Characteristic temporal patterns of attack by Sirex noctilio F. in Tasmania were obtained when Pinus radiata trees were either felled, completely lopped or high trimmed and girdled. Felling resulted in immediate attack whereas lopped and girdled trees were not attacked until some 9–12 days later. Felled trees were susceptible to attack for about 14 days, but lopped and girdled trees were attacked for longer periods. In some instances girdled trees remained susceptible for more than one season. Oviposition by caged S. noctilio females on healthy trees was followed by attack from wild females about 9 days later. It is shown that the timing and duration of attack by S. noctilio are correlated with the degree of stress undergone by the host tree.