Risk Management Proposal:   
Measures for  Melon  necrotic  spot virus  on Cucumis melo  
(melon), Cucumis sativus  (cucumber) and Citrullus lanatus  
(watermelon)   
(Impo rt Health Standard  155.02.05 : Seeds for Sowing )   
   
 
Prepare for public consultation  
by the An imal and Plant Health Directora te 
 
 
  
 
 
 
 
April 2021  
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Plant Germplasm Imports  
Animal and Plant Health Directorate  
Biosecurity New Zealand   
Ministry for Primary Industries  
25 The Terrace  
Pastoral House  
PO Box 2526  
Wellington  6140 
New Zealand  
 
Tel: +64 4 894 0100  
Fax: +6 4 4 894 0662  
 
Email: plantimports@ mpi.govt.nz  
  
  
Contents  
Submissions  1 
OFFICIAL INFORMATIO N ACT 1982  2 
Objective  3 
Purpose  3 
Background  3 
Commodity description  4 
Trade  4 
Current requirements  4 
Source  information  4 
Context  5 
Domestic legislation  5 
International obligations  5 
Summar y of Risk  5 
Likelihood of introduction  6 
Impact  8 
Risk Management  9 
Current measures  9 
Proposed m easures  9 
Feasibility and Practicality of Measures  12 
Proposed IHS Requirements  12 
References  13 
Appendix 1 – Proposed new schedule for Import Health Standard 155.02.05: Seeds for Sowing  16 
Appendix 2 – Changes to current Cucurbitaceae  schedule for the Import Health Standard 
155.02.05: Seeds for Sowing  17 
Appendix 3 – Clarification for the phytosanitary measures not proposed to manage risk fro m 
MNSV  22 
Appendix 4 – Technical advice on Melon necrotic spot virus  (MNSV)  24 
  
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 1 Submission s  
The Ministry for Prim ary Industries (MPI) invites com ment f rom interested parties on the 
new proposed  measures for Melon necrotic spot virus  on Cucumi s melo  (melon) , Cucumis 
sativus  (cucumber) and Citrullus lanatus  (water melon)  seeds imported under I mport Health 
Standard  155.02.05: Seeds for Sowing1. The proposed import health standard (IHS) is 
supported by this ri sk management proposal.  
 
The purpose of  an import health standard  is def ined in sectio n 22(1) of the Bios ecurity Act 
1993 (the Act): “An i mport health standard specifies requirements that must be met to 
effectively manage ris ks associated with im porting risk goods , incl uding risk s arising becau se 
importi ng the goods  involves or might involv e an incidentally i mported new organism”.  
 
In accordance with Section 23 of the Act, MPI must  consult with interested p arties  before 
issuing or amending an imp ort health standar d under sect ion 24A of the Act.  Ther efore , MPI  
seeks formal comment on the pro posed import requir ements .   
 
Tips for  preparin g comments:  
• Make your comment s speci fic to a particular change in  IHS requirements or a question 
asked in this d ocument (referencing s ection numbe rs or commodity  names as 
applicable).  
• Provide  reasons, data and supporting publis hed references to support comments .  
• Use examples to illus trate your points . 
This will help us bette r understa nd yo ur feedback.  
 
Please send  your comments elect ronically. Include the follow ing in you r sub mission:  
• The title of the consu ltation document in the subject line of your email;  
• Your name an d title (if ap plicab le);  
• Your  organisation’s name (if applicable);  
• Your address.  
 
Send  submiss ions to: plantimports@mpi. govt.nz .   
 
If you wish to send your submission  by post , please send it to:  
Plant Germplasm Im ports  
Animal and Plant Health Directorate  
Biose curity New Zealand  
Ministry for Primary  Industries  
25 The Terrace , Pastor al House  
PO Box  2526  
Wellington 614 0 
New Zealand  
 
All submissions must arrive by close of business on 19 May 2021. Submissions re ceived by 
the clos ing date will be considered during the development  of the fi nal IHS. Submi ssions 
received after the clos ing date may be hel d on file for consideration when the issued standard  
is next revised/ reviewed . 
                                                 
1 Import Health Standard 155.02.05: Seeds for Sowing   
  
2 • RMP : C. me lo, C. lanatus  and C. sativus seed Ministry for Pri mary Indus tries  
Official Information Act 1982  
Please note that your submission is publ ic information , and it is MPI policy to publis h 
submiss ions and a review of the submi ssions on t he MPI w ebsite. Sub missions may also be 
the subject of requests for information under the O fficial Information Act 1982 (OIA).   
 
The OIA specifies that information is to be ma de available to requesters unles s there  are 
sufficient grounds for wi thholding i t, as se t out in th e OIA. Submitters may wish to indicate 
grounds for withholding specific infor mation contained in their submis sion, such as 
information  being  commercially sen sitive or personal . 
 
Any decision to wi thhold informa tion requested u nder the OIA is rev iewable by t he 
Ombudsman . 
 
 
 
Disclaimer  
 
While every effort has been made to en sure the information in this publication is accurate, the 
Ministry for Pri mary I ndustrie s does not accept any responsibility or  liability fo r error of fact, 
omission, interpret ation or opi nion that may be present, nor f or the consequences of any 
decisions based on this information.  
  
To request  further copies , please contact :  
  
Publications  Logistics Officer  
Ministry for  Prim ary Industries  
PO Box 2526  
WELLINGTON 6140  
  
Email: brand@mpi.govt.nz   
Telephon e: 0800 00 83 33  
Facsimile: 04  894 0300  
  
This publication is also availab le on  the Ministry fo r Primary Industries website at 
http://www.mpi.govt. nz/news-and-resources/publications/  
  
 
© Crown Copyright - Ministry for Primary Industries   
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 3 Objective  
1. MPI’s objective is to ensure  that the known biosecur ity risks associated with  Melon 
necrotic spot virus (MNSV)  on Cucumis melo , Cucumis  sativu s and Citrullu s lanatus  
seeds  for sowing  are mana ged appropriately and are consistent with New Zealand ’s 
domestic  legislation and interna tional obl igations.  
 
