T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Puccinia psidii (Myrtle rust)

Kingdom: Fungi
Phylum: Basidiomycota
Class: Urediniomycetes
Subclass: Incertae sedis
Order: Uredinales
Family: Pucciniaceae
Genus: Puccinia
Species: P. psidii
Binomial name: Puccinia psidii
Common names: Myrtle rust, Guava rust, Eucalyptus rust, Ohia rust

Puccinia psidii is a type of rust fungus, a plant pathogen. This fungus is indigenous to Central and South America and the Caribbean. It can have very serious consequences to various species of plants in the myrtle family (Myrtaceae). It infects the foliage and causes dieback of actively growing tips.

In April 2017 the Department of Conservation reported that approximately 400 square metres of Kermadec pohutukawa trees on Raoul Island were found in late March 2017 to be infected with myrtle rust. The report said that if Puccinia psidii were to enter mainland New Zealand, it could affect iconic New Zealand plants such as pohutukawa, kanuka, manuka and rata, as well as commercially-grown species such as eucalyptus, guava and feijoa. This fungi infects the foliage and causes dieback of actively growing tips on several myrtaceous plants.

Further information about myrtle rust
Individual myrtle rust spores cannot be seen with the naked eye; however large amounts of spores grouped together are visible as yellow rust bodies. Rust spores can carry long distances on the wind
The identifying signs of myrtle rust are purple/black splotches or patches (lesions) with yellow dots on leaves and stems. These can appear as bright yellow powdery eruptions on leaves. Leaves and stems especially when young can become buckled or twist and die off.
Severe infections can kill infected plants.
By the time lesions are visible, spores are already dispersing. This makes eradication difficult as the disease is already spreading by the time it can be seen.

We are asked to reporting all sightings.
Anyone believing they have seen myrtle rust on plants in New Zealand should call MPI’s Exotic Pests and Diseases hotline on 0800 80 99 66. Do not attempt to collect samples as this may aid in the spread of the disease.

The orange uredinia. They are the fruiting body of the myrtle rust fungi and they bear urediospores.

Myrtle rust on a guava.

Myrtle rust on guava leaves.

Myrtle rust on Chamelaucium uncinatum (Geraldton wax)  

Myrtle rust on Geraldton wax flower buds.

Myrtle rust on Syzygium jambos (Malabar Plum)

Thanks to Wkipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/