66
Pre- and post-border biosecurity
New Zealand Plant Protection 68: 66-75 (2015
)
www.nzpps.org
D.A.J. Teulon
1,5
, T.T. Alipia
1,5
, H.T. Ropata
2,5
, J.M. Green
2
, S.L.H. Viljanen-
Rollinson
1,5
, M.G. Cromey
1,5
, K. Arthur
2
, R.M. MacDiarmid
2,5
, N.W. Waipara
3
and
A.T. Marsh
4
1
The New Zealand Institute for Plant & Food Research Limited, Private Bag 4704,
Christchurch 8140, New Zealand
2
The New Zealand Institute for Plant & Food Research Limited, Private Bag 92169,
Auckland, New Zealand
3
Auckland Council, Bledisloe House, Aotea Square, Private Bag 92300, Auckland
4
The New Zealand Institute for Plant & Food Research Limited, Private Bag 11600,
Palmerston North, New Zealand
5
Better Border Biosecurity (B3), New Zealand (http://b3nz.org)
Corresponding author: david.teulon@plantandfood.co.nz
Abstract Myrtle rust, caused by the pathogen Puccinia psidii, is a disease of plants in the
Myrtaceae that is currently not known to be present in New Zealand. Its origin is Central/
South America, but it has steadily spread around the world and is now found in Australia.
All New Zealand Myrtaceae species, including indigenous species, are at risk from myrtle
rust infection, but the extent of the impact on plant health is not known. While the potential
economic and environmental impacts of myrtle rust establishment in New Zealand have
been well documented, this paper explores potential socio-cultural consequences for Māori.
All indigenous Myrtaceae species can be considered as taonga (or treasure) by Māori, who
have and continue to use the properties of some species in many ways (both tangible and
intangible). Preparedness and response plans for a myrtle rust incursion in New Zealand
should consider the values that Māori derive from these plants.
Keywords myrtle rust, Puccinia psidii, Māori, taonga species, Myrtaceae.
The threat of myrtle rust to Māori taonga plant species
in New Zealand
INTRODUCTION
There is considerable concern about the likely
arrival, establishment and impact of myrtle rust
on introduced and indigenous plant species of the
Myrtaceae in New Zealand (Clark 2011). Myrtle
rust, caused by the pathogen Puccinia psidii in
the Order Pucciniales, is a disease of many plants
belonging to the Myrtaceae. Its origin is thought to
be Central and South America (Glen et al. 2007),
but it has been steadily moving around the world
in recent years and is now found in New Zealand’s
close neighbours, Australia (including recently
Tasmania) and New Caledonia (CABI 2014).
Clark (2011) provided a comprehensive
review of the taxonomy, biology, host range and
plant associations, geographic distribution, risk
of entry, spread and establishment for P. psidii
into New Zealand and its potential economic
and environmental impact. In summary, she
concluded that there is a high likelihood of arrival
of entry to New Zealand and subsequent climate
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Pre- and post-border biosecurity
modelling identified that much of the North
Island and a very small area in the north of the
South Island are climatically suitable for P. psidii
(Kriticos et al. 2013; Narouei Khandan 2014).
Clark (2011) identified variable economic and
environmental impacts and recognised moderate
to high potential socio-cultural consequences
for all New Zealanders. However, the socio-
cultural consequences for Māori have not been
explored in any detail. Similarly, Loope (2010),
in summarising the risk of additional strains of
P. psidii to Hawai’i, provided only a short
paragraph on the threat to Hawai’ian indigenous
culture. There appears to be no comment in
the literature on the the impact of P. psidii to
Australian Aboriginal communities and culture.
