Pest Risk Assessment:  
Orchid fleck virus associated with  imported whole plants of  
Oncidium and other orchid genera  
 
Biosecurity New Zealand Technical Paper No:  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Version 1.0 
14 June  2021 
  
 
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i 
 Pest Risk Assessment: Orchid fleck dichorhavirus  associated with imported whole plants of Oncidium  
and other orchid genera  
 
 
 
Version 1.0 
 
 
14 June  2021 
 
EPerotti  
 
 
Approved for general release  
 
 
 
Dr Enrico Perotti  
Associate Director,  
Animal and Plant Health Directorate,  
Biosecurity New Zealand  
 
 
   
ii 
 Version information  
 
Version number  Comments  Date of release  
1.0 Peer -reviewed and current at 
date of release  14/06 /202 1 
 
Sign-off for internal use :  
Shola Olaniyan  17/05/2021  
   
New Zealand is a member of the World Trade Organisation and a signatory to the Agreement on the 
Application of Sanitary and Phytosanitary Measures (“The Agreement”). Under the Agreement, 
countries must base their measures on an International Standard or an  assessment of the biological 
risks to plant, animal or human health.  
This document provides a scientific analysis of the risks associated with Orchid fleck dichorhavirus  on 
whole plants  of Oncidium and other genera of orchids . It assesses the likelihood of entry, exposure, 
establishment and spread of Orchid fleck dichorhavirus  via the nursery stock pathway and  assesses 
the potential impacts should the virus  enter and establish in New Zealand. The document has been 
internally p eer reviewed and approved for external release .  Any significant new science information 
received that may alter the level of assessed risk will be included in a review, and an updated version 
released.  
   
iii 
 Contributors to this risk assessment  
The following people provided significant input into the development of this risk a ssessment : 
 
1. Primary contributors  
 
Deb Anthony  Senior Adviser  
Plant Risk Analysis , 
MPI Wellington, New Zealand  
2. Internal peer review  
 
Oluwashola Olaniyan  Acting Manager  
Plant  Risk Analysis  
MPI Wellington, New Zealand  
 
Helen Harman  Senior Adviser  
Plant  Risk Analysis  
MPI Wellington, New Zealand  
 
Stephan Halloy  
 Senior Adviser  
Plant Risk Analysis  
MPI Wellington, New Zealand  
 
Karen Wilson  
 
 
 
Abigail Durrant  Senior Adviser  
Plant Risk Analysis  
MPI Wellington, New Zealand  
 
Senior Adviser  
Plant Risk Analysis  
MPI Wellington, New Zealand  
 
Joe Tang  Scientist, Virology  
Plant Health and Environment Laboratory (PHEL)  
MPI, Auckland , New Zealand  
 
   
iv 
 Table of Contents  
1 Introduction  1 
1.1 Purpose  1 
1.2 Background  1 
1.3 Scope  2 
1.4 Risk management questions and existing measures  2 
1.5 Summary of conclusions  2 
2 Orchid fleck dichorhavirus  (OFV)  4 
2.1 General notes biology and taxonomy  4 
2.2 Hazard identification: Regulatory status and commodity association  5 
2.3 Risk assessment  7 
2.3.1  Likelihood of entry  7 
2.3.2  Transfer (exposure)  7 
2.3.3  Likelihood of establishment and spread  8 
2.3.4  The impacts in New Zealand  10 
2.4 Conclusions regarding risk management question  12 
  
Biosecurity New Zealand   {Name of paper in here} • 1 1 Introduction  
1.1 Purpose  
This Pest Risk Assessment (PRA) is to enable the Plant Germplasm (ornamental ) Imports team , of the 
Ministry for Primary Industries (MPI) , to decide on whether Orchid fleck dichorhavirus  (OFV) should 
be regulated as a quarantine pest for New Zealand, and if  import health standard (IHS) 155.02.06 
(Importation of Nursery Stock) should be amended to include additional measures against OFV in the 
Calanthe  and other schedules  (Anubias , Epipremnum , Phalaenopsis ) under which orchid genera can 
be imported . 
1.2 Backgroun d 
Plant Germplasm (ornamental)  Imports  received a request for the addition of all Oncidium  spp. and 
their hybrids to the plant s biosecurity index (PBI) and made eligible for import ation  into New Zealand  
under the nursery stock import health standard 155.02.06: Importation of Nursery Stock . This 
request  followed non -statutory advice given by the Environmental Protection Agency (EPA) under 
the application code BER00001 , which determined that ‘Oncidium spec ies and cultivars’ were  
present in New Zealand, and not new organisms.  There are currently 13 1 Oncidium  spp. listed in the 
PBI, as eligible for import under the Calanthe  schedule in the Import Health Standard 155.02.06: 
Importation of Nursery Stock.  Plant Risk Analysis was asked to determine if there were any pests or 
pathogens on Oncidium , which would require measures additional to those  currently specified in the 
Calanthe  schedule .  
 
Broad searches of the literature and MPI’s emerging risks system (ERS) were carried out to identify  
new or currently unmanaged pests and diseases  on Oncidium  whole plants , which are not known to 
be in New Zealand . The virus, Orchid fleck dichorhavirus  (OFV) was found to be  associated with 
Oncidium  and determined to be potential ly unmanaged  by the Calanthe  schedule . Therefore, a risk 
assessment for OFV on Oncidium  was initiated.  
 