Purpose  
2. The purpose of this document  is to:  
a) Summarise the known  biosecurity ris ks associated with MNSV ; 
b) Propose phy tosani tary measures to ma nage the risk of MNSV on  the known 
hosts Cucumis melo , Cucum is sativus  and Citrullus lanatus , which are eligi ble 
for import into N ew Zealand  under specific re quireme nts in the  ‘Cucurb itaceae ’ 
schedule  in IHS 155.02.05: Seeds  for Sowing . 
c) Show  how the measure s proposed for Cucumis melo , Cucumis sativu s and 
Citrullus lanatus  seeds for sowing will effective ly manage known  biose curity 
risks; 
d) Provide informatio n to support the  consultation o n the draft amendments to 
IHS 155.02.05 : Seed s for Sow ing; and 
e) Seek stakeholder feedback on the proposed phy tosanitary measures2 or provide 
the basis for co nsultat ion with interested  parties for the amendment . 
 
3. The subject of public consultation is the specific amendments proposed in the draft 
Standard. This risk management proposal supports the draft Standard and should be read 
in full, and in c onjunction with the draft standard, to u nderstand the rationale behind the 
proposed import requirements. The risk manag ement proposal itself is not the subject of 
public consultation  
 
Background  
4. Melon necrotic spot  virus  was captured by  MPI’ s em erging risk  system  in 2017  and 2018  
as a seed -trans mitted pathogen with an expanding ge ographical distribution . 
5. MNSV belongs to the genus C armovir us of the family To mbusvir idae (Herrera -Vásquez 
et al.  2009) . It is not known t o be present in New Zealand an d is regulat ed in the Official 
New Zealand Pest Regi ster.  
6. MNSV  is a serious pathogen  of melons ( Cucumis melo ), cucumbers  (Cucumis sa tivus) 
and wat ermelo ns (Citrullus  lanatus ) worldwide  (Herrera‐Vásquez  et al. 2009 ; Kwak  et al. 
2015) . The virus is reported to cause significant yield losses and reduction  in fruit quality  
in glasshouse  crops  and field crops o f these three species , leading to economic losses  
(Mackie et al.  2020).  
7. The first detection of MNSV in Australia was in the state of Victoria in May 2016 . In 
September 2016,  emergency measures were intr oduce d to manage  the risk of more  
introduction s of MNSV to Australia  (DAWE 2 020). 
8. MNSV is a seedborne  vector -assisted path ogen  (Mac kie e t al. 2020) . MNSV is not 
known to occur in New Zealand  (Veer akone et al. 2015). Howeve r, the soil-borne fungal 
vector is like ly to be present in New Zeal and (altho ugh th ere is some uncertainty)  (see 
Summary of Risk ). There are eight Olpidium  spp. recorded in New Zealand , and two are 
reported p lant-virus vector s, O. radicale  and O. brassicae  (Guy 2014) . 
                                                 
2 All public consultations now inc lude informa tion that outlines how sub missi ons can be made an d infor mation on the Official In formation 
Act.  
4 • RMP : C. me lo, C. lanatus  and C. sativus seed Ministry for Pri mary Indus tries 9. The vegetable se ed trade has  become globalised and is evolving —seed lines  are usually 
devel oped, commercially multiplied and p rocessed in various countries rather than  at a 
single  origin (DA WE 202 0). There fore, there is a  likelihood that MNSV can enter into 
New  Zealand th rough impo rted seeds if the risk  is not m itigated.  
10. MPI has identified that the impo rt requirements fo r Cucurbitaceae  seeds in IHS 
155.02.05: Seeds f or Sowing  do not manage the risk to  New Zealand  posed by this vi rus. 
New Zealand h as ac tive import pathway s from countries i n Europe, Asia,  North America, 
Central Amer ica and Oceania  where MNSV is  known to be present. 
11. Theref ore, this risk management proposal includes proposed  measu res to manage 
potenti al risk from MNSV on imported melon, cucumber and water melo n seeds fo r 
sowing . 
 
COMMODIT Y DESCR IPTION  
12. The proposed measu res only apply to seeds of the following plant species that are listed 
on the MPI Plants B iosecurity Index (PBI)  as eligible to be impo rted into New Zealand  
under specific requi rements  for ‘Cucurbitaceae ’ in Part 2 of the import healt h standard 
(IHS)  155.02.05 : Seeds for Sow ing. 
a) Cucum is melo (melon)  
b) Cucumis s ativus  (cucum ber) 
c) Citrullus la natus  (watermelon)   
TRADE  
13. Cucumbers and  melons are  economically important  crops for New Z ealand. Cucum ber 
sales were es timated t o be worth NZ$20 million domestically in 2018 (Plant & Food 
Research 2 019). Melo n sales  were es timated t o be wort h $28 million domestically in 
2018, and  exports were worth $ 2.2 million (Plant & Food Res earch 201 9). 
14. Since 2015, approximately 160 consignments of Citrullus  lanatus  and Cucumis  melo 
seeds  and 380 consi gnments  of Cucumis  sativus seeds have been impo rted into New 
Zealan d (Qua nCargo d ata, October  2020). 
15. Since 2015, seeds of the  MNSV  host species  (Cucumis  melo, Cucumis  sativus and 
Citrullus lanatus ) have been imported f rom the following regions  where MNSV is known  
to be present : Europ e [France, Italy, N etherla nds, Spa in], North America [Me xico, USA], 
Central America  [Guatemala, Honduras ], Asia [ China , Israel, Japan]  and Oceania 
[Australia] (Quan Cargo data, October  2020). 
CURREN T REQUIREMENTS  
16. Cucumis  melo , Cucumis s ativus and Citrullus  lanatus  can b e impo rted under the speci fic 
requiremen ts for Cucurbitace ae in Part 2  of IHS 155.02.0 5: Seeds for So wing. 
Cucurbitaceae -specific measures are in place for the management of Cucumber g reen 
mottle mosaic virus  (CGMMV) and Kyuri green mo ttle mosaic virus  (KGMMV) . 
17. In addition to the specific requirements  in Part 2 , all imported  seeds must meet Part 1: 
General Requ irements  of IHS 155.02.05:  Seeds for  Sowing. 
SOURCE  INFORMA TION  
18. The following information w as use d to a ssess th e risk o f MNSV  and the appropria te 
measures to manage its entry and establi shment in New Z ealand:  
a) MPI technica l advice  (MPI 20 21a) (Appendix 4) 
b) MPI Em erging Risk System /emerging risk alerts   
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 5 c) Relevant literature and  database searc hes 
d) Final r eview of  impor t conditions f or cucurbitaceous vegetable seeds fo r sowing, 
Department of  Agriculture, Wate r and the Environmen t, Canbe rra (DAWE 
2020 ) 
e) Stakeholder discu ssions during the d evelopment of this risk managemen t 
propos al 
Context 
DOMESTIC  LEGISLATION  
19. The New Zealand bio security  syste m is regulated through the Biose curity Act 1993 . 
Section 22 of the Act de scrib es the  meani ng of an import health  standard  and req uires the 
import heal th standard to specif y require ments to be met for the effect ive management of 
risks a ssociated with i mporting risk goods (inc luding p lants and plant products) into New 
Zealand. 
20. The Ministry for Pr imary Industries  (MPI) is the government authority res ponsi ble for the 
effective management of risks asso ciated with importing risk goods into New Zealand 
(Part 3, Biose curity Act 1993 ). 
21. MPI engages with interested  parties and/o r affected New Zealand stake holders when 
amendments are made to an import health standar d. 
22. MPI fo llows MPI gui dance for d ecision -makers and procedur es for the amendme nt of an 
IHS and consultation.  
INTERNATIONAL OBLIGATION S 
23. Where pos sible, phytosanitary measures are alig ned wi th international standar ds, 
guidelines and rec omm endations3 as per N ew Z ealan d’s obligatio ns under Ar ticle 3.1  of 
the W orld Trade Organization  Agreement on the Applica tion of Sani tary and 
Phytosanitary Measures (SPS A greem ent), WTO 1995  and section 23(4)(c) of t he 
Biose curity  Act 1993 .  
24. The SPS Agreement  states that phyto sanitary measures must not  discriminate unfa irly 
between coun tries or between imported or domestical ly produced goods, and where there 
is a choi ce of phyto sanitary m easures to reduce risk to an a cceptabl e leve l, WTO 
mem bers must select th e least trade-restrictive measure .  
 
