RESULTS METHODS INTRODUCTION Fig. 1: A, C. eucalypti; B, B. occidentalis; C, G. brimblecombei; D, S. cf. plicatuloides; E- H, infestation of the respective psyllids on eucalypt leaves and shoots; I, P. pilosus (known parasitoid of A); J, P. blastopsyllae (known parasitoid of B); K, P. bliteus (known parasitoid of C). Table 3: Antennation, probing and oviposition attempts by P. blastopsyllae when exposed to B. occidentalis, G. brimblecombei and C. eucalypti; and of P. bliteus when exposed simultaneously to G. brimblecombei and S. cf. plicatuloides, in choice tests. The known host psyllid of each parasitoid is indicated in bold. No-choice host specificity testing Behavioural assay • The three Psyllaephagus species were collected from their known hosts. • Each Psyllaephagus species was separately exposed to B. occidentalis, C. eucalypti, G. brimblecombei and S. cf. plicatuloides. • Antennation, probing and oviposition behaviour of the parasitoids was monitored for 3 h. Choice host specificity testing • Based on the results of the no-choice tests, host preference of P. blastopsyllae was tested between G. brimblecombei, C. eucalypti and B. occidentalis, and host preference of P. bliteus was tested between G. brimblecombei and S. cf. plicatuloides, using the same methods as for the no- choice tests. No-choice host specificity testing Parasitoid development assay • The four psyllids were reared on their hosts. • For each psyllid-parasitoid combination, 10 infested trees were sleeved and a pair (female and male) of the parasitoid was introduced. • After 40 days, the number of Psyllaephagus wasps that emerged from the sleeve was recorded. Table 2: Average numbers of parasitoids that emerged from the test psyllid species and known hosts in the para- sitoid development assays. The known host psyllid of each parasitoid is indicated in bold. REFERENCES 1. Bush SJ, Slippers B, Dittrich-Schröder G, Hurley BP. 2020. Host specificity tests reveals new host of a global biological control agent Psyllaephagus bliteus (Hymenoptera: Encyrtidae. African Entomolo- gy 28: 238–248. 2. Hodkinson ID. 1999. Biocontrol of Eucalyptus psyllid Ctenarytaina eucalypti by the Australian parasi- toid Psyllaephagus pilosus: a review of current programmes and their success. Biocontrol News and Information 20: 129–134. ACKNOWLEDGEMENTS Tree Protection Co-operative Programme (TPCP), DSI – NRF Centre of Ex- cellence in Plant Health Biotechnology, University of Pretoria, South Africa for financial support. DISCUSSION AND CONCLUSION • P. pilosus only parasitised nymphal instars of C. eucalypti, its known host, which agrees with previous observations [2]. • G. brimblecombei was identified as a potential new host for P. blastopsyllae, and S. cf. plicatuloides was confirmed as an alternate host for P. bliteus. • Our findings indicate that some Psyllaephagus spp. have a wider host range, whereas others are highly host specific. Future work • Determine relative parasitism of the Psyllaephagus spp. on their different psyllid hosts in natural (Australia) and planted (e.g. South Africa) eucalypt forests. • Increase our knowledge on the host range of Psyllaephagus spp. in their native range, to inform future biological control programmes. • Two free-living eucalypt-feeding psyllids, Blastopsylla occidentalis and Ctenarytaina eucalypti, and two lerp-forming eucalypt-feeding psyllids, Glycaspis brimblecombei and Spondyliaspis cf. plicatuloides, all native to Australia, have been accidentally introduced into South Africa (Fig 1A-D). • The pest status of these psyllids varies but damage to eucalypts include bud degeneration, necrosis, defoliation, dieback and death (Fig 1E-H). • The co-evolved parasitoids (Psyllaephagus spp.) of three of the psyllid species were unintentionally intro- duced into South Africa with their insect hosts (Fig 1I-K). • A previous study showed that the parasitoid of G. brimblecombei, namely, Psyllaephagus bliteus, also parasitised S. c.f. plicatuloides [1],