However, d uring the course of th e work , it became  apparent that OFV can also infect at least 30 
other genera of orchid s, including some very popular and commonly imported genera such as 
Cymbidium  and Phalaenopsis . As such, the scope of the assessment was broadened to include other 
orchid genera . The Plant Germplasm Import team agree d that th is approach had added value, as it 
would inform  IHS review to have a single schedule for importation of Orchidaceae, which is being 
considered. Currently,  orchid genera  (apart from Oncidium ) can be imported under either basic 
requirements , or under Anubias , Epipremnum  and Phalaenopsis  schedules of the nursery stock IHS.  
Commodities imported under these schedules, for example Phalaenopsis , are often high volume 
pathways, with single consignments of up to 7000 plants (QuanCargo 2021).  Thus, this pest risk 
assessment is undertaken to determine if OFV constitutes a risk to New Zealand on plants for 
planting of Oncidium  and other orchid genera that are eligible for import under existing import 
requirements.  
Under current provisions in the IHS, nursery stock (whole plants, cuttings and tissue culture) of 
Oncidium  species  and other orchid genera are approved for importation into New Zealand from any 
country . A p hytosanitary certifica te is required  and, in most cases  an import permit is also required . 
In addition, all cuttings and whole plants of Oncidium and other orchid genera must be treated for 
fungi, insects and mites prior to export and imported into post -entry quarantine level 2 (PEQ  L2). 
Whole plants of Oncidium  and other  genera  listed  under the Calanthe  schedule are required to spend 
a minimum growing and inspection period of 1 year in PEQ L2 and meet the requirements of the  
“additional declarations ” listed in the schedule ” in the IHS 155.02.06 (Importation of Nursery Stock) . 
The minimum PEQ growing and inspection period is 3 months for orchid genera imported under the 
Anubias , Epipremnum  and Phalaenopsis  schedules.  PEQ is not required for tissue culture , which are  
Biosecurity New Zealand   {Name of paper in here} • 2 considered a lower risk for introduction of pests and diseases , given their production methods. They 
must , however, meet entry conditions for tissue culture in section 2.2.2 of the IHS.   
1.3 Scope  
The scope of this risk assessment is limited to Orchid fleck dichorhavirus  (OFV) on the pathway – 
whole plants of Oncidium  spp. and other orchid genera  listed on the Plant Biosecurity Index  (PBI), as 
eligible for import  into New Zealand . Whole plants were chosen for assessment, given they present a 
higher level of risk for the introduction of OFV than cuttings and tissue cultur e. Cuttings are easier to 
inspect and tissue culture are (usually) considered a lower risk commodity due to their production 
method s. Seeds for sowing  and cut flowers  and foliage are out of  scope.  
 
This risk assessment includes the following:  
• Brief notes on the biology and taxonomy of the pest.  
• Hazard identification: name and taxonomy of the organism, New Zealand status, commodity 
association, potential for establishme nt in New Zealand and potential for impacts  in New 
Zealand . 
• Risk assessment: currently known  geographic distribution , assessment of entry, 
transfer/exposure, establishment and spread, and assessment of impact s (economic, 
environmental, and social/cultural) . 
1.4 Risk management question s and existing measures  
The risk management question s for this PRA are: 
• Does Orchid fleck dichorhavirus  (OFV) meet the requirements to be a regulated pe st on 
plants for planting  of Oncidium  and other orchid genera?  
• Does OFV  meet the criteria for additional measures  on plants for planting of Oncidium  and 
other orchid genera ? 
OFV would meet the criteria for being a regulated quarantine pest if it is not present in New Zealand 
and has the potential to enter, establish and cause unacceptable impacts in New Zealand1.  
OFV would meet the criteria for additional measures on Oncidium  and other orchid genera, if existing 
import requirements are deemed in adequate to prevent entry and establishment  of OFV, leading to 
unacceptable impacts in New Zealand.  
This risk assessment considers the likelihood of entry , exposure to a suitable host, establishment and 
spread , and the potential impacts in New Zealand , of OFV associated with whole plants of Oncidium  
and other orchid genera  – given current measures  (import requirements)  in the nursery stock IHS .  
1.5 Summary of conclusions  
 
Orchid fleck dichorhavirus  meets the criteria to be a regulated quarantine pe st for New 
Zealand : 
• OFV is not known to be present in New Zealand, is associated with Oncidium  and other 
orchid genera , and has the potential to enter, establish and cause unacceptable impacts in 
New Zealand.  
 
OFV may  be considered for additional measures on plants for planting  of Oncidium  and other 
orchid genera, mainly due to potential impacts  and the high level of uncertainty around 
spread and impacts:   
 
1 Refer to ISPM 5  for the definition of a quarantine pest under the IPPC, and the Biosecurity Act 1993 , for factors to consid er when defining 
“harm”.   
Biosecurity New Zealand   {Name of paper in here} • 3 • The likelihood of OFV  entering New Zealand associated with plants for planting of Oncidium  
and other orchid genera is low, with low uncertainty.  
• The likelihood of e xposure/transfer of OFV to host plants in New Zealand is low, but if 
exposure were to occur, the likelihood of OFV  establishing in New Zealand is cons idered to 
be moderate -high, with low uncertainty , and the likelihood of spread is  low, with high 
uncertainty .   
• The level of economic impact caused by OFV is likely to be low for New Zealand overall, but 
could be high for the orchid industry and , potentially , the citrus industry , with high 
uncertainty.  Eradication may be possible, especially if the virus establishes within a protected 
(glasshouse) environment.   
• The likelihood of  OFV causing social impacts is moderate, with low uncertainty.  
• The li kelihood of OFV causing environmental impacts is low -moderate, with high uncertainty.  
• The likelihood of OFV causing human health impacts is negligible, with low uncertainty    
Biosecurity New Zealand   {Name of paper in here} • 4 2 Orchid fleck dichorhavirus  (OFV) 
 
Scientific name: Orchid fleck dichorhavirus   
Order/Family /Genus : Mononegavirales/Rhabdoviridae/Dichorhavirus  
Other names: orchid fleck virus, OFV , orchid fleck disease . 
2.1 General notes biology and taxonomy   
Orchid fleck dichor havirus  (OFV) is the type species  of the genus Dichorhavirus , and it is recognised as 
an important viral pathogen that naturally infects  commercial orchids , caus ing localised chlorotic and 
necrotic lesions . In severe cases, these lesions  can result in the decline and death of infected  plant s 
(Peng et a l. 2013; Kondo et al. 2017).  
 
