Risk Management Proposal:  
Persea americana  plants for planting import 
health standard  
MPI.IHS.PERSEA.PFP  
 
 
 
 
 
 
 
 
 
 
 
Prepared for  public consultation   
by Plant Germplasm Imports  
Animal and Plant Health Directorate  
 
 
 
 
 
 
 
 
June 2022 
 
 
Disclaimer  
 
While every effort has been made to ensure the information in this publication is accurate, 
the Ministry  for Primary Industries does not accept any responsibility or liability for error of 
fact, omission, interpretation or opinion that may be present, nor for the consequences of any 
decisions based on this information.  
 
This publication is also available on t he Ministry for Primary Industries  website at  
http://www.mpi.govt.nz/news -and-resources/publications/   
 
 
© Crown Copyright – Ministry  for Primary Industries   
i Contents  Page 
 
1. Submissions  1 
1.1 Official Information Act 1982  1 
2. Context to consultation  2 
2.1 International regulation of risk goods  2 
2.2 Domestic regulation of biosecurity risks associated w ith plants for planting  2 
3. General information  3 
3.1 Purpose  3 
3.2 Background  3 
3.3 Scope of the draft standard  3 
3.4 Scope of the import risk analysis  4 
4. Pests associated with Persea americana  plants for planting  5 
5. Rationale for the proposed phytosanitary measures  7 
5.1 Environmental conditions in post -entry quarantine  8 
5.2 Pests to be managed under existing specific measures  10 
5.3 Pests requiring only inspection in PEQ  10 
5.4 Fungal pests requiring inspection in PEQ and specific testing  10 
5.5 Non-fungal pests requiring specific testing  11 
6. Feasibility of proposed measures  12 
6.1 Level 3B for Persea americana  plants for planting from non -approved sources  12 
6.2.   Post -entry requirements for Persea americana  plants for planting from MPI -approved 
sources  13 
6.3 The availability of specific testing methods  13 
6.4 Changes to presentation in the inspection and testing requirements  14 
7. References  15 
8. Appendix 1: Pests proposed for risk management in the proposed new standard  16 
8.1 Avocado sunblotch viroid  16 
8.2 ‘Candidatus Phytoplas ma’ spp.  17 
8.3 Colletotrichum  spp. 18 
8.4 Diaporthe perseae  20 
8.5 Lasiodiplodia pseudotheobromae  and Neofusicoccum nonquaesitum  21 
8.6 Neocosmospora perseae  23 
8.7 Pestalotiopsis longiseta  24 
8.8 Phytophthora palmivora  25 
8.9 Potato spindle tuber viroid  26 
8.10  Xylella fastidiosa  28  
Ministry for Primary Industries   Persea americana  risk management proposal  • 1 1. Submissions  
The Ministry for Primary Industries (MPI) invites comment from interested parties on the 
proposed new  import health standard  Persea americana  Plants for Planting  (the standard). 
The proposed import health standard is supported by this risk mana gement proposal.  
 
An import health standard (IHS) “specifies requirements to be met for the effective 
management of risks associated with importing risk goods, including risks arising because 
importing the goods involves or might involve an incidentally imported new organism.” 
(Biosecurity Act , 1993 , sec. 22) 
 
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 would like fee dback  on the proposed risk management measures for the importation of 
P. americana  leafless cuttings . 
 
Include the following  in your submission :  
• The title of the consultation document in the subject line of your email  
• Your name and title  
• Your organisation’s name (if applicable)  
• Any technical information you have that supports your submission.  
Send submissions to  PlantImports@mpi.govt.nz  by 10 August 2022.   
 
While w e prefer email, if  you would like to send your submission by post, you can mail it  to: 
 
Plant Germplasm Imports  
Animal and Plant Health  Directorate  
Biosecurity New  Zealand   
Ministry for Primary Industries  
PO Box 2526  
Wellington 6140  
New  Zealand   
 
Submissions received by  10 August 2022  will be considered during the development of the 
final  standard . Submissions received after the clos ing date may be held on file for 
consideration when the issued standard  is next revised/reviewed.  
1.1 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 Of ficial Information Act 1982 (OIA). The OIA 
specifies that information is to be made available 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 info rmation contained in their submission, such as information being  
commercially sensitive or personal. Any decision to withhold information requested under the 
OIA is reviewable by the Ombudsman . 2 • Persea americana  risk management proposal  Ministry for Primary Industries  2. Context to consultation  
2.1 International regulation of risk g oods  
“The World Trade Organization Agreement on the Application of Sanitary and Phytosanitary 
Measures (SPS Agreement) sets in place rules that protect each country’s sovereign right to 
take the measures necessary to protect the life or health of its peopl e, 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 the international movement of goods. 
The SPS Agreement guides how New  Zealand  sets sta ndards and makes decisions related to 
biosecurity.” (MAF et al., 2009, p. 1)  
 
“In particular, [it is] important to maintain the standards of transparency and scientific rigour 
required by the SPS Agreement and to make decisions as quickly as possible. This  will 
encourage other countries to comply with the rules of the SPS Agreement and also 
demonstrate that New  Zealand ’s strict controls are justified to countries that challenge them.” 
(MAF et al., 2009, p. 13)  
2.2 Domestic regulation of biosecurity risks as sociated with plants for planting  
The New  Zealand  biosecurity system is regulated through the Biosecurity Act 1993 (the Act).  
Section 22(1) defines the purpose of an import health standard: “An import health standard 
specifies requirements that must be met  for the  effective manage ment of  risks associated with 
importing risk goods, including risks arising because importing the goods involves or might 
involve an incidentally imported new organism”.  
 
MPI is the New  Zealand  government ministry responsible for maintaining biosecurity 
standard s for the effective management of risks associated with the importation of goods and 
craft into New  Zealand  (Part 3, Biosecurity Act 1993).  
 
MPI is committed to the principles of transparency and evidence -based technical justification 
for all phytosanitar y measures, new and amended, imposed on importing pathways.  
 