The flora and fauna of the bush are taonga
(or treasure) species and the Māori relationship
with them is one of kaitiakitanga (guardianship);
this relationship is multifaceted and intimate,
developing over more than 40 generations
(Waitangi Tribunal 2011). Taonga species may be
part of a defined list (e.g. DOC 2006) or more
generally any species of importance to Māori,
and may include both indigenous and non-
indigenous species (e.g. kūmara, taro, kiore,
wild pig) (Roberts 2009). The WAI 262 claim Ko
Aotearoa Tēnei (This is Aotearoa or This is New
Zealand) (Waitangi Tribunal 2011) informs us
that “iwi have relationships with species which
are emblematic and have a spiritual element to
them and their connection to the wider ecosystem
particularly with regard to native plants such
as harakeke, koromiko, pōhutukawa, kōwhai,
puawānanga, poroporo, kawakawa, mānuka
and kūmara” (Katene 2011). Taonga include
tangible things such as land, waters, plants,
wildlife and cultural works, and intangible things
such as language, identity and culture, including
Mātauranga Māori (the Māori way of viewing the
world) (Waitangi Tribunal 2011).
This paper provides information on the
invasive biology of myrtle rust, a list the
indigenous Myrtaceae found in New Zealand, and
a summary of the modest amount of information
known about P. psidii infection for these New
Zealand species. The Māori uses, values and
relationships of these species is explored and the
possible impact of myrtle rust considered in this
context if myrtle rust was to become established
in New Zealand.
MYRTLE RUST BIOLOGY AND IMPACT
Myrtle rust (also known as guava rust, eucalyptus
rust and ōhi’a rust) was first described from
Psidium guajava (native guava) in Brazil (Winter
1884). The native range of myrtle rust was
reported to be South and Central America and
the Caribbean (Coutinho et al. 1998; Silva et al.
2013). In the 1970s, the pathogen caused severe
damage in nurseries and eucalyptus plantations
in Brazil (Coutinho et al. 1998). The literature
reports numerous strains of P. psidii that have
differential ability to infect different suites of host
plants (Loope 2010). It is considered that there
is only a single strain in Australia (Carnegie &
Cooper 2011). Like many rusts, myrtle rust has
a complex life cycle (Glen et al. 2007), which
needs to be understood for the development of
effective contingency plans for readiness and
response to potential incursions. The spores are
easily dispersed and can remain viable in the
environment for several weeks (Clark 2011).
Since the 2000s, P. psidii has steadily
spread around the world and is now found in
Australia (including Tasmania) (Carnegie et
al. 2010), South Africa (Roux et al. 2013) and
New Caledonia (CABI 2014). Currently, 346
species from 57 genera (73 worldwide) from
the Myrtaceae are reported to be susceptible to
myrtle rust in Australia and elsewhere (Giblin &
Carnegie 2014a,b).
Myrtle rust attacks young, actively growing
leaves, shoots, fruits and flowers (Glen et al.
2007). Leaves and stems become deformed and
in severe infections growing tips (Coutinho et
al. 1998) and the whole plants (Uchida & Loope
2009) can die. Previous rust infection can also
result in defoliation and prolific branching and
galling. Floral buds and fruits can also be affected,
with subsequent impacts on nectar production
and reproduction (Glen et al. 2007).
Puccinia psidii effects can be variable. It
is rarely severe on native Central and South
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Pre- and post-border biosecurity
American flora, although can cause occasional
epidemics on native guava plantations (Ribeiro
& Pommer 2004). Similarly, over a period of 30
years, this rust has done little damage to any of
the scattered native Myrtaceae in Florida (Loope
2010). Florida’s native Myrtaceae are among the
roughly 1,100 neotropical species that are largely
resistant to P. psidii but the 3,000 species of non-
neotropical Myrtaceae of the Pacific, Australia,
Asia and Africa are expected to prove much more
vulnerable to P. psidii (Loope 2010). In Hawai’i,
crown dieback and complete tree death was
recorded at a landscape scale from stands of the
non-native Syzigyium jambos (Uchida & Loope
2009) and the damage to Eugenia koolauensis, a
federally listed endangered species, is of major
concern (Loope 2010). The impact of P. psidii
on individual trees and shrubs in Australia has
ranged from minor leaf spots, foliage, stem and
branch dieback to reduced fecundity. Tree death,
as a result of repeated infection, has been recorded
for Rhodomyrtus psidioides. The full impact of
this disease in Australia may not be realized for
some years (Pegg et al. 2014). Puccinia psidii is
currently not causing serious disease in eucalypt
plantations in Australia (Carnegie 2015).
