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.
Landcare Research (2024a) - a second consignment of T. acaciaelongifoliae galls was collected in the Cape Town region [Western Cape province] of South Africa and hand-carried to New Zealand in November 2023. One hundred and eighty wasps emerged in containment and were released in the field.
Landcare Research (2025c) - in collaboration with the University of Cape Town, a further 2,000 galls infested with T. acaciaelongifoliae larvae were collected in South Africa and hand-delivered into containment in New Zealand in November 2024. Due to biosecurity concerns the galls containing the larvae couldn’t be directly released; rather, adult wasps emerging from the galls were collected for release. The sheer number of galls imported compared to previous years, and a better knowledge of the conditions required to keep the galls healthy, meant that plenty of wasps could be released in several different parts of the country [see Landcare Research (2025c) entry in ‘Release details’ section below].
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.
Landcare Research (2024a) - one hundred and eighty adult wasps, that had emerged from galls imported into containment in New Zealand in November, were released (within days of their emergence as they only live for a few days) in the Manawatu-Whanganui region.
Landcare Research (2025c) - Trichilogaster acaciaelongifoliae has been released at two sites in the Manawatu-Whanganui region in December 2022 and 2023 [see Landcare Research (2023a, 2024a) entries above in this section]. Further releases of adults reared from the galls imported in November 2024 [see Landcare Research (2025c) entry in ‘Import notes’ section above] took place in December 2024 in the Canterbury and Tasman regions of the South Island and Bay of Plenty in the North Island. Releases of 150-200 females were made at various release sites in each region (including Matakana Island in Bay of Plenty), with over 1,000 wasps released in total.
Landcare Research (2025f) - 10 releases made in the year Sep 2024 - Aug 2025.
Establishment:
Landcare Research (2023g) - establishment of T. acaciaelongifoliae is not yet confirmed [as at August 2023].
Landcare Research (2024a) - Trichilogaster acaciaelongifoliae has shown positive signs of establishment following its release last summer, with galls detected in August 2023 at release sites.
Landcare Research (2025c) - previous monitoring the release sites at Castlecliff beach in the Whanganui District and Waitarere beach in the Horowhenua District of Manawatu-Whanganui in November 2023 showed early signs that the wasp has successfully established. This season [the 2024-25 summer] these sites were monitored again, and higher numbers of galls were found, indicating T. acaciaelongifoliae has successfully established at both sites, with numbers expected to expand quickly. One sub-site of the first release site at Castlecliff beach looks particularly promising, with over a hundred galls located during a brief search.
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/
Landcare Research (2024a). A flying start for a bud-galling wasp. Weed Biocontrol: What's New? February 2024, 107: 5 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/a-flying-start-for-a-bud-galling-wasp/
Landcare Research (2025c). A newly established wasp unanimously welcomed. Weed Biocontrol: What's New? May 2025, 112: 4-5 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/Issue-112/weed-biocontrol-issue-112.pdf
Landcare Research (2025f). Biocontrol agents released in 2024/2025. Weed Biocontrol: What's New? August 2025, 113: 12 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/Issue-113/weed-biocontrol-issue-113.pdf