   
Ministry for Primary Industries   Persea americana  risk management proposal  • 3 3. General information  
3.1 Purpose  
(1) The purpose of this document is to:  
a. provide relevant background information about the proposed draft Persea 
americana  plants for planting import health standard  (‘the standard ’); 
b. clarify the scope of the draft standard including a description of the 
commodity ; 
c. provide the rationale for the proposed risk management measures  and how they 
manage risk; and  
d. provide informatio n to support consultation about  the draft standard . 
3.2 Background   
(2) Avocados a re one of  New  Zealand ’s dominant fruit export products , reaching a record 
export revenue of NZ$112 million for the year ending June 2020.  Most commercial 
production is in the Bay of Plenty and Northland  (Fresh Facts , 2020) . 
(3) The New  Zealand  avocado industry has developed a strategy for continual growth 
(New  Zealand  Avocado) . Having a ccess  to the varieties that are released for 
commercialisation in  other parts of the world will help the industry meet growth targets . 
Additionally, new imported varieties are necessary to maintain active breeding 
programmes , which will further support the growth of the industry . 
(4) P. americana  plants for planting have previously been imported under the Persea  
schedule of MPI ’s import heath standard  Importation of Nursery Stock  (155.02.06 ). 
Import requirements have been reviewed to ensure that biosecurity risks known to be 
associated with P. americana  leafless cuttings  are appropriately managed . The publication 
of a new import health standard will allow importation to resume on a pathway that has 
not been traded on since 2006.  
(5) The proposed import requirements are based on information in the MPI I mport Risk 
Analysis : Persea americana  Plants for Planting . The risk analysis is available on the 
biosecurity consultations page of the MPI website under the heading Draft import health 
standard for Persea americana  plants for planting . 
3.3 Scope of the draft standard  
(6) The draft standard  proposes phytosanitary import requirements for importing 
P. americana  from all countries, into New  Zealand  for the purpose of  propagation. The 
commodity types that will be eligible for import under the new standard  are P. americana  
leafless cuttings and plants in vitro.  
(7) The existing  Persea  schedule  in the MPI standard Importation of Nursery Stock  
(155.02.06 ) will be removed and replaced by the new Persea americana  Plants  for 
Planting  import health standard once it is issued.  
(8) Other species listed in MPI’s Plants Biosecurity Index  (i.e. Machilus thunbergii , Persea 
borbonia , P. lingue  and P. thunbergii ) will not be eligible for importation under this 
standard  because there was no desire to import these species, and they are unlikely to be 
needed in the future. T he risk assessment therefore only investigated  pests and disease s 4 • Persea americana  risk management proposal  Ministry for Primary Industries  associated with P. americana . The nursery stock import specification  on the Plants 
Biosecurity Index  for the  remaining Persea schedule species will change  from ‘L3 see 
155.02.06 under Persea’  to ‘requires assessment’. This means that further  risk assessment 
will be required before  a permit to import for those species  can be is sued.  
(9) Our risk assessment did not identify which pests and diseases are specifically associated 
with plants in vitro. Because of this, plants in vitro  will need to meet the same import 
requirements as leafless cuttings .  
3.4 Scope of the import risk analysis  
(10) The draft standard  is underpinned by the Import Risk Analysis: Persea americana  
Plants for Planting . The purpose of  the risk analysis  is to determine the level of risk that 
pests and disease s, which  could be associated with an imported plant for p lanting,  pose to 
New  Zealand .  
(11) For this import risk analysis,  when assessing risk from individual pests, it was 
assumed that a set of minimum phytosanitary measures will be applied to all avocado 
plants imported under the standard. Any pests that were identified as being managed by 
the minimum measures were not considered beyond the hazard ID stage of the import risk 
analysis.  
a. Pests that were identified as being managed by the minimum measures are not 
listed in the IHS, but are identified in the Official New Zealand Pest Register  
(ONZPR).  
(12) Pests and diseases  that meet , or pote ntially meet , the criteria for phytosanitary 
measures over and above those minimum measures are pests  that: 
a. cannot be contained in a Level 3A post -entry quarantine facility  (and therefore 
need to be in Level 3B) ; and/or  
b. cannot be detected based on expressi on of visual symptoms during a period of 
active growth over a minimum  12 months , which is the minimum post-entry 
quarantine time currently required for P. americana ). 
(13) Some traits that indicate that additional measures will be required include:  
a. ability of the pathogen to produce wind -dispersed spores.  
b. ability of the pathogen to be latent for long periods (more than the minimum 
post-entry quarantine period , such as fungi that are endophytic  for part of their 
life cycle ); 
c. tendency of the pathogen t o only show symptoms under certain growing 
conditions, such as when the plants are stressed . 
(14) Each pest risk assessment  in the risk analysis  addresses the following : 
a. Likelihood of entry ; 
i. the strength or frequency of the association with P. americana  leafles s 
cuttings . 
ii. the likelihood of entry given the application of treatments  (i.e. 
pesticides and sodium hypochlorite treatment) and pre-export  plant 
health  inspections.  
b. Likelihood of exposure and establishment ;   
Ministry for Primary Industries   Persea americana  risk management proposal  • 5 i. the ability of the pest or disease to move from imported P. americana  
leafless cuttings  and into a suitable environment to allow establishment 
(exposure) . 
ii. the suitability of the New  Zealand  environment for the pest or disease 
(including climate, host plants an d vectors) . 
iii. the conditions necessary for the pest or disease to spread . 
c. The potential impacts in New  Zealand . 
i. economic impacts on P. americana  and other economically important 
plants (symptoms on individual plants, crop yield, costs of management 
practices , trade restrictions, etc .). 
ii. environmental impacts . 
iii. sociocultural impacts . 
iv. human health impacts . 
(15) Measures proposed in this risk management proposal are based on a consideration of 
the above factors .  
4. Pests associated with Persea americana  plants for planting  
 
(16) The p ests in this section  meet MPI’s  criteria for additional  measures1 (over and above 
inspecting plants grown under ambient conditions in a quarantine greenhouse) . This is  
based on evidence that : 
a. the pest s may not be detected  by gro wing season inspection under ambient 
greenhouse conditions; and/or  
b. the pests may have unacceptable economic impacts  and sometimes 
environmental impacts ( potential economic and environmental impacts for 
each pest are given in more detail in Appendix 1).  
(17) Table 1 summarises the pests for which MPI proposes additional measures to manage 
the risk on imported P. americana  leafless cuttings . To appropriately manage each pest 
listed in Table 1 , MPI is proposing  some or all of the following phytosanitary  measures : 
a. Growing -season inspections  while plants are in  Level 3B post-entry quarantine  
for a minimum period of 12 months ; 
i. There will be regular plant inspections by facility operators when plants 
are in active growth and scheduled inspection s by an MPI inspector 
during this period.  
b. Applying  specific environmental conditions conducive to expression  of visible 
disease symptoms and/or increasing pest  titre.  
i. This will facilitate the retention of a minimum 12 -month quarantine 
period because some  pests would require longer quarantine times if 
plants were  grown at ambient temperatures.  
 
1 Pests that did not meet the criteria for requiring pest risk assessment and the rationale for their exclusion, are listed in Appendix 1 of Import 
Risk Analysis: Persea americana  Plants for Planting.  6 • Persea americana  risk management proposal  Ministry for Primary Industries  c. Specific pest testing using methods such as polymerase chain reaction (PCR) 
assay or plating onto suitable isolation medium . 
i. This is in combination with growing seas on inspections while plants 
are in post -entry quarantine.  
Table 1. Pests of Persea americana  proposed for management in accordance with measures in 
the draft standard  
Pest  Proposed measureǂ Season to 
be tested  Minimum 
level of 
containment  
Bacteria     
Xylella fastidiosa ^ Two sets of PCR  and 
growing season inspection in 
a temperature -controlled 
environment  Summer  Level 3 A  
Fungi     
Colletotrichum spp.*  Growing season inspection  
in a temperature -controlled 
environment   Level 3A or 
Level 3 B  
Diaporthe perseae ^ Growing season inspection  
in a temperature -controlled 
environment   Level 3B  
Lasiodiplodia pseudotheobromae  Plating onto suitable isolation 
medium  or PCR  Summer  Level 3B  
Neocosmospora perseae  Growing season inspection  
in a temperature -controlled 
environment   Level 3B  
Neofusicoccum nonquaesitum  Plating onto suitable isolation 
medium  or PCR  Summer  Level 3B  
Pestalotiopsis longiseta  Growing season inspection  
in a temperature -controlled 
environment   Level 3A   
Ministry for Primary Industries   Persea americana  risk management proposal  • 7 Oomycetes     
Phytophthora palmivora ^ Two sets of PCR  and 
growing season inspection in 
a temperature -controlled 
environment  Summer  and 
on-arrival  Level 3A  
Phytoplasmas     
‘Candidatus  Phytoplasma’ spp.  PCR  Summer  Level 2  
Viroids     
Avocado sunblotch viroid ^ Two sets of PCR  Summer  Level 2 
Potato spindle tuber viroid ^ PCR  Summer  Level 3A  
* Colletotrichum aenigma , C. chrysoph ilum, C. endophyticum , C. jiangxiense , C. nymphaeae , C. queenslandicum , and C. 
tropicale . 
ǂ Specific testing is in addition to growing season inspection . 
^ These pests are managed on the existing Persea  schedule in the IHS:  Importation of Nursery Stock  
5. Rationale for the proposed phytosanitary measures  
 
(18) For P. americana  leafless cuttings  being imported from anywhere in the world from a 
non-approved source  (i.e. not from an MPI -approved offshore facility) , MPI is proposing 
a minimum quarantine period of 12 months in a Level 3 B post-entry quarantine 
greenhouse.  
(19) Containment in a Level 3B gre enhouse is considered to appropriately manage 
biosecurity risk for the following reasons:  
a. Pests which can be transmitted by wind are appropriately managed in a Level 
3B quarantine facility (this applies to Lasiodiplodia  pseudotheobromae , 
Neofusicoccum  nonq uaesitum , Colletotrichum  spp. in the gloesporiodes  
species complex2, and potentially Neocosmospora  perseae  and 
Diaporthe  perseae ). 
i. Level 3B greenhouses are fitted with HEPA filtration and operate under 
negative pressure, which will suitably contain any windborne spores.  
ii. Windborne spores produced by these pests may not be managed in a 
lower level of quarantine facility, given that spo res could pass through 
insect mesh if sufficient air movement occurs.  
b. Risk from insect borne pests, including X. fastidiosa  and Phytoplasma spp., are 
appropriately managed in a Level 3B greenhouses given that this type of 
greenhouse will exclude all insect  vectors of these pests . 
c. Risk from water - and soil -borne pests, for example Phytophthora palmivora , 
are appropriately  managed in a Level 3B quarantine facility via requirements 
to decontaminate wastewater, and implement facility hygiene measures that 
preve nt the removal of any untreated soil or plant debris from the facility . 
 
