lower level of certainty that plants are free from certain fungal 
pathogens if plants are  held in Level 2 PEQ , and thereby  not exposed to a broad range 
of temperatures conducive to disease expression. This applies to pathogens that MPI 
are proposing to manage only with growing season inspection  AND that are known to 
be present in Australia.  This is important because , there are no specific measures 
applied to manage these pathogens  at EMAI  other than regular plant health 
inspections .  
- This is particularly the case for Diaporthe  spp., Lasiodiplodia  spp., Australian citrus 
dieback and  Citrus blight. The import risk analysis did not provide specific details on 
temperature for these pathogens which emphasises the importance for exposing 
plants to a broad temperature range. This proposed level of risk management 
provides a greater level o f confidence that imported material is free from these 
pathogens.  
iii. It is important to note that the application of specific temperature requirements is 
required in the existing standard (i.e. plants must be held at temperatures between 18 –
25°C for the dura tion of quarantine). MPI are proposing to expand this regime to 
increase the effectiveness of growing season inspection as measure for pests that do 
not require specific testing.  
5.1.3 Transitional arrangement for plants imported from MPI -approved offshore 
facilities  
(121) With this option, MPI is proposing to institute a two -year transitional period whereby Citrus plants 
for planting sourced from MPI -approved offshore facilities can continue to complete post -entry 
quarantine in Level 2 greenhouses. This arrangeme nt will not  apply to plants from non -approved 
sources.  
Reasons for proposal for a transitional period  
(122) MPI routinely uses transitional arrangements when the changes being made to import 
requirements are so significant that industries need time to be able to comply with them.   
(123) However , this often means that there needs to be an accept ance of  the previous level of 
protection  during the transitional period, and a  concomitant  acceptance of the risks that are not 
managed by the previous level of protection . For Citrus  plants for planting,  it means accepting the 
previous level of protection for fungi, bacteria and oomycetes.   
(124) The most recent use of th e provision for a transitional period in the plants for planting context has 
been for Prunu s. MPI allowed a t wo-year transitional period whereby imports of Prunus  plants for 
planting from MPI -approved sources could continue to go into a Level 2 post -entry quarantine 
facility. This has allowed importation to continue while providing industry some time to make the 
necessary investments to meet the Level 3A requirements.   
Ministry for Primary Industries   • 35 
 New Zealand horticultural produce exports in 2019 were a record $6.2 billion*. Considering  
the value of these industries , the investment being made to expand export portfolios  and the 
essential need to continue to import new germplasm to maintain and further develop  these 
industries , there may be opportunity for the main industry bodies to coordinate investment 
into ensuring an ongoing supply of germplasm in a safe way.  
(125) After considering and balancing three  factors, MPI has proposed that the previous level of 
protection associated with Citrus  plants for planting be accepted for the transitional period . The 
considerations were :  
a) The challenge s for importers and the wider h orticulture sector  of adapting immediately to the 
new Level 3A post-entry quarantine  requirements . MPI  recogni ses that additional 
infrastructure investment  may be necessary , as currently there is more Level 2 post-entry 
quarantine capacity than there is Le vel 3A.  
b) The Plant Germplasm Import Council , comprising MPI and plant sector representatives , is 
currently  developing a plant germplasm import strategy . The  strategy work  will contemplate 
strategic choices affecting the plant germplasm import system, includ ing matters such as the 
potential for future government investment in quarantine infrastructure , cost recovery,  views 
about appropriate level of protection,  and risk management pre -border, at the border, and 
post-border . MPI acknowledges that there is some  uncertainty for importers and users of the 
import system while that work takes place, and that the uncertainty can affect investment 
decisions .  
c) The i mportance for the citrus industry to resume importation as quickly as possible . Allowing 
citrus material from MPI -approved facilities to continue to go into a Level 2 greenhouse 
enables importation to resume while the plant importers adapt to the new requirements.  
