Research underway at Charles Sturt University (CSU) in Orange aims to save Australia’s multi-billion dollar plantation pine industry from the dual threats of exotic pests and climate change.

 

The north eastern American bark beetle, Ips grandicollis, was accidentally introduced to Australia in the 1940s living and feeding on logging debris.

 

But the bark beetle population has undergone an unexplained boom in recent years; the tiny creatures are now responsible for wide-scale tree mortality and are interfering with the control of another exotic pest, the European Wood Wasp, Sirex noctillio.

 

The CSIRO blames Sirex, which introduces a wood-rotting fungus and toxic mucous into pine trees, for wiping out a third of New Zealand’s pines in the 1940s and almost destroying the Tasmanian pine industry in the 1950s.

 

It estimates the wasp would cost the Australian pine industry up to $4 billion per plantation rotation if not for the work of CSIRO researcher Dr Robin Bedding who pioneered the use of a species of nematode (an unsegmented worm) as a biological control in the 1960s.

 

The nematode, which feeds on the fungus and parasitises and sterilises the female wasp, has been introduced to plantations via treated ‘trap trees’ to effectively control the wasp since the 1980s, but CSU researcher Ms Fazila Yousuf said the bark beetle explosion threatens to once again set Sirex free.

 

“Each year the plantation managers select plots of about 10 trees which are treated with herbicide to weaken them and attract the wasps,” she said.

 

“The nematodes, which feed on the fungus spread by the wasps, are then introduced to be spread throughout the wasp population.

 

“But in recent years the bark beetles are interfering with that process by attacking the trap trees and introducing a second type of fungus which spreads faster than the wasp fungus and which the nematodes cannot feed on.”

 

Working with Professor Geoff Gurr from CSU’s School of Agricultural and Wine Sciences, Ms Yousuf is researching the comparative growth rates of both fungi, as well as the effects of temperature on each species.

 

“It is a mystery at the moment why the beetle population has grown so much, and why they are attracted to the trap trees so specifically,” she said.