OFV has the ability to infect taxonomically distant plant hosts;  about 75 plant species belonging to 48 
genera of 12 families can be infected by OFV  and of these, about 50 plant species in 31 genera, all of 
which are from the  Orchidaceae, can be naturally infected  (Peng et al. 2013).  OFV is persistently 
transmitted  by the false spider mite, Brevipalpus californicu s (Maeda et al. 1998) . The mite  is very 
small  (0.2–0.3mm long ), globally widespread and  has a wide host range;  reported to have been 
collected from 316 wild and cultivated hosts in 67 genera from 33 families (Childers et al . 2003, cited 
in Vacante 2016). According to Ali (2013) g lobal trade has likely expanded the distribution and host 
range  of B. californicus , and this could, potentially, further increase the host range of OFV. Power 
(2000) notes that expansion in host range by this means has been observed many times before in 
viruses that are transmitted by insect vectors.  Mechanical transm ission of OFV has been  
demonstrated experimentally, via inoculation of sap from infected leaves , to seedlings of 
Dendrobium , tobacco, Nicotiana glutinosa , Chenopodium amaranticolor , C. quinoa , Petunia hybrida , 
Nicotiana glutinosa , and four varieties of N. tabacum , but only in summer when the temperature in 
the experimental greenhouse was higher than 30 °C (Chang et al. 1976) . There are no reports of 
mechanical transmission OFV via tools during pruning and other cultivation practice s. 
 
There are two types (nuclear and cytoplasmic) of Brevipalpus transmitted viruses  (BTVs) , and OFV is 
of the nuclear (N) type  (Kubo et al 2009) . The virus was described originally from chlorotic lesions on 
Cymbidium  leaves  in Japan , has short, rod -like non -enveloped particles of 32 –40 nm diameter and 
100–150 nm length, and is found in the nucleus of the plant cell  (Chang et al. 1976; Doi et al. 1977; 
Kondo et al. 2003) . Phylogenetic analysis has shown that OFV isolates separate into two subgroups, 
based on nucleotide sequences of N gene fragments (RNA 1). Subgroup 1 includes most isolates 
collected from Australia, Germany, South Africa, and the Americas. Subgroup 2 includes only five 
isolates from Germany, Costa Rica and East Asian countr ies (Kondo et al. 2017).  
 
According to Kondo et al. (2017), there are two known strains of OFV: the orchid strain of OFV 
(subgroups 1 and 2), and the citrus strain of OFV. However, more recently, Cook et al. (2019) found 
the orchid strain of OFV  infecting  orange ( Citrus  sinensis ) in South Africa  and causing citrus leprosis 
symptoms on infected orange trees and fruit; there is more detail on this in Appendix 2 . A distinct 
cytoplasmic (C) type  virus causing orchid fleck symptoms was  detected  by transmission electron 
microscopy (TEM) in lesion fragments from plants of the orchid genera , Jumellea  and Coelogyne  
(Kubo et al. 2009) . This virus had bacilliform particles 70 –80 nm in diameter and 110 –120 nm in 
length, induce d electron -dense viroplasm inclusions in infected cells, and resemble d the cytoplasmic 
type of Brevipalpus  transmitted virus (BTV) , such as Citrus leprosis virus C  (Kubo et al. 200 9). 
Experiments have demonstrated that th is cytoplasmic type (C) virus  that clearly also infects orchids , 
is distinct from OFV, which is  a nuclear (N) type  virus  (Kubo et al. 2009).  
 
  
Biosecurity New Zealand   {Name of paper in here} • 5 2.2 Hazard identification : Regulatory status and commodity association  
 
Regulatory status  
Orchid fleck dichorhavirus  meets the criteria to be a quarantine pest for New Zealand , given 
that:   
Orchid fleck dichorhavirus is not known to be present in New Zealand:  
• OFV is not recorded in: P lant Pest Information Network (PPIN  2021), N ew Zealand Organisms 
Register  (NZOR 2021), or Veer akone et al. (2015).  
• Its regulatory status  is listed as ‘not assessed’ in the Official New Zealand Pest Register  
(ONZPR 2021) and as ‘undetermined’ in the Biosecurity Risk Analysis Database  (BRAD 2021). 
 
Orchid fleck dichorhavirus has the potential to establish and spread in New Zealand:  
• OFV is reported from many areas with a very similar climate to the whole of New Zealand, 
indicated  by a Composite  Match Index (CMI , a measure of similarity of climates ) of ≥0.7 
(Phillips et al. 2018) . These areas include parts of Australia, Brazil, Japan  and USA (Peng et al. 
2013).  
• The availability of host plants is not likely to be a barrier to establishment , as the host range 
of OFV includes Oncidium  and 30 other orchid genera (Peng et al. 2013) , many of which  are 
commercially grown in glasshouses in New Zealand for use as houseplants and cut flowers . 
New Zealand also has 84 species of endemic  orchids  growing outdoors  (NZ flora 2021) that 
could serve as hosts for OFV.  Additionally, orange ( Citrus  sinensis ), which is a commercial 
crop in New Zealand, has been reported to be infected by the orchid strain of OFV in South 
Africa (Cook et al. 2019).  
• OFV is transmitted by the globally widespread false spider mite Brevipalpus californicus  
(Kondo et al. 2003; Pen g et al. 2013)  which is present in New Zealand (NZOR 202 1), and 
vector transmission, as well as experimental mechanical inoculation of OFV has been shown 
in 25 species in 11 non -orchid families (Peng et al. 2013).  
 
Orchid fleck dichorhavirus has the poten tial to cause economic, soci o-cultural and environmental  
impacts to New Zealand:  
• OFV has the potential to harm commercial orchids and citrus (oranges) of economic 
importance to New Zealand , as it causes chlorotic and necrotic leaf lesions  which, in severe 
cases, can result in the decline and death of infected  plant s (Peng et al. 2013; Kondo et al. 
2017).  
• OFV has the potential to have social -cultural impacts  – orchids are valued as  cut flowers, 
indoor plants in  homes and some businesses, and there are strong hobbyist grower groups 
(e.g. NZ Orchid Society) in New Zealand.  
• The reported hosts of OFV  are primarily orchid genera , and its vector, B. californicus , is 
present in New Zealand. It is, therefore, possible that the host range of the virus could 
expand to include some native orchids  as well as s pecies  in other plant families  in New 
Zealand , which fall within the host range of the vector.  
 
