SOS Dieback

Reporter: Andrea Burns

It's the stealth bomb threatening WA's bush. A microscopic pathogen that leaves plant graveyards in its wake. Scientists call it phytophthora dieback. The name translates to 'plant destroyer'.

Professor Giles Hardy from Murdoch University says "40-50% of south west of Western Australia's plant species are susceptible, so there's some 3000 plant species…that's more than the whole of the British Isles".

It was once known as Jarrah dieback, but it's not only jarrah that's affected by this killer. Other trees such as Banksias and Kangaroo Paws are now at risk. Homes to tiny marsupials, birds, even insects are threatened. Important links in WA's ecological chain.

Machinery used to clear roads in the bush have transferred the disease, so have vehicle tyres, even people, trampling through can carry it on their shoes.

"One little teaspoon of soil can have thousands or hundreds of thousands of these little spores that swim…they get attracted to plant roots and then they'll come in contact with a plant root and then they'll germinate and invade it very quickly".

Research scientist at Alcoa and chairman of the Dieback Working Group, Ian Colquhoun says "The infuriating thing is we know what causes it, we know how to stop it spreading, how to manage it and so it's trying to get that word across to people".

Here in our South West, amongst the green, vast tracts of dead, black plants, killed by dieback. Gravel taken from old dieback sites that's been re-used has also infected newer areas, state-wide.

"Today we still have people moving it around. They buy gravel when they build new houses and they get a gravel road put in and they haven't asked the right questions and suddenly their plants die, Banksias die, the little bit of Banksia woodland they've bought dies because they've bought in infested gravel. This happens all the time and we're always getting called out from people saying "oh my plants are dying" and you know why they're dying before you even get there".

First symptoms of dieback were identified in the 1920's but it wasn't until the 1960's that scientists worked out the cause.

A water bourne mould that girdles plants, rotting their roots and preventing the uptake of water. Trees literally dying of thirst.

Invisible to the naked eye, this is what dieback looks like under a microscope. Spores, powered by two tails, are attracted to the root. They colonise, eventually killing the plant.

A huge cost to the community, but no longer just a country problem. Here dieback, in suburban Leeming.

Immunising trees is one treatment. Phosphite injected into the trunk won't prevent dieback but can help fight it.

But, immunising every tree in WA would be expensive and impractical. Preventing the spread of dieback makes more sense.

Whiteman Park's Chris Rafferty says people need to realise conservation and tourism can co-exist.

"It is a challenge. We have bush walkers, horse riders, as well as other traffic coming through, and ourselves and management vehicles so really we just have to put the signage up and communication with the public is another big one".

DIE BACK PREVENTION

* Stay out of infected areas

* Observe hygiene regulations

* Buy soil and gravel from reputable agents

* "Dieback free" plants from nurseries, not stalls or markets

To prevent spreading dieback, our experts say stay out of infected areas.

If there are hygiene practices like washing boots and tyres, adhere to them.

Get soil and gravel from reputable agents.

And only buy plants certified "dieback free" from nurseries. Plants from stalls or markets may have been sourced from infected areas.