Risk Management Proposal:  
Amendment to the import health standard  
Grain and Seeds for C onsumption, Feed, or 
Processing   
GCFP.IHS  
 
 
Prepared for  public consultation by the Animal and Plant Health Directorate 
 
 
 
  27 October  2023   
Disclaimer  
While every effort has been made to ensure the information in this publication is accurate, 
the Ministry  for Primary Industries does not accept any responsibility or liability for error of 
fact, omission, interpretation, or opinion that may be present, nor for the consequences of 
any decisions based on this information. 
 This publication is also available on the Ministry for Primary Industries  website at  
http://www.mpi.govt.nz/news -and-resources/publications/
  
 
 
© Crown Copyright – Ministry  for Primary Industries   
i  
Contents  Page 
1 General information  2 
1.1 Purpose  2 
1.2 Timing and consultation  2 
1.3 Summary of the proposed changes to the standard 2 
2 Background 3 
2.1 Maize production in New Zealand 3 
2.2 Imports of maize grain into New Zealand  3 
2.3 Zea mays  schedule in the standard  4 
3 Review of the Zea mays regulated pathogens  5 
3.1 Changes to the phytosanitary measures under Option 3  5 
3.2 Pathogens proposed to be removed from the Zea mays  regulated pest list  6 
3.3 Pathogens proposed to be retained on the Zea mays schedule  9 
4 Feasibility of proposed changes to the standard 16 
References  17 
Appendix 1: List of current and proposed Zea mays regulated pathogens 22  2 1 General information  
1.1 Purpose  
(1) The purpose of this document is to:  
a. Provide relevant background information about the import health standard Grain  
and seeds  for consumption, feed, or processing (GCFP.IHS ), 
b. Outline the proposed changes  to the s tandard ,  
c. Provide the reason  for the proposed changes  and explain how they will manage 
risk, and 
d. Ask for  feedback on the proposed changes . 
1.2 Timing and consultation 
(2) The proposed amendment was released for consultation on 2  Novem ber 2023  and will 
remain open for consultation until 14  December  2023. 
1.3 Summary of the p roposed changes  to the st andard 
(3) Biosecurity New Zealand aims to manage biosecurity risks on imported  grain s to 
achieve an appropriate level of protection for New Zealand, whil e facilitating trade of 
grains .  
(4) We have  review ed the pathogens associated with maize ( Zea mays ) and propose the 
following changes to the standard:  
a. Requiring m aize grain imported into  New Zealand to be dried to a moisture 
content of 14% or less  before  export . 
b. Remov ing 11 pathogens from the list of regulated pests for maize . 
   
Ministry for Primary Industries   RMP: Amendment to GCFP.IHS  • 3 2 Background  
2.1 Maize production in New Zealand  
(5) Maize is the third most important grain crop in New Zealand after barley and wheat with 
production of about 160,000 tonnes of grain per year . Nearly all maize grain is grown  in 
the North Island regions of  Waikato, Gisborne, Bay of Plenty and Hawkes Bay  
(NZGSTA, 2020) . Northern New Zealand is a sub -tropical climate zone, with warm 
humid summers and mild winters. Typical summer daytime maximum air temperatures 
range from 22°C to 26°C, but seldom exceed 30°C.  Winter daytime maximum air 
temperatures range from 12°C to 17°C . 
(6) Maize is primarily used for animal (dairy, beef, pig, and poultry ) feed and human 
consumption and silage (NZIER 2016).  
 
