Glycaspis brimblecombei (Hemiptera: Aphalaridae) is an invasive, sap-sucking eucalypt pest in various parts of the world. Psyllaephagus bliteus (Hymenoptera: Encyrtidae) was first released as a biological control agent against this pest in California in 2000. Since then, P. bliteus has been found with its insect pest host, with no intentional introduction, in various South American, European and North African countries, and recently South Africa. Here we report on host specificity studies of P. bliteus in South Africa in order to determine potential risks to non-target hosts. Non-target test insects included the only native lerp-forming psyllid in South Africa, Retroacizzia mopani (Hemiptera: Psyllidae), as well as two free-living and one lerp-forming psyllid that are not native but also feed on Eucalyptus species. Psyllaephagus bliteus was monitored during no-choice tests for antennation, probing and oviposition behaviours towards the test insects. In addition, P. bliteus was enclosed on live plants infested with the test insects which were then monitored for offspring of P. bliteus. Retroacizzia mopani and the non-native free-living psyllids were not attacked, but P. bliteus did attack and develop on the non-native lerp psyllid, Spondyliaspis cf. plicatuloides (Hemiptera: Aphalaridae). Choice tests were then undertaken with G. brimblecombei and S. cf. plicatuloides, and G. brimblecombei was found to be the preferred host. The results indicate that the risk of P. bliteus to native insects is low, but that the host range of P. bliteus is not restricted to Glycaspis spp. and Creiis costatus (Hemiptera: Aphalaridae) as previously thought. The host range of P. bliteus may thus include other lerp-forming insects on eucalypts, especially those within the Spondyliaspidinae.