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Eucalyptus/guava rust
What is it?
Eucalyptus rust or guava rust is a serious disease caused by the fungus Puccina psidii. This pathogen is very unusual in that it has a very wide host range in the plant family Myrtaceae, which includes about 3000 tree and shrub species—many of which are of great economic and conservation significance. Plants native to Australia that are known to be susceptible to this disease include eucalypts (Eucalyptus and Corymbia), bottlebrush (Callistemon) and paperbark (Melaleuca).
Where is it found?
Puccina psidii is native to parts of South America. It now also occurs in North America (Mexico, Florida (USA)) and parts of Central America including the Caribbean.
What are its effects?
Eucalyptus/guava rust causes disease of young shoots, flower buds and young fruit depending on the host plant. Eucalyptus species are the most important hardwood forest plantation trees in the world and are grown in many countries.
Puccina psidii is the only rust known to infect eucalypts and causes serious disease in eucalypt plantations. The disease is particularly severe on susceptible eucalypt seedlings, cuttings, young trees, coppiced or damaged mature trees. Highly susceptible trees may be grossly malformed or even killed. Growth rates of infected trees are diminished and plantation productivity reduced.
What's the risk to Australia?
Eucalyptus/guava rust can be managed in plantations by producing resistant trees through selection and breeding. This is happening in countries such as Brazil, but the disease would be impossible to manage in natural environments and would have devastating effects on Australian ecosystems where susceptible species occur.
Eucalyptus/guava rust spores are easily dispersed in air currents and could enter Australia on clothes, hair or luggage.
Forestry workers or tourists who have visited plantations or forest areas in countries with eucalyptus/guava rust should make sure they thoroughly clean their clothing before returning to Australia.