Maize -growing areas in New Zealand 
 
2.2 Imports of m aize grain  into New Zealand 
(7) New Zealand does not produce enough maize grain to meet domestic demand, and so 
we import maize to supplement our production. T he volume of import ed grain varies 
depending on domestic production levels and the prices of alternative grains , such as 
wheat and sorghum.  In 2020, New Zealand imported approximately 200,000 tonnes  of 
maize grain .  
(8) Before export , maize grains are usually dried until they have a moisture content below 
14%. This helps to prevent fungi and rot and improves storage .  
 4 2.3 Zea mays  schedule in the standard 
(9) Maize grain can be imported  into New Zealand for consumption, feed, or processing 
under three options  specified in the Zea mays  schedule of the standard. All imported 
maize grain is processed and no viable seed can be released under any of the options :  
• Option 1 : requires the grains to be rendered non- viable by treating them before 
they arrive in New Zealand.  
• Option 2: requires the grains to be rendered non- viable by treating them  in a 
transitional facility  in New Zealand.  
• Option 3 : allows viable maize grains to be import ed and directed into approved 
transitional facilit ies in New Zealand for processing to render them non- viable . 
2.3.1  Current phytosanitary measures in the Zea mays  schedule   
(10) There are 19 regulated pathogens  on the Zea mays  regulated pest list, of which six 
pathogens1 require additional phytosanitary measures  for import under Option 3 of the 
Zea mays  schedule (Appendix 1).  
(11) The r egulated pathogens  specified in the Zea mays  schedule are associated with 
maize grain  and either are not present in New Zealand, or if present , not widely 
distributed and under official control .  
(12) The Standard  outline s the following phytosanitary measures to manage the risk of Zea 
mays  regulated pathogens  entering and establishing in New Zealand: 
For all regulated pathogens :  
a. pre-export inspection of grains by the Official Plant Protection Organisation 
(NPPO)  from the exporting countr y to issue a phytosanitary certificate  
b. verification inspection up on arrival  by MPI inspectors  
c. seed devitalisation through grain processing at a transitional facility . 
For regulated pathogens requiring additional measures :  
a. sourcing grains from  a ‘pest free area’ or ‘pest free place of production’ or  
b. laboratory test ing with negative results , and 
c. commercially drying grains  to a moisture content of 14% or less . 
  
  
 
1 Peronosclerospora maydis, P. philippinensis, P. sacchari, P. sorghi, Sclerophthora rayssiae var. zeae and Stenocarpella 
macrospora   
Ministry for Primary Industries   RMP: Amendment to GCFP.IHS  • 5 3 Review of the Zea mays regulated pathogens  
(13) The Zea mays  regulated pest list and phytosanitary measures for the regulated 
pathogens have not been reviewed since the development of the standard over 20 
years ago.  
(14) Biosecurity New Zealand has initiated this review with the aim to determine if:  
a. regulation of the pathogens listed in the standard is still justified . 
b. current phytosanitary measures are adequate to manage the risks posed by the 
Zea mays  pathogens .  
c. additional phytosanitary measures are required to mitigate the risks pose d by the 
Zea mays  pathogens .  
d. any new pathogen is associated with this pathway that needs  to be regulated. 
(15) The review focused on the existing Zea mays  regulated pathogens  outlined in the 
standard. Additionally, it involved checking the literature for any new pathogens 
associated with this pathway.  For this review, we primarily used published scientific 
reports.   
(16) In reviewing the literature, we identified two pathogens that had not been identified in previous assessments as associated with maize seed. The first of these Pyrenophora 
teres  is present in New Zealand (Biota of NZ, 2023) and is non- regulated. The second 
pathogen ‘ Candidatus  Phytoplasma cynodontis’ is seed- borne but it is not seed 
transmitted ( Çağlar  et al. 2019; CPC, 2023). Instead, this pathogen is known to spread 
through infected vegetative propagating materials (CPC, 2023). Considering that 
Bermuda grass is the main host of this pathogen and we do not import vegetative 
materials on this pathway, the risk is very low.    
(17) We therefore consider that both pathogens do not meet our criteria to be considered 
regulated and were not considered further . 
(18) We considered the following criteria for each pathogen in the Zea mays  schedule of the 
standard  in our review : 
a. whether the pathogen is present/absent in New Zealand, 
b. whether the pathogen is associated with maize grains ( i.e., seed- borne and or 
seed transmitted) , 
c. whether the pathogen can establish in New Zealand ( i.e., available hosts, 
favourable climate conditions , presence of the vectors ), and 
d. whether the pathogen can cause adverse economic or environmental impacts to New Zealand if  it establishes .  
3.1 Changes to the phytosanitary measures under Option 3  
(19) Biosecurity New Zealand  proposes adding  the following measure to the Zea mays  
schedule of the standard:  
‘Zea mays grain must be dried to moisture content of 14% or less  before export to New 
Zealand.’   
(20) Currently, drying maize grains to a moisture content of less than 14% is an additional 
phytosanitary requirement for certain pathogens . We propose making this m easure a 
general requirement for all maize grains imported for processing at New Zealand transitional facilities (Option 3).  
(21) This will ensure that all imported maize grains follow this commercial practice before 
being exported  to New Zealand. Moreover , it will provide assurance that the risk of  6 pathogens that can only be transmitted through freshly harvested seeds, is effectively 
managed. 
(22) Since drying maize grains to a moisture content of less than 14% is a standard industry practice , grains coming in under options 1 and 2 will also be dried. However, as these 
import options require treatment (heat treatment or irradiation),  there is no need to 
specify a drying requirement in these options.  
 
Question for your submission  
Do you agree with the proposed changes? If no, why not?  
 
