What does it look like?
Myrtle rust is a serious fungal disease that affects plants in the myrtle family (family Myrtaceae). The myrtle family consists of trees and shrubs originating in both tropical and temperate regions. Impacted New Zealand native species include pōhutukawa, mānuka, kānuka, rātā, swamp maire, and ramarama. The pathogen also impacts exotic plant species such as feijoa, guava, and eucalyptus.
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. Symptoms also sometimes affect flowers and fruit. Infection of highly susceptible plants may result in plant death.
Myrtle rust spores are microscopic and travel large distances by wind, or by insects, birds, people, or machinery. These modes of dispersal can transport spores very long distances. It is believed that wind carried spores here from Australia, where myrtle rust was first found there in 2010.
Why is it a problem?
Myrtle rust has been identified as a threat to New Zealand. The impact of myrtle rust has been particularly severe in Australia where it affects over 200 plant species. New Zealand has a number of species in the myrtle family considered to be at risk, among them iconic natives such as pohutukawa, ramarama, rata and manuka, but also feijoa, plantation and amenity eucalypts and numerous ornamental plants
Myrtle rust can cause deformation and dieback of new leaves and shoots, and prevent flowers and fruit developing, preventing regeneration. Seedlings and young plants are especially vulnerable and severe and repeated infection can result in plant death. Myrtle rust poses a major threat to New Zealand’s native biodiversity as it affects entire plant families including climbers, trees and shrubs. These plants provide essential ecosystem services.
This fungus has continued to expand the recorded range of susceptible species as it has spread from country to country. It seems likely that myrtle rust will continue to find new susceptible species, or even new susceptible genera, now it has reached New Zealand.
Control methods
Myrtle rust cannot be eradicated from Aotearoa, but there are things you can do to help us track the spread and protect the ngahere/forest.
- If you believe you have seen myrtle rust, do not touch the plant or the rust.
- Call Ministry for Primary Industries (MPI) Exotic Pest and Disease Hotline on 0800 80 99 66.
- Note the location and if possible, take photos, including the type of plant the suspected rust is on.
- Do not attempt to touch or collect samples as this may increase the spread of this disease.
- If you accidently come in contact with the affected plant or the rust, make sure you bag your clothing and wash clothes, bags and shoes/boots when you get home.
More information
The fungus has spread rapidly since the first case in New Zealand was identified in 2017. Initially,MPI and the Department of Conservation (DOC), with the help of iwi, the nursery industry and local authorities, ran a response operation to try to contain myrtle rust.
Within months, it became apparent that the disease was widely dispersed in New Zealand. Spores carry on the wind and there is an abundance of suitable plants that can be infected in our environment. In May 2018, the response was closed, and the focus moved to science to find ways to manage the disease in the longer term. Myrtle rust is now widely found across the North Island and in some areas of the South Island.
Related links
Management Programme
Notifiable Organism
Any organism specified under the Biosecurity Notifiable Organisms Order 2016 must be reported to MPI if spotted. If any of these organisms become established in New Zealand, they could severely affect our primary production, trade, and market access. If you spot a notifiable organism, you have a legal obligation under section 44 of the Biosecurity Act 1993 to tell MPI. Call the pests-and-diseases hotline on 0800 80 99 66.
More informationUnwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
More informationNational Interest Pest Responses programme
Nine harmful weeds are managed under the National Interest Pest Responses (NIPR) programme. These pests could cause serious harm to New Zealand's environment and economy if they are allowed to spread.
More informationTaxonomies
FamilySphaerophragmiaceae
TypeDiseases
GroupFungi and rust
HabitatLand
Management ProgrammeNotifiable OrganismUnwanted OrganismNational Interest Pest Responses programme
