Biocontrol introduction
Target pest: Acacia longifolia (Fabales: Fabaceae), Sydney golden wattle
Agent introduced: Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae)
Imported:
2022
Import source:
South Africa
Import notes:
Landcare Research (2023a) - in November 2022, a consignment of galls containing T. acaciaelongifoliae was hand-carried from South Africa, despite EPA approval to release the wasp still pending. This presented the prospect of losing high numbers of adult wasps that emerged but could not yet be released, as adults are extremely short-lived, usually only surviving a few days. Galls were kept at cool temperatures to slow the development of larvae and pupae and delay adult emergence. When EPA approval was granted [see EPA (2022b) entry in ‘EPA applications’ section] galls were transferred to warm conditions and five days later the first releases were made.
Released:
2022
Release details:
Landcare Research (2023a) - between early- and mid-December 2022, 201 adult T. acaciaelongifoliae were released at two sites where A. longifolia is a serious problem the Manawatu-Whanganui region of the North Island. The site of the first release was in Whanganui.
Establishment:
Landcare Research (2023g) - establishment of T. acaciaelongifoliae is not yet confirmed [as of August 2023].
Impacts on non-targets:
Hill (2022) - in its native Australia, T. acaciaelongifoliae has been reared from Acacia longifolia subspecies longifolia, A. longifolia subspecies sophorae, and A. floribunda (a sister species to A. longifolia). There is also one unconfirmed record from A. implexa. Trichilogaster acaciaelongifoliae has been released as a biocontrol of A. longifoliae in South Africa (1981-82) and Portugal (2014). Pre-release host range testing in South Africa assessed nine species of Acacia native to Africa (now re-assigned to the genera Senegalia and Vachellia) and 13 Australian Acacia species, with galls only being formed on A. longifolia. In Portugal, 40 species, 30 outside the family to which Acacia belongs (Fabaceae), were tested; no galls were observed on any plants outside the genus Acacia. In the field in South Africa, small, sparsely distributed galls have been observed on A. melanoxylon (Tasmanian blackwood, a timber tree in New Zealand) and Paraserianthes lophantha (brush wattle, a weed in New Zealand) growing in the vicinity of heavily galled A. longifolia. Paraserianthes is considered a sister genus to Acacia. The damage has been insignificant to the non-target plants because galling has been so weak and rare. No other non-target attack has been observed in the field despite 40 years of observations. It is concluded that T. acaciaelongifoliae is highly host-specific and can consistently attack only A. longifolia and A. floribunda, which are in the mimosoid clade of Fabaceae. All New Zealand native legumes, and economically important crop, forage and vegetable legumes, belong to the papilionoid clade of Fabaceae, only distantly related to wattles.
EPA Applications:
EPA (2022b) – 11 August 2022: application by Horizons Regional Council to import for release and to release from containment the bud-galling wasp, Trichilogaster acaciaelongifoliae as a biological control agent for the Sydney golden wattle, Acacia longifolia. EPA Application # APP203934, approved without controls 30 November 2022.
References
EPA (2022b). Application to EPA (APP203934) to import and release the bud-galling wasp, Trichilogaster acaciaelongifoliae, as a biological control agent for Sydney golden wattle, Acacia longifolia. Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/APP203934
Hill RL (2022). Application to EPA (APP203934) to import for release, or release from containment, a new organism, Trichilogaster acaciaelongifoliae. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/APP203934/APP203934-Application-.pdf
Landcare Research (2023a). A wasp for a weedy wattle. Weed Biocontrol: What's New? 103, February 2023 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/a-wasp-for-a-weedy-wattle/
Landcare Research (2023g). Who's who in the biological control of weeds. Weed Biocontrol: What's New? 105, August 2023 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/whos-who/
