Biocontrol introduction
Target pest: Arundo donax (Poales: Poaceae), Giant reed
Agent introduced: Rhizaspidiotus donacis (Hemiptera: Diaspididae), Arundo scale
Imported:
2016
Import source:
France and Spain, via USA
Import notes:
Landcare Research (2017c) - the opportunity to utilise R. donacis in New Zealand arose opportunistically after it was imported into containment in Auckland as part of a Cook Islands project and it was subsequently found that giant reed in the Cook Islands had been confused with the similar-looking elephant grass.
Landcare Research (2025i) - Rhizaspidiotus donacis, sourced from France and Spain, has been established in the USA and Mexico to control A. donax since 2009. A shipment of R. donacis was obtained from the USA and reared [in containment in Auckland, New Zealand] in anticipation of approval to release them in the Cook Islands. However, it turned out that what had been assumed to be A. donax in the Cook Islands was a different invasive grass, and an application was made to release R. donacis in New Zealand.
Released: 2021
Release details:
Landcare Research (2018i) - first field release planned for spring 2018.
Landcare Research (2019i) - first field release now planned for spring 2019.
Landcare Research (2020g) - first field release now planned for spring 2020.
Landcare Research (2021e, 2021f) - first field releases made in early 2021; two releases made in the year Sep 2020 - Aug 2021.
Landcare Research (2022h, 2023f) - two releases made in the year Sep 2021 - Aug 2022, three in the year Sep 2022 - Aug 2023.
Establishment:
Landcare Research (2021f) - establishment success unknown (as of Aug 2021).
Landcare Research (2023g) - establishment likely at one site in Auckland.
Landcare Research (2025g) - establishment not yet confirmed.
Landcare Research (2025i) - signs of establishment have not been promising. A year after releases were made R. donax was recovered from one A. donax plant at one site, but last year there was no sign of the scale insect at two Auckland release sites. The heavy clay soil - waterlogged after heavy rain and at times rock hard in summer - at both sites may be unsuitable for the scale insect, which mainly infests the rhizomes. In addition, the climate in New Zealand and the genotype of A. donax in New Zealand may be suboptimal for the genotype of R. donacis released in New Zealand. Studies have suggested this is the case for the other biocontrol agent released in New Zealand against A. donax, the gall wasp Tetramesa romana [see the T. romana introduction entry], with the wasp performing better in warmer climates, and against an A. donax genotype from the same region as the wasp. Molecular studies have identified several A. donax genotypes; the invasive genotype in the USA and Mexico originates from the Mediterranean region, from where R. donacis was sourced (for North America, and New Zealand via North America), while genotypes in New Zealand and Fiji have been matched to plants native to the Himalayas and China.
Impacts on non-targets:
Landcare Research (2016k, 2017c) - R. donacis is highly host specific and is expected to attack only giant reed in New Zealand. Significant testing before this agent was released in the USA indicated it was specific to A. donax in the field, but might produce occasional offspring on a few closely-related species. Although New Zealand has no native species in the same sub-family (Arundinoideae) as A. donax, three native species (the endemic Isachne globosa and Zoysia minima, and the indigenous Spinifex sericeus) representing the sub-families most closely related to the Arundinoideae (Chloridoideae and Micrairoideae) were tested, and found to be unsuitable hosts.
EPA Applications:
EPA (2017a) - 12 Sep 2016: application by Northland Regional Council to introduce a gall forming wasp (Tetramesa romana) and a scale insect (Rhizaspidiotus donacis) to control giant reed (Arundo donax). EPA Application # APP202887, approved without controls 17 Jan 2017.
References
EPA (2017a). EPA application APP202887: to introduce a gall forming wasp (Tetramesa romana) and a scale insect (Rhizaspidiotus donacis) to control giant reed (Arundo donax). Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/APP202887
Landcare Research (2016k). The host ranges of Tetramesa romana and Rhizaspidiotus donacis, potential control agents for giant reed, Arundo donax. http://www.landcareresearch.co.nz/__data/assets/pdf_file/0017/112742/The-host-range-testing-for-giant-reed.pdf
Landcare Research (2017c). Tiny insects to attack giant reed Weed Biocontrol: What's New? 80: 4-5 http://www.landcareresearch.co.nz/__data/assets/pdf_file/0013/141133/Issue-80.pdf
Landcare Research (2018i). Who's who in biological control of weeds? Weed Biocontrol: What's New? 85, August 2018 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-85/whos-who-in-biological-control-of-weeds
Landcare Research (2019i). Who's who in biological control of weeds? Weed Biocontrol: What's New? 89, August 2019 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/weed-biocontrol-issue-89/whos-who-in-biological-control-of-weeds
Landcare Research (2020g). Who's who in biological control of weeds? Weed Biocontrol: What's New? 93, Aug 2020. https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/status-of-agents/
Landcare Research (2021e). Further reading and agents released. Weed Biocontrol: What's New? 97, August 2021 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/further-reading
Landcare Research (2021f). Who's who in biological control of weeds? Weed Biocontrol: What's New? 97, August 2021 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/whos-who-in-biological-control-of-weeds
Landcare Research (2022h). Further reading and agents released 2021/22. Weed Biocontrol: What's New? 101, August 2022 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/further-reading-and-agents-released-202122/
Landcare Research (2023f). Further reading and biocontrol agents released in 2022/23. Weed Biocontrol: What's New? 105, August 2023. https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/further-reading-and-agents-released
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 (2025g). Who's who in biological control of weeds? Weed Biocontrol: What's New? August 2025, 113: 10-11 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/Issue-113/weed-biocontrol-issue-113.pdf
Landcare Research (2025i). Biocontrol of giant reed encounters hurdles. Weed Biocontrol: What's New? November 2025, 114: 4-5 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/Issue-114/weed-biocontrol-issue-114.pdf
