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Biocontrol introduction

Target pest: Cytisus scoparius (Fabales: Fabaceae), Scotch broom, broom

Agent introduced: Gonioctena olivacea (Coleoptera: Chrysomelidae), broom leaf beetle


1981, 1995 (and repeatedly after 1995 prior to 2006), 2006? [see Hill (2006) entry in 'Import notes' section]

Import source:


Import notes:

Cameron et al. (1989) - Gonioctena olivacea was introduced into quarantine in December 1981 from Britain for host specificity testing.

Hill (2006b) - Gonioctena olivacea has been imported repeatedly for evaluation since 1995 into the containment facility at Landcare Research, Lincoln, under the following MPI import permits: G95/INV/11, 1997000250, 1998003226, 20030018389, 2005026871. If the 2006 application to EPA to release G. olivacea is approved [as it was - see 'EPA applications' section] it is proposed that approximately 200 G. olivacea larvae will be collected in England and shipped to New Zealand in July 2006 to complete development in containment. Progeny of paired adults will be line-reared prior to release.

Gourlay (2010b) - Gonioctena olivacea is native to Europe and was first imported for host range testing in 1995. An application to release the beetle was declined in 1997 due to insufficient information about the potential beneficial and harmful impacts. A subsequent cost-benefit analysis led to a successful re-application in 2006.



Release details:

Hill (2006) - it is proposed that the initial releases will be approximately 20 adults onto each of five sleeved broom bushes at at least one site in Canterbury.

Gourlay (2010b) - the first release was made towards the end of 2006. Widespread releases have now been made and are continuing.

Landcare Research (2014c) - recently released widely (including 6 sites 2013/14).


Gourlay (2009) - now established at two sites in Canterbury.

Gourlay (2010b) - the establishment success of the beetle is still uncertain.

Landcare Research (2014c) - establishment appears likely at a few sites so far.

Landcare Research (2016i) - established at a few sites but not yet abundant anywhere.

Landcare Research (2017g) - establishment confirmed at sites in both North and South Island, and numbers appear to be building.

Landcare Research (2019h) - it is thought this beetle has established quite widely but is not abundant; more information is required.

Impacts on target:

Paynter et al. (2018) - G. olivacea is generally rare and impacts are minor.

Paynter (2024) - factors influencing the success of weed biocontrol agents released and established in New Zealand were investigated. Each agent’s impact on the target weed in New Zealand was assessed as ‘heavy’, ‘medium’, ‘variable’, ‘slight’ or ‘none’, where a ‘heavy’, ‘medium’ or ‘variable’ impact have all been observed to reduce populations or percentage cover of their target weed in all or part of their respective target weed ranges in New Zealand. Results showed that: (i) agents that are highly damaging in their native range were almost invariably highly damaging in New Zealand; (ii) invertebrate agents with a closely related ‘native analogue’ species are susceptible to parasitism by the parasitoids that attack their native analogues and failed to have an impact on the target weed, and (iii) agent feeding guild helped predict agent impact - in particular, agents that only attack reproductive parts of the plant (e.g., seed and flower-feeders) are unlikely to reduce weed populations. Damaging impacts of G. olivacea, a defoliating beetle, have not been reported in its native range, it does not have a New Zealand native ecological analogue and its impact in New Zealand is assessed as ‘slight’.

Impacts on non-targets:

Cameron et al. (1989) - following importation into quarantine in 1981, G. olivacea was successfully reared on several species other than broom (Cytisus proliferus [tree lucerne] and species of lupin) and adults fed on a wider range of leguminous plants.

Hill (2006b) - host range testing against 106 plant species of 37 families was conducted in Europe and in containment in New Zealand from 1982 to 2002. The results indicate that no native plants, or economically valuable plants outside the tribe Genisteae, would be at risk from this agent in New Zealand. Twenty-one species from this tribe were exposed to the beetle. Larvae could complete development on some species of the genera Cytisus, Genista and Lupinus but not others. When exposed in the field Genista tinctoria [dyer’s broom], Lupinus arboreus, [tree lupin], L. polyphyllus [garden lupin] and Cytisus proliferus [tree lucerne] plants were colonised by the beetle, but the number of eggs deposited and the survival of larvae were lower than on broom controls. Field host records from UK suggest the laboratory tests may overestimate the true field host range of G. olivacea. However, taking a conservative view, the evidence presented cannot rule out the possibility that if released in New Zealand, G. olivacea might occasionally be found on ornamental European brooms, tree lupin, and possibly other lupin species. Tests suggest that these species are far less acceptable hosts than broom, but the level of attack, especially in the absence of broom, cannot be predicted with certainty.

