Myrtle Rust (Uredo rangelii) in Melaleuca alternifolia (Tea Trees)

Tea Tree Oil (Oil of Melaleuca alternifolia) is produced and grown from the tree Melaleuca alternifolia on plantations in NSW from just south of Port Macquarie to the Tweed Valley. Tea tree oil is an essential oil distilled from the leaf and terminal branchlets of the tree and has wide- ranging antibacterial and antifungal activity as well as some antiviral activity. Tea trees of course also grow in the wild – the original source of material for the genetically selected stock now used in plantation production. Some tea tree oil is still distilled from trees growing in national and state forests in NSW. Myrtle Rust (Uredo rangelii) is a newly described fungus that is closely related to the Eucalyptus/Guava rusts. These rusts are serious pathogens which affect plants belonging to the family Myrtaceae including Australian natives like bottle brush (Callistemon spp), tea tree (Melaleuca spp) and eucalypts (Eucalyptus spp). ATTIA Ltd sent seedlings of Melaleuca alternifolia to the CSIRO for host testing in mid 2010. The tests were positive. The disease, which originated in South America, was first identified in April 2010 on the Central Coast of NSW with incursions now identified at Coffs Harbour, Byron Bay, Lismore and Caboolture. Myrtle Rust is distinctive in that it produces masses of powdery bright yellow or orange-yellow spores on infected plant parts. It infects leaves of susceptible plants producing spore-filled lesions on young actively growing leaves, shoots, flower buds and fruits. Leaves may become buckled or twisted and may die as a result of infection. Sometimes these infected spots are surrounded by a purple ring. Older lesions may contain dark brown spores. Infection on highly susceptible plants may result in plant death The disease particularly attacks new leaf or young growth. Trees planted in plantations have been genetically selected to produce higher and higher volumes of oil each year. As the oil is only found in the leaf, this means that the trees are continuously producing new leaf ie the trees are always extremely vulnerable to attack by this disease. As the disease damages the leaf of Melaleuca alternifolia this also means that each tree will produce less oil or possibly that the leaf/tree will dies. Either way the tea tree farmer is losing income. It is difficult to know for certain but it is estimated that there are something in the vicinity of 60million tea trees in plantations in NSW. Trees are planted at different densities but overall, the commonest planting density seems to be 30,000/ha. On a 100ha plantation this would mean there are 3,000,000 trees planted. Because the trees are planted so closely it is extremely difficult for a tea tree farmer to monitor anything except the edges of the paddocks for signs of myrtle rust. Tea tree oil is positioned as a natural product – sometimes it is classified as an organic product. Either way, there are no minimum residue levels of chemical allowed to be found in the oil. Oil with as little as 1 ppm of chemical will be rejected. It is therefore problematic for the industry how best to try to manage a response to this rust. Several chemicals have been permitted to be used by the APVMA and are currently being tested in tea tree. So far, very early results seem to indicate that no chemical residue is being found in the oil of trees sprayed. However, longer term results and possible withholding periods are yet to be established – especially if trees close to harvest time need to be sprayed. The tea tree industry produces something in the order of 400-500tonnes of oil per annum. Of that, approximately 90% is exported. The industry is worth approximately $15-$20million at the farm gate. This income is generated on the mid-North and far-North coasts of NSW with some oil also being produced on the Atherton Tableland in Queensland.

ACN 077 019 204 ABN 48 077 019 204 PO Box 930, Casino NSW 2470 Tel: 02 6674 2925 Fax: 07 5604 1629 Email: [email protected]

Chemical treatment is extremely expensive for a tea tree plantation with one of the chemicals permitted costing $5000 for treatment of a 100ha plantation for one application. This is before the costs of application are calculated. Chemical treatment, whilst a management tool, is therefore not a viable long term solution for the industry. The long term solution is to breed trees that are resistant to the disease. This may take as long as 10 years to determine. Myrtle Rust affects nearly all native plants in Australia. First identified in April 2010, NSW I&I took the decision at that time not to try to control the disease because such diseases are notoriously difficult to control – almost always ending in failure. From late May 2010, a containment/eradication effort was commenced on review of the previous decision but on December 22, 2010 the National Management Group agreed that containment or eradication was impossible. Since April 2010 the disease has moved from the Central Coast of NSW into adjacent State Forests with incursions now identified at Coffs Harbour, Byron Bay, Lismore and Caboolture. This disease affects every home garden with a native plant in it. It affects koala feed trees. People need to be alert for this disease and be careful when examining any native plant in any location. People seem to be the biggest spreaders of the disease at this point in time – hence the huge jumps in locations. The disease can be spread on the wind.

Tony Larkman IDO – ATTIA Ltd Phone: 07 5465 2095 Mobile: 0434 263 664

ACN 077 019 204 ABN 48 077 019 204 PO Box 930, Casino NSW 2470 Tel: 02 6674 2925 Fax: 07 5604 1629 Email: [email protected]