Summary  of Risk 
25. Risk orga nisms are regulat ed on the commodity if they : 
a) are presen t in the exp orting country and not known t o be present in New Zea land 
(or are present but under  official cont rol); 
b) have  the potential to b e introduced on the  import pathway if the risk is  
unmitiga ted; 
c) are known to be  associated with the commodity;  
d) their hosts include species that are present  in New Z ealand , including 
environmentally and economically  significant h osts; 
e) have  the potential  to establ ish in New Zea land (climate matching) ; and 
f) have  the poten tial to cause  a significant impact to the New Zealand economy.  
                                                 
3 Note that in ternational stand ards, guidelines or recommend ations  referred to in t he WTO agreement are  those of Codex, the Worl d 
Organisation for Anima l Health  (OIE ) and th e International Plant Protection Conventi on (IPPC ).  
6 • RMP : C. me lo, C. lanatus  and C. sativus seed Ministry for Pri mary Indus tries  
26. As per th e risk assessment by MPI, Melon nec rotic spot virus  is assessed as  a hazard  to 
New Zealand with potential  to enter on the  seeds  for sowing import pathway . A summary 
of the assessment follows  (see MPI technical advi ce 2021 in Appendix 4). 
LIKELIHOOD OF I NTRODUCTION  
Likelihood of entry  
27. The likeliho od of MNSV enter ing New  Zealand associated wi th seeds for sowing  is 
considered moderat e with high un certai nty (MPI 2021 a), as assessed below .  
28. The virus has been detecte d in internationall y traded seeds. In 2016 , MNSV was d etected 
in two watermelon s eed lots a rriving in Au stralia  (MPI  2021 a).   
29. MNSV  is seedborne a nd occurs both externally  and internally in  infec ted seeds  (Kwak et 
al. 2015 ; MPI 2021 a). Infected seeds enable t he virus to move between co untries and/or 
areas . 
30. Comm ercial seeds may undergo treat ments  designed to re move ex ternal contamination,  
such as acid was hing. Such seed treatments are likel y to remove an externall y 
contaminating virus  and reduce it to a low level,  although  they would not completely 
remove MN SV from seed lots  (MPI  2021 a). 
31. Seed tran smission (from infected s eed to  seedlings ) has been reported  from  Citrullus 
lanatus  (Kwak et al . 2015) and Cucumis melo (Lecoq and Katis 2014 ; Kwak et al . 2015 ) 
(FAO  2016)  and large volume of seeds of these s pecies are imported to New Zealand 
every year (MPI 2021 a), providing an e ntry pathway fo r MNSV .  
32. MNSV is known to be present in over 10 countries that expo rt Citrullus and Cucum is 
seeds  to New Zeala nd, and MNSV  has su ccessfully  spread within countr ies in Asia,  
Africa, North Ame rica, South America Europe  and Oceania . This is an emergi ng 
pathogen in Australia, wh ich is currentl y under eradicatio n. Emergency measures were 
introduc ed in 2016  to manage t he risk of more  introduction s to Australia  (DAWE 2 020).  
33. The high uncertainty  of moderate likelihoo d of ent ry estimated is  due to  the lack of dat a 
around  the prevalenc e of the virus in traded seeds , and there is no informa tion as to how 
many seed lots were tested  (MPI 2021 a). 
 
Likelihood of exposure  
34. The likelihood of exposure of MNSV via infected seed fo r sowin g to a plant in New 
Zealand  is considered  high, w ith low unc ertainty (MPI 2021 a), as assessed below.   
35. Seeds for sowing a re planted and su bsequen tly treated in suc h a way as to promote 
growth of the host. MNSV is report ed to be seedborne and seed-trans mitte d (MPI 2021 a). 
36. Varyin g rates of seed transmi ssion  of MNSV  are reported. For example, in melon 
(Cucumis melo ), the seed t ransmission rate varies as 10 –40%, 2 2.5%, 1 –6% (MPI 2021a) 
and 11.3 –14.8% (Herrera ‐Vásquez et al.  2009). Seed -to-seedling transmission of MNSV 
is reported from Citrullus lanatus  (Kwak et al . 2015) and Cucumis melo  (Lecoq and Katis 
2014; Kwak et al . 2015).  
37. Therefore, if the virus is present  in seeds,  it does not  need to spr ead beyond the pathway 
in order to be exp osed to a suitable host and environment  (MPI 2021 a). 
38. Furthermore,  a soilborne  fungal vector is also known to transmit MNSV  (see next 
section) , meaning that if seeds  are planted , MNSV will also come into con tact with  the 
vector if it is present  (MPI 2021 a). 
 
