Eucalypt Dieback on the Northern Tablelands of New South Wales

Abstract

This study was initiated in order to attempt to describe the nature and extent of eucalypt dieback on the Northern Tablelands. It was found that the typical symptoms of eucalypts exhibiting dieback involved general deterioration of the crown with thinning of foliage and progressive death of twigs and branches. Most of the declining trees were severely defoliated by a variety of native insects, in particular paropsine and scarabaeid beetles. Partial recovery usually occurred in the form of bursts of epicormic shoots, but the new growth was also liable to deterioration. The trees usually died, with a few intact leaves remaining, but occasionally trees wilted while still bearing a significant portion of their leafy crown. Wood decay was common in the affected eucalypts, but the rotting of live sapwood was only occasionally evident. Semi-quantitative scales were constructed to facilitate the assessment of tree vigour and foliage cover. A broadscale road survey of the Northern Tablelands was undertaken during 1980 to ascertain the extent of eucalypt dieback and which species were involved; 48 species of naturally occurring eucalypts were encountered. The stretch of country in which most dieback had occurred runs from Bendemeer and Yarrowitch in the south to Tenterfield in the north. ... It is argued that lignotuberous advanced growth is critical for the survival of eucalypt populations during periods of intense dieback.