In late 2010 a highly contagious, debilitating and potentially deadly disease spread rapidly across the Blackall Range.
Now that I’ve got your attention… and just to reassure you – this is a plant disease. The disease is known as Myrtle Rust (Uredo rangelii) and its potential victims include plants within the Myrtle Family (Myrtaceae). This family includes all of our Gum trees, Bottle Brushes, Paperbarks, Ti-tree, Lillypilly’s and many other rainforest shrubs. Plants in the Myrtle Family dominate the Australian landscape and so the potential for this disease to wreak ecological havoc is quite scary!
Myrtle Rust evolved in South America. From some of the articles I have read it leapt from their native myrtles, such as Guava, onto the many Eucalypt plantations that have been established there, evolving as it made this leap. This new “Frankenfungus” has then spread rapidly across the world, through movement of infected plant materials – yet another good reason for growing local native plants wherever you live on the planet!
Myrtle Rust was imported into New South Wales on infected plant material early last year. Unfortunately this has coincided with a record breaking wet humid summer, just perfect for the rapid spread of a fungal disease. The disease appears to have spread rapidly through the Sunshine coast over the last few months. Due to this rapid spread of the disease control of the disease has moved from” Containment” i.e. infected properties were quarantined, through to “Management” of the disease.
The first visible rust symptoms are the red or brown spots that appear on the leaves in varying densities. The spots go all the way through the leaf. Mature spots produce masses of bright yellow or yellow-orange spores (powder) on their surface – this is the contagious bit that can spread the disease – don’t touch them! The spores have a bright yellow colour, and generally form on the underside of the leaf first. Older infections can be dull yellow/brown, and although the majority of the spore masses may have disappeared, close examination will usually reveal a few spores. Death of new growth may occur and, at the very least, plant vigour and health will be affected.
Now what to do? How can you help stop the spread of this disease? Is it too late and has the horse already bolted!
Myrtle Rust is spread by spores carried by wind, water, insects, birds and other animals! We can also spread Myrtle Rust by coming into contact with the spores, moving infected plant material such as prunings or obtaining infected stock from nurseries. We can’t do much about natural processes moving Myrtle Rust, but we can reduce our continued spread of the disease. Be sure to check that any nursery stock you are buying is clear of the disease and is from an accredited nursery that a) still free of the disease or b) is are aware of Myrtle Rust and are managing accordingly. If you prune diseased material don’t dump it: bag it or burn it! Be especially careful of buying stock from markets.
So far the plants that are being affected dramatically on the Blackall Range include the Thready-bark Myrtle (Gossia inophloia) and its cultivars: Aurora & Blushing Beauty; Scrub Ironbark (Gossia acmenoides; Scrub Ironbark (Rhodamnia rubescens); Silky Myrtle (Decaspermum humille) and Scrub Cherry (Syzygium australe).
The potential ecological impacts of Myrtle Rust are many and varied. Infected plants, at the very least, will lose health and vigour. This will affect their ability to fruit, reproduce and compete within nature. Severe infections of some vulnerable species will result in death, either immediately or through their loss of ability to compete with surrounding vegetation. There are many rare native plants in the Myrtle family in our area that have very limited populations. This disease could tip them over the edge.
This unfortunately is a story without a happy ending, and to some degree we have to sit back and watch the spread of yet another exotic pest. We may not be able to stop the spread of this disease but let’s make sure we don’t assist it. As this ecological drama unfolds we may need to intervene and save some of our rare plants, but cross-fingers Myrtle Rust is not as devastating within Australia as it has been with our Eucalypts overseas. Keep your eyes out for this new disease and make sure you don’t help it spread.
What do you do if you see Myrtle Rust?
Do not move the infected plant material, to avoid spreading the disease, and report all suspected plants immediately to Biosecurity Queensland or by calling the Exotic Plant Pest Hotline.
Biosecurity Queensland – Ph: 13 25 23, Exotic Plant Pest Hotline – Ph: 1800 084 881
Myrtle Rust Update
In last month’s Hinterland Times, I was fortunate enough to be given the opportunity to raise awareness of the rapid spread of Myrtle Rust (Uredo rangelii) across the Blackall Range. This plant disease had only been officially recorded for the first time in central coast New South Wales in April 2010, but had spread rapidly up the east coast, in what has been a perfect wet summer for this fungus. It had been officially recorded in Maleny in late February 2011, and from there has spread quickly across the range.
At first there was a great wailing and gnashing of teeth as it appeared the end of the world was upon us, with a potential plague to be released upon all of the plants in the Myrtaceae Family (all of our Gum Trees, Paperbark’s, Bottle Brushes, Lillypillys etc.) … but like so many threats of imminent apocalypse, the story so far isn’t too bad. That said however, we still could have done without this problem, but that is perhaps another story. (Do you know we even buy Australian Eucalypt timber from South America? Talk about selling snow to the Eskimos! And of course Eucalypt timber imports have been found to contain Myrtle Rust spore…thanks to unrestricted international trade!)
Our personal experience is that Myrtle Rust arrived with a grand flourish, appearing on a wide range of rainforest type myrtles, including Decaspermum humille, Rhodamnia spp. and Gossia spp. In the first wave it affected and killed all the new growth of some plants. Subsequently we began a treatment regime as dictated by Biosecurity Queensland, to prevent infection of stock in our nursery, which has been very successful. In our revegetation areas however we haven’t treated all infected plants, as I believe the use of fungicides is a stop gap measure and that we need to look toward assisting the development of resilience to Myrtle Rust. The good news is after the initial infection many of our untreated plants do appear to be bouncing back with lots of healthy new growth. I expect there will be a re-infection, but I’d also suggest that many of the plants affected so far appear to be showing some resilience to the disease now. The important message is that this disease is now widespread in our area and has become an environmental factor that our local plants in the Myrtaceae Family are going to have to adapt to.
Most importantly when dealing with Myrtle Rust (at least now) is don’t panic. This is yet another invader that Australia could have certainly done without, and we can only cross our fingers and hope that if we look after the bush, it will be able to look after itself.
