Myrtle rust

Myrtle rust is a serious fungal disease that affects plants in the myrtle family. Plants in this family include the iconic pōhutukawa, mānuka and rātā as well as some common garden plants such as ramarama and lilly pilly.

If you think you've seen myrtle rust, don't touch it, take a photo, and call 0800 80 99 66.

UPDATE

1 May 2018 – New approach being taken to manage myrtle rust

Background

– Myrtle rust on ramarama (Lophymyrtus bullata)
Myrtle rust on ramarama
(Lophomyrtus bullata)

Myrtle rust (Austropuccinia psidii) has been found in 11 North Island regions – Auckland, Thames-Coromandel, Waikato, Bay of Plenty, Taranaki, Taupo, Gisborne, Manawatu, Wellington and Tasman. It is also widespread on Raoul Island in the Kermadec group north-east of Northland.

The fungus attacks plants belonging to the Myrtaceae family, also known as the myrtle family. It is found in many parts of the world including New Caledonia and all along Australia's eastern seaboard.

 

 

 

 

 

 

Spores can spread easily

Upper and lower surface of same leaf of pohutukawa (Metrosideros). Red/brown lesions with pustules on top, orange/yellow pustules underneath
Upper and lower surface of same leaf of pōhutukawa (Metrosideros). Red/brown lesions with pustules on top, orange/yellow pustules underneath

Myrtle rust spores are microscopic and can easily spread across large distances by wind, or via insects, birds, people, or machinery.

Evidence suggests the fungus arrived in New Zealand carried by strong winds from Australia where it is well established all down the eastern coast.

The Ministry for Primary Industries (MPI) and the Department of Conservation (DOC), with the help of local iwi, the nursery industry, and local authorities ran a year long operation to attempt to contain and control myrtle rust and determine the extent of its spread.

What you can do

Look out for signs of myrtle rust. If you think you see the symptoms of myrtle rust:

  • don't touch it
  • call the MPI Exotic Pest and Disease Hotline immediately on 0800 80 99 66
  • if you have a camera or phone camera, take clear photos, including the whole plant, the whole affected leaf, and a close-up of the spores or affected area of the plant.

Remember, don't touch it or try to collect samples as this may increase the spread of the disease.

Do not attempt to self-treat trees and plants with fungicide, either for a cure or to try to prevent myrtle rust infection. We are still building a picture of whereabouts the disease is present nationally, and if people use preventative sprays, it could suppress symptoms, and prevent us from making the best management decisions for the country.

Identifying myrtle rust

List of plants in the myrtle family [PDF, 477 KB]

Lower and upper surface of same pohutukawa (Metrosideros) leaf. Red/brown lesions with pustules on top; orange/yellow pustules underneath
Lower and upper surface of same pōhutukawa (Metrosideros) leaf. Red/brown lesions with pustules on top; orange/yellow pustules underneath

Symptoms to look out for

Raised yellow pustules and red/brown lesions on lilly pilly (Syzygium)
Raised yellow pustules and red/brown lesions on lilly pilly (Syzygium)
Raised yellow pustules and red/brown lesions on bottle brush (Callistemon) leaves and stem
Raised yellow pustules and red/brown lesions on bottle brush (Callistemon) leaves and stem.

It generally attacks soft, new growth, including:

  • leaf surfaces
  • shoots and buds
  • flowers, and fruit.

Symptoms to look out for on myrtle plants are:

  • bright yellow powdery eruptions appearing on the underside of the leaf (young infection)
  • bright yellow powdery eruptions on both sides of the leaf (mature infection)
  • brown/grey rust pustules (older spores) on older lesions.
  • grey, 'fuzzy' spore growth on undersides of leaves.

Some leaves may become buckled or twisted and die off.

Pictures of some types of trees that may be affected

Myrtle family plants
Five examples of plants out of the 104 species in the myrtle family that grow in New Zealand. Clockwise from top left: pōhutukawa, mānuka, bottlebrush, ramarama and blue gum.

Videos on YouTube featuring 'Bug Man' Ruud Kleinpaste

Advice for specific groups

All myrtle species in New Zealand are at some risk from myrtle rust infection, but there are actions you can take to give your myrtle plants the best chance.

Planting and restoration programmes

If you are planning large-scale planting and restoration programmes using myrtle plants, follow the advice in Managing native plants susceptible to myrtle rust: Guide for large-scale planting and restoration programmes. This guide was developed in collaboration with the Department of Conservation and Council representatives.

Download the Guide for large-scale planting and restoration programmes [PDF, 917 KB]

Specific groups that may have contact with myrtle species

Our information sheet has specific advice for:

  • beekeepers
  • feijoa growers
  • other orchardists
  • nursery owners
  • home gardeners
  • walkers and trampers.

Download the information sheet [PDF, 522 KB]

Risk to New Zealand

Myrtle rust could affect iconic New Zealand plants including pōhutukawa, mānuka, rātā, kānuka, swamp maire and ramarama, as well as commercially-grown species such as eucalyptus.

Severe infestations can kill affected plants and have long-term impacts on the regeneration of young plants and seedlings.

It is not yet known how this disease will affect New Zealand species. Overseas its impacts have varied widely from country to country and plant species to species.

What MPI is doing from 1 May 2018

Myrtle rust has now spread to many parts of New Zealand that have a suitable climate. We also have limited tools available to manage the disease. From 1 May 2018, we have adopted a new approach which involves:

  • scaling back our operations and stopping surveillance in areas that are known to be infected
  • conducting surveillance only in new areas where myrtle rust has not yet become established
  • treating new infections only at sites with isolated low-level infections where we can quickly suppress symptoms and attempt local elimination in the short term
  • lifting movement restrictions in known infected areas
  • allowing landowners with myrtle rust infection on their property to decide how to manage their plants
  • issuing permissions to landowners in known infected areas allowing them to dispose of infected myrtle plant material in local landfills as general waste
  • working with DOC, iwi, the nursery industry, scientists, and local authorities to explore options for future management.