2 The Colletotrichum  species identified for management i n the Colletotrichum gloeosporioides species  complex are:  Colletotrichum 
aenigma, C. chrysophilum, C. endophyticum, C. jiangxiense, C. queenslandicum and C. tropicale  8 • Persea americana  risk management proposal  Ministry for Primary Industries  d. Risk from pests which are dispersed by rain splash ( Colletotrichum spp in the 
acutatum species complex3 and Pestalotiopsis longiseta ) will be appropriately 
managed in a Level 3B facil ity given that requirements for filtration of 
outgoing air will prevent rain -borne spores exiting the facility.  
(20) The infrastructure offered by Level 3 B facilities, such as the ability to apply temperature 
regimes to increase pest titre , is considered necess ary to increase the likelihood of disease 
expression or detection using specific testing.  
a. Ambient greenhouse temperatures will not achieve the temperature ranges 
known to maximise the likelihood of visible symptom development  and/or 
increased disease titre  prior to testing.   
b. Exposing plants to specific temperature ranges will allow the quarantine period 
to remain at a minimum of 12 months. If plants are only grown in ambient 
temperatures, it is likely that they will require a longer quarantine period to 
capture additional growth flushes.  
(21) A minimum of 12 months in post -entry quarantine is considered necessary because:  
a. Periods of summer -like, spring -like, and autumn -like environmental conditions  
in post -entry quarantine  (which equates to approximately 12 months) will 
maximise pest titre and increase the likelihood of detection either by 
expression of visible symptoms, or by enabling reliable detection using 
specific testing.  
i. Two summer flushes are required to favour sym ptom expression or 
testing titre of some pests in Table 1 , such as Xylella fastidiosa, 
Avocado Sunblotch Viroid, and Phytoplasma spp. These pests can have 
uneven distribution , non-linear expression , or latent periods  which can 
lead to false -negative testin g results . 
ii. Periods of spring -like and autumn -like environmental conditions are 
required to mimic the natural plant lifecycle. The  changes in 
environmental conditions could also  favour pest symptom expression 
where the conditions required for expression are  unknown , or where 
the pest is unknown .   
b. A 12 -month quarantine period is only indicative and will start when  grafted 
plants are observed to be in active growth. The actual time that plants are in 
post-entry quarantine could be longer if plants are slow to  enter active growth.  
5.1 Environmental conditions in post -entry quarantine  
(22) The following environmental conditions are proposed during post-entry quarantine to 
maximise the detection of pest s4. The proposed conditions are based on the natural 
lifecycle of the plants, with temperatures which favour pest symptom expression and 
testing titre  without overly stressing the plant . The conditions omit a winter -like period 
because avocado plants do not e nter a period of true dormancy.  
a. Growing plants in summer -like conditions, with temperatures within the  range 
of 25±3 ºC, for the first four months of post -entry quarantine.  
 
3 The Colletotrichum species identified for management in the Colletotrichum acutatum species  complex is Colletotrichum  nymphaeae.  
4 Work is underway to clarify the operational parameters for implementing temperature ranges. Amendments to the standard regard ing this 
may be made at a later date.   
Ministry for Primary Industries   Persea americana  risk management proposal  • 9 b. Following this, growing plants in autumn -like conditions, with temperatures 
that ca n range between 21±3  ºC, for two months.  
c. Following this, growing plants in spring -like conditions, with temperatures that 
can range between 19±3 °C, for three months.  
d. Following this, growing plants in summer -like conditions, with temperatures 
that can range  between 25±3 ºC, for three months.  
(23) Periods of increased or decreased relative humidity are not proposed  during  
P. americana post-entry quarantine . Rather, standard operational humidity conditions 
during quarantine  (those required for active  plant growth which do not  supress pest 
symptom expression ), should be sufficient to allow for pest symptom express ion.  
(24) To ensure measures remain feasible and consistent  with other recently published 
standards , where pests are common between P. americana and other  recently  published 
import health standards, the risk management measures are being kept consistent , unless 
otherwise justified. Growing the plants under ambient humidity and varying temperatures  
aligns with the recently published Citrus Plants fo r Planting , and Prunus Plants for 
Planting IHSs.  
a. Pests in common between P. americana and other recently published IHS’s are 
summarised in Table 2. Of the pests which are common between existing 
standards , only Lasiodiplodia pseudotheobromae  is proposed to be managed 
by different measures on P. americana  (by testing during post -entry 
quarantine ). The additional level of protection is considered justified due t o the 
uncertain conditions for pest symptom expression  (including th e potential for  
latent or endophytic infection) com bined  with the shorter quarantine period 
proposed for P. americana . 
Table 2. Pests in common on Actinidia, Prunus, Citrus, and Persea americana , from non -
approved sources, with instituted and proposed meas ures 
Pests  Generic and/or specific risk management measures in place  Proposed measures  
Actinidia  Prunus  Citrus  Persea americana  
Colletotrichum spp. Growing season in 
temperature and 
humidity -controlled 
environment   Growing season in 
temperature -
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  Growing season in 
temperature -
controlled  
environment  
Lasiodiplodia 
pseudotheobromae    Growing season 
inspection  Growing season 
inspection  
AND PCR or Plating  
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  Growing season in 
temperature -
controlled  
environment AND 
PCR or plating  
Phytoplasmas  PCR  PCR  PCR  PCR  
Xylella fastidiosa   Growing season in 
temperature -
controlled  
environment AND 2x 
PCR  Growing season in 
temperature -
controlled  
environment AND 2x 
PCR  Growing season in 
temperature -
controlled  
environment AND 2x 
PCR  10 • Persea americana  risk management proposal  Ministry for Primary Industries   
(25) The next subsections (5. 2 to 5.5) summarise the common themes that were considered 
when determining the appropriate strength of measure for each of the pests below. The 
detailed risk management evaluation of the risk assessment evidence for each pest is given 
in Appendix 1.  
5.2 Pests to be managed under existing specific measures  
(26) For Avocado sunblotch viroid  and Diaporthe perseae , MPI is proposing to retain the 
existing phytosanitary measures for  the following reason s: 
a. the risk assessment concluded that Avocado sunblotch viroid  could be 
contained in L evel 2 post -entry quarantine and specific testing via PCR is 
warranted; and  
b. the risk assessment concluded that D. perseae  does not appear to be a high 
impact pest of avocado and additional measures are not needed at this time . 
5.3 Pests requiring only inspection in PEQ   
(27) For Colletotrichum spp., Neocosmospora perseae  and Pestalotiopsis longiseta , MPI is 
proposing to: 
a. expose plants to summer -like temperatures within the range of 25±3  ºC during 
quarantine  to encourage disease  symptom development ; and  
b. inspect plants for any signs or symptoms of disease while they  are growing in a 
Level 3B post-entry quarantine facility  for a minimum period of 12 months .  
(28) This proposal has considered the following findings . 
a. These pests have  been isolated from avocado trees exhibiting disease 
symptoms  in the field . 
b. These pests have been isolated from  parts of avocado trees that could be used 
for leafless cuttings . 
c. There is no evidence to suggest that symptoms would not be observed in 
imported  P. americana  plants for planting during a minimum 12 -month 
post-entry quarantine period.  
d. Pathogenicity testing of these pests indicates that exposing plants to a 
minimum of 25 ºC during active growth favour s disease expression.  This would 
enable the new standard to retain a minimum 12 -month quarantine period.  
e. These pests produce conidia that can be transferred by rain/water splash 
carried by  wind.  
5.4 Fungal p ests requiring inspection in PEQ and specific testing  
(29) For Lasiodiplod ia pseudotheobromae  and Neofusicoccum nonquaesitum , MPI is 
proposing to :  
a. expose plants to summer -like temperatures of 25±3  ºC during quarantine  to 
encourage disease symptom development; and /or increase  pest titre ;   
Ministry for Primary Industries   Persea americana  risk management proposal  • 11 b. inspect plants for any signs or symptoms of disease  while they are growing in a 
Level 3B post-entry quarantine facility  for a minimum period of 12 months ; 
and  
c. test samples taken from plants during summer by PCR or plating  onto suitable 
isolation medium.   
(30) This proposal has considered the  following findings . 
a. These pests have been isolated from avocado trees exhibiting disease 
symptoms in the field . 
b. These pests have been isolated from parts of avocado trees that could be used 
for leafless cuttings . 
c. These pests produce conidia that can be tr ansferred by rain/water  splash 
carried by  wind .  
d. These fungi all originate from the same family . Fungi in this family are  known 
to live inside plants without causing symptoms.  
i. L. pseudotheobromae  has been isolated from asymptomatic tissues in 
other host plants and therefore have the potential to be associated with 
avocado without causing symptoms.  
e. Pathogenicity testing of these pests indicates that exposing plants to a 
minimum of 25 ºC during active growth would favour the development of the 
pest to e nsure a sufficient titre for likely detection by plating  or PCR . This 
would enable the new standard to retain a minimum 12 -month quarantine 
period.  
5.5 Non-fungal p ests requiring specific testing  
(31) For ‘Candidatus  Phytoplasma’ spp., Phytophthora palmivora , Potato spindle tuber 
viroid  and Xylella fastidiosa , MPI is proposing to:  
a. expose plants to summer -like temperatures of 25±3  ºC during quarantine  to 
encourage disease symptom development and/or increase pest titre;  
b. inspect plants fo r any signs or symptoms of disease  while they are growing in a 
Level 3B post-entry quarantine facility for a minimum period of 12 months; 
and  
c. test samples taken from plants during at least one of the summer growing 
seasons  for PCR testing.  
i. For Phytophthora palmivora , MPI propose t wo PCR tests, the first on -
arrival at the quarantine facility, and the second during the second 
summer -like growing season. The on -arrival test provides some level of  
assurance of pest absence very early in the quarantine process and 
aligns with the appropriate level of protection applied for this pest in 
other recently published IHS’s ( Prunus Plants for Planting  and Citrus 
Plants for Planting ).  
ii. For the high impact pest, Xylella fastidiosa , MPI pro pose s two PCR 
tests, one completed in each ‘summer -like’ growing season of post -
entry quarantine. This is because Xylella fastidiosa  can be unevenly 12 • Persea americana  risk management proposal  Ministry for Primary Industries  distributed throughout infected plants, which could produce false 
negative test results (section 8.10 provi des more detail on this).  
(32) This proposal has considered the following findings . 
a. These pests have been frequently isolated from asymptomatic host plants 
including avocado , meaning that inspection alone is not an effective risk 
mitigation . 
b. These pests have been isolated from parts of avocado trees that could be used 
for leafless cuttings . 
c. These pests are known to inflict unacceptable economic and environmental 
impacts , a factor which elevates the risk of the pest.  A sensitive molecular test 
provides the appropriate level of assurance of pest freedom  and is considered 
to be a measure commensurate with the pest risk . 
d. Phytophthora palmivora  can produce spores  that can be transferred by water 
and wind (via water droplets) . 
e. Some pests can be vectored by aphids , therefore  the facility  must be capable of  
physically excluding aphids.  Level 3A and 3B quarantine facilities  can 
provide the necessary insect exclusion . 
f. Pathogenicity testing of these pests indicates that exposing pla nts to a 
minimum of 25ºC during active growth would favour the development of the 
pest to ensure a sufficient titre for likely detection by PCR. This would enable 
the new standard to retain a minimum 12 -month quarantine period.  
g. Managing the risk of these pests on imported P. americana  with PCR aligns 
with the level of protection currently in place for other horticulture and 
ornamental species that these pests are also regulated on.  
6. Feasibility of proposed measures  
 