5.2 Import permit  
(126) As described in Part 1. 5 of the draft standard , an import permit will identify:  
a) The regulated pests for which screening  is required in New Zealand ; 
b) The minimum quarantine  period ; and  
c) The level of post -entry quarantine greenhouse in which consignments must be held . 
(127) Listing these requirements on the import permit is considered the best way to clearly identify the 
phytosanitary  measures that will be required for each consignment of Citrus  plants for planting 
after they arrive in New Zealand. This is because when plants are produced under an Export Plan  
or are  obtained from an MPI-approved offshore facility , some phytosanitary measures will have 
been applied prior to export. However, the exact measures which are applied will differ between 
facilities.  
(128) If plants are not obtained from an  MPI-approved source, the import permit will indicate that all 
phytosanitary measures described in the draft standard  must be applied after plants arrive in New 
Zealand, namely that:  
a) Plants must undergo all screening described in Part 2.3 of the draft standard  on arrival in 
New Zea land before they can become eligible for a biosecurity clearance . 
b) The minimum quarantine period will be 17 months , although this may be extended if 
regulated pests are detected  or if plants are slow growing . 
c) Plants must be deflasked and held in a Level 3B greenhouse for the first growing season . 
d) Plants may be transferred to a Level 3A greenhouse for the second growing season provided 
that all mandatory  testing has been completed with negative test results returned and plants  
36 • were effectively treated for any  regulated pests that were detected during the first growing 
season . 
(129) If plants are obtained  under an Export Plan , or from an MPI-approved o ffshore facility , some of 
the required phytosanitary measures will have been applied prior to import. In this case, t he 
import permit will identify the residual requirements that must be applied in New Zealand, 
including:  
a) The requirements of Part 2.3 of the draft standard that must applied in New Zealand ; 
b) The minimum quarantine period ; and  
c) The level of post entry quarantine greenhouse . 
(130) In this case, the length of the quarantine period and type of post entry quarantine greenhouse will 
depend on the specific regulated pests for which phytosanitary measures have been applied prior 
to export. This will be different for  each Export Plan or MPI-approved o ffshore facility . 
(131) The outcome of including the above details on the import permit will be that for all Citrus  plants for 
planting, regardless of source, all phytosanitary measures described in the draft standard  will be 
applied before plants become eligible for clearance.  
(132) As will be stated on the permit application form, when any permit assessment begins it is 
unknown if or when a permit will be issued. This is because until an assessment is started , MPI 
does not know what , if any, circumstances exist that would delay or prevent issuance of a permit. 
The MPI assessment will include checking the emerging risk register to ensure that any newly 
identified or emerging risks can be appropriately managed.  
5.3 Biosecurity clearanc e 
(133) Meeting the requirements of the standard is necessary  before imported plants for planting can be 
considered for biosecurity clearance. However, meeting all requirements  does not automatically 
guarantee biosecurity clearance. There are other restrictions for biosecurity clearance, as 
identified in sections 27 and 28 of the Act.  
(134) Section 27(2)(a) of the Act applies when considering biosecurity clearance for  consignments of 
plants for planting . This section states that an inspector must not give a clearance f or goods if 
they are  aware of any circumstances or documents associated with the goods that makes it 
unwise for the  goods  to be given biosecurity clearance.  
 As part of verifying that no such circumstances apply to high -value crops that may have been 
in po st-entry quarantine for a prolonged period, MPI will check the emerging risk register 
before goods are cleared.  
 If any risks are newly  identified , MPI may require additional phytosanitary measures to 
ensure that risk has been appropriately managed before plants are cleared. This may result 
in plants having to remain in quarantine whil e the newly identified risk is managed.  
 
  
Ministry for Primary Industries   • 37 References  
Ahmed, Y., Hubert, J., Fourrier -Jeandel, C., Dewdney, M.M., Aguayo, J. and Ioos, R (2019) A Set of 
Conventional and Multiplex Real -Time PCR Assays for Direct Detection of Elsinoe fawcettii , E. australis , 
and Pseudocercospora angolensis  in Citrus Fruits. Pl ant Disease, 103.  