3.2 Pathogens proposed to be removed from the Zea mays  
regulated pest list  
(23) The pathogens listed in Table 1 are proposed to be removed from the Zea mays  
regulated pest list because they pose negligible biosecur ity risks to New Zealand 
through this pathway. These pathogens meet at least one of the following criteria:  
a. they are present in New Zealand and are not under official control  
b. current scientific evidence indicates that the pathogen is not associated with maize grains  
c. they do not survive in dried maize grains (moisture content of 14 % or less)   
d. they cannot establish in New Zealand 
e. the import options available, all requiring seed devitalisation, manage the risk 
sufficiently . 
 
Table 1. Pathogens proposed to be removed from the Zea mays  regulated pest list and 
the justification for removing them  
1 Claviceps gigantea  
C. gigantea  is of low economic importance, has moderate seedborne incidence and is 
seed transmitted (CPC 2023). Maize is  the only host plant for this fungus.  
This fungus only occurs in high humid mountain valleys in central Mexico and has not 
been able to spread to any other areas (Ullstrup, 1973) due to its restricted ecological 
niche. It produces large sclerotia (5- 8 x 2- 5 cm) that can readily be detected by visual 
inspection (Fuentes et al., 1964).  
This pathogen is not an economically significant pathogen worldwide (CPC 2023).  
Conclusion:  We consider this fungus cannot establish in New Zealand due to its 
restricted ecological niche.  
2 Cochliobolus tuberculatus (preferred name:  Curvularia tuberculata)  
Maize  is not a host for this fungus (CPC 2023). Host plants include rice, coconut, 
potato, chickpea, and betel pepper (Imran, et al. 2020; Majeed et al. 2016; Naim, 2007, Shahzad, 2001).  
Conclusion:  We consider this fungus  is not associated with Zea mays  grains and 
therefore cannot enter  New Zealand through this pathway.    
Ministry for Primary Industries   RMP: Amendment to GCFP.IHS  • 7 3-
5 High Plains virus (preferred name Emaravirus tritici )  
Maize dwarf mosaic virus (MDMV)  
Pantoea stewartii (Syn: Pantoea stewartii subsp. stewartii ) 
High Plains virus is seed -borne  and seed transmitted in maize at very low rates 
(0.008 %; Forster et al. 2001).  
The virus is mainly transmitted by a vector, the eriophyid mite, Aceria tosichella  
(Seifers et al., 1997). This mite is not present in New Zealand and being regulated 
(ONZPR, 2023) , border measures are in place to prevent its entry and establishment .  
Maize dwarf mosaic virus (MDMV)  - There is weak evidence that this virus is seed -
borne or seed -transmitted in maize at very low rates (0.004 - 0.006% ; Mikel et al. 
1984; Williams et al. 1968 ).  
The virus is mainly transmitted by aphid species feeding on infected growing plants 
(Kannan et al. 2018) . 
Pantoea stewartii is seed -borne and seed transmitted in maize at a low- rate (0.06% ); 
Ivanoff, 1933 in Block et al. 1998; Michener et al., 2002).  
The bacterium can only be transferred from an infected plant to other plants via a 
vector, the corn flea beetle (Chaetocnema pulicaria). This is because the bacterium 
survives the winter in the body of the vector and cannot overwinter in soil or crop 
residues (Pepper, 1967; Claflin, 1999; Agrios, 2005). The corn flea beetle is not present in New Zealand and is regulated (ONZPR 2023).  
While the bacterium has occasionally been isolated from  another beetle (C. 
denticulata) and other insects, none of these is  significant vector of the bacterium 
under field conditions (Elliot & Poos, 1940).  
Given that maize grains must be either fumigated or inspected for regulated insects 
and mites, we have confidence that the vectors cannot be introduced into New 
Zealand. Therefore, the potential for the establishment and spread of these 
pathogens via their vectors is negligible.   
Furthermore, it is important to consider that all imported maize gr ains under this 
pathway are required to be devitalised. This means even if infected seeds were introduced into the environment , they would not be able to grow and serve as a 
source of infection, even if  the vectors were present in New Zealand.  
Conclusion:  Considering that maize  grain imported under this standard is 
devitalised, w e do not consider  that these pathogens can establish in New Zealand 
via this pathway.  
6-
10 Peronosclerospora heteropogoni  
Peronosclerospora  philippinensis  
Peronosclerospora maydis ( syn Sclerospora maydis)  
Peronosclerospora sacchari (syn Sclerospora sacchari)  
Sclerophthora rayssiae var. zeae   8 P. heteropogoni  is a seed -borne pathogen that is only transmitted through seeds with 
high moisture content (Thakur and Mathur 2002).  The fungus survives as mycelium 
within maize seed (Rathore et al. 1987 in Thakur and Mathur 2002). However, when 
the seed moisture content drops below 22%, the mycelium loses its viability and 
cannot infect plants (Rathore et al. 2002).  
P. philippinensis  is a seed- borne pathogen that is only transmitted through seeds with 
high moisture content  (Bains and Jhooty, 1982). The fungus survives as mycelium 
within maize seeds. It can be transmitted through seeds, but transmission occurs only when the seed moistu re content is above 30%. No evidence of transmission was 
found when seeds were dried to a moisture content range of 14 -30% (Exconde, 1976 ,
 
