Driving along Richmond-Blacktown Road towards Richmond, glance to the left and the right around the Driftway and you’ll see lots of dead or almost dead trees.
After residents asked the Gazette to find out what’s happening to them, we found it was an insect infestation which has been moving our way from Blacktown since 2012.
It only affects grey box trees — eucalyptus mollucana — which grows on much of the flat open areas around western Sydney.
The trees’ sap is sucked by psyllids, minuscule insects that look like tiny cicadas.
A Local Land Services spokesperson said professional opinion differs as to whether they are native or not.
The infestations are worst in areas of waterlogging and heat stress and the psyllids are present throughout the low-lying areas of the Hawkesbury.
The north side of the Driftway in particular is damaged.
They were first noted in Plumpton Park near Woodstock Avenue in Blacktown in 1999 but it wasn’t until 2010 that it was realised they’d become a broadscale, serious problem.
Dr Markus Riegler of the Hawkesbury Institute for the Environment at UWS Richmond, said about two thirds of western Sydney’s Cumberland Plains woodland is currently affected by psyllid dieback, which tends to come in booms and busts. The booms last about five to seven years.
He is researching the dieback and said about 30 per cent of trees attacked don’t recover but most do once the infestation dies down. He said there was no short-term solution, but that the psyllids do have natural enemies — a tiny parasitoid wasp, but they weren’t keeping on top of the psyllid boom.
At Kurrajong the problem is a bit different, with what’s called ‘bell miner associated dieback’. Bell miners (bellbirds) are thought to eat the sugary secretions of psyllids, but not the insect, and as they are very territorial they keep other birds away from their turf which would eat the psyllids. Dr Riegler said these psyllids are a different species from those down on the flats.
Hawkesbury Environment Network’s Robin Wood said there had been ‘‘lots of outbreaks of psyllids up in the Kurrajong-Grose Vale area in the last 12 months as well as increasing areas of dieback due to heavy populations of bell miners’’.
She said a program to get rid of the lantana in areas where bellbirds nest was currently being considered, in association with Greater Sydney Local Land Services and NSW Nature Conservation Council.
She said ‘‘the problem with psyllids was that they were attacking the dominant species in treed areas’’.
‘‘Once that happens, the canopy loss leads to major changes of light and heat coming onto the shrub and ground layers, as causing shifts in temperature of the soil.
‘‘Fauna and invertebrate species will be affected. So it is like any plague which has the potential to wipe out whole forest and woodland ecosystems bit by bit .
‘‘Apart from that, there is a cost to community of lots of dead and dying trees which may fall on assets such as houses, wires and roads.’’
