Myrtle rust

Myrtle rust is a serious fungal disease that affects plants in the myrtle family. Plants in this family include pōhutukawa and mānuka. The first detection of the disease in mainland New Zealand was at a Northland nursery in early May 2017. The disease is likely to affect some of our iconic native plants as well as commercially-grown species.


Background

Myrtle Rust growing on leaves
Myrtle rust on the leaves of an affected plant.

Myrtle rust has been found in Kerikeri in Northland and in Waitara, Taranaki. It is also widespread on Raoul Island in the Kermadec group, about 1,100km to the north-east of New Zealand.

Myrtle rust (Austropuccinia psidii) is also known as guava rust and eucalyptus rust.

The fungus attacks various species of plants in 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.

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

The spores are thought to be capable of crossing the Tasman Sea from Australia to New Zealand on wind currents.

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, feijoa and guava.

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

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

Identifying myrtle rust

Myrtle rust shows up as yellow bumps and brown patches on leaves.
Yellow bumps and brown patches typical of myrtle rust.

 

Myrtle rust only affects plants in the myrtle family.

It generally attacks soft, new growth, including leaf surfaces, shoots, 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.

Some leaves may become buckled or twisted and die off.

 

What MPI is doing

MPI is working with the Department of Conservation (DOC), iwi, industry, scientists, and local authorities on addressing the myrtle rust incursions in Northland and Taranaki.

The affected nurseries are in lock-down. Restrictions are in place on the movement of people and plants in and out of the properties. Fungicide is being used as a treatment. Work has begun to determine the scale of the incursions and to trace where materials and products from the respective nurseries have gone. Inspections are underway in areas in a 500m radius from the infected properties.

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

Reasons for rust showing in nurseries first

There are 2 main reasons why the rust has been seen first in nurseries. 

  1. Growing conditions in nurseries are ideal for the fungus with many vulnerable young plants in sheltered, warm and damp environments.
  2. A lot of information has been given to the nursery industry and growers have been particularly vigilant in checking their plants.

What you can do

If you think you've seen the symptoms of myrtle rust, do not 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/affected area of the plant.
  • Don't touch it or try to collect samples as this may increase the spread of the disease.

Don't plant 

Our advice is to avoid planting any myrtle species, particularly in the regions known to be affected by myrtle rust – Northland, Taranaki and Waikato.

Advice for specific groups

Refer to our information sheet for specific advice for:

  • beekeepers
  • feijoa growers
  • other orchardists
  • nursery owners
  • home gardeners.

Download the information sheet [PDF, 141 KB]

Media releases

Find out more

Myrtle family in New Zealand

This image shows some of the common myrtle family plants found in New Zealand.

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

Who to contact

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

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