Almeida, R  P; Pereira, E  F (2004) Multiplication and movement of a citrus strain of Xylella fastidiosa  
within sweet orange. Plant Disease , 85(4):  382–386. 
Bragard, C ; Dehnen‐Schmutz, K ; Di Serio, F ; Gonthier, P ; Jacques, M A ; ... Milonas,  P (2019) Update of 
the Scientific Opinion on the risks to plant health posed by Xylella fastidiosa  in the EU territory. EFSA 
Journal , 17(5) : e05665.  
Dechassa, N (2019) Occurrence, Distribution, Biology and Management of Coffee Thread Blight 
(Corticium koleroga ): A Review. Journal of Environmental and Earth Science, 9(2).  
Donovan, N, Chambers, G ; Englezou, A (2018) Protecting Australian citrus germplasm through 
improved diagnostic tools -CT14009. Hort Innovation Final Report.  
European Food Safet y Authority (EFSA)  (2014) Scientific opinion on the risk to plant health of 
Xanthomonas citri  pv. citri and Xanthomonas citri  pv. aurantifolii  for the EU territory. EFSA Journal, 
12(2): 3556.  
Ference, C  M; Gochez, A  M; Behlau, F ; Wang, N ; Graham, J  H; Jones, J  B (2018) Recent advances in 
the understanding of Xanthomonas citri  ssp. citri pathogenesis and citrus canker disease management. 
Molecular Plant Pathology , 19(6):  1302 –1318.  
Folimonova , S Y; Robertson , C J; Garnsey , S M; Gowda , S; Dawson , W O (2009) Examination of the 
responses of different genotypes of citrus to Huanglongbing ( citrus greening) under different conditions. 
Phytopathology , 99(12): 1346 –1354.  
Francis, M ; Lin, H ; Rosa, J  C; Doddapaneni, H ; Civerolo, E L (2006) Genome -based PCR primers for 
specific and sensitive detection and quantification of Xylella fastidiosa . European Journal of Plant 
Pathology , 115:  203–213. 
Frison , E A; Taher , M M (eds) (1991) FAO/IBPGR technical guidelines for the saf e movement of Citrus 
germplasm. Food and Agriculture Organization of the United Nations, Rome/International Board for 
Plant Genetic Resources, Rome.  
Markham, P  G (1983) Spiroplasmas in leafhoppers: a review. The Yale Journal of Biology and Medicine , 
56: 745–751. 
Mirzaee, M  R; Mohammadi, M ; Nasrabad, A  A (2009) Relative susceptibility of citrus genotypes to fruit 
rot caused by Ceratocystis radicicola in Iran. Tropical Plant Pathology , 34(5):  329–332. 
MPI (2016) Pest Risk Assessments: Citrus  spp. nursery stoc k. Ministry for Primary Industries; 
Wellington, New Zealand.  
MPI (2020) T echnical advice on:  Considerations for the import of leafless budwood of Citrus  spp. from 
Elizabeth Macarthur Agricultural Institute (EMAI) . Ministry for Primary Industries; Wellingto n, 
New Zealand.  
Navarro, B ; Minutolo, M ; De Stradis, A ; Palmisano, F ; Alioto, D ; Di Serio, F (2018a) The first phlebo -like 
virus infecting plants: a case study on the adaptation of negative -stranded RNA viruses to new hosts. 
Molecular Plant Pathology , 19(5): 1075 –1089.  
Navarro, B ; Zicca, S ; Minutolo, M ; Saponari, M ; Alioto, D ; Di Ser io, F (2018b) A negative -stranded RNA 
virus infecting citrus trees : The second member  of a new genus within  the Order Bunyavirales. Frontiers 
in Microbiology , 9: 2340.   
38 • Plant & Food Research (2019) Fresh Facts: New Zealand Horticulture . The New Zealand Inst itute for 
Plant and Food Research Ltd, Auckland , New Zealand.  
Ribeiro, R  V; Machado, E  C; Oliveira, R  F (2004) Growth and leaf temperature effects on 
photosynthesis of sweet orange seedlings infected with Xylella fastidiosa . Plant Pathology , 53: 334–
340. 
