Scientific name
Austropuccinia psidii (formerly Puccinia psidii)
Common Names
Myrtle Rust, Guava Rust
Myrtle Rust is a highly contagious fungal disease affecting plants in the Myrtaceae family, including lilly pilly, bottlebrush, paperbark, tea tree, eucalyptus and many native Australian species. It spreads by airborne spores and is most active during warm, humid conditions with prolonged leaf wetness. Early symptoms include bright yellow or orange powdery pustules on young leaves, shoots, flowers and stems. Severe infections can cause leaf distortion, shoot dieback, defoliation and, in susceptible species, plant death.
Similar Diseases
- Rust (Puccinia spp.)
- Powdery Mildew (Erysiphe spp.)
- Leaf Spot (Cercospora spp.)
- Anthracnose (Colletotrichum spp.)
SCENARIOS AND SOLUTIONS
At the first signs of yellow or orange pustules: Apply Copper-Oxychloride to protect healthy foliage and reduce further spore production.
On lilly pillies, bottlebrush and other Myrtaceae: Apply Apparent Mancozeb 750 preventatively during warm, humid weather and rotate with Copper-Oxychloride.
In nurseries and landscape plantings with recurring Myrtle Rust: Remove infected growth, disinfect tools and maintain a preventative fungicide program using Copper-Oxychloride and Apparent Mancozeb 750.
When managing valuable native or ornamental Myrtaceae: Inspect plants regularly, dispose of infected material in sealed bags and rotate fungicides with different modes of action to minimise resistance.
References
https://www.agric.wa.gov.au/myrtle-rust