Commodity  association  
Orchid fleck dichorhavirus is associated with whole plants of Oncidium  and other orchid 
genera . 
Oncidium  and several other orchid genera are reported hosts of Orchid fleck dichorhavirus : 
• OFV has been reported from Oncidium  in Australia, Brazil, Colombia, C osta Rica, Germany, 
Japan and Korea (Kitajima et al. 2010).  
• OFV is reported from 30 other genera of orchid including the very common and popular 
genera such as Cattleya , Cymbidium , Dendrobium  and Phalaenopsis  and their hybrids   
Biosecurity New Zealand   {Name of paper in here} • 6 (Bratsch et al. 2021; Peng et al. 2013; Kitajima et al. 2010).  See Appendix 1  on page 14 for the 
currently known [as at March 2021 ] full host list ). 
 
Orchid fleck dichorhavirus  can be present in the leaves of infected orchid plants : 
• OFV is characterised by the presence of localised chlorotic and necrotic lesions (Figure 1) on 
the leaves  of infected plants (Doi et al . 1977 , cited in Kondo et al . 2003) . 
• OFV has been detected in plants showing these lesions , by electron microscopy (Kondo  et al. 
2013; Peng et al. 2013)  and, using reverse transcription polymerase chain reaction (RT -PCR) 
(Blanchfield 2001; Ali et al.  2014; 2014 ; Bratsch et al. 2021).  
 
 
 
 
Aceneta  sp.  Brassia  sp.       Dendrochilum  sp. 
 
 
Lycaste  sp.  Oncidium  sp.       Cymbidium  sp. 
 
Figure 1.   Symptoms on various orchid species that tested positive for Orchid fleck dichorhavirus  in 
South Africa.  Photos are from Cook et al. (2019).  
 
  
 
Biosecurity New Zealand   {Name of paper in here} • 7 2.3 Risk assessment  
2.3.1 Likelihood of entry 
The likelihood of Orchid fleck dichorhavirus  entering New Zealand on whole  plants of  
Oncidium  or other orchid s is considered low, with low uncertainty.  
Orchid fleck dichorhavirus  is associat ed with 31 genera of orchid, including Oncidium, and causes 
visible lesions on the leaves  of infected plants : 
• Natural infections of OFV in orchid species are well reported in the literature (e.g. Chang et al 
1976; Kondo et al. 2003; Peng  et al.  2013;  Cook et al 2019).  
• OFV is not a systemic virus and causes  localised chlorotic and necrotic lesions  (Figure 1) . And 
the virus  has been reported to cause systemic leaf symptoms in experimental ly infected 
hosts , this only occurred  at high temperature  (above  30°C ) (Chang et al. 1976; Kondo et al. 
2003 ).  
• There is a very low likelihood of visibly infected plants being exported  to New Zealand , as 
healthy -looking plants would be selected for export.  
 
OFV is likely to be detected on imported infected plants, given c urrent  import requirements for 
nursery stock  of Oncidium  and other Orchidaceae : 
• Visual inspection of plants is likely to detect plants with obvious lesions , but it is noted that 
symptoms of OFV infection in plants may not become visible until  after 2-3 weeks (Kondo et 
al. 2003). So, should plants become infect ed just prior to export, they  may  be asymptomatic , 
on arrival, although the transport (shipping ) duration may be sufficient to allow development 
of symptoms.   
• Alternatively, if a lesion is new, small and in a tight or compacted position between leaves, it 
may go undetected and be imported into PEQ. However, the minimum period required in 
Level 2 PEQ for orchid genera  (apart from Oncidium ) is 3 months , and it is expected that any 
symptoms of OFV from infection prior to importation would be expressed and detected 
within that timeframe.  For Oncidium , the minimum PEQ period is 1 year, which makes it even 
more likely that OFV -infected plants would be detect ed. Furthermore, t here have been no 
reports of long term asymptomatic OFV infections.  
• In addition, whole plants (Oncidium , other orchids and all other importable genera)  are 
required to  be treated with miticide before arriving in New Zealand or on arrival  in PEQ.  
Therefore, any OFV-infected mites on an imported plant are expected to have been killed.  
• However, if any OFV-infected mites were to survive, it is known that  they  can be difficult to 
contain or exclude in Level 2 PEQ (pers . comm. R. Lardner) , given their small size ; the holes in 
mesh over ventilation openings in Level 2 PEQ are 0.6 mm diameter (MPI 201 7), whereas B. 
californicus  is 0.2 -0.3 mm long  and <2 mm in diam eter,  and can be transported on clothing 
and equipment  (Vacante et al. 2016).  
• If viruliferous mites are not detected and escape quarantine,  there is potential for OFV to be 
spread to another host outside of the quarantine.  
2.3.2 Transfer ( exposure)  
Orchid fleck dichorhavirus  has a low likelihood of exposure ( transfer ) from imported plants 
of Oncidium and other orchid genera  to host plants in New Z ealand   
When a pest or pathogen arrives in a new area, it usually needs to find (or come into contact with ) a 
growing host plant in order to establish. The process of a pest or pathogen coming into contact with 
a growing host plant is termed “exposure” in MPI risk assessments and “transfer” under the IPPC.  
• Transfer/exposure  of pathogens from nursery stock  is usually considered to be highly likely , 
because  imported material is maintained in a habitat favourable for plant growth  and is   
Biosecurity New Zealand   {Name of paper in here} • 8 often  multiplied up to  substantial numbers , which promotes the survival and persistence of 
both the plant material and associated pathogens , thus making the transfer/exposure of 
such pathogens highly likely . 
However,  
• OFV causes localized infections  that are visually detectable on the leaf surface of infected  
hosts  within 2 -3 weeks  (Chang et al, 1976; Kondo et al. 2003) , and it is unlikely that an 
infected plant would be released from PEQ to allow  transfer to host plants in New Zealand . 
• Therefore, t ransfer of OFV from imported plant s of Oncidium  and other orchids  would be  
largely dependent upon the presence of the mite vector, Brevipalpus  californicus , in a PEQ 
facility where there are undetected OFV -infected plants.   
• The vector  must either already be in the PEQ facility or enter the facility  and feed on OFV 
lesions on infected plants to acquire the virus. The mite would then need to exit PEQ and 
feed on other plant species susceptible to OFV.  
• While B. californicus  is small enough to move through ventilation mesh  or small gaps and 
could  also be carried on clothing and equipment , the likelihood of the mite entering PEQ, 
feeding on an OFV -infected plant, then exiting PEQ  and landing and feed ing on a suitable 
host , is considered to be low . This is attributed to the f act that Brevipalpus  spp. have poor 
natural dispersal abilities and even if passively dispersed by wind , there is no guarantee that 
they will land on a suitable host, as they have no ability to control where they land  (Alves et 
al. 2005).  
 
