Scourge of NSW Eucalypt forests
March 2007
BMAD, the acronym for Bell Miner associated dieback disease in Eucalypt forests
along the NSW coast and ranges, is causing alarm among forest industry interests,
Federal and State Departments of Environment, and environmentalists.
In what is a rare collaborative effort between the stakeholders, a BMAD working
group was set up some years ago in an attempt to determine the causes of this
insidious disease, and what actions should be taken to halt its spread.
It is estimated that approximately 2,500 hectares of forest is infected, with another
4.5 million hectares potentially under threat. The implications for the timber industry
are dire, with large areas of NSW forests now showing serious effects.
Unfortunately the picture is still incomplete, with the emergence of several divergent
views on how to tackle the problem. However, a consensus has been reached, with
agreement that the dieback is the result of repeated psillid attack. These sap-sucking
insects (sometimes known as lerp insects, by a sugary secretion, or lerp, they create
to form a shield around the nymphs), occur naturally in Eucalypt forests. A severe
outbreak of psillids can defoliate entire trees, which in itself is not fatal. However,
repeated defoliation results in permanent damage, which is first manifested by the
death of terminal branches and twigs, followed by a general decline in health,
leading eventually to permanent damage and finally the death of the tree.
BMAD at work. A graveyard of Sydney Blue Gums (
Eucal yptus saligna)
in the
Kumbatine National Park, South of Kempsey.