McGee, 1988).   
P. maydis  is a seed -borne pathogen in maize (Lukman et al. 2016). Transmission to 
seedlings only occurs when freshly harvested seeds are planted. No transmission occurs once the seeds are dried to the moisture content required for storage (CPC 2023) or when seeds are dried in the sun (Bonde et al., 1992).
 P. maydis  may survive 
as mycelium in kernels, but this is thought to be a minor source of inoculum. Oospores have not been reported (Smith and Renfro, 1999).  
P. sacchari is a seed -borne pathogen (Singh et al. 1968) and only seed -transmitted in 
seeds with high moisture content. No transmission occurs from seeds dried below 20% moisture content (McGee 1988; Bonde et al.,  1992). Greatest conidial 
production occurs at 22°C to 25 °C at 95% RH; but do not germinate below 90% RH 
(Matsumoto, 1964 ). 
Sclerophthora rayssiae var. zeae is primarily soilborne but can also be seed- borne in 
maize. The disease can be transmitted at low rates (less than 1%) from infected fresh maize seeds (Singh et al. 1968; Sangam and Thakur 1989). Maize is the main host 
plant (Khehra et al 1981).  
The primary source of inoculum is oospores that overwinter in soil or plant debris and mycelium found in infected seeds (Sangam et al 1989). The disease development is 
favoured by high soil temperatures (28- 32oC) (Munkvold and White,  2016) and high 
rainfall (100- 200 cm)  (Frederiksen & Renfro, 1977; Putnam, 2007 ). 
Infected seeds that are dried to 14% moisture or less and stored for at least 4 weeks 
do not transmit the disease (White, 1999).  
Conclusion:  The commercial  practice of drying seed s to moisture content of 14% or 
lower  successfully manages the risk of  these pathogens  being transmitted through 
seed. Therefore, we consider that these pathogens cannot enter New Zealand 
through this pathway.  
11 Rhizopus maydis (preferred name: Rhizopus oryzae ) 
This fungus  occurs  as a saprotroph in  soil, dung, and rotting  vegetation . It is present 
in New Zealand (Biota of NZ, 2023) and is not under official control or eradication 
programme. We found no information  on the impact of this fungus on maize in the 
literature . This indicates that it is not a significant disease of maize.   
Conclusion:  Given that this fungus is already established  in New Zealand, we have 
no justification to regulate it on this pathway.  
 
   
Ministry for Primary Industries   RMP: Amendment to GCFP.IHS  • 9  
Question for your submission  
Can you think of any reasons that any of the pathogens listed on Table 1  needs to be 
regulated on maize import for consumption, feed, or processing pathway?  
Is there any scientific literature that contradicts the findings we have presented in Table 1, 
especially for  the remov al of pathogens that require additional measures on this pathway  
(i.e., Peronosclerospora maydis, P. philippinensis, P. sacchari and Sclerophthora rayssiae 
var. zeae) ?    
 
