Diversity in Eucalyptus susceptibility to the gall-forming wasp Leptocybe invasa

1 Extensive variation to damage by the invasive gall-forming wasp Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae) is known to exist amongst Eucalyptus genotypes. 2 In the present study, 30 of the 50 tested genotypes were susceptible to gall formation and development of the wasp. Gall development on the petiole and leaves of plants was compared to calculate the percentage of infestation per plant and per genotype. 3 A positive correlation between galls on petioles and leaves indicated an absence of specificity at this level, and also that either leaves or petioles could be used to obtain an accurate estimate of the level of infestation. 4 Genotypes of E. nitens × E. grandis and E. grandis × E. camaldulensis were most susceptible, with a maximum damage index value for leaves and petioles of 0.52 and 0.39, respectively. Eucalyptus dunii, E. nitens, E. smithii, E. urophylla and E. saligna × E. urophylla showed little or no infestation. 5 The results obtained in the present study suggest that the selection and planting of resistant/less susceptible genotypes will be an important aid in managing damage from L. invasa invasion.The University of Pretoria, members of the Tree Protection Cooperative Programme (TPCP) and The Technology and Human Resources for Industry Programme (THRIP) of the Department of Science and Technology (DST).http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1461-9563

Interactions between hymenopteran species associated with gall‐forming wasps : the Leptocybe invasa community as a case study

1. Leptocybe invasa is native to Australia and induces galls on various species of Eucalyptus. Two genetically distinct lineages of this wasp have been detected outside its native range, namely, Leptocybe Lineage A and Leptocybe Lineage B. 2. The parasitoid Selitrichodes neseri was released in South Africa as a biological control agent against L. invasa. Another parasitoid of L. invasa, Quadrastichus mendeli, as well as Megastigmus zebrinus (parasitoid) and Megastigmus pretorianensis (role unknown), have also been recorded emerging from L. invasa galls. The objective of this study was to investigate the interactions between the different hymenopterans associated with L. invasa galls in South Africa. 3. L. invasa galls were dissected and species‐specific primers and restriction enzymes were used to identify the larvae where interactions were noted. 4. S. neseri, Q. mendeli and M. zebrinus were confirmed to parasitize Leptocybe Lineage A, and S. neseri was confirmed to parasitize Leptocybe Lineage B. Furthermore, there were direct interactions between these parasitoids, where parasitoids were found parasitising each other. The gall forming experiment confirmed that M. pretorianensis is not a gall former, but other potential roles remain uncertain.Supporting Information: Table S1. Species specific primers and their annealing temperatures for the hymenopteran species associated with Leptocybe invasa galls and the expected fragment sizes amplified by each species‐specific primer for the region Cyt b. Table S2. The fragment sizes of digested Cyt b amplicons using the AseI restriction enzyme for Leptocybe invasa (A and B), Selitrichodes neseri, Megastigmus zebrinus, Megastigmus pretorianensis and Quadrastichus mendeli.https://onlinelibrary.wiley.com/journal/146195632021-10-13hj2021BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyZoology and Entomolog

Evidence that Quadrastichodella nova (Hymenoptera: Eulophidae) is the only gall inducer among four hymenopteran species associated with seed capsules of Eucalyptus camaldulensis (Myrtaceae) in South Africa

Three chalcidoid wasp species, Megastigmus zebrinus Grissell (Torymidae), Quadrastichodella nova Girault (Eulophidae) and Leprosa milga Kim & La Salle (Eulophidae), have each been described independently as gall inducers associated with Eucalyptus species (Myrtaceae). The finding that at times they emerge together from seed capsules of river red gum (Eucalyptus camaldulensis Dehnhardt) collected at the same site in South Africa, cast doubt on the accuracy of these earlier interpretations. The current study examined the gall inducing abilities of each of the three wasp species. During geographical surveys, all three species coexisted in seed capsules at 16 of the 61 sites sampled. A study of the seasonal emergence pattern of the three species, together with a fourth, locally abundant gall associate, Aprostocetus sp., showed that Q. nova and L. milga emerge during early summer, while the remaining two species emerge in smaller numbers throughout the year. Oviposition trials on sleeved branches of E. camaldulensis, from which all insects had previously been excluded, verified that Q. nova had the ability to induce galls, while both M. zebrinus and L. milga failed to do so. Only one type of gall of characteristic structure was encountered, which repudiates the possibility of a second gall inducer, and no indication of inquilinism was found. Megastigmus zebrinus, L. milga and Aprostocetus sp. are thus more likely to be parasitoids.DNA sequences were obtained for the adults of all four these species. By matching the DNA of identified adults with that of juvenile hymenopterans in the galls, it was confirmed that all four hymenopterans species developed within the seed-capsule galls of E. camaldulensis. Regrettably, this technique failed to give a clear indication of the exact host relationships between the various gall inhabitants. By dissecting seed capsules at different stages of gall development, the origin of the gall was proven to be in the placenta of one of the locules of a flower bud, and not in a seed or ovule, as previously reported.The Agricultural Research Councilhttp://reference.sabinet.co.za/sa_epublication/entohttp://www.entsocsa.co.za/Publications.htm2017-03-30am201

