Minimizing the disruptive effect of Ips grandicollis (Coleoptera: Scolytinae) on biocontrol of Sirex noctilio (Hymenoptera: Siricidae)

Sirex noctilio Fabricius (Hymenoptera: Siricidae) is an invasive wood wasp that can cause significant tree mortality to Pinus. Trees treated with herbicide are used to attract S. noctilio to oviposit and are the means by which the nematode biocontrol agent, Deladenus (=Beddingia) siricidicola Bedding (Nematoda: Neotylenchidae), is introduced into the pest population. In Australia, these trap trees are also attacked by the invasive bark beetle, Ips grandicollis Eichhoff (Coleoptera: Curculionidae; Scolytinae). This study investigated the effect of herbicide dose and timing of application on subsequent attractiveness of trap trees to S. noctilio and I. grandicollis. Two replicated trials were conducted concurrently in two major pine growing regions of Australia.