Sydney trees dying due to root disease killer

This row of dead trees in Pyrmont has revealed the insidious threat of a little-known root disease killing off flora across the inner city.

More than 10 trees are sick or dead in Giba Park at Pyrmont.

A ROW of dead trees in Pyrmont has revealed the insidious threat of a little-known root disease killing off flora around the inner city.

The collection of around 10 banksia trees in Giba Park, situated in front of sweeping views of the Sydney foreshore, declined rapidly and were confirmed dead by the City of Sydney last month.

While there have been cases of tree poisoning by residents looking to improve their aesthetic vantage points over the past few years, deliberate targeting of the trees was deemed unlikely – instead, the culprit may be the same hidden killer targeting trees in some of the city’s most iconic green destinations.

Horticulturalist Graham Ross, well known for his work on Better Homes and Gardens and for establishing the Australian Garden Council, said he suspects the likely cause of death is armillaria, a parasitic fungi which causes trees and shrubs to rot.

These trees are suffering from armillaria, says Graham Ross.

The disease, which has been present in Australia since before settlement, has recently caused the deaths of greenery in Centennial Park, Hyde Park, along Macquarie St in the CBD, all along Anzac Pde and in inner city gardens.

Mr Ross said the problem of armillaria had been “swept under the carpet” for many years by authorities and he called for the problem to be treated seriously to stop it spreading further.

Brett Summerell, Deputy Executive Director for Science and Conservation at the Royal Botanic Gardens and Centennial Parklands, said the rot “chews away at the root system” of trees.

Horticulturalist Graham Ross.

Dead trees in Giba Park, Pyrmont.

The disease is especially rife throughout the gardens of the eastern suburbs – making the disease hard to contain unless infected soil is removed and quarantined.

“Most people aren’t aware until they see the tree get really­ sick or die, because all of the really bad stuff is happening underground, chewing at roots for 10 years and slowly killing the tree off,” Mr Summerell said.

Trees can collapse once their root systems have crumbled – the recent fate of several Hyde Park figs – posing a danger to the community. The only way to establish a disease-free garden is to take steps to ensure the soil is clean and healthy, otherwise the cost to dig up and remove the infected root system can be very costly.