The distribution and diversity of Leptocybe invasa (Hymenoptera: Eulophidae) and its gall associates in South Africa

Leptocybe invasa is an invasive gall wasp and pest of Eucalyptus trees, which has become widely distributed in Africa, Asia, Europe and the Americas. Several other wasp species have been found to co-occur in L. invasa-induced galls. In South Africa, this includes an introduced biological control agent, Selitrichodes neseri; two known, accidentally introduced parasitoids, Megastigmus zebrinus and Quadrastichus mendeli; and M. pretorianensis, whose role in the gall is uncertain. In addition to the gall associates, a second lineage of L. invasa or cryptic species was discovered in South Africa in 2015. To determine the distribution and prevalence of these species across South Africa, a national monitoring scheme was initiated. Galled Eucalyptus material was collected at infested sites and emerging adults were collected and identified. Morphology, DNA barcoding and polymerase chain reaction (PCR) Restriction Fragment Length Polymorphism analyses were used to differentiate between the species and lineages. Results from the first two sampling periods indicated that L. invasa lineage A has spread throughout South Africa while lineage B had a more limited distribution in the country. Subsequent samples recorded the further spread of L. invasa Lineage B, which now occurs in all provinces sampled. The Leptocybe lineages were found to co-occur on individual trees, increasing the potential for admixture. From the Eucalyptus genotypes sampled, there was no indication of differences in host association between the Leptocybe lineages. Selitrichodes neseri, M. zebrinus and M. pretorianensis were present throughout South Africa and emerged from trees that contained both Leptocybe lineages, but their frequency varied with site. This study will inform future distribution of parasitoids as well as monitoring of potential changes in plant host resistance, admixture and parasitoid resistance in future.The Department of Science and Innovation–National Research Foundation, Centre of Excellence in Plant Health Biotechnology and Forestry South Africa (FSA).http://www.tandfonline.com/loi/tsfs20hj2023BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyZoology and Entomolog

Selitrichodes neseri n. sp, a new parasitoid of the eucalyptus gall wasp Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae: Tetrastichinae)

Selitrichodes neseri Kelly & La Salle n. sp. (Hymenoptera: Eulophidae: Tetrastichinae), is described as a parasitoid of the invasive eucalyptus gall wasp Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae: Tetrastichinae), which is causing substantial damage particularly in commercial Eucalyptus plantations. Selitrichodes neseri was originally collected in Australia in 2010 when searching for biological control agents of L. invasa. It has since been reared in quarantine in South Africa where it is being evaluated for release as a biological control agent of L. invasa.The University of Pretoria, Forestry and Agricultural Biotechnology Institute and the Tree Protection Co-operative Programme.http://www.mapress.com/zootaxa/ab201

Invasive gall-forming wasps that threaten non-native plantation-grown Eucalyptus : diversity and invasion patterns

Gall‐forming hymenopterans of Eucalyptus species are highly successful invaders causing significant damage in non‐native plantation forests. To date, at least 16 of these species have been recorded as invasive eucalypt gall formers, of which less than half are known from Australia where they are thought to be native. About 80% of the species have become invasive only in the last two decades, <10%, of which were known from Australia beforehand. Two species, Leptocybe invasa and Ophelimus maskelli are global invaders that have become established in 43 and 23 countries, respectively, since 2000. They belong to a large number of wasps that cause similar damage and that could become invasive in the future. The problem of identification is exacerbated by the fact that many species lack taxonomic descriptions; over 80% of the invasive eucalypt gall wasps were first described from their invasive range. The small number of taxonomists able to identify these insects slows accurate diagnoses. Even when initial identifications have been made, these may be confused with morphologically similar but distinct cryptic species, which may differ in their host range and natural enemy interactions. Furthermore, detailed information regarding their biology and native distribution is typically sparse or unknown. This lack of information delays the initiation of management actions because breeding for resistance and biological control requires accurate identification of the target pest. The gall‐forming hymenopterans associated with Eucalyptus represent an important group on which to focus the development of pre‐emptive quarantine, monitoring and potential management options. Given the global nature of invasions by these insects, an international and collaborative research approach is required, where knowledge and tools for study can be shared in a more effective manner.Supporting information: Table S1.Data used to estimate the spread of Leptocybe invasa between neighbouring countries. Simultaneous discoveries in neighbouring countries (e.g. Ethiopia, Kenya, Uganda) were considered a single discovery.National Sirex Coordination Committee; Plant Health Australia; HQPlantations Pty Ltd; Queensland Department of Agriculture and Fisheries, Forest and Wood Products Australia and Advance Queensland Fellowship.https://onlinelibrary.wiley.com/journal/146195632021-09-04hj2021Forestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyZoology and Entomolog

Six recently recorded Australian insects associated with Eucalyptus in South Africa