Therefore, the likelihood of transfer/ exposure for  OFV on whole plants of Oncidium  and other orchid 
genera  is considered to be low, with low uncertainty  
 
2.3.3 Likelihood of e stablishment and spread  
 
If exposure were to occur, t he likelihood of Orchid fleck dichorhavirus  establishing in New 
Zealand is considered to be moderate -high, with low uncertainty .  
Establishment and spread  of Orchid fleck dichorhavirus  would depend on a combination of several 
factors: the presence of suitable host plants, the presence of vectors and the suitability of the 
environment.  
The suitability of the New Zealand environment for Orchid fleck dichorhavirus  to establish is 
considered to be moderate (outdoors) to high (greenhouses) :  
• The current global distribution of OFV  is shown below in Table 1  and the CMI range for each 
country/state is given.  
• OFV is reported from many areas that have very similar climate conditions to the whole of 
New Zealand, indicated by a Composite Match Index (CMI , a measu re of the similarity 
between two climates ) of ≥0.7 modelled by Phillips et al. (2018).  Climate is , therefore, 
unlikely to limit the establishment of OFV in New Zealand , because the virus is reported from 
many areas with very similar climates to New Zealand, e.g. southern regions of Brazil, 
Australia (Tasmania, Victoria, NSW etc.), some provinces of South Africa  and areas of the USA  
(Table 1 ).  
• Some  orchid genera that are OFV hosts are often grown in greenhouses worldwide, including 
New Zealand . Greenhouses with temperature control can extend the geographic range 
within New Zealand , of the hosts for OFV and , therefore , that of the virus.   
 
 
 
 
  
Biosecurity New Zealand   {Name of paper in here} • 9 Table 1. The geographical d istribution of OFV  
 
Region  Country  State/Province (if 
recorded)  Reference  CMI range 
(Phillips et al 2018)  
Africa  South Africa  Eastern Cape  Cook et al. (2019)  0.7–0.9 
Mpumalanga  0.7–0.8 
North West Province  0.6–0.7 
Asia China  Xiamen, Fujian 
Province  Peng et al. (2017)  0.6 
Japan   Kondo et al. (2003)  0.6–0.8 
Korea  Gyeonggi Province  Kim et al. (2010)  0.6 
Chungnam Province  0.6 
Gyeongbuk Province  0.7 
Europe  Denmark   Kondo et al. (2003)  0.8–0.9 
France   Sauv être et al. 
(2018)  0.9 
Germany   Kondo et al. (2003)  0.9 
North America  USA   Bratsch et al. 
(2015)  0.5–0.8 
 Mexico  Zihuateutla, Edo. 
Puebla.  Ortero -Calina et al. 
(2021)  0.3–0.8 
Central America  Costa Rica   Freitas -Astúa et al. 
(2002)  0.3–0.6 
South America  Brazil  Paraná  Kubo et al. (2009)  0.6–0.8 
Rio Grande do Sul  0.7–0.9 
Santa Catarina  0.7–0.9 
São Paulo  0.5–0.7 
Colombia*   Kitajima & Freitas -
Astúa (unpubl. 
data) in Kubo et al. 
(2009)  0.3–0.8 
Paraguay   Ramos -Gonzalez et 
al. (2015 ) 0.5–0.7 
Oceania  Australia  Australian Capital 
Territory  Blanchfield et al. 
(2001)  0.8–0.9 
New South Wales  0.6–0.9 
Tasmania  0.9–1.0 
Victoria  0.7–0.9 
Queensland  Dietzgen et al. 
(2018)           0.4–0.8 
 
CMI values of ≥0.7 show  very similar climate conditions to the whole of New Zealand (Phillips et al.  2018) . 
 
*Ramos -Gonzalez et al. (2015) comment that molecular confirmation for OFV in Colombia hasn’t been done , but c itrus leprosis virus -N has been sequenced 
from sweet orange in Colombia (Roy et al. 2014) . 
 
 
Suitable hosts are available for the establishment of OFV in New Zealand  
• Of the known orchid hosts (Appendix 1 ), about 27 are listed in the Plant Biosecurity Index 
(PBI 2021) as eligible for importation, and many of those orchids are likely to already be in 
New Zealand; Cymbidium , Dendrobium , Oncidium , Phalaenopsis  and Zygopetalum , for 
example, are present in New Zealand   (personal experience  of the author ). 
• Of the non -orchid hosts listed in Appendix 1, most genera and/or species are present in New 
Zealand , e.g.  Liriope , Alcea , Citrus  and Cordyline  species. Additionally, experimental hosts 
such as Amaranthus  lividus , Chenopodium  species, Tetragonia  tetragonoides (syn= T. 
expansa , NZ spinach), beetroot, bean, Petunia  and Nicotiana species are present in New 
Zealand (NZFlora 2021, NZPCN 2021; NZOR 2021). OFV has been reported from oranges 
(Citrus  sinensis ) in South Africa (Cook et al. 2019), and there are  783 hectares  of commercial 
oranges  in the northern parts of the North Island of New Zealand  (Citrus New Zealand  2019 ).   
Biosecurity New Zealand   {Name of paper in here} • 10 • The full host range of OFV may , to a large  extent , be determined by the host range of its mite 
vector, B. californicus, and so there is the possibility of new unidentified hosts.  
 