(33) This section will assess the feasibility of achieving the suite of measures being 
proposed to appropriately manage the risk s associated with  imported  P. americana  
leafless cuttings .  
6.1 Level 3 B for Persea americana  plants for planting from non -approved 
sources  
(34) The level of containment that is proposed for Persea americana  budwood from non -
approved sources, anywhere in the world is Level 3B. As detailed above in Table 1, this 
level of containment is appropriate for c ontaining the spread of some fungal pests for 
which MPI is proposing to manage with growing season inspection only. Furthermore, 
this aligns with the level of containment required for other horticulture crop species 
imported from non -approved sources, for which MPI has no prior knowledge of the 
phytosanitary measures applied to the plants before export.  
(35) MPI is aware that there is Level 3B capacity reserved to accommodate importation of 
Persea americana  budwood with the issue of the new standard.  
(36) The infras tructure in Level 3B allows for the application of specific environmental 
controls such as temperatures that are likely to be conducive to symptom expression or 
increased pest titre for specific testing. Additionally, as stated earlier, the HEPA filtration   
Ministry for Primary Industries   Persea americana  risk management proposal  • 13 and negative air pressure will prevent any airborne conidia from entering the environment 
outside containment.  
6.2. Post -entry requirements for Persea americana  plants for planting from MPI -
approved sources  
(37) MPI is not proposing risk management measures f or P. americana imported from an 
MPI approved offshore facility at this time. Historically, there has not been an MPI  
approved source for P. americana  leafless cuttings . This means that imported material 
must undergo the full suite of testing and growing s eason inspections to be considered for 
biosecurity clearance into New  Zealand.  
(38) Plants from MPI -approved offshore facilities are expected to have a lower risk profile 
than plants from non -approved sources . This is because some pest risk is managed before 
export , through generic risk management measures  that include:  
a. Containing source plants in screenhouses that exclude many disease vectors 
(such as aphids and whiteflies) . 
b. Insect control programmes ( e.g. regular spray programmes and/or monitoring 
of sticky traps) . 
c. Growing plants in sterilised or inert medium and out of contact with the 
ground, with watering generally done using drip irrigation, thereby reducing 
likelihood of association with some pests including some fungi, bacteria and 
oomycetes.  
d. Regularly monitoring plant health and applying preventative or curative 
pesticide treatments as needed . 
e. Specific pre -export testing for some pests listed in the import health standard. 
In particular, on other commodities, this is done for phytoplasmas, viroid s and 
viruses.  
(39) MPI’s offshore facility  approval process assesses a facility’s structural and operational 
phytosanitary screening programme against MPI’s Standard for Offshore Facilities 
Holding and Testing Plants for Planting  (MPI, 2019). This process not only indicates if a 
facility meets  the requirements of this standard , and therefore can be approved under this 
standard, but assists with determining the residual pest risk that needs to be managed in 
post-entry quarantine.  Key information on  offshore mana gement of  P. amerciana  is not  
currently  available, so a decision on the onshore quarantine requirements cannot be made 
at this stage . 
a. For other plants for planting species such as Citrus , Malus  and Prunus  that are 
imported from facilities that have a long history of being MPI -approved, there 
is a comprehensive understanding of the phytosanitary operations carried out at 
those facilities. Therefore, MPI has a good understanding of the phytosanitary 
status o f the plants before they arrive in New  Zealand  and the residual risk that 
needs to be managed during post -entry quarantine.   
6.3 The availability of specific testing methods  
(40) For all non-fungal  pests which MPI is proposing to manage with PCR, optimised and 
validated PCR assays are available at MPI’s Plant Health and Environment Laboratory .  14 • Persea americana  risk management proposal  Ministry for Primary Industries  (41) We are recommending p lating for  Lasiodiplodia pseudotheobromae  and 
Neofusicoccum nonquaesitum  at this stage because we do not yet have validated  PCR 
assays for these pest s. The option for PCR is given to future proof  the draft standard . If 
there is fungal growth on the selective medium being used to detect these pests, they can 
be identified by  sequencing the DNA extracted from the growth ; this is consistent with the 
approach taken for other fungal pests where we do not yet have a validated PCR assay .  
6.4 Changes to presentation in the inspection and testing requirements  
(43) Presentation of the “ inspection and testing requirements ” in schedule 2 of the draft 
standard has changed from other recently issued standards (e.g. Citrus  and Prunus  
plants for planting ). The changes are to reduce specific detail on sampling and 
inspectio n times. This is to allow flexibility in timing and sample selection when 
specific test methods are updated.  
   
