Biocontrol introduction
Target pest: Arundo donax (Poales: Poaceae), Giant reed
Agent introduced: Tetramesa romana (Hymenoptera: Eurytomidae), Arundo gall wasp
Imported:
2016
Import source:
France and Spain, via USA
Import notes:
Landcare Research (2017c) - the opportunity to utilise T. romana 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) - Tetramesa romana, sourced from France and Spain, has been established in the USA and Mexico to control A. donax since 2009. A shipment of T. romana 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 T. romana in New Zealand.
Released:
2017
Release details:
Landcare Research (2017c) - permission to remove T. romana from containment has recently been granted and mass-rearing is underway in Auckland with the aim of making the first field releases in spring 2017.
Landcare Research (2018a) - the first release of the giant reed gall wasp was made in Kohukohu, in Northland (upper North Island), in early-December 2017. A further release was made in Northland just before Christmas, and two releases made in the Manawatu−Wanganui region (lower North Island) in January 2018. Two releases are planned for the Auckland region this summer (2017-18).
Landcare Research (2018h, 2019j, 2021e, 2022h) - five releases made in the year Sep 2017 - Aug 2018, two in the year Sep 2018 - Aug 2019, one in the year Sep 2020 - Aug 2021, two in the year Sep 2021 - Aug 2022.
Establishment:
Landcare Research (2022g) - it is not known if T. romana is successfully establishing in New Zealand.
Landcare Research (2023g) - establishment has been confirmed at one release site near Auckland.
Landcare Research (2025g) - establishment not yet confirmed.
Landcare Research (2025i) - signs of establishment have not been promising. A year after releases were made an A. donax stem with couple of T. romana exit holes was found at one site, but last year there was no sign of the wasp at two Auckland release sites. A study in North America (where T. romana has also been released as a biocontrol agent) that found warmer climates favoured higher gall wasp damage suggests the climate in Auckland may be too cool for T. romana to thrive and inflict significant damage on A. donax infestations. Even if it does establish, very low attack rates in New Zealand might be expected. In addition, molecular studies have identified several A. donax genotypes; the invasive genotype in the USA and Mexico originates from the Mediterranean region, from where T. romana was sourced (for North America, and New Zealand via North America). In laboratory tests, T. romana from the Mediterranean produced more offspring on the Mediterranean A. donax genotype compared with other wasp genotypes, indicating that genetic matching may be crucial to success. Arundo donax genotypes in New Zealand and Fiji have recently been matched to plants native to the Himalayas and China. A combination of a suboptimal climate and a suboptimal host genotype in New Zealand may have been too big a hurdle for T. romana to overcome to establish.
Impacts on target:
Landcare Research (2025i) - a suboptimal climate and suboptimal host genotype in New Zealand [see Landcare Research (2025i) entry in ‘Establishment’ section above] means that even if T. romana does establish in New Zealand it may not thrive and inflict significant damage on A. donax infestations.
Impacts on non-targets:
Landcare Research (2016k, 2017c) - T. romana is highly host specific and expected to attack only giant reed in New Zealand. Because of the significant amount of work done before these agents were released in the USA no further testing for the gall wasp was needed for New Zealand.
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 (2018a). First release of new agents. Weed Biocontrol: What's New? 83, February 2018 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-83/first-release-of-new-agents
Landcare Research (2018h). Biocontrol agents released in 2017/18. Weed Biocontrol: What's New? 85, August 2018 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-85/biocontrol-agents-released-in-201718
Landcare Research (2019j). Biocontrol agents released in 2018/19. Weed Biocontrol: What's New? 89, August 2019 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/weed-biocontrol-issue-89/biocontrol-agents-released-in-201819
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 (2022g). Spring activities. Weed Biocontrol: What's New? 101, August 2022 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/spring-activities-3/
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 (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
