Sirex wood wasp update from Australia

Sirex wood wasp (Sirex noctilio) has been established in Australia since the 1950s and has spread to all pine-growing regions except Western Australia and tropical/sub-tropical Queensland. A sirex biocontrol program was developed in Australia in the 1960s–1970s that identified the parasitic wasps Ibalia leucospoides and Megarhyssa nortoni and the nematode Deladenus siricidicola. Sirex is a major pest in Australia, with an impact of AU$35 million since it established; a single outbreak killed five million trees. Aerial and ground surveys are conducted to map the extent and severity of sirex, with trap tree plots and panel traps used to detect spread into new areas. Remote sensing and machine learning has shown promise but is currently too expensive. Outbreaks are targeted with inoculation of naturally struck trees and trap tree plots for later inoculation. Efficacy of biocontrol is evaluated by monitoring emergence from inoculated and uninoculated trees for parasitism, as well as annual assessments of trees killed by sirex. Stocking management to reduce tree stress is recognised as a key management tool. The National Sirex Coordination Committee has commissioned research in the past two decades in response to emerging needs: ips bark beetles attacking trap trees; establishment of sirex in Queensland; refining and standardising trap tree plot establishment to increase effectiveness; molecular investigations into variability in sirex, nematode and fungus; quantitative monitoring of a sirex outbreak. In 2018, research inadvertently and surprisingly revealed a new strain of nematode, designated Lineage D, which occurred widely in many regions. This information, combined with research findings from previous studies, provided evidence that the Kamona strain now seems to be ineffective at controlling sirex wood wasp in Australian pine plantations. Australia is at a crossroads in sirex biocontrol and is investigating options to continue effective sirex management.