NEW ZEALAND INDIGENOUS MYRTACEAE
AND MYRTLE RUST
In New Zealand the Myrtaceae is represented
by some of our best-known native plants
such as the iconic pōhutukawa (Metrosideros
excelsa), rata (Metrosideros diffusa), kanuka
(Kunzea spp.) and manuka (Leptospermum
scoparium), as well as lesser-known species such
as swamp maire (Syzygium maire) and ramarama
(Lophomyrtus bullata) (Clark 2011), and species
that are considered nationally critical, such as
Metrosideros bartlettii, with only 29 individuals
left in the wild (De Lange et al. 2004). The
Flora of New Zealand database (Landcare
Research 2015) lists 29 indigenous taxa from the
Myrtaceae, 27 of which are endemic. De Lange
(2014a) has recently increased the number of
New Zealand indigenous Kunzea species to ten,
further increasing the number of indigenous
Myrtaceae. New Zealand also has a large number
of exotic Myrtaceae species, many of which have
commercial value, such as Eucalyptus species
and feijoa (Acca sellowiana (O. Berg.)), and some
myrtaceous species that grow in New Zealand are
weeds (e.g. Syzygium smithii) (Clark 2011).
All myrtaceous species (introduced and
indigenous) found in New Zealand are considered
to be potential hosts for myrtle rust. Some,
mostly introduced plant species, found in New
Zealand are known hosts for myrtle rust overseas
(Giblin & Carnegie 2014a,b). Nine New Zealand
indigenous species from four genera are known
to be susceptible to myrtle rust from observations
made on these plant species in the laboratory
and in the field in Australia and Hawai’i (Table
1). In addition, numerous non-New Zealand
species from the genera found in New Zealand
(including Syzgium) have been recorded as
myrtle rust hosts (Giblin & Carnegie 2014a,b),
but little is known about the potential degree
of susceptibility of New Zealand myrtaceous
species. All species (including some New
Zealand indigenous species) listed as myrtle rust
hosts in New South Wales are considered to be
susceptible to severe infestation under conducive
conditions (Anonymous 2012). Loope (2010)
reported that a few inviduals of pōhutukawa in
the Lyon Arboretum in Hawai’i were seriously
damaged by myrtle rust. Even though all New
Zealand plant species from the Myrtaceae are
at risk from myrtle rust it is not known which
myrtaceous species will be susceptible, or how
susceptible they will be.
MĀORI USE, TAONGA AND MYRTACEAE
A number of New Zealand’s Myrtaceae species
were extensively used by Māori, including
for medicine, construction and food, or have
significant cultural value as summarized
in Appendix 1 (collated by Scheele 2014).
Information on the current use of these plants by
Māori is likely to be iwi- and hapu-specific and
difficult to obtain and catalogue (Scheele 2014).
A number of plant species from the Myrtaceae
have been explicitly identified as taonga species
(e.g. DOC 2006; Waitangi Tribunal 2011), in
particular, the importance of pōhutukawa and
mānuka to Māori (the WAI 262 claim; Waitangi
Tribunal 2011).
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Pōhutukawa (New Zealand Christmas tree)
is one of New Zealand’s most widely recognised
trees, with brilliant red flowers and is a treasured
ornamental plant. Pōhutukawa’s deep-red wood
is exceptionally strong (Metrosideros means ‘iron
hearted’) with various uses (Appendix 1). The
flower nectar and bark preparations were used for
various medicinal purposes (Appendix 1). Pale
cream-coloured pōhutukawa honey is produced
commercially. Pōhutukawa also has significant
cultural and spiritual value to Māori. A specific
named tree, Te Rēinga (older than 800 years),
found on a cliff face at Te Rerenga Wairua (Cape
Rēinga), has a central place in Māori tradition
as it is said to guard the entrance to the sacred
cave through which spirits pass on their way to
the next world (Hawaiki). Another significant
pōhutukawa is Karewa, in Kawhia Harbour, said
to be the tree to which the Tainui waka was tied
after completing its voyage across the Pacific from
Hawaiki (Waitangi Tribunal 2011). At least 350
years old, Te Waha o Rerekohu, at Te Araroa, near
the East Cape, is probably New Zealand’s largest
pōhutukawa (19.8 m high × 38.5 m wide). The
pōhutukawa is the subject of numerous stories.
