Home Threat Realised
The threat to Perth homes from European House Borer (EHB) has been elevated with infested pine trees for the first time being seen as the likely source of an EHB infestation in a Perth home.
The infestation was found in a Brigadoon house, which is a suburb close to Perth’s Gnangara/Ellenbrook area.
EHB larvae and one exit hole were found in untreated structural pine timber beams supporting a second storey floor. Over time the infestation could have caused the floor to collapse.
The find comes on top of continuing success of the EHB Response, which is committed to containment and surveillance with a view to EHB eradication.
Already 113 out of 144 infested properties have been cleared of EHB host material in an effort to minimise the migration of EHB to susceptible wood materials, including houses built or renovated with untreated structural pine.
However, the Brigadoon house infestation has reinforced the need for home owners to be vigilant for signs of EHB, and to provide continued support for the removal of host materials, including live pine trees, from identified Priority Management Zones (PMZ).
Costs
The EHB Response team has acknowledged community concerns about the level of government funding allocated to the EHB Response to date. However, a Benefit Cost Analysis, conducted with assistance from the Australian Bureau of Agriculture and Resource Economics, showed that a nil control approach would create economic damage across Australia to an amount of $2.4 billion over a 30 year period and more than $6 billion over 100 years.
In fact, a cost benefit analyses shows a cost:benefit ratio of 64:1. That is, every $1 spent on eradication will eliminate $64 worth of damage and timber treatment across Australia.
Even limited containment would cost Western Australia approximately $345 million over 30 years. In comparison, the cost of eradication from 2004 to 2021 (17 years) has been estimated to be only $50 million, and this cost is currently funded through a national cost sharing agreement by all States and Territories, and the Federal Government.
Delaying Pine Tree Removal
 Removal of pine trees as the primary food resource for EHB remains the best means of ensuring EHB does not become a serious concern for home owners, and any others dealing with untreated pine products and timbers.
While the risk in the hills region is reduced due to homes being built primarily with non-susceptible materials, such as jarrah, there remains the chance that EHB from infested areas may migrate to newer suburbs.
In Ellenbrook, for example, housing
development commenced in 1992 and many houses have been built with untreated structural pine framing, particularly those built since 2000.
Migration of original EHB populations from the hills region to Gnangara is considered likely as DNA testing has indicated populations to be closely related.
The prevailing easterly and south-easterly winds in Perth summers, which coincide with the EHB flight season, and the presence of pine tree host bridges (some infested) between the two areas, have added to the speculation that further migration is possible.
Summer Temperatures
Speculation that high summer temperatures in Perth roofs will prevent the laying of EHB eggs and larvae development has not been evident in initial investigations.
Internal temperatures of timbers in volunteer Perth roofs have to date not exceeded 60ºC, but have reached between 50ºC and 55ºC, which is not high enough to kill beetles nor larvae.
Purpose built research roofs were completed last year to assess the survival of EHB in high temperatures. Some indicators showed EHB survival in all phases of development, although further research is needed.
The Department of Agriculture and Food WA (DAFWA) suggests that the lack of infestations in roofs is due to the fact that untreated pine has only been used since 2000, and that it is too soon to see infestations because of the EBH long life cycle.
Surveillance Options
EHB has a long life cycle which results in a slow build-up of EHB populations and a low rate of natural spread. For this reason public argument has been made that pine tree removal in infested areas can be delayed to allow for further research in surveillance options.
This suggestion is not supported by the specialist Scientific Advisory Panel (SAP) overseeing the EHB program for national and State Government partners. Any delay of host material removal will only lead to further spread and increase the risk of eradication failure. Without eradication, other States in Australia would also become at risk.
A major problem in surveillance options is that EHB is difficult to detect due to larvae being able to bore through timber without breaking the surface. It is only when they emerge as beetles that exit holes can be seen.
DAFWA EHB Research Officers have been developing alternative detection options since 2004. Surveillance options to date include the use of trap logs, development of EHB acoustic sensing device prototypes and the training and use of EHB detector dogs.
However, effective completion of surveillance research will be long term, and in the end will most likely only play a role in verifying EHB eradication from previously infested areas.
The Future
The removal of healthy trees from infested areas will never be without good reason.
Additionally, the use of treated pine in the future will not change the fact that current untreated pine may already be or may become infested.
In fact, there is a significant risk that many structural infestations have not yet been discovered. It is only when larvae reach adulthood that exit holes are made and that EHB infestation becomes detectable.
Media Release: 27 May 2009, Latest Weapon In Fight Against Timer Pest Unveiled
Media Release: 30 April 2009, European House Borer Infests House |