Likelihood of establishment  and spread  
39. The likelihood of MNSV establi shing and spreading in New Zealand from infested seed 
for sowing is considered moderate, with low uncertainty  (MPI 2021 a).  
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 7 40. MNSV can b e transmi tted via zoospores of th e soilborne fungal vector  Olpidium 
bornovanus  (=Olpidium radicale ). The two mechani sms involved  are (1) ‘in vitro’  
acquisition , whereby the virus is adsorbed onto the outside of zoospores, from s oil or 
water  and ( 2) ‘in viv o’ acquis ition, where by the virus is absorbed  by the zoospore when 
attached to the root system  of an infected plant  (MPI 2021 a).  
41. The virus can also survive a nd remain infectious in soil associated with the fungal vector ; 
thus, MNSV can remain in s oil betwe en crops . Ther efore, t he fungal vector plays a n 
important role in the transmission of MNSV, as well as its long -term establishmen t in 
plant debris and soil without a living host  (MPI 2021 a; DAWE 2 020).  
42. The presence of  O. radicale  is uncertain  in New Zealand . Howev er, it is assume d that  it 
is present in New Zealand  because,  
a) Olpidium radicale is listed as present in N ew Zealand , althoug h O. bornovanus is 
not listed as a synonym and O. bornovanus  is not  listed  as recorded in  New 
Zealand  (MPI  2021a).  
b) There  are eig ht Olpidium spp. recorded in  New Z ealand  (Guy 2014) . 
c) Olpidium  spp. are plant parasites but not pathogens . It is unlikely that  this fungus 
would be dete cted during routine surveillance o f crops, as symptoms  would not be 
visible . For ex ample,  the presence of  O. bornova nus in Australia was uncertain 
until the incursion of MNSV  (MPI 2021 a). 
d) There is som e disagreement over the taxonomy of the Olpidium , and it may be 
that these represent an O. bornovanus  specie s complex  (MPI 2021 a). 
43. If MNSV  enter s New Zea land, it may be difficu lt to e liminate because , in associa tion 
with the  known fungal vector (or un known related vector) , the virus can  persist in the soil 
for several y ears.  
44. Because viru ses can establ ish wherever hosts a re present, temperature does not affect 
viral establishment (MPI 2021 a). New Zealand ’s climate is suitable for t he host plants of 
MNSV . MNSV has a very narrow host ran ge limited to C ucurbitaceae , but it is known to 
infect a  wide range of cucurbit  hosts (FAO 2016; DAWE 2020).  The natural hosts that 
are primarily infected are melon ( Cucumis melo ), cucumber ( Cucumis sativus ) and 
watermelon ( Citrullus lanatus ), but occasionally  pumpkin ( Cucurbita  maxima ), squash 
(Cucurbita pep o), fluted pumpkin ( Telfairia occidentalis ) and bott le gourd ( Lagenaria 
siceraria , syn. Cucurbita lagenaria ) (Mackie et al.  2020). These crops are grown in 
New Zealand in glasshouse s and open field s and provi de the suitable host range for th is 
virus  to establish .  
45. MNSV can also be spread by mechanical transmission through  Diabroti ca 
undecimpunctata  (spotted cucumber beetle) and Diabrotica balteata  (banded cucumb er 
beetle) (Fact sheet, Australia 2019). Neith er beetle i s present in New Zeala nd. However , 
the v irus may be spread by ot her beetles present in New Ze aland (MPI 20 21a). 
46. The vi rus can also be mechanically spread within a crop from infected plants during 
pruni ng with contaminated tools and equip ment , as well as by d irect contact betwe en 
plants  (MPI 20 21a). MNSV has also been rep orted to have spread through a hydroponic 
glasshouse within the water system . This is significant , as all of New Zealand’s 
cucumbers are grown in glasshouses  (MPI 2021 a). 
47. The virus has successful ly spread in other  countries following its initial detection . For 
example : 
a) MNSV  was first de tected in Korea in 2001,  and within five to six  years , the virus 
had spread nationwide  (MPI 2021 a).  
b) The virus has sp read within China and between different hosts since 2008 . It was  
first reported in melon plants in Jiangsu Province in 2008 , it was subsequently 
reported in  Xinjiang  Province from melon plants in 2014, and in 2016 , it was 
isolated from watermelon pl ants in Shandong Province (MPI 2021 a).  
8 • RMP : C. me lo, C. lanatus  and C. sativus seed Ministry for Pri mary Indus tries IMPACT  
48. The o verall economic impact of MNSV to New Zealand  is considered low, with low 
uncertainty , although  the economic imp acts for t he relative industries are likely to be 
higher  (MPI 2021 a).  
49. MNSV  may lead to a reduction in crop yield and fruit quality if it becomes  establish ed in 
New Zea land. The e stablishment of MN SV in New Zealand w ould threaten 
New  Zealand’s watermelon, cucumber a nd melon industries  (MPI 20 21a). 
50. There are 20 melon growers in New Zealand . Melons had a domestic market value of $28 
million in 2018 and an e xport value of $2.2 million in 2019 . These cro ps have a low 
export value, but they have a significant domestic mar ket. Therefore, econo mic impacts 
are most likely to be through l oss of domestic trad e, rather than the loss of exp ort revenue 
or trade re strictions  (MPI 2021 a). 
51. An outbreak of MNSV is likely to disrupt cucumber production  and increas e cleaning 
costs before  crops can be planted again , because all cucumbers in New Zealand  are 
grown in glassh ouses , and crop rotation , which is an important field method for 
controlling the fungal vector a nd virus , cannot be done in glasshouses (MP I 2021 a). 
52. Severe fruit los ses ar e desc ribed as a re sult of MNSV . In Korea, almost no frui t could be 
sold due to 100% infe ction with MNSV  in glasshouse cultivation  (MPI 20 21a). 
53. MNSV affected  more  than 60% of hydropon ically gro wn cucumbers , and the yield was 
greatly re duced (MPI 20 21a). 
54. MNSV was r eported  in a watermelon glasshouse . Almost  all plants were se verely 
affected , and 80% died  (DAWE 20 20).  
55. An outb reak of M NSV in Austral ia affecte d growers , who  suffered significant economic 
losses. Some g rowers reported up to 100% losses in waterme lon and melon crops due to 
poor fruit quality resulting from necrosis  (MPI 2021 a). 
56. In melons aff ected with MNSV, leaves may  curl, wilt a nd show necro tic spots. On the 
fruit surface, in dentations and brown s pots can appear. The flesh  may beco me dar k, 
hollow and rott en (MPI 20 21a). 
57. In waterm elon, initially small,  transpa rent, yellow s pots appear  on the y oungest leaves of 
the plant . The spots m ay turn b rown , enlarge and cause the leaves to w ilt, curl or die. 
Spots are often found on the s kin of the wate rmelo n. The fruit  may also be missha pen an d 
the flesh/rind may beco me discoloured, holl ow or water y (MPI 20 21a).  
58. In watermelon s, symptoms occur suddenly at the fruit ripening stage  (Kwak et al . 2015). 
MNSV can be asymp tomatic in youn g plants  (García -López  et al. 2018).   
59. Symptoms of MNSV are mainly seen in cool, low light condi tions . During  summer , 
plants may show no sympto ms (MPI 20 21a). 
60. The socio cultural  impacts of MNSV to Ne w Zealand are considered mode rate with low 
uncertainty , because cucumber  and melon plan ts are introd uced crops with no known 
traditional uses  for M āori, although th ere are many traditional uses of cucumber for 
Europeans, Indians, Middle Easterners and Southeast Asians. New Zealanders also val ue 
the ability to buy locally grown crops, and the impacts of MNS V may t hreaten  the supply 
and cost of locally  grown crops.  The plants  are not considered culturally si gnificant  for 
home gard eners in New Ze aland (MPI 2021 a), but impacts o f MNS V on home gar dners ’ 
ability to grow healthy crops at home would likely cause upset for many growers .  
61. The environmental impa cts of MNSV to New Ze aland are considered negligible  because  
MNSV has never been reported in native  plants  (MPI 2021 a). 
  