Ministry for Primary Industries   Persea americana  risk management proposal  • 15 7. References  
Plant & Food Research (2020) Fresh Facts: New Zealand  Horticulture . The New  Zealand  
Institute for Plant and Food Research Ltd, Aucklan d, New  Zealand . 
https://freshfacts.co.nz/files/freshfacts -2020.pdf  
MAF; MFAT; FSA (2009) Balance in Trade.  Ministry of Agriculture and Forestry, Ministry 
of Foreign Affairs and Trade, New  Zealand , Food Safety Authority; Wellington, NZ. 
https://www.mpi.govt.nz/dmsdocument/12576 -balance -in-trade  
MPI (2022) Import Risk Analysis: Persea americana Plants for Planting.  Ministry for 
Primary Industries; Wellington, NZ.  
MPI (2019) Standard for Offshore Facilities Holding and Testing Plants for Planting . 
Ministry for Primary Industries; Wellington , NZ.   
Liang, L; Li, H; Zhou, L; Chen, F (2020) Lasiodiplodia pseudotheobromae causes stem 
canker of Chinese hackberry in China. Journal of Forestry Research 31(6): 2571 -2580.   16 • Persea americana  risk management proposal  Ministry for Primary Industries  8. Appendix  1: Pests proposed for risk management in the 
proposed new standard5 
8.1 Avocado sunblotch viroid  
 
1) MPI determine d that PCR during two summer growing seasons  continues to be the 
appropriate level of protection to manage the risk of Avocado sunblotch viroid  on 
imported P. americana  plants for planting. When  determini ng this measure , MPI  
considered the following  points.  
 
a. Avocado sunblotch viroid  is associated with avocado and could unknowingly 
be associated with imported leafless cuttings . 
i. Avocado sunblotch viroid  can be present in avocado trees 
asymptomatically . 
− Some infected avocado trees are reported to have been 
asymptomatic for their entire life.  
ii. Avocado sunblotch viroid  symptom s may not be observed during 
quarantine.  
iii. A symptomatic plant infected with Avocado sunblotch viroid  can later 
become asymptomatic and vice versa.  
− Symptom development is highly variable and the disease 
mechanism generating symptoms is not yet known.  
 
b. Avocado sunblotch viroid  could inflict high impacts to the avocado industry if 
it were to establish in New  Zealand . 
i. The New  Zealand  climate is suitable for the establishment of avocado 
sunblotch viroid . 
ii. There  is no cure for Avocado sunblotch viroid , and infected trees would 
need to be removed . 
iii. Avocado sunblotch viroid  is reported to cause yield losses of 
approximately 14 –95%, depending on the infected P. americana  
cultivar.  
− There  have been  yield losses of 50 –80% in symptomatic  Hass  
trees . 
− Approximately 50% of Hass fruit produced by symptomatic 
trees may be downgraded in quality . 
 
c. A PCR assay completed during two summer growing seasons  provides an 
appropriate level of assurance that plants are free from Avocado sunblotch 
viroid . 
i. Avocado sunblotch viroid  can be unevenly distributed in an infected 
plant , which can lead to false negative results. The requirement for two 
testing opportunities will provide greater confidence in negative results . 
 
 
5 All reasoning and evidence given below has b een taken from the Persea americana  Import Risk Analysis   
Ministry for Primary Industries   Persea americana  risk management proposal  • 17 d. Avocado sunblotch viroid is likely to be appropriately contained in a minimum 
of Level 2 post -entry  quarantine if present on imported leafless cuttings , given 
that it  is only known to be seed, pollen, graft and mechanically transmitted.  
8.2 ‘Candidatus Phytoplasma’ spp.  
 
1) MPI propose that a PCR completed during the first summer growing season is 
appropriate to manage the risk of ‘ Candidatus  Phytoplasma’ spp. on imported 
P. americana  plants for planting. MPI considered the following points when  
determin ing this measure . 
 
a. Phytoplasmas are reported to be associated with P. americana  and could 
unknowingly be associated with imported leafless cuttings . 
i. Phytoplasmas belonging to the “stolbur” group, quite possibly 
‘Candidatus  Phytoplasma solani ’, have been isolated from 
symptomatic leaves of avocado trees .  
ii. While there are no reports of phytoplasma causing asymptomatic 
infection in P. americana , asymptomatic infections occur on other 
hosts . 
 
b. Phytoplasmas have the potential to establish in New  Zealand  if they are 
introduce d on imported leafless cuttings . 
i. The regions of Chile and Spain where phytoplasmas have been isolated 
from symptomatic P. americana  trees, have a similar climate to parts of 
New  Zealand  where commercial avocado orchards are located .  
− Therefore, climate is unlikely to be a limiting factor for 
establishment of phytoplasmas in New  Zealand . 
ii. New  Zealand  has many known hosts of phytoplasma diseases.  
Phytoplasma  diseases are known from more than a thousand plant 
species worldwide . 
− ‘Candidatus  Phytoplasma solani ’ in particular has been known 
to infect more than 100 plant species including wild and 
ornamental plant species, and major and minor crop species 
including grapevines, tomato, potato and capsicum , which are 
all grown in New  Zealand . 
iii. Phytoplasmas could be tra nsmitted by the insect vectors reported to be 
associated with avocado plants in the wild in New  Zealand . 
− The known vectors of ‘ Candidatus  Phytoplasma solani ’ are not 
present in New  Zealand  but other species in the same family 
that are present in New  Zealan d have been reported to be 
associated with avocado plants in the wild.  
 
c. While t here is no direct evidence of phytoplasmas having an impact on 
P. americana , phytoplasmas are known to have a heavy impact on other hosts.   
i. Phytoplasmas from the stolbur group have been described as having 
unacceptable impacts on other hosts , including some that are important 
commercial crops in New  Zealand .  18 • Persea americana  risk management proposal  Ministry for Primary Industries  − ‘Candidatus  Phytoplas ma solani ’ was demonstrated to cause 
yield losses of 53.3 –75.3% in grapes harvested from diseased 
vines in Hungary.  
− ‘Candidatus  Phytoplasma solani ’ affected up to 70% of Salvia 
miltiorrhiza  (a medicinal perennial) in a commercial field in 
China . 
− ‘Candidatu s Phytoplasma solani ’ has affected up to 60% of 
potato plants in commercial fields . 
 
d. Phytoplasmas are likely to be appropriately contained in a minimum of Level 2 
post-entry quarantine if present on imported leafless cuttings . 
i. The infrastructure  of at least a Level 2 facility will exclude phloem -
feeding insect vectors  such as planthoppers and psyllids  that could 
potentially transmit phytoplasma s. 
 
2) Managing the risk of phytoplasmas on imported P. americana  aligns with the level of 
protection currently in place for many high value horticultural crop species such as 
Actinidia , Citrus , Fragaria , Malus , Prunus , Rubus , Vaccinium  and Vitis. 
 
a. Phytoplasmas are currently managed with specific measures, including PCR , 
on multiple schedules within the Nursery Stock  import health standard . 
i. MPI has an IANZ -accredited generic phytoplasma PCR that can detect 
all phytoplasmas.  
ii. Testing during the summer is likely to be the optimum time for 
detecting phytoplasmas . 
  
8.3 Colletotrichum  spp. 
 
1) The Colletotrichum  spp. this proposal is referring to includes C. aenigma , C. 
chrysoph ilum, C. endophyticum , C. jiangxiense , C. nymphaeae , C. queenslandicum , 
and C. tropicale . While other species in the Colletotrichum  genus are already  present 
in New  Zealand , those mentioned above are not , and they have the potential to form 
complexes with the species already present in New  Zealand  and possibly increase 
disease severity.  
 
2) MPI propose s that growing season inspection for Colletotrichum  spp. during post -
entry quarantine is appropriate to manage  the risk of Colletotrichum  spp. associated 
with imported P. americana  plants for planting. MPI considered the following when  
determin ing this measure . 
 
a. Colletotrichum  spp. are reported to be associated with avocado and could be 
associated with imported leafless cuttings . 
i. Colletotrichum  spp. have been isolated from fruit, leaves and twigs of 
avocado trees in the field.  
ii. Leaves and stems of avocado plants are thought to be the source of 
Colletotrichum spores affecting fruit.  
  
Ministry for Primary Industries   Persea americana  risk management proposal  • 19 b. Colletotrichum  spp. have the potential to establish in New  Zealand  if they are 
introduced on imported leafless cuttings .  
i. Colletotrichum  spp. have a wide global distribution and collec tively, 
they have an extensive host range , which includes plant species of 
economic significance to New  Zealand  including Actinidia , Capsicum , 
Fragaria , Malus , Prunus , Vaccinium  and Vitis. 
ii. Other Colletotrichum  spp. present in New  Zealand  are associated with 
native plant species. As Colletotrichum  species are known to have a 
wide host range, it is likely that  natives could serve as potential hosts 
for additional Colletotrichum  spp. that are introduced.  
iii. Colletotrichum  spp. are present in count ries that have a similar climate 
to New  Zealand .  
− Other species of Colletotrichum  have become  established in 
New  Zealand , so climate is unlikely to be a limiting factor for 
establishment of new Colletotrichum  spp.  
 
