Parasitism levels and seasonal phenology of the introduced species leafblister sawfly, Phylacteophaga froggatti, in south-western Australian blue gum (Eucalyptus globulus globulus) plantations were investigated. Leafblister sawfly was found at all times of the year, with overlapping generations. However, it became locally rare or extinct on a frequent but temporary basis at all sampled plantations for unknown reasons. Cirrospilus margiscutellum and Bracon confusus were the only parasitic wasps reared from leafblister sawfly larvae and pupae, with both species occurring at such low levels that they did not have a significant impact on leafblister sawfly populations. The parasitic wasp B. phylacteophagus, successfully used in the biological control of leafblister sawfly elsewhere, was not found. Its absence indicates that the elevated pest status of leafblister sawfly in south-western Australia may be a result of inadequate biological control, and a 'classical' biological control program using B. phylacteophagus is recommended for the pest.