Horizons Regional Council in the Manawatū-Whanganui region has applied for approval to import and release the bud-galling wasp (Trichilogaster acaciaelongifoliae) as a biological control agent for Sydney golden wattle (Acacia longifolia).
The application has been made on behalf of the National Biocontrol Collective, a group of regional and district councils and the Department of Conservation (DOC).
Native to Australia, this wattle is a fast-growing shrub or small tree that was introduced in New Zealand as an ornamental and became naturalised before 1897. It has since become widespread throughout coastal areas of the North Island, and is considered a threat to biodiversity and to the conservation of dune and other ecosystems. The dense thickets it can form also increase the frequency and intensity of fires.
The proposed biological control agent is a small Australian wasp that lays its eggs in flower buds, inducing abnormal growths (galls) that prevent flowers forming and seed production. Galls can also form in growing points, preventing shoot growth.
Bud-galling wasps do not bite or sting, and there are no native New Zealand insects that are closely related. There are no native insect species known to form galls in Sydney golden wattle.
Horizons Regional Council notes that this host-specific wasp has been introduced in South Africa and Portugal, “achieving a high degree of control of Sydney golden wattle within a few years of establishment”.
EPA New Zealand, 24-08-22