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 9 Risk Manage ment  
CURRENT MEASURES  
62. Species o f Cucurb itaceae eligibl e for impor t into N ew Z ealand  under  the import he alth 
standard  (IHS)15 5.02.05: Seed s for Sowi ng must meet  the Part 1 general requirements of 
the IHS and the Part 2 specific r equir ements for Cucurbita ceae.  
a) The gene ral requirements (Part 1 ) require seeds to be package d in cl ean p ackets, 
clearly labelle d with the scien tific/botanical name  and clean  of any 
contaminating plan t material,  debris, soil and con taminating seeds. Seeds are 
visually inspect ed at the border to  verify that the basic cond itions have bee n met.  
b) The current measures  for Cucurbitaceae  do not ma nage the risk of MNSV . 
1. The tw o quarantine pe sts that currently require  specific measures are 
CGMMV and  KGMMV . 
2. The specifi c require ments in the ‘ Cucurb itaceae ’ schedu le (Part 2)  state 
that a ph ytosanitary certificate is  requir ed fr om the exportin g count ry to 
certify that t he seeds  are sourced from pest-free area  or pest-free place 
of production  or have been officially te sted on a represe ntative sample, 
using the appropriate ELISA or PC R method, and have b een found  free 
from the above  viruses prior to import. 
63. The following  measures are p roposed to manage the biosecurity risks of MNSV . 
PROPOSED MEAS URES  
For Cucumis:  
64. Measures at the hos t genu s level  are proposed for Cucumis .  
65. Given tha t one species of the genus has e vidence of  seed transmission  (and it is expected 
that not al l natural oc currences of MNSV  and seed tran smissi on are reporte d), it is 
reasonab le to assume that Cucumis  species that lack natural host records  (i.e. C. anguria , 
C. melo, C . metulifer us, C . myriocarpus  and C. sat ivus) are also biologically capab le of 
being  suscep tible hosts of  MNSV and of transmitting  MNSV  through their seeds . 
66. C. melo and C. sativus  are the  only Cucum is seed species  currently being i mported into 
New Ze aland; therefore , the scope  of this RMP is limited to these two s pecies . The 
measures ar e proposed  for all Cucumis  spp. eligible for import  on the P lant Biosecurity  
Index . 
67. Australia’s requirement s for MNSV only apply to Cucumis melo , the species of Cucum is 
that shows evidence of seed transmission  (DAWE 2020).  
 
For Citrullus : 
68. Citrull us lanatu s is the only sp ecies in the  Citrullu s genus  that is eligible for export to 
New Zealan d (Plant Biosecurity Index ). Therefore , the only Citrul lus species with 
measures proposed in  this RMP is Citrullus lanat us.  
69. Australi a also regu lates MNSV on imported seeds of C. lanatu s (DAWE 2020).   
 
The proposed measures are as follows : 
Pest-free area (PFA)  
70. MNSV  has a wor ldwide distri bution, and therefore, pest-free area declara tions  will o nly 
be possi ble for a limited number o f countries. For the countries wh ere a pest -free area can 
be declared f or MNSV , this  measure offers a good level of assurance that consignment s 
are free f rom this pat hogen.  
71. Guidelines for  determin ing a pest-free area can be found i n the International Standard  for 
Phytosanit ary Measures  4 (FAO 2017c) . 
  
