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A little over a year ago a new ecological threat was introduced. A fungus called Uredo Rangelli, better known as Myrtle Rust. It was first noticed near Gosford on the New South Wales Central Coast. It effects plants in the Myrtaceae family which includes Lemon Myrtle, Paper Gum and many species of Eucalyptus. Its predicted that the rapid spread of the fungus through forests, nurseries and private gardens could make Myrtle Rust one of the biggest threats to the Australian ecosystem. This could effect many industries including logging, floristry, bush food and possibly ecotourism.

 

To date Myrtle Rust has spread  as far south as Shoalhaven and as far north as the Sunshine Coast with little sign of slowing down. This is partly due to the number of tourists that travel to these destinations. They accidentally spread it by carrying the spores with them. This would most likely be on their clothes or on their car.  Bees and birds are also likely to have unintentioanlly spread it. The fungus is thought to have slipped through quarantine during a period when there were funding disputes.

 

Since the discovery of Myrtle Rust in Australia efforts have been made to contain and eradicate it. So far the NSW government has spend $5 million, the QLD government has spent $970,000 and the federal government has spent $1.4million on schemes to contain and eradicate the fungus. There has also been a combined efforts between Australia and Brazil to manage the spread of the fungus. Brazil is offering a screening process that will help determine regions most in danger of the fungus. By screening a wide range of Myrtaceae they will be able to determine which species are more susceptible to the fungus (so far the most susceptible species are in tropical and sub-tropical areas). After they determine which species are most vulnerable they will be able to create a  map of the regions where these species grow. They hope this process will allow them to detect the presence of fungus before it begins to spread. However the National Management Group believes that it may not be possible to eradicate the fungus.


The first sign of rust infection are tiny raised spots or pustules. After a few days, the pustules turn into yellow or orange spores (resemble Wattle flowers) which spread to the plant’s leaves, buds, shoots and fruit. The  Myrtle Rust  spreads by creating lesions, then filling them with spores. As it progresses, the disease can cause leaves to become deformed, heavy defoliation of branches, die-back, stunted growth or death. If a younger plant isn’t killed by the fungus it can become stunted. Sometimes the infected spots will be surrounded by a purple ring. However Older lesions may contain dark brown spores. The rust poses no known threat to human health.

 

Myrtle Rust, which is a relative of Guava Rust, originates from South and Central America (including the Caribbean and Florida).  Although Myrtle Rust’s milder relative has been shown to cause some damage in Australia and America, it is generally restricted to Guava plantations. When Myrtle Rust was first recorded in South America it was restricted to nurseries who were growing Eucalyptus species.  Unfortunately, Australia has a much higher number of native Myrtaceae and in many communities this is the dominant vegetation.

 

Although the spread of Myrtle Rust could add to the difficulties many people are are already facing, there is good news. Myrtle Rust only attaches itself to the Myrtaceae family. Even though this plant family is wide-spread though out Australia a recent study by the CSIRO has shown some encouraging results. It discovered some species of Myrtaceae are more resistance to the fungus, which has been heralded as possibly the biggest threat to Australia’s ecosystem.

Published: Apr 30, 2011 2:07pm by tames.

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