Roistacher, C  N (1991) Graft -transmissible diseases of citrus, Handbook for detection and diagnosis of 
graft-transmissible diseases of citrus. FAO (Food and Agriculture Organization of the United Nations).  
Shi, J ; Pagliaccia, D ; Morgan, R ; Qiao, Y ; Pan, S ; Vidalakis, G ; Ma, W (2014) Novel diagnosis for citrus 
stubborn disease by detection of a Spiroplasma citri -secreted protein. Phytopathology , 104(2) : 188–195. 
Silveira, L  K; Pavão, G  C; dos Santos Dias, C T ; Quaggio, J  A; de Matos Pires, R  C (2020)  Deficit 
irrigation effect on fruit yield, quality and water use efficiency: a long -term study on Pêra -IAC sweet 
orange. Agricultural Water Management , 231:  1–9. 
Timmer , L W; Garnsey , S M; Broadbent , P (2000) Compendium of Citrus Diseases  (2nd edition). AP S 
Press ; St Paul, Minnesota, USA.  
Yokomi, R  K; Mello, A  F S; Saponari, M ; Fletcher, J (2008) Polymerase chain reaction -based detection 
of Spiroplasma citri  associated with citrus stubborn disease. Plant Disease , 92: 253–260. 
Zespri 2019/2020 Annual Report - kiwifruit product hectares  
Suggest reference: Zespri (2020) Annual Report 2019/20.  
Fresh Facts 2019  - wine production hectares  
  
0 • Appendix : Proposed schedule of testing for pests on Citrus  plants for planting  
Pest  Proposed Test  Season 1 Testing Schedule  
On-arrival  Spring (4 months)  Summer (4 months)  
After three months at 
25°C  After one month at 
29°C  
Ceratocystis spp. PCR  ✓    
Phyllosticta citricarpa  PCR  ✓    
Phytophthora spp. PCR  ✓    
Apple stem grooving virus  PCR   ✓   
Citrus chlorotic dwarf -associated 
virus  PCR or biological indexing   ✓   
Citrus leaf rugose virus  PCR   ✓   
Citrus leprosis virus C  PCR   ✓   
Citrus leprosis virus C2  PCR   ✓   
Citrus psorosis virus (strains not in 
New Zealand)  PCR or biological indexing   ✓   
Citrus sudden death -associated 
virus  PCR or biological indexing   ✓   
Citrus variegation virus  PCR   ✓   
Citrus yellow mosaic virus  PCR   ✓   
Citrus yellow vein clearing virus  PCR   ✓   
Indian citrus ringspot virus  PCR   ✓   
Olive latent virus 1  PCR   ✓   
Satsuma dwarf virus  PCR or biological indexing   ✓   
‘Candidatus Liberibacter  spp. PCR    ✓  
Xanthomonas citri subsp . citri  PCR    ✓  
‘Candidatus Phytoplasma’ spp. PCR    ✓  
Citrus bark cracking viroid (Citrus 
viroid IV)  PCR AND biological indexing    ✓  
Citrus bent leaf viroid (Citrus viroid 
I) PCR AND biological indexing    ✓   
Ministry for Primary Industries   • 1 Citrus viroid V  PCR AND biological indexing    ✓  
Citrus viroid VI  PCR AND biological indexing    ✓  
Hop stunt viroid (Citrus viroid II)  PCR    ✓  
Spiroplasma citri  PCR     ✓ 
Xylella fastidiosa  PCR     ✓ 
  Season 2 Testing Schedule  
   Spring ( 3 months)  Summer (4 months)  
    After three months at 
25°C  After one month at 
29°C  
Ceratocystis spp. PCR    ✓  
Phyllosticta citricarpa  PCR    ✓  
Phytophthora spp. PCR    ✓  
‘Candidatus Liberibacter  spp. PCR    ✓  
Spiroplasma citri  PCR     ✓ 
Xylella fastidiosa  PCR     ✓