Whats the Fuss About Myrtle Rust?

The latest plant biosecurity news is summarised in the Plant Biosecurity Cooperative Research Centre’s (PBCRC)  The Leaflet. The latest edition was packed full of information on the disease called myrtle rust (Puccinia psidii). Read on to find out what really is the fuss behind myrtle rust.

A picture of a branch affected by the disease myrtle rust

Suspect myrtle rust symptoms should be reported to the Pest and Disease Information Service (Emergency Plant Pest Hotline) on 1800 084 881 or email info@agric.wa.gov.au.

The Australian Myrtaceae family of plants, including eucalypts, tea tree and paperbark, and associated plant industries are under threat from a devastating disease called myrtle rust (Puccinia psidii). Myrtle rust was introduced in 2010 and was detected for the first time in Australia on the central coast of New South Wales. With the wind-borne nature of the disease and the abundance of suitable plant hosts in the Australian environment, the disease spread rapidly and is now considered established and widespread along the entire east coast of Australia. The disease is very effective at spreading  making it a threat to the health of Western Australian native species.

What is Myrtle rust?

Dr Geoff Pegg from the Queensland Department of Agriculture and Fisheries is the PBCRC myrtle rust expert,  in the following video he provides some interesting insights into this devastating disease and the research that is building knowledge to help affected industries.

Myrtle rust threatens Australian Industry-

The latest edition of The Leaflet outlined three main industries effected by Myrtle rust.

  1. The $800 million production nursery industry is an important part of the Australian economy and is vital for supporting a range of other industries such as fruit and vegetables. Myrtle rust has already damaged the nursery and garden industry significantly, with immediate restrictions on interstate trade following detection and the removal of popular commercial varieties of plants that are highly susceptible to the disease. Some states still maintain trade restrictions from areas where the disease is present.
  2. The forest industry contributes over $20 billion of economic turnover each year and employs over 70,000 people (ABARES, 2014). While initially considered a significant risk to the forestry industry, impacts to date have fortunately been minimal with reports of the disease restricted to minor damage in young eucalypt plantations in New South Wales (Carnegie, 2015) and Queensland (Pegg, unpublished).
  3. The developing lemon myrtle (Backhousia citriodora) industry has been one of the hardest hit by the disease. Lemon myrtle leaves contain oil with the highest citral content of any known plant in the world – citral is the lemony aroma compound used for its citrus effect. The leaves are dried and milled for use in teas or as a spice and steam distillation is used to extract the essential oil from the leaf material, which can then be used as food flavouring, in aromatherapy products, cosmetics and toiletries. In 2012, production of lemon myrtle was estimated to be between 575 and 1,100 tonnes of leaf and 3 to 8 tonnes of oil, with a farm gate value of between $7 and $23 million.

Overview of the lemon myrtle industry

Lemon myrtle leaves contain the highest amount of citral, more than 90 per cent, of any plant in the world- it has been described as ‘lemonier than lemon’!

The leaves are dried and milled for use in teas or as a spice. Steam distillation is used to extract the essential oil from the leaf material which can then be used as food flavouring, in aromatherapy products, cosmetics and toiletries.

In 2012, production of lemon myrtle was estimated to be between 575 and 1,100 tonnes of leaf, and three to eight tonnes of oil, with a farm gate value of between $7 and $23 million.

So how do we manage it?

The Australian lemon myrtle industry have been loosing out since the introduction of the disease in 2010. The Plant Biosecurity CRC are conducting research to help develop management strategies to reduce production losses from affected plants. Myrtle rust leads to to branch defoliation, dieback and stunted growth – yield losses can be to be up to 70 per cent. Production losses can be severe if the disease is left untreated.

Through a PBCRC research project with the NSW Department of Primary Industries (NSW DPI) and Queensland Department of Agriculture and Fisheries (QDAF), scientists are investigating how to manage the impact of myrtle rust – a disease that has the potential to cause widespread change in native plant species and impacts on the ecological communities they support. This research is being led by Dr Suzy Perry and Dr Geoff Pegg from QDAF, with significant support from Dr Angus Carnegie (NSW DPI). The research project Managing myrtle rust and its impact in Australia is investigating myrtle rust management options for industry and the impact on native ecosystems. This research hopes to finalise a nationally standardised myrtle rust rating system for a range of myrtaceous species growing under different environmental conditions which will enable affected stakeholders to better manage myrtle rust and its consequences in Australia.

For further information on the project take a look at – Managing myrtle rust and its impact in Australia, Further information: Dr Geoff Pegg, Queensland Department of Agriculture and Fisheries, Participants: NSW Department of Primary Industries, Queensland Department of Agriculture and Fisheries

A poster warning New Zealand residents to keep a look out for myrtle rust

Even New Zealand residents are asked to keep a look out for the disease.

Keeping myrtle rust out of Western Australia-

The Department of Primary Industries and Regional Development (DPIRD) gives these tips for managing the biosecurity risk of myrtle rust-

Bush walkers and home gardeners are likely to be the first people to find myrtle rust if it enters WA. Naturalists are invaluable as “eyes on the ground” but are also those most likely to inadvertently bring this disease into WA.

Wind disperses myrtle rust spores but wind alone is unlikely to carry them across the desert which separates WA from the eastern states. However, the tiny spores are highly transportable and can stick to clothing, hats, footwear, vehicles and equipment. Consequently anyone who visits NSW, Victoria or Queensland and then returns to WA should take the following precautions:

  • If travelling by road, shake out floor mats, wash down tyres and check that the vehicle, caravan, trailer and any gardening equipment contain no plant material. Do this before leaving NSW, Victoria or Queensland and do it again before crossing the border back into Western Australia. The reason for performing the first clean-up is that if any spores are accidentally transported even a short distance into other states they could allow myrtle rust to become established further westward and, consequently, begin the spread of the disease towards WA.
  • If possible, change into fresh clothing and footwear before re-entering WA and pack away the attire that was worn in NSW and Queensland. Once home, wash everything that was used on the trip.
  • Rail and domestic airline passengers are reminded that any plant material or items contaminated by soil are prohibited entry into WA. If friends or relatives from eastern Australia are planning to visit WA please pass on this advice.

More information on the DPIRD website about myrtle rust can be found here.

Anyone who finds what they suspect is myrtle rust should ring the Pest and Disease Information Service (PaDIS) on Freecall: 1800 084 881 to report the location. If possible take a photograph and email it to info@agric.wa.gov.au.

Symptoms can also be reported through the MyPestGuide reporter app or by making an online report.

Do not take a sample to post to the Pest and Disease Information Service, because snipping off a piece of diseased plant could dislodge the spores and accelerate the local spread of myrtle rust.

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