 
3.3 Pathogens proposed to be retained  on the Zea mays schedule  
(24) Biosecurity New Zealand proposes to keep the pathogens  listed in Table 2 as 
regulated on import of  maize  grains. There is no change to their status, so this section 
is included only for interest and transparency . 
(25) These pathogens are not present in New Zealand, they are seed- borne and/or seed-
transmitted on maize grains, and therefore can get into New Zealand on imported 
maize grains . New Zealand’s climate conditions in maize growing areas are suitable for 
establishment and spread of these pathogens and they  could have adverse impact.  
(26) Appropriate measures are required to prevent the establishment of these regulated 
pathogens in New Zealand.  
a. For pathogens with low impact or a high chance of detection, basic phytosanitary 
measures such as pre -export inspection and verification inspection upon arrival 
are considered sufficient.  
b. Where the pathogen is of  significant concern,  or the basic measures would not be 
effective , stronger measures have  been applied. The additional phytosanitary 
measures that can be applied are sourcing grains from a ‘pest free area ’ or ‘pest 
free place of production’, or laboratory testing to provide assurance the grains are 
free from the pathogen.   
(27) We propose that t wo of the regulated pathogens ( Peronosclerospora sorghi  and 
Stenocarpella macrospora) should continue to require additional phytosanitary 
measures .  
(28) The rationale for maintaining the regulation of each pathogen, along with its  key 
characteristics  and phytosanitary measures to manage it , are outlined in Table 2.  
   10 Table 2. Pathogens proposed to be kept regulated on  the Zea mays schedule  
1 Acidovorax avenae subsp. avenae (bacterial leaf blight)  
This bacterium  is seed- borne and seed- transmitted on maize (Anan et al. 2013; 
Dange et al 1978). Maize, sorghum, and sugarcane are main hosts . It also infects 
oats, barley, wheat, millet, sorghum, rye, and rice (Ji et al 2014; Dhkal et al 2019; Wu 
et al 2018)  but the bacterium has not been recovered from any of these plants in 
nature (Munkvold and White, 2016) .  
Maize grains contaminated with the bacterium are important sources of primary inoculum and a means of spreading the disease internationally (Anan et al. 2013). 
Local spread is primarily through movement of contaminated farm equipment.  It does 
not survive well in soil or plant debris ( Munkvold and White, 2016 ; Sumner and 
Schaad, 1977 ). 
The disease develops and spreads well in warm, humid weather (Saddler, 1994; 
Vesminsk et al., 1978; Cottrell -Dormer 1932) with optimum temperature for growth of 
36°C ( Munkvold and White, 2016) .  
The disease is generally of minor economic importance in maize (Munkvold and 
White, 2016; Dange et al 1978) with yield losses up to 15% reported in the USA under 
suitable climate conditions (Pataky et al 1997).  
Conclusion:  This bacterium if present on imported maize is unlikely to establish 
because it  does not survive well in soil or plant debris. Moreover, considering that the 
temperatures in New Zealand’s maize growing regions are lower than the optimum 
temperature for growth of this bacterium , the conditions are expected to restrict the 
development of the disease and minimise impact even if it establishes  in New 
Zealand. 
The basic measure including a generic phytosanitary certificate is  adequate to 
manage this regulated pathogen.  
2 Botryosphaeria zeae ( anamorph  Macrophoma zeae) (grey ear rot)  
This fungus  is seed -borne in maize but is not seed transmitted (Bezuidenhout and 
Marasas 1978) .  
Ascospores of  the fungus  are produced only on the leaves, not in the ears (Ullstrup, 
1953), but mycelium can be present in the rotted kernels and ears and serve as a 
source of new infections and spread (Shurtleff, 1980). The fungus  can form sclerotia 
on the husks and pericarps of the kernels (Bezuidenhout and Marasas, 1978) . 
Infected maize seeds are usually visibly damaged, so infections can be detected 
during production and phytosanitary inspection.  
The disease has been reported in USA, France, Zimbabwe, and French Equatorial Africa (present G abon, Congo, and Chad).  
Ullstrup (1973) reported no economic importance of this disease in maize. The disease was found to be widely distributed but rarely severe in the eastern part of the 
Corn Belt in USA (Dickson, 1956).  
Conclusion:  The basic measur es including inspection and generic phytosanitary 
certificate are adequate to manage this regulated pathogen.   
3 Cephalosporium maydis ( preferred name Magnaporthiopsis maydis)   
Ministry for Primary Industries   RMP: Amendment to GCFP.IHS  • 11 This fungus  is mainly a soilborne pathogen  (Michail et al., 1999) . It is also seed- borne 
in maize ( Kumar & Agarwal 1998) and there is weak evidence it is  seed transmitted 
(Degani et al. 2014) .  
While m aize is the primary host, it can also infect other plants such as cotton, 
watermelon and setaria as secondary hosts  (Sivanesan, 1990 ). The fungus primarily  
spreads through the movement of infested soil, crop residue, or seedborne inoculum  
(Singh and Siradhana, 1987) . Munkvold and White (2016 ) noted that seed -borne 
infection has a minor role in the epidemiology of the disease.  
It survives in soil and on maize debris in the form of sclerotia , which can remain viable 
for at least 15 months ( Sabet 1984; Dawood et al. 1979) . The sclerotia  are dark brown 
pigmented clusters of thick -walled cells (Samra et al., 1963)  and can be detected  
during routine phytosanitary inspections. 
Singh and Siradhana (1987) reported that the fungus  could survive for up to 2 months 
in seeds stored in laboratory conditions and up to 10 months in seeds stored at high 
temperature and low humidity  in India.  
The optimal conditions for the development of the disease symptoms  are air 
temperature between 26 °C and 28°C and humidity of 43.6 % to 45.3% . However, t he 
pathogen’s impact is most severe when temperatures rise to 27°C and above.  
Official reports confirm the presence of the disease on maize in seven countries, and 
there are unconfirmed reports from three additional countries where the persistence 
and economic impact of the disease have not been quantitatively evaluated ( Pecsi 
and Nemeth, 1998) . In optimal conditions in Egypt and India, the fungus is considered 
a potentially significant pathogen, leading to yield losses of 40- 70% in susceptible 
cultivars (El -Shafey and Claflin, 1999; Satyanarayana, 1995).   
Conclusion:  Considering that New Zealand’s climate conditions differ from those of 
the countries where this pathogen has had a significant impact , it is not expected to 
have a high impact  in New Zealand if it establishes . 
The basic measures including inspection and generic phytosanitary certificate that 
ensures consignments are free of sclerotia, soil and plant debris are sufficient to 
mitigate  the risk of introducing this pathogen.  
4 Clavibacter nebraskensis (Goss’s bacterial wilt)  
This bacterium is seed- borne and seed transmitted in maize at a very low -rate 
(Osdaghi  et al. 2022; Block et al. 2019). Maize is the main host, but other hosts 
include wheat, sorghum, sugarcane, and foxtail.  
Although infected seed can be a source of inoculum, the main source of inoculum is 
infested plant debris on which the bacterium overwinters (Gross and Vidaver, 1979) 
and survives for at least 10 months (Ahmad et al., 2015).  
The disease has established in Ontario, Canada and in some states of USA (Osdaghi et al. 2022). The optimum temperature for growth is 27° C and day/night temperature 
regime of 32/25°C favours its growth (Smidt and Vidaver, 1986 ).  
Losses from this disease  are minor over large areas but may be severe in individual 
fields (Wysong et al., 1981). Maize hybrids susceptible to the disease have sustained 
yield los ses of up to 50% in the USA (Claflin, 1999).  
Phytosanitary measures:  The basic measures including inspection and generic 
phytosanitary certificate that ensures consignments are free of plant debris are 
adequate to manage this regulated pathogen .  12 5 Cochliobolus pallescens ( preferred name Curvularia pallescens)  
This fungus is seed -borne in maize ( Kumar & Agarwal 1998 ) but it is not seed 
transmitted. It causes leaf spot disease in maize  and wheat . Infections have been 
reported in pericarp and tip cap of maize seeds but not the embryo (Kumar and 
Agarwal 1998).  Agarwal (1998) reported that this fungus  was associated with 
discoloured maize seeds . The fungus can overwinter in soil and crop residue as  
sclerotia (Sivanesan, 1990). The discoloured infected seeds and dark -coloured 
sclerotia are detectable during routine phytosanitary inspections.  
The fungus  has a wide host range, such as  maize, wheat, barley, rice, sugarcane, 
millet, capsicum, asparagus, potato, onion, citrus, brassica, a nd rubber (Sivanesan, 
1990). Optimum temperatures for mycelial growth and germination of conidia are 
between 20°C  and 28°C (Sivanesan, 1990). This fungus has also been reported  in 
countries with similar climatic conditions as New Zealand like Denmark, Canada, Japan, and USA and therefore may be able to establish here considering host 
availability and favourable climatic conditions.  
It causes minor disease in temperate regions;  although, it is reported as an  important 
pathogen in India ( Grewal & Payak, 1976). If this pathogen were to enter New 
Zealand through this pathway, it would have a low chance of establishing  considering 
the end use of the grains is for feeding. It is also expected to have low impact under 
our climatic conditions.  
Conclusion:  The basic measures including inspection and generic phytosanitary 
certificate that ensure consignments are free of infected seeds, sclerotia plant debris , 
and soil are adequate to manage this regulated pathogen. A dditional phytosanitary 
measures are not necessary .  
Ministry for Primary Industries   RMP: Amendment to GCFP.IHS  • 13   Peronosclerospora sorghi  
This fungus  is seed -borne and seed -transmitted in maize (Sireesha and Velazhahan 
2018 ; Rao et al. 1985; Adenle & Cardwell 2000). Maize and sorghum are the main 
hosts plants (EPPO , 2023).  
The fungus  produces oospores and mycelium in infected host tissues. The fungus can 
survive within grains for up to 9 months even when dried to 11% moisture content. 
Adenle & Cardwell (2000) reported that grains infected by  the fungus  and dried to 
8.5% moisture content could still produce infected seedlings after 9 months of storage. Hence drying maize grains cannot effectively eliminate the oospores  of this 
fungus .  
The fungus can enter New Zealand through bulk maize shipment as oospores in seeds. The oospores can survive in infected seeds, plant tissues or soil for at least 
three years under a variety of conditions (Frederiksen, 1980). 
It can spread in New Zealand, as oospores can be spread long distances by wind, in 
seed and crop residues, and in soil on farm machinery. Conidia can also spread the 
fungus locally within crops and between adjacent crops and weed hosts. The fungus 
requires soil temperatures of between 21°C  and 25°C for spore germination and 
spore production (CIMMYT , 2023), and these temperatures occur in summer at many 
maize growing regions  in New Zealand.  
The fungus
 can establish in New Zealand because the main hosts are grown in New 
Zealand, and climatic conditions in maize and sorghum growing areas are favourable for development of the pathogen. This  fungus
 has established in many countries of 
every continent (except Antarctica) including many regions with a similar climate (CMI 0.8) to New Zealand.  
Peronosclerospora sorghi is reported as a significant pathogen capable of causing 
substantial maize yield losses. We consider  that this pathogen can cause significant  
yield losses in maize and sorghum  if introduced into New Zealand. 
 
