The Psyllid Outbreaks On Cumberland Plain Grey Box


Assoc Prof Markus Riegler is leading a team of researchers investigating what is killing Grey Box eucalypts on the Cumberland Plain in Western Sydney. The project, which has been assisted by the New South Wales Government through its Environmental Trust and in partnership with the Royal Botanic Gardens and Domain Trust, aims to develop measures to try to conserve this once dominant tree species.

psyllid adults, nymphs and eggs on leaves (Photo: Dr Markus Riegler)
psyllid adults, nymphs and eggs on leaves (Photo: Assoc Prof Markus Riegler)

"The widespread and ongoing defoliation of Grey Box (Eucalyptus moluccana) in the Cumberland Plain Woodlands (CPW) of Western Sydney has resulted in extensive canopy dieback and tree mortality", says Assoc Prof Riegler.

"Given the importance of the Grey Box tree species within the woodlands, this ecological community is at risk of extinction."

The Cumberland Plain Woodlands is a significant habitat that occurs throughout and alongside Australia's largest human population centre.

The dominant Grey Box is an important source of nectar and pollen for bees, native insects and birds (including the endangered swift parrot and regent honeyeater).

It also supports flying foxes and koalas.

Grey Box defoliation is known to be caused by a previously undescribed species of the family of Psyllidae (jumping plant-lice).

The dominant Grey Box is an important source of nectar and pollen for bees, native insects and birds (including the endangered swift parrot and regent honeyeater)...

Past land clearing and subsequent natural (or assisted) re-growth may have resulted in 'genetic bottlenecks' which can cause plant susceptibility to pests and other environmental stressors.

This project will explain the characteristics and genetic diversity of the Grey Box.

It will investigate psyllid population dynamics and genetics and its expansion potential – there are significant stands of Grey Box in other parts of NSW and Queensland.

An assessment of natural enemies of the psyllid, such as parasitic wasps and fungi and predatory arthropods, will help to develop novel management strategies for psyllid outbreaks on eucalypts.

Male and female psyllid adults

A Fragile Woodland Under Threat

In 1877, Cumberland Plain Woodlands covered 107,000 hectares, or about 30 per cent of the Sydney Basin.

Farming and urban development have seen it shrink to 6400 hectares.

Psyllid-affected eucalypts being removed
Having regrown after defoliation by psyllids, these Cumberland Plain Grey Box eucalypts are making way for road widening in Western Sydney (Photo: David Thompson)

Ecological and sustainability issues around the defoliation of the CPW have been widely reported.

This outbreak threatens biodiversity and ecosystem function, and has biophysical consequences, including changed local climate and increased soil salinity.

Research will open opportunities for natural pest control, with the aim of restoring woodlands' health. 

This project (P00021691) "Psyllid-induced dieback of Grey Box (Eucalyptus moluccana) on the Cumberland Plain" is funded by the New South Wales Environmental Trust