c. Colletotrichum spp. have the potential to inflict unacceptable impacts if 
allowed to establish in New  Zealand . This is evidenced by some 
Collectotrichum  spp, including those currently in New Zealand, causing 
unacceptable impacts to horticultural crops in other countries and requiring in -
field management.  For example : 
i. In avocados, 90% of avocado trees in backyards in the Leonardo Bravo 
municipality in Guerrero, Mexico had symptoms of fruit anthracnose 
caused by C. jiangxiense .  
− The export values for avocado was  $112.3 million and the 
domestic value was $50.6 million .  
ii. Epidemics of C. acutatum causing anthracnose in strawberries has been 
observed in Florida and North Carolina , Israel, Brazil and Bulgaria . In 
Bulgaria, disease incidence reached 90% in some regions and 
percentage of diseased plants averaged 50% in some fields.  
− C. acutatum is present in New  Zealand  but other species in the 
acutatum species complex  have been recorded on strawberries 
and are not present in New  Zealand  (e.g. C. nymphaeae and 
simmondsii ) 
iii. Bitter-rot of apple caused by C. acutatum and C. gloeosporioides 
species complexes (species currently in New  Zealand ) can result in the 
loss of up to 50% of crops in optimal conditions . In some cases, greater 
than 75% tree defoliation is observed by harvest time which weakens 
trees and reduces yield . 
iv. Appropriate in -field fungicides and management options are used in 
New  Zealand  to control Collectotrichum sp  anthracnose symptoms , but 
fungicide resistance has been reported for some Colletotrichum species . 
 
d. Colletotrichum  spp. are likely to be detected during growing season inspection 
in post -entry quarantine.  
i. There is no direct evidence to suggest that symptoms would not be 
observed during post -entry quarantine.  20 • Persea americana  risk management proposal  Ministry for Primary Industries  − While most of the Colletotrichum  species listed above  have 
been reported as endophytes  on other hosts, no evidence  could  
be found to indicate endophytic activity in association with 
avocado.   
ii. Growing plants in specified environmental conditions conducive t o 
disease expression  could increase the likelihood of detection during 
growing season inspection.  
− This could be achieved by exposing plants to temperatures of at 
least 25ºC during active growth.  This increases the effectiveness 
of growing season inspectio n as a measure and facilitates the 
retention of a quarantine period of at least 12 months.  
− Level 3A a nd 3B facilities can apply temperature regimes to 
expose plants to temperatures conducive to pest development.  
 
e. Colletotrichum  spp. are likely to be appropriately contained in a Level 3B 
post-entry quarantine if present on imported leafless cuttings . 
i. Colletotrichum  spp. produce conidia which are transmitted via 
watersplash  and/or wind . 
− Conidia transmitted by  water splash and  rain splash are unlikely 
to escape a Level 3A greenhouse  because r ain splash 
transmission is commonly a localised event. The conidia are 
unlikely to successfully transmit through the facility mesh and 
past the facility buffer zone .  
− Conid ia transmitted by wind can potentially pass through the 
0.04 mm2 mesh of a Level 3A quarantine facility . However, the 
conidia will be suitably contained within a Level 3B quarantine 
greenhouse by the operational infrastructure such as  HEPA 
filtration and negative  air pressures.  
8.4 Diaporthe perseae  
 
1) MPI determine that growing season inspection continues to be the appropriate level of 
protection to manage the risk of Diaporthe perseae (listed under the existing standard 
as Phomopsis pe rseae ) on imported P. americana  plants for planting. When  
determini ng this measure , MPI  considered the following  points.  
 
a. Diplodia persea  has been  reported to be associated with P. americana  and 
could unknowingly be associated with imported leafless cuttings . 
i. Diaporthe perseae  has been isolated from symptomatic branches and 
trunks of avocado trees . 
ii. Diaporthe perseae  can occur endophytically on all parts of an avocado 
tree. 
 
b. Based on currently available information, additional measures to manage 
Diaporthe perseae  on imported P. americana  plants for planting  are not 
needed at this time.   
Ministry for Primary Industries   Persea americana  risk management proposal  • 21 i. Diaporthe perseae  does not appear to be a high impact pest of avocado  
and therefore a higher level of protection would not be commensurate 
with the risk and impact of this pest .  
− The Hass variety , which is the main commercial variety grown 
in New  Zealand , has been observed to be the least susceptible to 
stem -end rot disease  caused by Diaporthe perseae than other 
varieties . 
− Diaporthe perseae appeared to be a weak pathogen of stem -end 
rot disease in avocado , as determined in pathogenicity tests 
using several pathogens that cause stem -end rot disease . 
− Diaporthe perseae  was the least frequently isolated organism  
from diseased avocado fruits , in relation to  other postharvest rot 
causing fungi.  
 
c. Diaporthe perseae is likely to be appropriately contained in a Level 3B post-
entry quarantine if present on imported leafless cuttings . 
i. Diaporthe perseae spores can be transmitted by rain and potentially by 
wind . 
− Conidia transmitted by rain splash are unlikely to escape a 
Level 3A greenhouse because rain splash transmission is  
commonly a localised event. The conidia are unlikely to 
successfully transmit through the facility mesh and past the 
facility buffer zone.  
− Conidia transmitted by wind can potentially pass through the 
0.04 mm2 mesh of a Level 3A quarantine facility. Howeve r, the 
conidia will be suitably contained within a Level 3B quarantine 
greenhouse by the operational infrastructure such as HEPA 
filtration and negative air pressures.  
 
8.5 Lasiodiplodia pseudotheobromae  and Neofusicoccum nonquaesitum  
 
1) Lasiodiplodia pseudotheobromae and Neofusicoccum nonquaesitum, are species  
within the Botryosphaeriaceae family. While species of  other genera within this family 
are already present in New  Zealand , those mentioned above are not and they have the 
potential to exacerbate disease currently being managed within commercial avocado 
orchards in New  Zealand .  
 
2) MPI propose that growing season inspection during post -entry quarantine and plating 
or PCR using samples taken  during the second  summer -like growing season are 
appropriate to manage the risk of  Lasiodiplodia pseudotheobromae and 
Neofusicoccum nonquaesitum  on imported P. americana  plants for planting. MPI 
considered the following when  determin ing this measure . 
 22 • Persea americana  risk management proposal  Ministry for Primary Industries  a. Lasiodiplodia pseudotheobromae and Neofusicoccum nonquaesitum are 
reported to be associated with avocado and could unknowingly be associated 
with imported leafless cuttings . 
i. Both species  have been isolated from symptom atic avocado stems and 
therefore could be associated with parts of the tr ee used for leafless 
cuttings . 
ii. All members of the Botryosphaeriaceae family are considered to have 
an endophytic phase. Therefore, the fungi may be associated with 
material used for leafless cuttings  without causing symptoms.  
− Lasiodiplodia pseudotheobromae  has been isolated from 
asymptomatic tissues in tree, shrub, and ornamental plant 
species from around the world.  
iii. Botryosphaeriaceae are opportunistic and enter hosts via wounds and 
natural openings such as lenticels and stomata.  
 
b. While there is no direct evidence to suggest that symptoms would not be 
observed during post -entry quarantine, there is uncertainty as to how long 
symptoms would take to develop in natural conditions with a level of inoculum 
that is likely to be realistic on imported leafless cutt ings.  
i. In pathogenicity studies, high levels of inoculum were used, and 
symptoms were induced within weeks of avocado plants being 
inoculated. These levels of inoculum are unlikely to be found on 
imported leafless cuttings . Furthermore, plants were grown i n 
environmental conditions favourable for disease expression.  
 
c. Lasiodiplodia pseudotheobromae and Neofusicoccum nonquaesitum could 
inflict unacceptable impacts on several horticultural crop species if they were 
to establish in New  Zealand .  
i. In the pathogen icity study conducted by Valencia et al. (2019), 
Neofusicoccum nonquaesitum  was the most virulent isolate in terms of 
the size of the necrotic lesions that formed on one -year-old Hass 
avocado trees  (which is the main commercial variety grown in 
New  Zealand ).  
ii. Lasiodiplodia pseudotheobromae has been reported to be one of the 
most virulent Lasiodiplodia  species, capable of causing disease on a 
broad range of host plants including Citrus , Malus  and Vitis.  
iii. Neofusicoccum nonquaesitum is known to infect other cr ops such as 
Malus , Vaccinium and Vitis. 
iv. Lasiodiplodia pseudotheobromae and Neofusicoccum nonquaesitum 
are found in countries that have a similar climate to parts of 
New  Zealand  where commercial avocado orchards are located.  
− Other species from the Botryosph aeriaceae  family are known to 
be established in New  Zealand  so climate is unlikely to be a 
limiting factor for establishment of Lasiodiplodia 
pseudotheobromae and Neofusicoccum nonquaesitum . 
  