Brevipalpus californicus , the known vector of Orchid fleck dichorhavirus , is present in New Zealand : 
• Transmission of OFV by B. californicus  is known to be persistent and very likely propagative 
(Kondo et al. 2003; Peng et al. 2013).  
• The mite acquires the virus by feeding on infected tissue and the nymphs and adults 
efficiently transmit OFV even  after moulting. Thus, once the virus is acquired , the mite can 
continue to transmit the virus to the end of its life (Kondo et al. 2003).  
• However, t he distribution of B. californicus  within New Zealand is unclear ; although for the 
purpose of this assessment, it is assumed to include most areas of the N orth Island, given 
how long the mite  has been present in New Zealand  – it was first reported from Cymbidium  
sp. in Tauranga , collected by C.S. Rondel on 30 June 1965 (Manson 1967). Its current 
distribution  is unreported and therefore, very uncertain ,  
• No evidence was found of other mite or insect vectors of OFV . 
 
 
If Orchid fleck dichorhavirus became established, the likelihood of spread is considered to be 
low, with high uncertainty  
 
Spread may occur via the movement of infected plants, transmission by the mite vector and 
potentially, mechanical transmission:  
• OFV spread within New Zealand is likely to be facilitated through movement of infected 
plants that are not yet showing symptoms or that have very minor symptoms , which  might 
be misdiagnosed by less experienced growers. However, trade and movement of 
sympto matic plant material is unlikely.   
• Mechanical transmission is thought to perhaps play a minor role in natural infections , 
although  OFV particles are unstable outside the host cell (Wilson 1999 cited in Ali 2013).  
• It is un reported (but possible) that mecha nical transmission may  facilitate plant to plant 
spread via sap on tools or equipment in a greenhouse within a narrow timeframe.  
Homogenate of the virus, in sap transmission studies , has been shown to remain infective for 
7-8 minutes following homogenisati on in summer and about 15 minutes in winter (Inouye et 
al. 1996 cited in Ali 2013). The experimental homogenate is assumed to be prepared in a pH 
stable buffer so that the virus infectivity should be much longer than that in the sap on tools.  
• Viruliferous B. californicus  may be moved on plant material, people, animals or by air 
currents to new hosts and thus facilitate OFV spread.  
 
There is low uncertainty regarding the ability of the virus to survive outdoors in New Zealand 
conditions, and greenhouses are likely to be highly suitable. However, the re is high  uncertainty  with 
regard to spread, as the re is no up -to-date reporting on the  geographical distribution, abundance 
and host range of the vector, B. californicus , in New Zealand . 
 
2.3.4 The i mpacts  in New Zealand  
 
Orchid fleck dichorhavirus  is likely to cause low-to-moderate impact  to New Zealand , with 
high uncertainty  
Damage and symptoms caused by OFV infection can reduce plant quality and may result in plant 
destruc tion, leading to economic losse s: 
• Chlorotic and necrotic lesions  and reddening of leaves  diminish the appearance of the orchid 
plant and consequently can reduce the value and saleability  (Bratsch et al 2021) .   
Biosecurity New Zealand   {Name of paper in here} • 11 • OFV reduces the number and quality of flowers and can  reduce the fitness of the plant 
rendering it susceptible to secondary infections  from fungal and bacterial pathogens (Bratsch 
et al 2021).  
• There is no cure for OFV and other orchid viruses. Meristem tissue culture has been reported 
to eliminate viral infe ction from high value plants, but it is expensive and laborious with 
variable success rates. Thus, management of disease spread is usually by testing for virus and 
then removing2 and destroying the infected plant (Ali 2013). Where multiple plants within a  
collection, especially a valuable or rare collection, are infected this can have a serious impact 
upon the grower.  For citrus growers, it may mean removal and destruction of infected trees.  
 
Establishment of OFV is likely to increase phytosanitary measur es required for orchid export s to 
countries where OFV is absent or regulated, or potentially where citrus leprosis is absent/regulated : 
• OFV is an A1 pest for the European Union (EPPO 20 21). French Polynesia, India and Mauritius 
all have international quara ntine regulations for OFV (ONZPR 202 1). 
• An incursion of OFV  in New Zealand could cause impacts due to removal of productive 
plants, costs of surveillance and loss of income from sales of orchids (and potentially fresh 
citrus) in domestic and export markets . 
• The exports of cut  flowers and foliage, seed, bulbs and live plants were worth $164.0 million 
to New Zealand in 2019. Cut  flower exports contributed $20.0 million, of which orchid 
flowers dominated earning $10.9 million ( Plant and Food Research  2019).  
• In 2019, export sales of fresh citrus fruit were worth $12 m and the value of domestic orange 
sales was $58.5 m illion  (Plant and Food Research  2019).   
• Containment and eradication of the virus would be possible if incursions are detected early , 
especially within individual glasshouses. Rate of spread is likely to be slow, as the virus is not 
systemic under normal growing temperature (< 30°C) and transmission is vector dependent 
(Kondo et al. 2003)  
  
There is a high level of uncertainty associated with economic impacts. The distribution and 
abundance of the vector, B. californicus , within New Zealand is unclear. If the mite is not currently 
present in citrus orchards this reduces the level of impact. Also, the OFV-orchid strain has only been 
found i n citrus in South Africa (Cook et al. 2019) and it is uncertain whether this strain would 
necessarily affect citrus in New Zealand.  
 
Environmental impacts from Orchid fleck dichorhavirus are likely to be low overall for New Zealand , 
with high uncertainty  
• Environmental impacts are largely dependent on a viruliferous mite vector moving from 
infected cultivated host plants into native orchids.   
• There are residential areas in New Zealand that border nature reserves and regional parks 
whe re native orchids occur.  A good example is East Harbour Regional Park (Greater 
Wellington Region) where several species of native and endemic orchid species are found 
growing on track edges and banks that join with the gardens of residential properties. It  is 
currently unknown if any of these native orchid genera are likely to become hosts of OFV . 
 
