Snow gums are experiencing dieback in Kosciuszko National Park, largely because of the impacts of the native longicorn (or ‘longhorn’) beetle. These beetles prefer to lay their eggs on moisture-stressed trees and, in warmer weather, the longicorn beetle can hatch and grow up to 75% faster (reports here). This has been linked to climate change because of warmer temperatures in alpine areas.
So far, impacts seem to be limited to areas in the Snowy Mountains among two distinct subspecies of snow gum – in the Guthega and Perisher areas and parts of Thredbo.
This is an update on the research into the impacts of dieback in these areas.
The following report comes from the Autumn 2020 issue of the Resort Roundup newsletter which is published by NSW Department of Planning, Industry and Environment (available here).
“With very hot dry weather right up until late January, alpine snow gums were again under increased moisture stress and hence were even more susceptible to attack from longicorn beetles (Phoracantha species). Over the summer there has been a lot of research and investigation work being conducted on the dieback, and hopefully you can help.
National Parks and Wildlife Service (NPWS) and Australian Alps National Parks Co-operative Management Committee are working closely with researchers from Australian National University (ANU), Department of Planning, Industry and Environment (DPIE), and others to gain more information in the following areas:
- Dieback cause – confirmation of the main beetle species responsible for the current outbreak. One of the techniques being used was establishment of ‘emergence traps’ to trap all woodborers that come out of the trees between December and March. ‘Funnell traps’ were placed in areas varying in attack severity with the aim of investigating links between insect abundance and attack severity.
- Extent and species affected – confirmation of the Eucalypt species affected by the beetle and the current extent of the outbreaks. Plots and transects have been established to investigate the dieback in detail and look at any patterns between individual stands and at the landscape-level. Tree cores are being used to estimate the timing of dieback.
- Moisture stress – investigating the severity of water stress within snow gum forests and its association with beetle attacks. Plot, transect and tree core data will be used to look for correlations between insect attack and changes in variables such as rainfall and climate.
- Public risk in ski resorts is being assessed using the following methods:
-Flights to obtain new highly accurate imagery of each resort
-Mapping of severity of dieback within each resort
-Mapping of high use areas and areas with heightened public safety risk due to unstable trees
-Risk management plans and work to assess safety issues.
Your help is required to map the location and scale of current outbreaks. This can be done by simply taking a photograph and filling out a basic form at each location on the Atlas of Living Australia Snowgum dieback webpage.