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Rust
Puccinia, Phragmidium, Uromyces and other rust fungi · Fungus
Also called myrtle rust (Austropuccinia psidii, a regulated rust).
Illustration
Powdery orange, yellow or brown pustules, mostly under the leaves. Each rust attacks only a few related plants. Pick off the first affected leaves and keep foliage dry, and in Australia and New Zealand watch for myrtle rust on eucalypts, bottlebrush and lilly pilly.
How to spot it
- Pale or yellow spots on top of the leaf.
- Raised, powdery pustules underneath: orange, yellow, brown or black depending on the rust.
- Rose rust: bright orange pustules under the leaves in summer, turning black in late summer.
- Badly affected leaves yellow and drop early.
- Myrtle rust: bright egg-yolk-yellow powder on soft new shoots and leaves of the myrtle family.
Easily confused with
Leaf spots and blights
Wipe a spot with a white tissue: rust leaves coloured powder, leaf spots leave nothing.
Rose black spot
Flat black patches with feathery edges and no powder.
Mite damage or sun bronzing
No powder at all.
Where it's a problem
- Worldwide: Garden rusts are common, especially in wet summers, and aren't regulated.
- Australia: Myrtle rust is established in the east; it's a declared pest in Western Australia, and several states ask for new finds to be reported.
- New Zealand: Myrtle rust is an unwanted organism; report sightings through iNaturalist.
What to do
- Pick off the first few affected leaves as soon as you see them.
- Water early in the day at the base, and space plants for airflow.
- Avoid too much nitrogen, which makes soft, rust-prone growth.
- Rake up fallen leaves in autumn.
- For myrtle rust, avoid touching heavily infected plants: photograph it and report it where your local rules ask.
If you use a fungicide, choose one labelled for rust and follow the label and local rules. The RHS recommends against fungicides in gardens.
Follow your local council's guidance for disposing of diseased plant material. Official guides usually advise against putting it in a home compost heap.
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Sources
- RHS: Rust diseases
- RHS: Rose rust
- University of California IPM: Rusts
- NZ Department of Conservation: Myrtle rust
- WA DPIRD: Myrtle rust
- ACT Government: Myrtle rust
Facts checked Sunday 27 September 2026. General guidance only: follow your local council, agency and product label.