There is a high degree of uncertainty associated with environmental impacts . This is because we do 
not know the current distribution or abundance of the vector, B. californicus , within New Zealand, 
and we do not know what the host plant range for it is in New Zealand . 
 
Social impacts of Orchid fleck dichorhavirus are likely to be low  to moderate , with  moderate -high  
uncertainty:  
• Orchid hobbyists have usually invested a considerable amount of time and money into their 
collections, especially when growing tropical species that require heated glasshouses. 
Infected plants would be a significant issue, especially if the mite vector is present and active.  
 
2 The term often used I for removing damaged/infected plants ‘rogueing’.   
Biosecurity New Zealand   {Name of paper in here} • 12 There is moderate -high uncertainty about this conclusion as there are no readily available figures for 
the cost of orchid hobby -growing  nor for the distribution of the mite vector . 
 
Orchid fleck dichorhavirus is unlikely to cause any d irect health impacts on human health:  
• OFV is a plant pathogen and has not been reported to affect human or animal health.  
 
2.4 Conclusion s regarding risk management question  
• Orchid fleck  dichorhavirus  virus  (OFV) meets the criteria to be added to the regulated pest list 
for New Zealand  
• Given existing import requirements, the likelihood of entry of OFV on Oncidium  and other 
orchid genera into New Zealand on the nursery stock pathway is considered to be low. 
However, the virus may be considered for additional measures, given that the moderate 
likelihood of establishment and the high uncertainty around potential impacts , especially as 
such impacts could be higher than estimated   
 
 
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Biosecurity New Zealand   {Name of paper in here} • 15 Appendix 1  
 
Table 2. Orchid  genera and other plants  reported as naturally infected by  OFV  
 
Family  Scientific name  Reference  Genus on 
PBI?  Number of species allowed 
into NZ (Includes 
synonyms)  
Orchidaceae  Amblostoma  sp. In: Peng et al. 2013  no n/a 
 Angraecum  sp. In: Peng et al. 2013  yes 25 
 A. sesquipedale  In: Peng et al. 2013  yes yes 
 Angulorea  sp. In: Peng et al. 2013  no n/a 
 Baptistonia 
echinata  In: Peng et al. 2013  yes yes 
 Bulbophyllum  sp. In: Peng et al. 2013  yes 41 
 B. elbertii  In: Peng et al. 2013  no Not listed  
 Calanthe  sp. In: Peng et al. 2013  yes 24 
 C. bicolor  In: Peng et al. 2013  yes yes 
 C. discolor  In: Peng et al. 2013  yes yes 
 C. hizen  In: Peng et al. 2013  no Not listed  
 C. triplicate  In: Peng et al. 2013  no Not listed  
 C. longicalcorata  In: Peng et al. 2013  no Not listed  
 C. satsuma  In: Peng et al. 2013  no  
 Cattleya  sp. In: Peng et al. 2013  yes 45 
 C. aclandii  In: Peng et al. 2013  yes as ‘aclandiae’  
 Cymbidium  sp. In: Peng et al. 2013  yes 34 
 C. formosanum  In: Peng et al. 2013  no Not listed  
 C. kanran  In: Peng et al. 2013  no Not listed  
 C. sinense  In: Peng et al. 2013  yes yes 
 Cymbidium  
hybrid  In: Peng et al. 2013  - - 
 Dendrobium  sp. In: Peng et al. 2013  yes 240 
Orchidaceae 
(cont’d)  Dendrobium  
hybrid  In: Peng et al. 2013  - - 
 D. fimbriatum  In: Peng et al. 2013  yes yes 
 D. moschatum  Ramos -Gonzalez et al. 
2015  yes yes 
 Dendrochilum  sp. In: Peng et al. 2013  yes 8 
 Diplocaulobium  
sp. In: Peng et al. 2013  no n/a 
 Encyclia  sp. In: Peng et al. 2013  yes 31 
 Epidendr on [sic] 
sp. In: Peng et al. 2013  no n/a 
 Epidendrum [sic] 
veroscriptum  Ortero -Calina et al 
2021  no n/a 
 Hamelwellsara  
hybrid  In: Peng et al. 2013  no n/a 
 Hormidium 
calamarium  In: Peng et al. 2013  no n/a 
 Liparis 
plantaginea  In: Peng et al. 2013  no n/a 
 Maxillaria  sp. In: Peng et al. 2013  yes 19 
 M. striata  In: Peng et al. 2013  yes yes 
 Miltonia  sp. In: Peng et al. 2013  yes 15 
 M. mourelliana  In: Peng et al. 2013  ? Maybe as mureliana?  
 M. rignelli x 
mourelliana  In: Peng et al. 2013  M. rignellii  
Is.  
 Octomeria  sp. In: Peng et al. 2013  No  
 Odontoglossum  
sp. In: Peng et al. 2013  yes 7  
Biosecurity New Zealand   {Name of paper in here} • 16 Family  Scientific name  Reference  Genus on 
PBI?  Number of species allowed 
into NZ (Includes 
synonyms)  
 Odontoglossum  
hybrid  In: Peng et al. 2013  - - 
 Oncidium  sp. In: Peng et al. 2013  yes 133 
 Oncidium x 
Odontoglossum  Kitajima et al. 2010  Not listed  - 
 Pescatorea  sp. In: Peng et al. 2013  no n/a 
 Phaius  sp. In: Peng et al. 2013  yes 4 
 Phalaenopsis  sp. In: Peng et al. 2013  yes 46 
 Pleurothallis  sp. In: Peng et al. 2013  no n/a 
 Prostechea  sp. In: Peng et al. 2013  no n/a 
 Schomburgkia sp. Kubo et al. 2009  yes 7 
 Stanhopea 
embreii  In: Peng et al. 2013  no But 13 other species are 
listed  
 Tetragamestus  
sp. In: Peng et al. 2013  no n/a 
 Trichopilia  sp. In: Peng et al. 2013  yes 6 
 Wilsonara  hybrid  In: Peng et al. 2013  no - 
 Zygopetalum  sp. In: Peng et al. 2013  yes 8 
Asparagaceae  Cordyline  
terminalis  (syn: 
C. fruticosa ) Dietzgen et al. 2018  yes (seed and NS)  
 Liriope spicata  Mei et al. 2016  yes (seed and NS)  
Malvaceae  Alcea rosea  Read et al. 2021  yes (seed -Basic)  
Rutaceae  Citrus sinensis  
(cv. navel and 
cv.Valencia)  Cook et al. 2019  yes (seed and NS)  
 