Conclusion:  Beside the basic measures including inspection and generic 
phytosanitary certificate, additional phytosanitary measures are also required to 
manage this regulated pathogen.  
The proposed additional phytosanitary measures are to require sourcing grains from a 
‘pest free area ’ or ‘pest free place of production’, or laboratory testing to provide 
assurance the grains are free from the pathogen.  14 7 Stenocarpella macrospora   
This fungus is seed -borne and seed -transmitted in maize (Romero  and Wise, 2015; 
Siqueira et al. 2014). Maize is the main host plant (Bradley et al. 2010). 
The pathogen overwinters as viable pycnidia and mycelium on seeds or maize debris 
in the soil (CPC, 2023). Under favourable conditions such as warm and moist 
condition, spores are extruded from the pycnidia and are disseminated by wind, rain 
or by insects.  
The fungus  has established in many countries in the world. It is widespread in the 
USA, in regions that have high climate similarity to New Zealand (CMI 0.8) and in Argentina (CMI 0.8). Therefore, if present on grains t his fungus  could establish in New 
Zealand because climatic conditions in maize growing areas are suitable for 
development of the pathogen. Although seed drying kills the mycelium, pycnidia can 
remain viable (depending on the drying process, temperature, and duration of dr ying 
and level of contamination with the pycnidia), leading to potential seed -transmission 
on maize.  
It is one of the causative agents of white ear rot, a destructive disease of corn 
worldwide (Petatán -Sagahón et al. 2011). Losses due to the disease vary from 
season to season and between regions but may be greater than 50%. It is considered a minor pest of maize in the USA, with yield losses of 10- 20% but as a major 
pathogen in humid sub -tropical regions (Cutler et al. 1980; Petatán- Sagahón et al. 
2011).  
The fungus  produces mycotoxin diplodiol,  which if ingested can be fatal to chickens 
and chicks (Cutler et al. 1980).  
 Without appropriate measures , this fungus, if introduced through infected grains could 
establi sh in New Zealand and could have significant impact on maize yield and feed 
quality.   
  
