Review Article

Gudrun Dittrich-Schröder, Brett P. Hurley, Michael J. Wingfield, Helen F. Nahrung and Bernard Slippers

* Department of Zoology and Entomology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa,†Forest Industries Research Centre, The University of the Sunshine Coast, Sunshine Coast, Queensland, Australia and‡Department of Biochemistry,Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, 0002, South Africa

Abstract

1. Gall-forming hymenopterans of Eucalyptus species are highly successful invaders causing signicant damage in non-native plantation forests. To date, at least 16 ofthese species have been recorded as invasive eucalypt gall formers, of which less thanhalf are known from Australia where they are thought to be native. About 80% ofthe species have become invasive only in the last two decades, <10%, of which wereknown from Australia beforehand.
2. Two species, Leptocybe invasa and Ophelimus maskelli are global invaders that havebecome established in 43 and 23 countries, respectively, since 2000. They belong toa large number of wasps that cause similar damage and that could become invasive inthe future.
3. The problem of identication 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 identifythese insects slows accurate diagnoses. Even when initial identications have beenmade, these may be confused with morphologically similar but distinct cryptic species,which may differ in their host range and natural enemy interactions.
4. Furthermore, detailed information regarding their biology and native distributionis typically sparse or unknown. This lack of information delays the initiation ofmanagement actions because breeding for resistance and biological control requiresaccurate identication of the target pest.
5. The gall-forming hymenopterans associated with Eucalyptus represent an importantgroup on which to focus the development of pre-emptive quarantine, monitoring andpotential management options. Given the global nature of invasions by these insects,an international and collaborative research approach is required, where knowledge andtools for study can be shared in a more effective manner.Keywords gall-forming Hymenoptera, invasive species, plant galls, plantation forestry.