The increased movement of goods and pathways to transport these goods around the world, combined with the global homogenisation of cultivated areas has resulted in an increase in insect movement and establishment (McCullough et al. 2006; Roques et al. 2008;Aukema et al. 2010; Garnas et al. 2012). This pattern has been evident in South Africa (Giliomee 2011), including plantations of Eucalyptus where an increase in the rate of introduction of non-native insect herbivores has been reported (Wingfield et al. 2008; Garnas et al. 2012; Hurley et al. 2016). Indeed, in just three years (2012–2014), at least six insect species native to Australia and associated with Eucalyptus trees have been detected in South Africa for the first time. This short communication serves to formally report these six species, namely Glycaspis brimblecombei Moore (Hemiptera: Psyllidae), Psyllaephagus bliteus Riek (Hymenoptera: Encyrtidae), Spondyliaspis cf. plicatuloides Froggatt (Hemiptera: Psyllidae), Ophelimus maskelli Ashmead (Hymenoptera: Eulophidae), Closterocerus chamaeleon Girault (Hymenoptera: Eulophidae) and Psyllaephagus blastopsyllae Tamesse, Soufo, Tchanatame, Dzokou, Gumovsky & Coninck (Hymenoptera: Encyrtidae).Members of the Tree Protection Co-operative Programme (TPCP), the Department of Trade and Industry (DTI) and the National Research Foundation (NRF).http://reference.sabinet.co.za/sa_epublication/entohttp://www.entsocsa.co.za/Publications.htm2018-09-30am2016Forestry and Agricultural Biotechnology Institute (FABI)GeneticsZoology and Entomolog

Population genetic analyses of complex global insect invasions in managed landscapes : a Leptocybe invasa (Hymenoptera) case study

Increased rates of movement and the accumulation of insects establishing outside their native range is leading to the ‘global homogenization’ of agricultural and forestry pests. We use an invasive wasp, Leptocybe invasa (Hymenoptera: Eulophidae), as a case study to highlight the rapid and complex nature of these global invasions and how they can complicate management options. To trace the invasion history of L. invasa globally, we characterised the genetic diversity within and between populations from its origin and invaded regions using mitochondrial and nuclear markers. Three mitochondrial Haplogroups were identified, of which two are likely different species that appear to have been independently introduced into different parts of the world. One type (Mitochondrial Haplogroup 1) occurs globally, and is the exclusive type found in Europe, the Middle East, South America and most of Africa. The second type (Mitochondrial Haplogroup 2) co-occurs with the first-type in Laos, South Africa, Thailand and Vietnam, while a third type (Mitochondrial Haplogroup 3) occurs exclusively in Australia, its native range. The distinction of the two invasive Haplogroups was supported by analysis of newly developed simple sequence repeat (microsatellite) markers in populations from 13 countries. Further analyses using clustering methods and approximate Bayesian computation suggested the occurrence of hybridisation in the Laos population and revealed that an unsampled population was the origin of Mitochondrial Haplogroup 1. The analyses also showed little genetic differentiation within the invasive populations, suggesting a limited original introduction from a very small population followed by rapid, global range expansion in a stepwise fashion. Results of this study should provide some guidelines for characterizing invasion pathways of new invasive insect pests.Members of the Tree Protection Co-operative Programme (TPCP), the THRIP Initiative of the Department of Trade and Industry and the National Research Foundation (NRF) (NRF Grant Number 88227).http://link.springer.com/journal/105302019-09-01hj2019Forestry and Agricultural Biotechnology Institute (FABI)GeneticsZoology and Entomolog

Diversity and introduction history of Glycaspis brimblecombei reflects a history of bridgeheads and distinct invasions

Glycaspis brimblecombei is an invasive insect pest of Eucalyptus that has spread rapidly around the world since its first report in California in 1998. The pest now occurs on at least four continents where Eucalyptus is grown as a non-native plantation species. To characterize global routes of invasion for this insect, we characterized the sequences of a portion of the Cytochrome Oxidase 1 (COI) gene from 105 individuals from the invasive and native range, including from Australia, Brazil, Chile, La Réunion, Mauritius, South Africa and the United States. In addition, we developed 13 polymorphic microsatellite markers, of which we used 11 to characterize the diversity in the same 105 specimens. Our results suggest that there have been two independent introduction events from Australia, which is assumed to be the origin, to distinct parts of the adventive range. The first introduction was into the United States, from where it appears to have spread to South America and eventually to South Africa. This finding highlights the threat of bridgehead populations to accelerate pest invasions in Eucalyptus, even if those populations are on widespread non-commercial populations of Eucalyptus (as in California). A second introduction appears to have occurred on the islands of Mauritius and La Réunion and provides another example of the establishment of independent lineages of invasive global insect pests. This complex invasion pattern mirrors that found in other Eucalyptus pests.Members of the Tree Protection Co-operative Programme (TPCP) and the DSI NRF Centre of Excellence in Plant Health Biotechnology.https://www.frontiersin.org/journals/forests-and-global-change#am2022BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyZoology and Entomolog

Host specificity tests reveals new host of a global biological control agent Psyllaephagus bliteus (Hymenoptera: Encyrtidae)

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: Aphalari- dae). 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. bliteusto native insects is low, but that the host range of P. bliteusis 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.The Tree Protection Co-operative Programme (TPCP) and the University of Pretoria (UP).https://journals.co.za/content/journal/ento2022-09-01pm2021BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyZoology and Entomolog