Conclusion:  Beside the basic measures including inspection and generic 
phytosanitary certificate, additional phytosanitary measures are also required to manage this regulated pathogen.  
The additional phytosanitary measures are sourcing grains from a ‘pest free area ’ or 
‘pest free place of production’, or laboratory testing to provide assurance the grains 
are free from the pathogen.   
Ministry for Primary Industries   RMP: Amendment to GCFP.IHS  • 15 8  Ustilago maydis  
This fungus is seed -borne in maize ( Rehman et al 2021) , but it is not seed transmitted 
(Crop Genebank, 2023) . Maize is the main host plant (Muradov et al 2019).  
It produces teliospores which can contaminate the surface of healthy seeds (Crop 
Genebank, 2023) and can accompany the seed lot (McGee, 1988), but they do not 
infect the kernels. Teliospores are also soil borne and can be carried from field to field 
by contaminated machinery.  
Infected seed and ear tissues become galls meaning seeds are not viable when 
infected with  this fungus  (McGee, 1988). C ontaminated seed is not considered an 
important source of inoculum for this pathogen (CPC, 2023, Munkvold and White, 
2016) and  the risk of introducing this pathogen by seed is considered low (CPC, 
2023).  
Teliospores are released from ruptured galls and overwinter in the soil  or crop debris 
where they can remain viable for more than a year  (Munkvold and White, 2016, 
Batiashvili, 1975, Crop Genebank, 2023). The spores are disseminated by wind and are the main inoculum source (Christensen, 1963).  
The pathogen  is widely distributed and has established in Canada and many 
countries in Europe (Bohm and Glaeser 1976 ; UK CAB International, 1986) with 
similar climatic conditions like New Zealand. Therefore, the climatic  conditions in New 
Zealand are likely to be suitable for establishment. The optimum temperature for spore germination, between 20°C and 25°C (Christensen, 1963) , is typical for maize 
growing regions in New Zealand.  
 Common maize smut, caused by  this fungus, has been observed in most maize-
growing countries, but it rarely causes economic losses (Crop Genebank, 2023). Recent maize yield losses are usually less than 1%, although this may be higher in 
sweetcorn (McGee, 1988). We consider the impact from this pathogen to be low  if it 
establishes in New Zealand.  
Conclusion:  The basic measures including generic phytosanitary certificate that 
ensure consignments are free of teliospore galls, plant debris  and soil are adequate to 
manage this regulated pathogen.  As the pathogen is not a significant concern for New 
Zealand, no additional phytosanitary measures are required.  
 