Perhaps the best-known tells of the young warrior,
Tawhaki, and his attempt to find help in heaven
to avenge his father’s death. The pōhutukawa’s
flowers are said to represent Tawhaki’s blood, shed
after he fell to earth. There are numerous stories
and pepeha (sayings) that tell of the relationship
between the blooms of the pōhutukawa and the
plume of red feathers worn as a headdress by the
Hawaiikian voyagers (Waitangi Tribunal 2011).
Mānuka (tea tree) is one of New Zealand’s
most common native trees and Māori use of this
tree has been extensive (Appendix 1). Mānuka
wood has been used for firewood, a range of
tools, building materials and weapons. Leaf and
bark preparations were used for a wide variety
of medicinal purposes (Waitangi Tribunal
2011). Today, mānuka oil is recognised for its
antibacterial, antifungal and antihistamine
properties, and is used to treat a number of
conditions. Mānuka honey is used as a general
tonic, in wound-care products and in cosmetic
skincare products. In 2014, New Zealand
honey exports had a total value of $NZ186.6M
(Fresh Facts 2014), mostly due to the premium
price achieved by mānuka honey, which is
approximately three times higher than that of
other table honey (Coriolis 2012).
Table 1 Records of myrtle rust (caused by Puccinia psidii) from New Zealand indigenous plant species.
Sources: All Australian records are from Giblin & Carnegie (2014a), except for Lophomyrtus obcordata,
which is from P. Symes (Royal Botanic Gardens, Melbourne, Australia, personal communication). All
Hawai’ian records are from Loope (2010). There are no additional records of New Zealand indigenous
plant species being infected by myrtle rust from the rest of the world (Giblin & Carnegie 2014b).
Host taxa
Natural infection = wild, open cultivation
or greenlife industry
Deliberate
inoculation test
Kunzea ericoides
1
Aust
Leptospermum scoparium
Aust
Lophomyrtus bullata
Aust: NSW
2
Lophomyrtus × ralphii
Aust: NSW& Vic
Lophomyrtus obcordata
Aust: Vic
Metrosideros carminea
Aust: Vic
Metrosiderus excelsa
Aust: NSW & Vic, Hawai’i
Aust
Metrosiderus kermadecensis
Aust: Qld & NSW, Hawai’i
Metrosideros thomasii
Aust: Qld
1
De Lange (2014a) has recently increased the number of New Zealand indigenous Kunzea species to ten,
so it is unclear which species is referred to here.
2
Abbreviations: Aust=Australia, NSW=New South Wales, Vic=Victoria, Qld=Queensland.
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Pre- and post-border biosecurity
POTENTIAL IMPACTS OF MYRTLE RUST
ON TAONGA SPECIES
Australia seems the most likely source for a New
Zealand myrtle rust incursion as it it one of our
major trading partners and the source of many
of our tourists. Rust spores are easily carried
on clothing and this pathway is a very likely
source of accidental introduction to new areas.
Additionally, a range of fungal rusts are thought
to have arrived in New Zealand from Australia
through prevailing westerly wind currents (Kim
& Beresford 2008; Viljanen-Rollinson & Cromey
2002). Therefore all New Zealand myrtaceous
genera and species are expected to be at risk
because the Australian biotype has a particularly
wide host range (see above). Currently, MPI has
suspended imports of cut flowers and foliage
from Australian states where P. psidii is present
(Queensland, New South Wales, Victoria and
Tasmania; http://www.mpi.govt.nz/) to prevent
their entry into New Zealand. Once established
myrtle rust is likely to spread quickly throughout
New Zealand at least in the North Island. Climate
matching models suggest that myrtle rust will have
the greatest impact in the North Island (Kriticos
et al. 2013, Narouei Khandan 2014) and species
found predominantly in the South Island, such as
southern rata (Metrosideros umbellata), may be
at reduced risk. Which particular New Zealand
genera and species will be most susceptible to
myrtle rust is unknown, but greater information
gathered from New Zealand native species grown
in Australia (and possibly Hawai’i), especially
from similar climates, may provide some clues,
especially on their relative susceptibility.
