26 March 2020 
 CTO Decision Document PP_Dec_Dir2020065: Urgent amendment of phytosanitary measures for 
Potato spindle tuber viroid  (PSTVd) on Solanum melongena  (eggplant) seeds for sowing  
 
ISSUE: 
 
Previously Potato spindle tuber viroid  (PSTVd) has not been seen as presenting a biosecurity risk 
on the Solanum melongena  seeds for sowing pathway. However, following testing by MPI’s Plant 
Health and Environment Laboratory (PHEL), PSTVd has been detected on three consignments of S. 
melongena  seed imported into New Zealand.  
 
Based on this new awareness the current measures are now considered insufficient. An urgent 
amendment is needed of the Import Health Standard 155.02.05, Seeds for Sowing (IHS) to include 
measures to manage the risk on this pathway. 
 
It is proposed the Chief Technical Officer (CTO) is to decide whether PSTVd poses a risk on the S. 
melongena seeds for sowing pathway, and whether urgent measures are necessary. The proposed 
measures are to change the import specification of S. melongena seeds for sowing from only general 
requirements, to include the specific requirements under the Solanum schedule on the IHS. 
 
BACKGROUND: 
 
PSTVd has been intercepted twice on the same pathway in consecutive months. The interception 
details are as follows: 
- C2019/507120  S. melongena  seeds for sowing from USA, 16 December 2019  
- C2020/52333 S. melongena  seeds for sowing from Netherlands (origin China), 9 February 
2020 
In both instances PSTVd was only detected because the seed was tested for re-export from New 
Zealand. Following tracing from the USA seed lot, it was also identified that an earlier shipment of 
S. melongena  seed had originated from the same seed lot. It was subsequently tested and also found 
to have PSTVd. 
 
Regarding the risk associated with PSTVd on S. melongena , seeds for sowing is the only pathway 
that is open, because S. melongena nursery stock cannot be imported. The requirements on the seed 
pathway are now considered insufficient for this new risk, because S. melongena seed only has to 
comply with the general requirements of the IHS. This means that no phytosanitary certificate or 
testing is required to import S. melongena  seed into New Zealand, and PSTVd is not able to be 
detected under those conditions. 
 
Previously, S. melongena  was not generally believed to be a natural host of PSTVd.  However, 
these recent interceptions suggest otherwise. It is worth noting that the PHEL diagnostics report 
states it is not known whether the detection of PSTVd in these seeds is the result of a natural 
infection, or of contamination of the seed during processing. The reason urgent measures are 
considered appropriate is due to the understanding that PSTVd is seed transmissible in other 
Solanaceae species (MAF Import Risk Analysis, 2012). 
 
The purpose of this assessment of measures is to consider whether urgent measures need to be put 
in place to manage PSTVd on S. melongena  seeds for sowing pathway. The proposed measures 
would consist of changing the import specification of S. melongena  seed on the Plant Biosecurity 
Index (PBI) from Basic requirements, to requiring this species to meet the specific requirements 
under the Solanum  schedule of the IHS.   The specific requirements for seed imported under part 2 
 
 
26 March 2020 
 2.73 Solanum of the IHS include measures to manage the risk of PSTVd. These include the 
additional declarations to the phytosanitary certificate or specific testing as follows: 
 
a) “The [insert species name]  seeds for sowing have been: 
i) Sourced from an ‘pest free area’ free from Potato spindle tuber viroid ; 
OR 
ii) Sourced from a ‘pest free place of production’ free from Potato spindle tuber viroid” ; 
OR 
b) “The [insert species name]  seeds for sowing have been officially tested, on a representative 
sample and using appropriate methods, and found to be free from Potato spindle tuber 
viroid”. 
 
The Solanum schedule was included in the IHS specifically to manage risk from PSTVd, and the 
same measures are used to manage risk from PSTVd under three other schedules in the IHS. As 
such, the proposed measures are the same as those previously considered by the CTO to effectively 
manage risk from PSTVd. Thereby, managing the risk of PSTVd on S. melongena . 
 
ASSESSMENT OF MEASURES: 
 
The International Standards for Phytosanitary Measures (ISPM) 1: Phytosanitary principles for the 
protection of plants and the application of phytosanitary measures in international trade, states 
“Contracting parties may adopt and/or implement emergency actions, including emergency 
measures, when a new or unexpected phytosanitary risk is identified”.  
 
Applying the ISPM 1 guidelines on emergency action, it is considered there is risk associated with 
PSTVd entering New Zealand by the S. melongena  seed pathway, and urgent measures are needed 
and justified for the following reasons: 
 
