Myrtle rust: what the agencies record
What the New Zealand Department of Conservation, Botanic Gardens Conservation International and the Australian National Botanic Gardens say about myrtle rust: the rust fungus, the myrtle family hosts, how spores travel, the pustule symptoms, where it is recorded and how sightings are reported.
Checked against the sources at the bottom of this page on October 8, 2026. Rules, fees and pay change: the source has the last word.
This page reports what the official source says. It is not legal advice: ask the office named here. It lists what the sources record about myrtle rust and does not diagnose any tree. The Department of Conservation calls myrtle rust an unwanted organism in New Zealand, so the exact wording of that status is on its page linked below. The list of other diseases is on the tree diseases page, and the reporting lines are in the New Zealand and Australia report-a-pest guides.
At a glance
| Item | What the sources say |
|---|---|
| Pathogen | Austropuccinia psidii, a rust fungus. Botanic Gardens Conservation International says it was formerly called Uredo rangeii and Puccinia psidii, and that it has been called eucalyptus rust or guava rust. |
| Hosts | Plants in the myrtle family, Myrtaceae. Botanic Gardens Conservation International says nearly 500 species are recorded and the number keeps growing. The Department of Conservation names pohutukawa, manuka, rata, swamp maire and ramarama, exotic bottlebrush and lilly pilly, and commercially grown eucalyptus. |
| Where | Botanic Gardens Conservation International says it is native to South America and lists introductions to North America in the 1970s, Hawaii in 2005, Japan in 2007, China in 2009, Australia in 2010 (widespread along the east coast), South Africa in 2013 and mainland New Zealand in 2017. The Department of Conservation says it has spread through the North Island, to parts of the South Island and to Chatham Island. The Botanic Gardens factsheet says there are no records in Europe. |
| Status | New Zealand: an unwanted organism that, per the Department of Conservation, cannot be eradicated there. |
| Report to | New Zealand: a photo report on iNaturalist labelled myrtle rust, or the local Department of Conservation office for public conservation land. Australia: the Exotic Plant Pest Hotline. See the New Zealand guide and the Australia guide. |
How the sources say it spreads
The Department of Conservation says the spores are microscopic and spread over large distances by wind, and that the fungus was probably carried to New Zealand by wind from Australia. It adds that spores can also travel on contaminated clothing, insects, rain splashes and equipment. Botanic Gardens Conservation International says introductions into new countries are commonly tied to imported live plants and plant products such as young fruit buds, fruit, cut flowers and foliage, and that spores also move on air currents and on clothing and luggage. It says spores can stay viable for up to three months. For germination it gives high humidity, leaf wetness for more than 6 hours and temperatures from 15 to 25°C, with new pustules able to release spores within 10 to 12 days.
Symptoms as the sources state them
- New infections. The Department of Conservation describes bright yellow-orange powdery pustules, usually first on the underside of the leaf. It says the rust attacks soft new growth: leaves, stems, buds, flowers and fruit.
- Older infections. Pale yellow-brown to grey pustules of old spores, and brown, buckled or twisted leaves and stems that are dying.
- Effects. The Department of Conservation says myrtle rust can deform and kill back new leaves and shoots, and stop flowers and fruit forming. It says seedlings and young plants are especially vulnerable and severe repeated infection can kill a plant.
- Speed. Botanic Gardens Conservation International says initial symptoms show within 3 to 5 days of infection.
- Season. Neither page ties symptoms to a season. Botanic Gardens Conservation International ties germination to humid, wet-leaf conditions and mild temperatures.
Look-alikes and lab confirmation
The three pages read name no look-alike disease and describe no laboratory test. The Department of Conservation asks for a photo of the rust and of the plant it is on, and says to avoid contact with highly infected plants and not to collect samples, because collecting might spread the disease. It also says to wash clothing, bags and boots after leaving.
What the agencies publish for management
The Department of Conservation says New Zealand has biosecurity measures against introduction, including an import ban on cut flowers and foliage of myrtle-family species from New South Wales, Queensland and Victoria, and strict procedures for staff travelling to Raoul Island, which is entered by permit only. The Australian National Botanic Gardens page, last updated September 1, 2025, gives the Exotic Plant Pest Hotline, 1800 084 881, for suspected myrtle rust and says suspect samples should not be brought to the gardens. None of the pages lists a treatment. Who may apply pesticides is covered on the pesticide licences page.
Credit
All three pages were read as ordinary web pages and are restated in our own words with a link.