Potential impacts of myrtle rust are likely to be
variable. It mostly affects young plants and young
tissues including flowers, and although tree death
has been reported it is not the norm (Pegg et al.
2014). Thus individual rakau rangatira (chiefly
trees) such Te Rēinga, Te Waha o Rerekohu and
Karewa are unlikely to be killed. However, their
outward appearance, especially during periods
of bud growth and flowering, might be affected.
Similarly, uses of pōhutukawa and mānuka
timber for construction and tools may not be too
seriously affected; impacts on long-lived trees
species, such as pōhutukawa, will be less obvious
in the short term but may be significant in the
long term. There are also likely to be intangible
impacts because of the close relationship between
Māori in their role as kaitiaki of taonga species,
and for smaller Maori groups who have close
connections to individual rakau rangatira, which
have a central role in various pepeha and stories.
Future regeneration may be at risk as a result of
increased seed and seedling mortality during severe
infestations, as has been reported for R. psidioides in
Australia (Pegg et al. 2014). This may be especially
apparent for species such as kānuka and mānuka,
which are important in the development of early
successional plant communities.
Loss of flowers and new growth has a
number of potentially significant implications.
Honey production for both pōhutukawa and
mānuka may be significantly affected in terms
of both productivity and quality. Similarly, the
quality of medicinal (traditional/rongoa and
modern) products from key species may also
be compromised. Impacts in this area may very
much depend on which elite honey and medicinal
plant biotypes are affected by myrtle rust.
WIDER DISCOURSE WITH MĀORI
Two summer students have been hosted by Better
Border Biosecurity/Plant & Food Research to
explore the potential impact of myrtle rust on
plant species of interest to Māori. Alipia (2014)
focussed more on the invasive biology of myrtle
rust and its potential impact on New Zealand plant
species whereas Ropata (2015) focussed more on
engagement with Māori communities and their
views of myrtle rust and its potential impact on
plant species of interest to them. In particular,
Ropata (2015) developed a focus group facilitated
discussion process that was trialled with two
Māori students (summer and post-graduate),
one Māori scientist and one Māori support staff
(total n=4) at Plant & Food Research in February
2015 to understand their knowledge of myrtle
rust, which taonga plant species were important
to them, and why and how they would like to be
involved in an incursion response (Ropata 2015).
While the makeup of this group was small and
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Pre- and post-border biosecurity
probably not representative of the wider Māori
community it did provide some insights into some
of the potential concerns that Māori have over
myrtle rust. Other commentators have indicated a
strong interest by Māori in biosecurity issues, e.g.
Flavell (2010).
One issue that clearly emerged from this
preliminary engagement was that Māori
communities and iwi authorities would very
much like, and prioritise, is early involvement
in the preparedness and response to myrtle rust
(Ropata 2015). A tāngata whenua (local people)
rōpū (group) was established in response to
the discovery of kauri dieback and a similar
partnership approach would provide strategic
insight and knowledge (mātauranga Māori) for
managing any myrtle rust incursions. Given the
threat and likelihood of myrtle rust incursion, an
early engagement approach to establish ongoing
interactions between practitioners of kaitiakitanga
(environmental stewards, guardians) and tāngata
whenua groups, land managers and research
scientists should be initiated. This approach
would enable the implementation of mahi (work)
to survey, catalogue and monitor sentinel plants
for their growth and health status. Tāngata
whenua are very familiar with their land and any
taonga species plants that are present in their
rohe (area), and can provide the local knowledge
and expertise for any surveys and cataloguing
of sentinel plants for their growth and health
status, or lack thereof, over time and space. This
knowledge and sentinel plant data could feed
into a larger repository of information that could
serve as a national network of plant health status.
Collectively, this nationwide sentinel network
may also form an ara (pathway) for two-way
knowledge exchange, resulting in increased
preparedness for a myrtle rust incursion and an
early and successful response.
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