FEATURE
A serious threat to our iconic native grass trees By Mary Bremner
The impact of the pathogen Phytophthora on our heathland and forest ecosystems is very real says Aireys Inlet resident and ecologist, Dr Mark Garkaklis. We might call them grass trees, kangaroo tails, yaccas or by their scientific name Xanthorrhoea australis. Our grandparents may have referred to them as black boys. First inhabitants in other places named them bukkup, baggup, balgaor kawee. The local Wadawurrung people used the word djuwutj for the plant’s resin used in spear making and for patching up water containers. With their skirts of long, wiry, bluegreen foliage and dramatic flowering spikes, these plants are a highlight of our native bushland. They flower prolifically following a bushfire, providing a perch for the native birds that feast on their nectar. Notoriously difficult to establish in our gardens and very slow growing, they are thought to live up to 450 years in the wild.
Dr Mark Garkaklis inspecting dieback infected grasstrees near the Great Ocean Road.
However, it is horrifying to find out that these iconic plants are under a very real threat of disappearing from our local heathlands. ‘Our grass trees are fighting what seems to be a losing battle, says Dr Mark Garkaklis.
Phytophthora plant killer ‘The enemy is the pathogen Phytophthora cinnamomi, commonly, but incorrectly, known as cinnamon fungus. It is actually more closely related to algae than fungi. Phytophthora draws its name from Greek words meaning “plant killer”. It is recognised as one of the 100 worst biosecurity threats on the planet.’ Mark was first involved in research into Phytophthora dieback in his home state of Western Australia. For his PhD, Mark studied the way ecosystems behave and what happens when you lose small elements from a system – how the ecosystem either stays resilient or transitions into something new. At the time, there was a lot of concern about the dieback of the jarrah forests, caused by Phytophthora. This destructive pathogen doesn’t only kill grass trees, but can also attack Victoria’s floral emblem, Epacrus impressa (pink heath), as well as Banksia marginata (silver banksia) and members of the Isopogon family. It can get into your garden, with roses and avocadoes also susceptible to its advances. It is the impact of the pathogen on our heathland and forest ecosystems that currently exercises Mark’s mind. Since 2000, Mark has been involved in relevant research 10
with colleagues across Australia and New Zealand. Mark also teams up with his wife, Dr Barbara Wilson, to trap and study populations of endangered native mammals in the Otways region. Very few animals, and certainly no endangered mammals are found in areas impacted by Phytophthora dieback. By contrast, where there are healthy grass trees, there is a diversity of animal fauna. The impact of the destruction of their habitat is clear and very worrying for these passionate ecologists. An understanding of how the pathogen spreads is essential to its control. It seems most likely the disease – a water mould – was carried to Australia on the cuttings and plants brought in by the first European settlers, but it was not recognised as a threat until the 1970s. It is spread largely by our network of roads and tracks, formed with contaminated gravel. Vehicles and bikes that move along the roads can also spread the pathogen.
Where will you see the damage? You can find evidence of this for yourself in the Anglesea Heath. Typically, the pathogen is carried very quickly downhill by water flowing from the road via a spoon drain. It infects the roots of plants in the path of the water – the roots and the vascular tissue that take water up to the plant degrade and it starts yellowing from the tips – it looks like it’s dying from drought. Eventually the plant succumbs. Once infection has taken hold, the pathogen can also progress laterally by root-to-root contact.
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