10 • RMP : C. me lo, C. lanatus  and C. sativ us seed Ministry for Pri mary Indus tries Pest-free place of production (PFPP)  
72. Pest-free place of production system s are a practical alternative for quarantine pathoge ns 
that have  visible symptoms. During the growing season, an  official inspection for disease 
symptoms and/or parent plant test ing for the a bsence of s pecific quarantine p ests can be 
used for the official  endorsement of a pest-free place of production  on the ph ytosanitary 
certificate.  
73. Growing se ason inspection is not suitable to determine a pest-free place of production  for 
MNSV because disease symptoms are no t always visible . Symptoms  in water melon s 
occur suddenly at the f ruit rip ening stage , and symptom exp ression is less likely during 
summer  (see paragraph s 57 and 58 ).  
74. MPI propose s managing  MNSV with an additional declaration on the phytosanita ry 
certificate to verif y that the seeds have been sourced f rom mother  plants that were 
sampled accordi ng to a n NPPO-approved methodol ogy and t ested us ing an NPPO -
approved PCR meth od during the  active gro wing period . Testing  during the active 
growth period verifies that a place of prod uction  is free of the pest. 
75. Guidelines for  deter mining a pest-free place o f production  can be fou nd in the 
International Standard  for P hytosanitary Measures 10 (FAO 2016c) .  
Seed te sting  
76. MPI p roposes testing either off shore or on shore on arrival in New Zealand  at the MPI 
labora tory. An NPPO -approved ELISA or PCR testing method  for testin g for MNSV , 
with testing  endorsed on the phyt osanitar y certificate , is proposed for  offshore  testing. 
Testing o nshore will be performe d using an MPI -approved testing method  (MPI 2021 b). 
77. MPI propose s the following  sampling re gime for testing fo r MNSV : 
a) For seed lots of 10,000 or more seeds : A representat ive sample of a minimum 
of 2,000 seeds , offic ially drawn acc ording to ISTA (Intern ational  Seed Testing 
Associa tion) or AOSA (Association of Offici al Seed Ana lysts) methodology , 
must be ta ken from each seed lot and tested by an NPPO -approved ELISA or 
PCR method . 
b) For seed lots with less than 10,000  seeds : A composit e sample of a mi nimum 
of 2,000 seeds m ust be officially draw n acros s all seed lots of the same seed 
speci es in a consignmen t, which must have been  produced at  the same place of 
production or productio n site.  To achieve a composite sample, pr oportionate 
samp ling must be car ried out across all l ots imp orted. A sample  of see ds must  be 
drawn from each imported lo t within  a consign ment, adding u p to 2 ,000 seeds. 
The size of the sample from each lot m ust be proportionate  to the size of the 
imported lot within the consignment.  
78. The sampling regime above is propose d because : 
a) As per  the International Seed Federation (IS F), Internati onal Seed Testing 
Associatio n (ISTA)  and Inte rnational Seed Health Initiative for  Vegetable Crops 
(ISHI -Veg), 2,000 seeds in t otal, i.e. 20 batch es (sub-samples)  of 100 seeds 
each, are require d to diagnos e seed stock material for cucurbit -infectin g viruse s, 
including  MNSV  (Dombrovsky  & Smith 2017) . 
b) This is consistent with the sampl ing req uirement for Cucurbitaceae  seeds for 
CGMMV , which has lower  rate of seed transmi ssion (0.9–8%; Dombrovsky & 
Smith 2017) than MN SV (1–40%; see pa ragraph 3 5). 
c) Most of the s peciﬁed sampling and testing requirements stip ulate a minimum of 
2,000 seeds for vir uses in order to achieve a nomina l 95% conﬁdence of 
selecting and detecting diseas ed seeds at a contamination rate of at  least 0. 15%. 
Sampling is  destruct ive, a nd this high  sample size makes import ing small 
quantities of seed s into New Zealand unfeasible (Lane et al.  2018) . Therefore , 
composite sampling is proposed for small seed lots .  
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 11 d) The size of the sample  will chan ge dep ending on the total size of the  lot4. Under 
New  Zealand requirem ents, a small seed lot5 should have a maximum of 10,000 
seeds for a ll species . 
1. For seed lots of 10,000 seeds or greater , a minimum sample size of 2,000 
seeds will provide at least a 95% co nfidence  level of detecting 0 .15% 
infestation. This m eans a maximum of 20% of the seed lot is sampled . 
2. When the seed lot size is reduced  below th e New Zealand -required 
maximum weigh t, a 20% sample will not provide the same  level of 
confidence of detecting  MNSV.  
3. Therefore, f or seed lo ts less than 10,000 seed s, a composite sampl e of 
2,000 seeds has been suggested to enable the same percentag e of each lot 
to be sampled . Otherwise , a larger percentage of the lot will need to b e 
sampled to provide the same  level of confidence of detecting MNS V at 
the same infestati on level . 
4. This sampling regime is in accordance with guidance in section 4.2.1 
“Sampl ing of small lots ” in ISPM 38: International movement of seed , 
which  states that for small lots , NPPOs should consider alte rnative  
sampling methodo logies (e. g. clustering s mall sample s of different lots 
for testing).  
5. A composite sample must  be drawn across  lots of a s eed species all 
origina ting from the same production site  based on the as sumption that 
the likelihood of exposure  to qua rantine pests in the envi ronment they 
were grown in  would be similar across the seeds i n these lots. When the 
sub-samples th at make up the composite sample all have similar levels of 
pest pr evalence, this incr eases the overall likelihood of detecti ng 
infestation at 0.1 5% levels wi th 95% confiden ce when the 2,000 seeds 
are tested .  
6. In creating the composite sample of 2 ,000 seeds  drawn across  multiple 
small lots (each < 10,000 seeds) in a consignment, the size of  the sample 
from each lot must be proportionate to the size of the lot a s part of the 
consignment . This is consistent with the sampling requirement for 
Cucurbitaceae  seeds  for CGMMV in the current import health standard 
(IHS)  155.02.05: Seeds for Sowing . 
e) In commercial s eed production , chemical disinfectio n treatmen ts followed by 
extensive wa shes could wash  out the virus from the seed coat and decrease 
considerably the vira l titre in the tested samples (Dombrovsky & Smith 2017). 
This may end up reducing the virus tit re below the detection threshold. See d 
analysis  under these con ditions will sh ow false negative res ults, because viable 
viral particles still exist in the inte rnal seed tissu es (Dombrovsky & Smith 2017 ). 
 
79. Seed dis infection treat ments (e. g. heat tr eatment and chemical treatment) are not 
propose d as options to mana ge risk from  MNSV  (see Appendix 3 for more details ). 
 
                                                 
4 A number  of unit s of a single commodity, identifiable by its homogeneity of composition, origin etc., forming pa rt of a consignment (FAO  
2017a ) 
5 A lot is considered  small when the sample size is m ore than 5% of the  lot size  (FAO 2017b  – see Appe ndix 2: Calculating  sample sizes for 
small lots: hypergeometric -based sampl ing (simple random sampling) .  
12 • RMP : C. me lo, C. lanatus  and C. sativ us seed Ministry for Pri mary Indus tries Feasibility and Practicality of Measures  
80. The New Zealan d melon , watermelon and cucumber  industries  would benefit from the 
measu res im plemented to miti gate the risk of importi ng MNSV  into New Zealand , which 
could help prevent  significant im pacts on production  for these industries.  
81. Seed testing al lows access t o seed produced for international markets  and gives a 
practical option fo r impo rting stored inven tory of seed where the country of origin is not 
specified and/or growing season inspections have not previou sly been unde rtaken.  
82. Any increased cost  of seed test ing for the importers would be o utweighed by managing 
the risk of entr y of MNSV.  
83. The f ollowing uncertain ties are potential barri ers for the trade . 
a) It is not known : 
1. whether a “pest-free area” declaration can be supplied by  all exporting 
countries fo r Cucumis mel o, Cucumis sativus  and Citrullus lanatus  seed for 
MNSV ; 
2. whether all exporting countries  could imple ment grow ing season testing of 
parent plants for MNSV ; or 
3. whether ELISA or PCR testing for MNSV is available in all exporting 
countries . 
b) The e fficacy of the sampling syste m for testing  is uncertain.  
c) It is possible that seed lots will take longer t o receive  biosecurity cl earance as a 
result of  waiting for lab results.  
 