Why are we changing our approach?

It is clear that eradication of myrtle rust from New Zealand is not feasible using the tools we have available. Restricting human activity at this time will not make a significant contribution to slowing the spread of the disease. Focusing our efforts on surveillance in areas where myrtle rust has not been found and undertaking spray and tree removal only at sites with isolated low-level infections will allow us to quickly suppress symptoms and attempt local elimination in these areas in the short term.

At the same time we are investing significantly in scientific research to develop new tools, build understanding of myrtle rust and explore possible treatment and management options. Regardless of where you live, myrtle rust continues to be considered an unwanted organism throughout New Zealand. We continue to encourage landowners to regularly check the health of their myrtle plants.

Our approach in areas where myrtle rust hasn't been found

We encourage residents in these areas who see signs of myrtle rust to call our Biosecurity Hotline (0800 80 99 66).

Our surveillance effort will target areas where myrtle rust has not become established.

Restrictions may still be used where infection levels are extremely low.

Our approach in known infected areas

We’ll be contacting affected owners and giving them self-management packs. The packs will:

  • set out their responsibilities under the Biosecurity Act
  • give advice about maintaining their property to minimise the spread of disease.

Other long-term planning activities

We are engaging with iwi and councils in affected regions to look at ways that MPI can support communities who wish to conduct their own biosecurity activities. We are also developing a programme to provide training to support community-based surveillance for interested groups in their regions. A long-term strategy will be developed over the next 2 years, with input sought from groups including iwi, councils, industry and DOC.

Research programme

Research is vital as it will result in a better understanding of myrtle rust that could help us limit the impact on our myrtle plants for future generations. MPI has commissioned a comprehensive research programme made up of more than 20 specific projects and valued at over $4.5 million. A bid for further research will be requested from Cabinet later in 2018.

The projects will be done over 2 years to June 2019.

Summary of research projects

New Zealand Plant Producers Inc. is scoping and developing a plant production biosecurity scheme for nurseries and garden centres.

Scion Research is working on several projects to:

  • build engagement and social licence through better understanding of potential options around the long-term management of myrtle rust
  • undertake a desktop review of potential disease control tools
  • map myrtle species
  • develop and test possible surveillance and management tools
  • scope a breeding programme for resistant myrtle species
  • develop monitoring approaches to assess environmental, economic, social and cultural impacts over time, and to understand the impact of potential management actions.

Plant & Food Research, in collaboration with Scion Research, Manaaki Whenua Landcare Research, Kew Gardens, and Australian myrtle rust researchers, also has several inter-linked research projects underway including

  • the identification of native and important exotic host species susceptibility to myrtle rust, including variability within species
  • identification of asymptomatic periods
  • assessment of the risk of introduction of other myrtle rust biotypes to New Zealand
  • initial identification of genetic markers linked to resistance
  • resistant plants and their potential relationship with endophyte populations
  • A. psidii de novo genome sequencing; and, a national seed banking and germplasm research strategy.

Plant & Food Research is also investigating seed storage methodologies and protocols for non-orthodox myrtle species, which cannot be stored by conventional methods. The research explores whether seeds or other tissues can be stored using cryopreservation methods and then subsequently propagated successfully. 

Karin van de Walt at Wellington Gardens is undertaking a PhD on non-conventional preservation techniques for swamp maire/maire tawake (Syzygium maire), supported by Plant & Food Research. She is also undertaking a trial cryopreservation conservation initiative for Bartlett’s rata/rata moehau (Metrosideros bartlettii), in collaboration with Otari Native Botanic Garden, Te Papa and Auckland University. Wellington Gardens is studying the seed characteristics and seed storage behaviours of ramarama (Lophomyrtus bullata) and NZ myrtle/rohutu (L. obcordata), to ensure that these fleshy-seeded species are stored at optimal conditions.

MPI, in collaboration with the New South Wales Dept. of Primary Industries, is investigating alternative fungicides and possible non-target impacts from the current fungicides being used for the treatment/control of myrtle rust infections.

Completed research projects

Lincoln University completed a non-market value impact assessment, of the potential losses to biodiversity and ecosystem values under low-, medium-, and high-impact disease outbreak scenarios.

The NZ Institute of Economic Research completed an economic impact assessment of the potential economic impact of myrtle rust on industry sectors on mainland
New Zealand.

NIWA (National Institute of Water and Atmospheric Research), in association with Plant & Food Research, developed a climate model of the potential risk of myrtle  rust spreading from Australia and Raoul Island, and around New Zealand.

MPI's Plant Health and Environment Laboratory and the Food and Environment Agency (UK) developed a rapid field monitoring tool that has been used in the myrtle rust response on mainland New Zealand.

Plant & Food Research completed an assessment of myrtle rust spore transmission risk via bees and beehives. The research shows that myrtle rust spores can survive for some time within beehives, but more research needs to be done to understand any potential risk that bees might pose to the spread of the fungus.

The research does not provide enough evidence to justify widespread restrictions on the movement of beehives, which would have significant financial implications for beekeepers, the honey industry and primary industries that rely on bee pollination.

Read the full report on Assessment of the risks of transmission of myrtle rust spores by honey bees [PDF, 262 KB]

Find out more

Who to contact

If you have questions about myrtle rust, email info@mpi.govt.nz

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