Ministry for Primary Industries   Persea americana  risk management proposal  • 23 d. Lasiodiplodia pseudotheobromae and Neofusicoccum nonquaesitum  are likely 
to be appropriately contained in Level 3B post-entry quarantine if present on 
imported leafless cuttings . 
i. Lasiodiplodia pseudotheobromae and Neofusicoccum nonquaesitum  
conidia can be transmitted by water /rain splash or wind . 
− Conidia transmitted by rain splash are unlikely to escape a 
Level 3A greenhouse. Rain splash transmission is commonly a 
localised event. The conidia are unlikely to successfully 
transmit through the facility mesh and past the facility buffer 
zone.  
− Conidia transmit ted by wind can potentially pass through the 
0.04 mm2 mesh of a Level 3A quarantine facility. However, the 
conidia will be suitably contained within a Level 3B quarantine 
greenhouse by the operational infrastructure such as HEPA 
filtration and negative air  pressures . 
8.6 Neocosmospora perseae  
 
1) MPI propose that growing season inspection during post -entry quarantine is 
appropriate to manage the risk of Neocosmospora perseae  on imported P. americana  
plants for planting. MPI considered the following when  determin ing this measure . 
 
a. Neocosmospora perseae  has been reported to be associated with avocado and 
could be associated with imported leafless cuttings . 
i. There are two reports of Neocosmospora perseae  from avocado, one 
report from Italy and the second from  Greece. In both cases, infected 
plants were symptomatic.  
b. Neocosmospora perseae  could inflict some impact to the avocado industry if it 
were to establish in New  Zealand . 
i. The report of branch cankers in Greece affected 40% of 5 -year-old 
Hass avocado trees i n a 2 -hectare orchard.  
 
c. While there is no direct evidence to suggest that symptoms would not be 
observed during post -entry quarantine, there is uncertainty as to how long 
symptoms would take to develop in natural conditions with a level of inoculum 
that is likely to be realistic on imported leafless cuttings . 
i. No evidence was found that Neocosmospora perseae  can be latent in 
plant stems for long periods without showing symptoms.  
ii. In the experimental study described above, a high level  of inoculum 
was used, and symptoms were induced  within a month  of avocado 
plants being inoculated . These levels of inoculum are unlikely to be 
found on imported leafless cuttings . Furthermore, plants were grown in 
environmental conditions favourable for disease expression (i.e. 25 ± 1 
°C and 95 % relative humidity (RH) under a 12 -h fluorescent light/dark 
regime).   24 • Persea americana  risk management proposal  Ministry for Primary Industries  iii. Growing plants in specified environmental conditions conducive to 
disease expression would manage some risk created by this uncertainty.  
− This could be achieved by exposing plants to temp eratures of at 
least 25ºC during active growth.  This increases the effectiveness 
of growing season inspection as a measure and facilitates the 
retention of a quarantine period of at least 12 months.  
 
d. Neocosmospora  perseae  is likely to be appropriately cont ained in Level 3B 
post-entry quarantine if present on imported leafless cuttings . 
i. Neocosmospora perseae  produce conidia that can be transferred by 
water splash , and possibly  by wind or air. 
− Conidia transmitted by rain splash are unlikely to escape a 
Level 3 A greenhouse. Rain splash transmission is commonly a 
localised event. The conidia are unlikely to successfully 
transmit through the facility mesh and past the facility buffer 
zone.  
− Conidia transmitted by wind can potentially pass through the 
0.04 mm2 mesh of a Level 3A quarantine facility. However, the 
conidia will be suitably contained within a Level 3B quarantine 
greenhouse by the operational infrastructure such as HEPA 
filtration and negative air pressures . 
 
8.7 Pestalotiopsis longiseta  
 
1) MPI propose that growing season inspection during post -entry quarantine is 
appropriate to manage the risk of Pestalotiopsis longiseta  on imported 
Persea  americana  plants for planting. MPI considered the following when  
determin ing this measure . 
 
a. Pestalotiop sis longiseta  is reported to be associated with avocado and could be 
associated with leafless cuttings .  
i. Pestalotiopsis longiseta  has been isolated from avocado trees 
exhibiting dieback symptoms on shoots and twigs.  
 
b. Pestalotiopsis longiseta  could inflict  unacceptable impacts to several 
horticultural crop species if it were to establish in New  Zealand .  
i. Pestalotiopsis longiseta  caused dieback symptoms on shoots and twigs 
on approximately 30% of avocado trees in an avocado nursery 
plantation in China.  
ii. Pestalotiopsis longiseta has been isolated from symptomatic leaves, 
twigs and fruit of kiwifruit in major kiwifruit orchards in Ir an. While 
the impact of this pest on kiwifruit was not described in this paper, it 
can be assumed that there was an impact by the fact that there is an 
existing research publication.  
iii. Pestalotiopsis longiseta causes one of the most important diseases of 
tea (Camellia sinensis ) in Japan and is controlled with the application  
Ministry for Primary Industries   Persea americana  risk management proposal  • 25 of chemical fungicides. However, this can be costly because 
Pestalotiopsis longiseta develops resistance to fungicide treatments.  
− New  Zealand  has a growing tea industry.  
iv. Pestalotiopsis lo ngiseta  is found in countries that have a similar climate 
to parts of New  Zealand  where commercial avocado orchards are 
located.  
− Other species of Pestalotiopsis are known to be established in 
New  Zealand  so climate is unlikely to be a limiting factor for 
establishment of  Pestalotiopsis longiseta.  
 
c. Pestalotiopsis longiseta  is likely to be detected during growing season 
inspection during post -entry quarantine.  
i. There is no direct evidence to suggest that symptoms would not be 
observed during post-entry quarantine.  
ii. In a pathogenicity study, symptoms of Pestalotiopsis longiseta  
developed one week after inoculation of two -year old Hass avocado 
plants grown in a high humidity environment at 28  ºC. 
iii. This pathogenicity study provides some assurance t hat symptoms 
would be observed during post -entry quarantine because the 
inoculation method used is similar to what would happen in the field.  
− Plants were inoculated with a conidial suspension which was 
sprayed onto the growing tips. Inoculating plants with  a conidial 
suspension aligns more closely with the natural transmission 
and spread of Pestalotiopsis longiseta  which is likely to be via 
spores dispersed by rain splash.  
iv. Growing plants in specified environmental conditions conducive to 
disease expression would increase the likelihood of detection during 
growing season inspection . This could be achieved by exposing plants 
to temperatures of 28  ºC during active growth.   
− This increases the effectiveness of growing season inspection as 
a measure and facilitate s the retention of a quarantine period of 
at least 12 months.  
 
d. Pestalotiopsis longiseta  is likely to be appropriately contained in a minimum 
of Level 3 A post-entry quarantine if present on imported leafless cuttings . 
i. Pestalotiopsis longiseta  produce conidia that can be transferred by rain 
splash . 
− Conidia transmitted by rain splash are unlikely to escape a 
Level 3A greenhouse. Rain splash transmission is commonly a 
localised event. The conidia are unlikely to successfully 
transmit through the f acility mesh and past the facility buffer 
zone.  
8.8 Phytophthora palmivora  
 
1) MPI propose that a PCR completed on-arrival and during the second  growing season  
in post entry quarantine , is appropriate to manage the risk of Phytophthora palmivora  26 • Persea americana  risk management proposal  Ministry for Primary Industries  on imported P. americana  plants for planting. MPI considered the following when  
determin ing this measure . 
 
a. Phytophthora palmivora  is reported to be associated with avocado and could 
unknowingly be associated with leafless cuttings .  
i. Phytophthora palmivora has been isolated from diseased leaves, stems, 
crowns and roots of P. americana . 
ii. While no records were found of Phytophthora palmivo ra causing 
asymptomatic infections on avocado , it has been isolated from 
asymptomatic hosts of other susceptible plants species.  
iii. A range of Phytophthora species are reported to colonise host plants 
asymptomatically.  
 
b. Phytophthora palmivora could inflict unacceptable impacts to several 
horticultural crop species if it were to establish in New  Zealand . 
i. The climate in the sub -tropical to tropical parts of New  Zealand , 
particularly from Northland down to the Bay of Plenty, is likely to 
facilitat e the establishment of this pest in New  Zealand . 
− Most of New  Zealand ’s avocado and kiwifruit commercial 
production is based in these two regions.  
− In 2015, Phytophthora palmivora  killed 100% of young 
kiwifruit vines in a region of Turkey within two years of  
establishing. Most of this region has a similar climate to 
New  Zealand . 
 
c. A PCR test completed on-arrival and during the second  summer growing 
season in post entry quarantine  provides the appropriate level of assurance of 
pest freedom in P. americana  plants imported into New  Zealand . 
i. This level of protection align s with other crops such as Citrus and 
Prunus . The first PCR is completed when plants arrive in New Zealand 
to provide some assurance of pest absence. However, it cannot be 
guaranteed that pest  titre will be sufficient for this test to be a 
standalone confirmation of pest absence. A second PCR is completed 
after exposing plants to environmental conditions  known to be 
conducive to pest development, where pest titre is likely to be high 
(between 2 4-30 ºC). For Persea americana , the quarantine period 
begins with summer -like conditions so there is limited time for pest 
development. Therefore, to ensure pest titre is sufficient, MPI propose 
to complete the second PCR test during the second summer -like period 
of post -entry quaranti ne.  
ii. MPI has a validated PCR assay that can detect Phytophthora 
palmivora . 
 