 
Proposed  IHS Require ments   
84. In summary , the proposed  changes to th e IHS are as fo llows : 
a) A new  schedule to the IHS named  ‘Cucumi s’ that applies to a ll Cucumis  spp. 
and Citrullu s spp. (Appendix 1) 
b) Removal of Citrullus lan atus, and all Cucumis  spp. g iven under the curren t 
schedule ‘Cucurbit aceae ’ (update the Plant Biosecurity Index accordingly ) 
(Appendix 2) 
c) Addit ion of r isk managment options  for MNS V in the new Cucumis schedule : 
1. A “pest-free area” declaration ; or 
2. Growin g season testing  of parent plants for MNSV ; or 
3. Seed testing  
• Offshore : NPPO -approved ELISA or PCR test with testing 
endorse d on the phy tosanitary certif icate  
• Onshore: Testing using an MPI -approved testing method   
85. The proposed requirements for MNSV on  Cucumis  melo, Cucumis  sativus and Citrullus 
lanatus  seeds  are that one of  the following additional declarations  will be pres ented on 
the phytosanitary certi ficate  (alternatively  if the option for  treatment or testing is selected, 
this can be completed  on arrival i n New Zealand) : 
 
“The [spe cies name] seeds have been:  
 
sourced fr om a “ pest-free area”, free from Melon necrotic spot virus. 
OR  
sourced from mother plants tha t were samp led according to an NPPO -
approved metho dology and test ed using an NPPO -approved ELISA or PCR  
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 13 method during the acti ve growi ng period and found free from Melon necrotic 
spot virus. 
OR  
sourc ed from a se ed lot off icially tested on a representati ve sample of a 
minimum of 2 ,000 seeds officially dra wn according to  ISTA or AOSA  
sampling method ology  using an NPPO-approved ELISA or PCR tes ting 
method and found free from Melon necroti c spot virus.” 
 
86. MPI propose s that specific requi reme nts for ‘Cucumis ’ are added to the IHS  in a new 
schedule name d ‘Cucumi s’ to manage MNSV o n Cucumis  melo, Cucumi s sativus and 
Citrullus lanatus seeds . The proposed  specific requirem ents for C. melo, C. sativus and 
C. lanatus  seeds can be  found in Appendix  1. 
87. MPI w elcome s comments on th e proposed measur es. 
 
References  
DAWE (2020 ) Department of Agricultu re, Water and the Environment 2020 , Fina l review of 
import conditions for cu curbitaceous vegetable  seeds for sowing,  Department of  
Agricul ture, Water a nd the Envi ronm ent, Canberra, June. C C BY 4.0  
 
Dombrovsky,  A.; Smith, E . (2017) Seed transmission of Tob amov iruses : Aspects of global 
disease distribution.  In Advances in Seed B iology. IntechOpe n; London , UK. pp. 233–60.  
 
Fact sheet, Australi a. Melon necr otic spot virus . Last reviewed  31 Jul y 2019 ; last updated  4 
October 2019.  
https://www.bu siness.qld.go v.au/industries /farms -fishing -forestry/agriculture/crop -
growing/pr iority-pest-disease/me lon-necrotic -spot-virus  Accessed  7 Jan uary 2021 .  
 
FAO (2016 a) AUS -75/2: Detection  of Melon necrotic spot virus in  Victoria . Food and 
Agricul ture Organiza tion of the United Nat ions. 
https://www.ip pc.int/en/co untries/austral ia/pestreports/2016/10 /detection -of-melon-necrotic -
spot-virus-in-victoria/ Accessed  8 Oct ober 2020 . 
 
FAO (201 6b) Methodologies for sampling  of consignments . International Standard for 
Phytosanitary Measures No. 31. Published by FAO on behalf of the Secretariat of the 
International Plant Prote ction Convention ( IPPC ); Rome, Italy.  
 
FAO (201 6c) Requirements for the establishment o f pest free pla ces of productio n and pest  
free sites . International Standard for Phytosanitary Measures No. 10. Published by FAO on 
behalf of the Secretariat of the Inte rnational Plant Pr otection Conv ention (IPPC); Rome, Italy.  
 
FAO (201 7a) Glossary of Phytosanit ary Term s. International Standard for Phytosanitary 
Measures No. 5. Published by FAO on behalf of the Secretariat of the International Plant 
Protection Convention  (IPPC); Rome, Ita ly. 
 
FAO (201 7b) Internati onal m ovement  of seeds.  International Standard for Phytosa nitary 
Measures No. 38. Published by FAO on behalf of the Secretariat of the International Plant 
Protection Convention (IPPC); Rome, Italy.  
  
14 • RMP : C. me lo, C. lanatus  and C. sativ us seed Ministry for Pri mary Indus tries FAO (201 7c) Requirements for th e establishme nt of pest free areas . International Standard for 
Phytosanitary Measure s No. 4. Published by FAO on behalf of the Secretariat of the 
International Plant Protection Convention (IPPC); Rome, Italy.  
 
Farr, D. F.; Rossman, A.  Y. Fungal Databases, U.S. Natio nal Fungus Collections, ARS, 
USDA. https://nt. ars-grin.g ov/fungaldata bases/  Accessed  10 September  2020.  
 
García -Lópe z, F. A.; González -Eguiarte,  D. R.;  Rodríguez -Macías,  R.; Zarazúa -Villas eñor, 
P.; Huitrón-Ramírez , M. V. (2018)  Watermelon production wi th rootstocks in soils infest ed 
with the necrotic melon spot virus . Revista Mexican a de Ciencias Agrícolas , 9(3): 577 –587. 
 
Guy, P. L. (2014)  Viruses of N ew Zealand pasture g rasses and legumes : a review.  Crop and 
Pasture Scie nce, 65(9): 841–853.  
 
Herre ra‐Vásquez, J. A. ; Córdoba‐Sellés, M. C.; Cebrián, M. C. ; Alfaro‐Fernández, A. ; Jordá, 
C. (2009)  Seed transmission of Melon necrotic spot virus  and efficacy of seed ‐disinfection  
treatments.  Plant  Pathology, 58(3): 436–442.  
 
Kubota, M. ; Hagiwara, N. ; Shiraka wa, T. (2012)  Disinfection o f seeds of cucurbit crops 
infested with Acidovorax citrulli  with dry heat treatment.  Journal of  Phytopatholog y, 160(7–
8): 364–368. 
 
