Leaves with myrtle rust in Hawaii
Image: Forest and Kim Starr | Creative Commons

Introduction

Myrtle rust is a fungal disease that severely attacks plants in the myrtle family including pōhutukawa, mānuka and rātā. It is now in New Zealand.

Highlights

Myrtle rust (Austropuccinia psidii), also known as guava rust and eucalyptus rust, is a serious fungal infection that could have serious impacts on a wide range of plants in the myrtle family.

What to do if you see myrtle rust call 0800 809966.

Where it's found:

  • in many parts of the world – the rust has rapidly spread on Australia's east coast
  • on pōhutukawa trees on Raoul Island – found in March 2017
  • on mainland New Zealand in Kerikeri and Taranaki – first found in May 2017. 

See the latest information about myrtle rust on the MPI website.

Look out for myrtle rust in New Zealand and contact MPI on 0800 80 99 66 if you see it. 

Why it's a threat

Myrtle rust on pohutukawa on Raoul Island.
Shoots on pōhutukawa on Raoul Island affected by myrtle rust 
Image: DOC

New Zealand has a number of species in the myrtle family at risk if myrtle rust arrives.

They include iconic natives such as pōhutukawa, kānuka, mānuka and rātā, as well as commercially-grown species such as eucalyptus, guava and feijoa.

View a list of native and exotic myrtle family plants in New Zealand (XLS, 49K) 

It is likely that myrtle rust will continue to find new susceptible species in New Zealand.

Myrtle rust attacks young, soft, actively growing leaves, shoot tips and young stems. Initial symptoms are powdery, bright yellow or orange-yellow pustules on leaves, tips and stems.

The developing lesions may cause a deformation of the leaves and shoots, and twig dieback if the infection is severe. It can also affect flowers and fruit. Infection may result in plant death.

Myrtle rust is notoriously difficult to control. However, it was caught early on Lord Howe Island and may have been controlled there. Unfortunately  by the time that the rust pustules are visible on plants, spores are already spreading. 

It will be extremely difficult to eradicate in New Zealand.

How it can spread

Myrtle rust spores are microscopic and can easily spread across large distances by wind. Myrtle rust is likely to be carried by wind to New Zealand from Australia, New Caledonia or Raoul Island.

We do not know where the rust has come from, and if it is the same type as that from Australia or New Caledonia. We need to still treat the rust in those countries as potentially different from that on Raoul Island or on mainland New Zealand.

Spores can also be transported on contaminated clothing, insects, rain splashes and equipment.

What it looks like

Myrtle rust generally attacks soft new growth including leaf surfaces, shoots, buds, flowers and fruit.

Symptoms to look out for are:

  • bright yellow/orange powdery patches on leaves
  • brown/grey rust pustules (older spores) on older lesions
  • leaves that are buckled or twisted and dying off.

The beginning of myrtle rust: newly formed bright yellow pustules, and small purple spots. Photo © The State of Queensland (through the Department of Agriculture, Fisheries and Forestry, 2014).
How the disease begins and forms - new yellow pustules and small brown spots

The legions then get bigger, along with masses of bright yellow spores. Photo © The State of Queensland (through the Department of Agriculture, Fisheries and Forestry, 2014).
The legions get bigger and produce masses of bright yellow spores

You can help

Keep an eye on the myrtaceous plants in your garden including: pōhutukawa, rātā, kānuka, mānuka, swamp maire, ramarama, rōhutu, eucalyptus, guava, feijoa, pacific rātā, bottlebrush, monkey apple, lilly pilly. 

The fungus attacks the new growth of leaves and shoots, and in some species also the buds and fruit of these plants. 

If you are traveling from Australia to New Zealand, make sure your shoes, clothing and luggage are free of rust spores which may be visible as yellow dust.

What to do if you see myrtle rust

  • Don't touch!
  • Don't collect samples as this might spread the disease.
  • If you can, take a photo of the rust and the plant it's on.
  • Phone MPI's exotic pest and disease hotline 0800 80 99 66.
  • If you accidently come in contact with the affected plant or the rust, bag your clothing and wash clothes, bags and shoes/boots when you get home.

Your reports of suspected cases are vital in helping determine where myrtle rust is in New Zealand, how far it has spread and whether eradication, containment, or even slowing the spread is feasible.

The earlier we find out about any New Zealand infection, the greater our chance of doing something about it.

Managing the threat

DOC is working closely with the Ministry for Primary Industries (MPI) to manage myrtle rust in New Zealand. Early detection of any outbreak in New Zealand will be vital to any attempt to manage it.

New Zealand already has stringent biosecurity measures to protect against myrtle rust introduction, including a complete ban on imports of cut flowers and foliage from myrtle species in New South Wales, Queensland and Victoria.

There are strict biosecurity procedures for DOC staff travelling between Raoul Island and the New Zealand mainland to prevent any people-assisted spread. Entry to the island is by permit only.

The Raoul outbreak will be used to learn more about myrtle rust – how it affects different species, trialing treatments and banking seed from local iconic species for future planting.

Seed banking: looking to the future

While MPI and DOC are dealing with the initial outbreak, we need to plan to secure the long term future of some taonga species by seed banking.

We know that internationally the effects of seed banking have varied between countries and plants.

Plans for seed banking in New Zealand:

  • Seeds of vulnerable species need to be collected to store for future propagation – it's our insurance policy against the rust.
  • Many of the priority seed sources are on public conservation land but we are aware that local knowledge of taonga species is with iwi Māori.
  • We need to work closely with tangata whenua throughout the country to identify specific plants that are important to iwi.
  • Some seeds have already been collected but there are many others to do.
  • Time is of the essence because the disease is already here and many of the relevant species have ripe seed right now.
  • Collection of seeds will continue at other times of year (when certain species have ripe seed) and over multiple years to ensure we have good seed diversity and fresh viable seed.

We must ensure whakapapa of these taonga are forever held. Whānau, hapū and iwi have been involved in development of protocols for plant protection.

You may be able to assist by supporting collecting or providing information. If you want to help contact your local DOC office.

More information on MPI website

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