(34) We consider that the risks associated with the regulated pathogens listed in Table 2 
can be effectively managed through the application of appropriate phytosanitary 
measures. Even in cases where potential risks exist, it is unlikely that these regulated 
pathogens would be released into the environment during transportation and grain 
processing. This is primarily due to the strict requirements outlined in the standard  for 
product and facility security, as well as waste treatment.  
(35) The potential risks are fur ther reduced through processing of the grains . While some 
pathogens may survive the processing, the chances of a significant amount of 
inoculum ( e.g. viable spores, sclerotia, or mycelium) persisting through pre -entry 
measures  are low.   
(36) The end- use of the maize grains  further reduces the risk. The chances of infected 
material being released into the New Zealand environment close to suitable plant hosts 
and establishing a population are extremely low.   
 
   16 Question for your submission  
Do you have evidence that any of the pathogens listed in Table 2 should not be regulated 
on maize import for consumption, feed, or processing? 
Do you have any evidence for other regulated pathogens that pose significant impact in 
New Zealand and should require additional phytosanitary measures?  
 
4 Feasibility of proposed changes to the standard  
(37) The proposed changes align  with our commitment to maintaining regulations that are 
current and supported by scientific  evidence. They work to ease restrictions on 
importers  of maize , while effectively managing biosecurity risks .  
(38) Addition of a generic measure (drying maize grains to a specific moisture content) for 
import of all maize grains for processing in New Zealand is not expected to increased 
costs for importers . This is because this measure  is already in place as a common 
commercial practice for import of maize grains and is accepted by the grain industry.  
  
 
Question for your submission  
Are the proposed changes not feasible?  
    
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   22 Appendix 1: List of current and proposed Zea mays 
regulated pathogens  
# Current regulated pathogens  Proposed regulated pathogens  
1 Acidovorax avenae subsp . Avenae  Acidovorax avenae subsp . avenae  
2 Botryosphaeria zeae ( anamorph  
Macrophoma zeae)  Botryosphaeria zeae ( anamorph  
Macrophoma zeae)  
3 Cephalosporium maydis  Cephalosporium maydis  
4 Clavibacter nebraskensis  Clavibacter nebraskensis  
5 Claviceps gigantea  - 
6 Cochliobolus pallescens ( anamorph  
Curvularia pallescens)  Cochliobolus pallescens ( anamorph  
Curvularia pallescens)  
7 Cochliobolus tuberculatus ( anamorph  
Curvularia tuberculata)  - 
8 High plains virus  - 
9 Maize dwarf mosaic virus  - 
10 Pantoea stewartii  - 
11 Peronosclerospora heteropogoni  - 
12 Peronosclerospora maydis*  - 
13 Peronosclerospora philippinensis*  - 
14 Peronosclerospora sacchari*  - 
15 Peronosclerospora sorghi*  Peronosclerospora sorghi*  
16 Rhizopus maydis  - 
17 Sclerophthora rayssiae var. zeae*  - 
18 Stenocarpella macrospora*  Stenocarpella macrospora*  
19 Ustilago maydis  Ustilago maydis  
* Pathogens r equir ing additional phytosanitary measures