Kwak, H . R.; Kim, J . S.; Cho, J . D.; Lee, J . H.; Kim, T .; Kim, M . K.; Choi, H . S. (2015 ) 
Charact erization of Melon  necrotic spot virus occurring on watermelon in Korea . Plant 
Patholog y Journal , 31(4): 379–387. 
 
Lane, S.  E.; Richards, R. S. ; McDonald, C. ; Robinson, A. P. (2018)  Sample size  calculatio ns 
for phytosanit ary testing of small lots of seed . CEBRA, Univer sity of Melbourne , Australia ; 
MPI, New Zealand.  https://cebra.unime lb.edu.au/__da ta/asse ts/pdf_file/0008/2796290/Att -A-
report -1606A.pdf   
 
Lecoq, H .; Katis, N. (2014 ) Control of cuc urbit viruses . In Lobenstein, G .; Katis, N . (eds)  
Control  of Plant Virus Diseases:  Seed-Propagated Crops . Elsevier Inc. ; Waltham, USA.  
 
Loebenstei n, G.; Katis, N. (eds) (2014)  Control of Plan t Virus Diseases: Seed -Propagated 
Crops . Elsevier Inc. ; Waltham, USA.  
 
Mackie, J. ; Higgins, E. ; Chambers, G.  A.; Tesoriero, L. ; Aldaoud, R. ; Kelly,  G.; Kinoti, W. 
M.; Rodoni, B. C.; Constable, F. E. (2020)  Genome anal ysis of mel on necrotic spot virus  
incursions and seed in tercept ions in Australia. Plant Disea se, 104(7): 1969 –1978 .  
 
MPI (2021a) Melon necrotic  spot virus  risk assessment . Biosecurity Sc ience and Risk 
Assessme nt. Ministry for Primary Industries , Wellington , New Zeala nd. 
 
MPI (2021b). Plant Health and Environmental  Science Laboratory (PHEL) . Ministry for 
Primary Industries , Wellington , New Zeala nd. 
 
Plant & Foo d Research (201 9) Fresh Facts. https://www.freshfact s.co.nz/file s/freshfacts -
2019.pdf   
  
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 15 Shi, Y.; Meng, S. ; Xie, X.; Chai, A. ; Li, B. (2016)  Dry heat treatment  reduces the occur rence 
of Cladosporium cuc umerinum, Ascochyta citrullina, and Colletotrichum orbiculare on the 
surface and interior of cucumb er seeds . Horticul tural Plant Journal , 2(1) : 35–40. 
 
Veerakone, S. ; Tang, J.  Z.; Ward, L.  I. et al. (2015)  A revie w of the pl ant virus, viroid, 
liberibact er and phyto plasma  records for New Zealand. Australasian Plant Pathol ogy, 44: 
463–514. https://doi.org/10.1007/s 13313 -015-0366 -3    
16 • RMP : C. me lo, C. lanatus  and C. sativ us seed Ministry for Pri mary Indus tries 
Appendix 1 – Proposed new sche dule for  Import Health 
Standard  155.0 2.05: Seed s for Sowing  
  
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 17 
  
18 • RMP : C. me lo, C. lanatus  and C. sativ us seed Ministry for Pri mary Indus tries 
   
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 19 
Appe ndix 2 – Changes to current Cucurbitaceae  schedule for 
the Impor t Health St andard  155.0 2.05: Seed s for Sow ing 
The proposed change is the remova l of Citrullus  and Cucumi s species from the schedu le for 
Cucurbitaceae , because these  hosts are to be  added to the newly  propose d Cucumi s schedule  
with the MNSV , CGMMV and KGMMV measures . The species  MPI propose s remov ing are 
crossed out  in red, while all other sections remain  the same . 
  
20 • RMP : C. me lo, C. lanatus  and C. sativ us seed Ministry for Pri mary Indus tries 
  
Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 21 
  
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Ministr y for Pr imary Industri es  RMP: C. melo , C. lanatus  and C. sa tivus seed • 23 Appendix 3 – Clarificati on for the phytosanitary measures not 
proposed to man age risk f rom MNS V 
 
Seed d isinfection  treatments  
Heat treatment  
88. A study by Herrera‐Vásqu ez et al. (2009) on Cucumis melo  seeds suggest s that heatin g 
seeds in single layers in an incubato r for 144 h ours at 70°C  (dry heat) eliminate s MNSV 
from the surface and inner tissues and increase s the g ermination rat e of treated seeds  
relativ e to untreated seeds.  
89. Australia provides the option of dry heat tre atment of Cucumi s melo  and Citrullus  lanatus  
seeds for MNSV  based on the study by  Herrera‐Vásquez et al. (2009)  (DAWE 2020) . 
90. However , MPI does not  propose heat tre atment of seeds a s a m easure for MNSV 
because : 
a) Although the viability of  Cucumis  seeds was not impacted at 70 °C for 144 h ours 
as per the study by  Herrera‐Vásquez et al. (2009) , these authors reported  that this 
was the most prolonged of all the trea tments assayed and  should only be applied 
by qualified laboratory personnel.  This implies t hat heat treatment  may require  
specialis t knowledge , which may no t always be possible . 
b) Exposure per iods at  high temperatures (above 75 °C) during dry heat treatment of 
Cucum is melon  and Cucumis s ativus have also been shown to reduce seed 
viability and seedling vigour (Kubota et al.  2012 ). 
c) Dry heat tre atment applied on Cucumis s ativus seeds at 70°C for 40–120 
minutes has reduced the seed moisture content as well as seed germ ination ( Shi 
et al. 2016 ). 
 
Chemical  treatment  
91. MPI does not propose chemical  treatment of seeds as a measure for MNSV because : 
a) Cucumis melo  seeds immersed in either 10% trisolium phos phate solution for 
three hours  or 0.1N  HCl solution for 30 min utes did not ef fectively eliminat e 
MNSV from see ds (Herrer a‐Vásquez et al. 2009 ; Loebenstein  & Katis  2014 , 
page 26 3). 
b) Seeds infected with MNSV may have virus particles locali sed both in the seed 
coat as well in the embryo (Herrera‐Vásquez et al.  2009) . 
c) Chemical treatment may be ineffective at eliminating the virus that may be 
present in inner seed tissues  (Herrera‐Vásquez et al. 2009) .  
24 • RMP : C. me lo, C. lanatus  and C. sativ us seed Ministry for Pri mary Indus tries Appendix  4 – Technica l advice on  Melon necrotic spot virus  
(MNSV)  
 
 
 
 
 
 
  
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