Gourlay (2010b) - while broom is the preferred host it is likely that the broom leaf beetle will attack tree lucerne (Cytisus proliferus) to some extent, and it occasionally may attack ornamental brooms (Cytisus spp.), tree lupin (Lupinus arboreus) and possibly other lupins (Lupinus spp.). A cost-benefit analysis came out strongly in favour of releasing G. olivacea despite some possible non-target attack, because of the serious threat broom poses to New Zealand.

General comments:

Cameron et al. (1989) - following importation into quarantine in 1981, G. olivacea was successfully reared on several species other than broom and adults fed on a wider range of leguminous plants. Thus, this beetle was considered unsuitable for release.

Gourlay (2010) - the broom leaf beetle was imported for testing in 1995. An application to release the beetle was declined in 1997 due to insufficient information about the possible positive and negative consequences.

EPA Applications:

EPA (2006) - 13 Mar 2006: application by the Canterbury Broom Group to release from containment Aceria genistae, Agonopterix assimilella and Gonioctena olivacea for biological control of the weed broom. EPA Application # NOR05003, approved for A. assimilella and G. olivacea with controls 25 July 2006.


Cameron PJ, Hill RL, Bain J, Thomas WP (1989). A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1874-1987. Technical Communication No 10. CAB International Institute of Biological Control. DSIR Entomology Division. 424p.

EPA (2006). EPA application NOR05003: to conditionally release from containment a mite, Aceria genistae (Eriophyidae), and two insects, Agonopterix assimilella (Lepidoptera, Oecophoridae) and Gonioctena olivacea (Coleoptera, Chrysomelidae), for biological control of the weed broom. Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/NOR05003

Gourlay H. (2009). The biological control of broom (Cytisus scoparius). IUFRO International Forest Biosecurity Conference, 16-20 March 2009, Rotorua, New Zealand. Popular Summaries. Compiled by Richardson M, Hodgson C and Forbes A. New Zealand Forest Research Institute Limited. 230-232

Gourlay H. (2010b). Broom leaf beetle, Gonioctena olivacea The Biological Control of Weeds Book - Te Whakapau Taru: A New Zealand Guide (Landcare Research) [Updated 2021] https://www.landcareresearch.co.nz/discover-our-research/biodiversity-biosecurity/weed-biocontrol/projects-agents/biocontrol-agents/broom-leaf-beetle/

Hill R (2006b). Application to import for release or release from containment new organisms (Aceria genistae, Agonopterix assimilella and Gonioctena olivacea). EPA Application Number NOR05003 https://www.epa.govt.nz/assets/FileAPI/hsno-ar/NOR05003/c38af9007b/NOR05003.pdf

Landcare Research (2014c). Who's who in biocontrol of weeds? What's new in biological control of weeds? 69: 10-11 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/WhatsNew69.pdf

Landcare Research (2016i). Who's who in biological control of weeds? Weed Biocontrol: What's New? 77: 10-11 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-77

Landcare Research (2017g). Who's who in biological control of weeds? Weed Biocontrol: What's New? 81: 10-11 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-81

Landcare Research (2019h). Spring activities. Weed Biocontrol: What's New? 89, August 2019 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/weed-biocontrol-issue-89/spring-activities

Paynter Q (2024). Prioritizing candidate agents for the biological control of weeds. Biological Control, Volume 188, January 2024, Article Number 105396 https://doi.org/10.1016/j.biocontrol.2023.105396

Paynter Q, Fowler SV, Groenteman R. (2018). Making weed biological control predictable, safer and more effective: perspectives from New Zealand. BioControl 63: 427–436 (first published online 8 Aug 2017) https://doi.org/10.1007/s10526-017-9837-5 https://link.springer.com/article/10.1007/s10526-017-9837-5