Summary This paper examines the essentials of the biology, impact and control of the European tree-killing wood wasp Sirex noctilio, which was found established in exotic Pinus radiata plantations in Australia about 1950–51. The wasp, with its pathogenic symbiont Amylostereum areolatum, has severely damaged some unthinned pine stands of intermediate-age, and valuable shelterbelts on farmland in Tasmania and Victoria. One-year life cycles are predominant, but three-month cycles and two or three-year cycles are also known. Emergence of adults, followed by attack on pine, occurs mostly between mid and late summer, when soil moisture levels, growth rates and tolerance of pine to pests and diseases are low. Various volatile substances produced by phloem/cambium tissues of stems and large branches, are important in the attraction of the pest. Susceptible trees are normally physiologically stressed, and attack on them is associated with a reinforcement of stress due to mucus injection, and a subsequent insect-pa...