 
 
Table 3    Non -orchid plants infected by OFV following experimental mechanical inoculation .  
Family  Scientific name  Reference  
Aizoaceae  Tetragona expansa  (synonym of T. 
tetragonoides  ) In: Peng et al. 2013  
Amaranthaceae  Amaranthus lividus  In: Peng et al. 2013  
Apocynaceae  Vinca major  In: Peng et al. 2013  
Chenopodiaceae  Beta vulgaris  In: Peng et al. 2013  
 B. vulgaris var. cicla  In: Peng et al. 2013  
 Chenopodium amaranticolor  In: Peng et al. 2013  
 C. foliosum  In: Peng et al. 2013  
 C. murale  In: Peng et al. 2013  
 C. quinoa  In: Peng et al. 2013  
Compositae  Lactuca laciniata  In: Peng et al. 2013  
Convolvulaceae  Pharbitis nil  In: Peng et al. 2013  
Euphorbiaceae  Acalypha australis  In: Peng et al. 2013  
Leguminosae  Cassia tora  In: Peng et al. 2013  
 Phaseolus vulgaris  In: Peng et al. 2013  
 Vigna sinensis  In: Peng et al. 2013  
Malvaceae  Hibiscus manihot  In: Peng et al. 2013  
 H. syriacus  In: Peng et al. 2013  
Rutaceae  Citrus hassaku  In: Peng et al. 2013  
Solanaceae  Datura stramonium  In: Peng et al. 2013  
 Nicotiana clevelandii  In: Peng et al. 2013  
 N. glutinosa  In: Peng et al. 2013  
 N. tabacum ssp. In: Peng et al. 2013  
 Petunia hybrida  In: Peng et al. 2013  
 
  
Biosecurity New Zealand   {Name of paper in here} • 17 Appendix 2 
 
A summary of Orchid fleck dichorhavirus  -orchid strain, reported from Citrus sinensis in South 
Africa  by Cook et al. (2019).  
 
Orchid fleck dichorhavirus  (orchid strain) is thought to have been introduced to South Africa in 1995 
via imported orchids (Cook et al. 2019). Symptoms resembling those of citrus leprosis (CL) were 
initially observed in 2018 in Valencia orange (‘Delta’ and ‘Midknight’) orchards in the Sundays River 
Valley region of the Eastern Cape Province. Samples were tested by two step RT -PCR for the 
presence of viruses associated with CL. Full genome sequences of OFV from citrus and OFV from 
orchids in South Africa were generated, and showed cl ose sequence identity to each other (99%) , 
which suggested the CL outbreak in the citrus may have come from orchids (Cook et al. 2019).  
 
Consequently, a South African Response plan for CL was developed and a delimiting survey was 
undertaken around the site s of the original CL find. All orchards with a boundary within 50 m of the 
infected orchard s were surveyed and Brevipalpus  mites collected and identified. Additionally, various 
orchid samples exhibiting OFV symptoms (chlorotic or necrotic ringspots or fleck s) were obtained 
from nurseries in Eastern Cape, Mpumalanga, North -West, Gauteng and Limpopo Provinces of South 
Africa. Twenty -six orchid samples were screened for dichorhaviruses (Cook et al. 2019).  
 
The delimiting survey found a total of 27 CL -infected orange orchards on 5 farms. Four of these farms 
were in the Sundays River Valley region and the fifth farm was in Gamtoos River Valley -still in 
Eastern Cape but 96km from the original C L find site. No symptoms of CL were found in mandarins or 
lemons in adjacent orchards despite Brevipalpus  mites being present in some of these orchards 
(Cook et al. 2019). This is quite different to the findings in Mexico where OFV -citrus strains were 
found in both mandar in and lemon, as well as  grapefruit, lime, sour orange and sweet orange (Roy et 
al. 2020).  
 
Mites collected at the sites showing CL were identified as Brevipalpus californicus  (Cook et al. 2019), 
which is the known vector of OFV. Most of the CL -infected or chards identified had sub -standard pest 
control measures (Cook et al 2019).  
 
The full genome sequence of OFV from an infected Brassia  sp. orchid (from Mpumalanga) displayed 
99% sequence identity to OFV found in citrus in South Africa. Phylogenetic analysis  of the complete 
L-gene showed that the OFV found in both citrus and orchids in South Africa cluster separately from 
the OFV found in citrus in Mexico  and are closely related to isolates from Japan and Korea identified 
in orchids (Cook et al. 2019).  
 
Concl usion  
Citrus leprosis -N3 symptoms seen in the navel and Valencia oranges in South Africa were associated 
with the presence of OFV. Full -genome determination showed closest sequence identity to a 
Cymbidium  isolate of OFV and not to isolates of OFV previous ly found in citrus in the Americas. Also, 
OFV was found in orchids in at least 3 provinces within South Africa. Genome determination of an 
orchid isolate showed 99% sequence identity to that found in citrus in South Africa. Based on these 
close identity se quences between the South African OFV genomes in orchid and in citrus, it is likely 
the CL -N outbreak in citrus originated from orchids (Cook et al. 2019).  
 
 
 
3 The N denotes that the virus responsible replicates in the host cell nucleus.   
Biosecurity New Zealand   {Name of paper in here} • 18  
 
 Figure 2.  ‘Delta’ Valencia orange fruit, leaves and twigs infected by OFV and showing citrus leprosis 
(CL) symptoms.  Images are from Cook et al. 2019  
 
 
 
 
Figure 3.  ‘Midknight’ Valencia orange twigs and fruit infected by OFV and showing CL symptoms  
Images are from Cook et al. (2019).