Biology of the bark beetle Ips grandicollis Eichhoff (Coleoptera: Scolytinae) and its arthropod, nematode and microbial associates: A review of management opportunities for Australia

The five-spined bark beetle, Ips grandicollis, is an exotic pest in Australia that preferentially attacks stressed pine trees, including Pinus radiata D. Don, but it can also attack healthy trees. The beetle has been present in Australia for 70 years, feeding principally on logging debris, with occasional outbreaks resulting in damage to plantations. Attack on trees stressed by drought, fire or storm damage leads to occasional significant losses. In recent years, I.grandicollis has been observed to attack 'trap trees' treated with herbicide to make them attractive to Sirex noctilio Fabricius as part of a successful biological control programme against this wood wasp. Ips grandicollis is able to tolerate a wide range of climatic conditions, and has an extensive geographical range (limited by host tree plantings). The economic impact of I.grandicollis is exacerbated by adults vectoring a fungus, Ophiostoma ips (Rumbold) Nannfeldt, which discolours the outer sapwood and contributes to tree death. Nematodes also are also associated with I.grandicollis, both in the body cavity and under the elytra. The dominant nematode is Contortylenchus grandicolli Massey, which is found internally, in haemocoel, the gut and the head region of the majority of adult beetles. Mites and bacteria are also associated with I.grandicollis but their biology is not well known. Since the first detection of I.grandicollis in Australia, various bio-control and other management strategies have been tested. While a better understanding of the microbial and nematode associates of I.grandicollis may yield novel approaches for the management of this exotic pest, semiochemical-based disruptants offer more immediate scope, particularly for protecting small areas of high value trees such as trap tree plots.