1) PSTVd has now been found thrice on the S. melongena  seeds for sowing pathway. Suggesting 
that PSTVd on this pathway is now a biosecurity risk that needs managing. 
2) According to CABI Invasive Species Compendium and EPPO, PSTVd is present in many 
countries throughout the Americas, Africa, Europe and Australia. And previous S. melongena  
seed imports have many sources of origin.  
3) The MAF import risk analysis (2012) states that transmission of PSTVd is highly contagious. 
The viroid can be transmitted by touch, pollen and seed of infected plants. 
4) While there is still a lack of direct evidence that seed transmission of PSTVd occurs specifically 
with S. melongena  seed, the MAF import risk analysis states PSTVd has been confirmed to be 
seed transmitted on other solanaceae, such as tomato and potato. Following these recent 
interceptions it can be extrapolated that seed transmission on S. melongena  seed is a likely risk. 
5) The S. melongena  seeds for sowing pathway is currently an open and active pathway. With over 
40 lines being imported per year from 2017 to 2019, and 7 lines in 2020 already. At least half of 
the countries of origin for these lines have PSTVd. It is a possibility that PSTVd may have 
entered New Zealand on S. melongena  seed already. There have not been reports of symptoms 
in the field, but without measures there are many opportunities for introduction of PSTVd on S. 
melongena  seed. 
6) The impact that PSTVd poses to S. melongena plants is not known, but the impacts are well 
known for other hosts of PSTVd which are present and important to New Zealand, e.g. tomato 
(Solanum lycopersicum ), potato ( Solanum tuberosum ) and capsicum ( Capsicum annuum ).  3 
 
 
26 March 2020 
  
7) If PSTVd established in New Zealand, the potential impact on industry would be undesirable to 
the producers of solanaceous crops. The Fresh Facts 2018 report shows the combined value of 
both domestic and export sales of potato exports was $280 million, and tomato domestic sales 
were worth approximately $200 million. Although the impact of PSTVd on S. melongena yield 
and marketability is unknown, the MAF import risk analysis (2012) states PSTVd has been 
shown to reduce size of tomato fruit and germination rates of tomato seed. PSTVd also causes 
changes in potato tuber growth which make them unsuitable for market and reduces yield. 
8) MPI is currently considering declaring that New Zealand has country freedom for PSTVd. 
Without a change in measures on the S. melongena  seed pathway, to prevent PSTVd entering 
New Zealand on that pathway, the country freedom status would be at risk. Country freedom 
would be important to the export industry as it would allow easier entry into other countries 
with PSTVd requirements. 
9) We are not the only country to consider that PSTVd is a risk needing management on the S. 
melongena seeds for sowing pathway. On 8 January 2020 Thailand’s Department of Agriculture 
and Ministry of Agriculture and Cooperatives submitted draft import conditions for importing S. 
melongena  seeds for sowing. These conditions require that S. melongena  seed must be 
confirmed to be: either produced in a country where PSTVd is not known to occur; or the S. 
melongena  seed must be officially tested using PCR and a sample size of 3000 seeds (or 10% of 
small seed lots). The Republic of Korea have already implemented measures for PSTVd on S. 
melongena  seed back in 2015. The measures require declarations of pest free area, pest free 
place of production or tested by PCR and found free from PSTVd. 
The continuance of the proposed measures, as per ISPM 1, will in time be subject to future 
assessment as to whether they are technically justified as new information becomes available. As 
part of this, scientists at PHEL are conducting an experiment using some of the infected seed to 
check whether PSTVd is seed transmissible on that particular variety of S. melongena . Results from 
this are expected in May 2020. 
 
CONCLUSION:  
 
It is considered that there is a new potential risk of PSTVd on the S. melongena  seeds for sowing 
pathway, and that urgent measures are required to manage this risk. The proposed measures would 
result in a change of the import specification for S. melongena  seeds from only general 
requirements, to include the specific requirements under the Solanum schedule of the IHS. This 
results in S. melongena  seed imports requiring additional declarations or testing to prevent the entry 
of PSTVd into New Zealand. 
 
LEGAL:  
 
24B Amendment, revocation, suspension, and reinstatement 
Amendment and revocation 
(1) Sections 23 to 24A  apply, to the extent to which they are relevant and reading in any necessary 
modifications, to— 
(a) proposed amendments to an import health standard: 
(b) a proposal to revoke an import health standard. 4 
 
 
26 March 2020 
 (2) However, if a chief technical officer considers that the standard needs to be amended or revoked 
urgently or that a proposed amendment is minor, the officer is not required to comply with section 
23(3). 
 
REFERENCES: 
- Horticulture New Zealand, Plant & Food Research (2018) Fresh Facts 20th edition, 
https://www.freshfacts.co.nz/files/freshfacts-2018.pdf  
- MAF (Ministry of Agriculture and Forestry) (2012) Import Risk Analysis: Tomato and 
Capsicum seed for sowing from all countries  (Draft), 
https://www.mpi.govt.nz/dmsdocument/2887/send  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 5 
 
 
26 March 2020 
 RECOMMENDATION:  
 
It is recommended that you accept the proposal described below: 
 
1. There is an unmanaged risk of Potato spindle tuber viroid  (PSTVd) on Solanum melongena  
seed, and urgent measures are required. 
 
AGREED / NOT AGREED 
 
2. That the seeds for sowing import specification for S. melongena  be changed from only 
general requirements, to include the specific requirements under the Solanum schedule of 
the IHS. This will be achieved through a change on the PBI from “Basic” to “see 155.02.05 
under Solanum”. This will apply measures to S. melongena  seed and manage the risk of 
PSTVd on this pathway. 
 
AGREED / NOT AGREED 
 
 
 
 
 
Sarah Clark, Manager Plant Germplasm Import team 
Deputy Chief Technical Officer 
Plant & Pathways Directorate 
Date: