Eucalyptus viminalis dieback in the Monaro region, NSW

SummaryOver the last decade, substantial numbers of Eucalyptus viminalis across the Monaro plains in south-eastern NSW have been observed as declining in health. Based on a systematic road survey, the affected area is estimated to cover around 2000 km², with almost all E. viminalis within that area either dead or severely affected. Other eucalypt species present show minor levels of health deterioration. Field observations include widespread infestation of an endemic but previously undescribed species of eucalyptus weevil (Gonipterus sp.). Eight sites were chosen to represent the range of management practices and recent fire history in the affected area. The structural complexity, tree health and level of weevil infestation were determined at each site, and despite large differences in structural elements and overall complexity, the severity of dieback was consistently severe across the range. There does not appear to be sufficient evidence to conclude that changed land management practices, recent fire history or declining levels of structural complexity are responsible for this Monaro dieback. If the dieback continues at the current rate, it seems inevitable that E. viminalis will disappear entirely from the Monaro region. As E. viminalis is the dominant species in most of the region, such disappearance will have very serious consequences on the ecology of the region. Further work is required to determine if the dieback is related to changes in climate or rainfall patterns. Trials of potential replacement E. viminalis genotypes and alternative eucalypt species should be undertaken as a precaution in case the dieback cannot be reversed.