8.9 Potato spindle tuber viroid  
 
1) MPI propose that a PCR test completed during the first summer growing season is 
appropriate to manage the risk of Potato spindle tuber viroid  on imported  
Ministry for Primary Industries   Persea americana  risk management proposal  • 27 P. americana  plants for planting. MPI considered the following when  determin ing this 
measure . 
 
a. Potato spindle tuber viroid is reported to be associated with P. americana  and 
could unknowingly be associated with imported leafless cuttings . 
i. Potato spindle tuber viroid has been isolated from symptomatic and 
asymptomatic avocado trees.  
− Potato spindle tu ber viroid  was detected in 72% of 
symptomatic and 21% of asymptomatic avocado trees surveyed 
in Peru.  
− Of the asymptomatic tree samples that were collected almost all 
of them tested positive for Potato spindle tuber viroid . 
ii. Potato spindle tuber viroid  has b een shown to move systemically 
through plant phloem. Therefore, it could be associated with leafless 
cuttings . 
 
b. Potato spindle tuber viroid  has the potential to establish in New  Zealand  if it 
were introduced on imported leafless cuttings .  
i. Potato spindle t uber viroid  may remain undetected for a prolonged 
period given the high rates of asymptomatic infection reported. 
Therefore, infected avocado trees plants would serve as reservoirs until 
such time as the viroid was identified.  
− Potato spindle tuber viroid  is known to be insect transmitted in 
other crops however this has not been demonstrated for 
avocado.  
ii. The natural host range of Potato spindle tuber viroid  is broad and is 
increasing.  
− Extreme climatic events have facilitated an increase in the host 
range o f Potato spindle tuber viroid as demonstrated in 
Australia where it  was detected in native plants and weeds after 
flooding.  
− Potato spindle tuber viroid  has been detected on a few 
occasions in New  Zealand  in tomato, tobacco  and capsicum 
glasshouse plants and in Cape gooseberry, but was eradicated 
each time. However, successful eradication of the viroid was 
likely aided by the fact that it was detected early and in an 
environment that was relatively easy to control (i.e. insi de a 
glasshouse and seeds).  
iii. The temperatures common in the main avocado growing regions in 
New  Zealand  are unlikely to be a limiting factor for establishment of 
Potato spindle tuber viroid in New  Zealand . 
 
c. Potato spindle tuber viroid is likely to be appropriately contained in a 
minimum of Level 3A post -entry quarantine if present on imported leafless 
cuttings . 
i. Potato spindle tuber viroid has been demonstrated to be aphid 
transmitted in other hosts such as po tatoes and cape gooseberry.  28 • Persea americana  risk management proposal  Ministry for Primary Industries  − Level 3A is required to have 0.04 mm2 mm mesh over any 
openings such as vents. This mesh size is expected to exclude 
adult stages of all aphids and whiteflies . 
 
2) A PCR  test completed during the first summer growing season is likely to provide the 
appropriate level of assurance that plants are free from Potato spindle tuber viroid . 
 
a. No evidence could be found to suggest that Potato spindle tuber viroid would 
not be detected w ith a single PCR test.  
b. MPI has a PCR assay that is optimised for the detection of Potato spindle tuber 
viroid.  
c. This measure  aligns with the level of protection currently in place for other 
horticulture and ornamental species such as Capsicum, Chrysanthemum , 
Dahlia, Petunia and Solanum spp.,  
i. Potato spindle tuber viroid  is currently managed with specific 
measures, including PCR, on multiple schedules within the Nursery 
Stock and Seeds for Sowing Import Health Standards.  
8.10 Xylella fastidiosa  
 
1) MPI propose to maintain the requirement for a PCR assay for Xylella fastidiosa  on 
imported P. americana  plants for planting. MPI considered the following when  
determin ing this measure . 
a. Xylella fastidiosa  is reported to be associated with avocado and could 
unknowingly be associated with imported leafless cuttings .  
i. Xylella fastidiosa  has been reported to be present in avocado plants 
both asymptomatically and with atypical symptom expression.  
− A single repor t was found reporting that Xylella fastidiosa  was 
found on avocados in California and that no direct symptoms 
were identified or linked to these positive cases.  
− Asymptomatic infections frequently occur in many hosts, often 
for a long time after inoculation . 
− A published record from Costa Rico, of avocado as a host of 
Xylella fastidiosa reported that disease symptoms were not 
uniformly distributed so some branches were symptomatic 
while others were not.  
− This observation aligns with that known for other crops such as 
Prunus  spp. where atypical symptoms have been reported on 
cherry in Spain.  
 
ii. Xylella fastidiosa  could inflict unacceptable impacts to horticulture crops and 
native plant species in the sub -tropical and tropical part of New  Zealand  if it 
were to esta blish.  
i. Diseases caused by Xylella fastidiosa  are more common in sub -tropical 
and tropical regions.   
Ministry for Primary Industries   Persea americana  risk management proposal  • 29 − CLIMEX predictions by MPI indicated that some of  the North 
Island is highly suitable for the establishment of Xylella 
fastidiosa . 
ii. There is the potential for Xylella fastidiosa  to be transmitted to other 
hosts if it were to arrive in New  Zealand .  
− At least one known vector of Xylella fastidiosa  is present in 
New  Zealand  – Philaenus spumarius . Many other insect species 
in the same family as the known vector are present in 
New  Zealand  and are potential vectors of Xylella fastidiosa . 
 
iii. Xylella fastidios a has had major impacts on some horticulture 
industries on other parts of the world.  
− Xylella  fastidiosa  has cause d devastating diseases in crops 
including grapes and citrus . 
− Xylella fastidiosa  has killed millions of olive trees in a region of 
Italy causing  unprecedented socio -economic issues . 
− One of the reasons for this severe outcome is because Xylella 
fastidiosa  is difficult to identify based on symptoms. In this 
case, growers attributed the cause to other factors before 
diagnostic testing was eventually carried out almost five years 
after initial detection.  
− It is worth noting that the report of Xylella fastidiosa  on 
avocado described by Montero -Astúa et al., (2008 ) stated that 
disease symptoms had been observed for several years before 
diagnostic testing was performed.  
iv. The ability of several New  Zealand  native plants to harbour the 
bacterium has been demonstrated.  
 
b. A PCR assay completed during the summer growing seasons  provides the appropriate 
level of assurance that plants are free from Xylella fastidios a.  
i. Xylella fastidiosa  has been observed to grow most rapidly at 
temperatures between 25ºC - 32 ºC. Testing plants after they have been 
exposed to these temperatures maximises the chances of detection.  This 
also facilitates the retention of the minimum 12 -month quarantine 
period.  
ii. Xylella fastidiosa  has been reported to have variable distribution and 
symptom expression in avocado plants. Two PCR tests provides greater 
certainty that the pest would be det ected if it is present in the plant.   
iii. This level of protection aligns with that currently in place for other 
horticulture crop species such as Citrus , Prunus , and Vitis.  
− For Citrus , Prunus , and Vitis plants for planting, two tests are 
required to verify that plants are free from Xylella fastidiosa , 
before plants can be given biosecurity clearance.  
− Xylella fastidiosa  is currently managed with specific measures, 
including PCR, on over 100 schedules for ornamental and food 
crop species, as specified in the Nursery Stock Import Health 
Standard .  30 • Persea americana  risk management proposal  Ministry for Primary Industries   
c. Xylella fastidiosa  is likely to be appropriately contained in a Level 3A post-entry 
quarantine if present on imported leafless cuttings . 
i. Level 3A PEQ has physical and operational measures in place to 
manage the risks associated with the known vectors in New  Zealand , 
wastewater, waste and accidental transfer, therefore insect ve ctors 
carrying X. fastidiosa  are unlikely to escape Level 3A PEQ to infect a 
suitable host .