Biocontrol introduction
Target pest: Tradescantia fluminensis (Commelinales: Commelinaceae), tradescantia, wandering willie, wandering jew
Agent introduced: Lema basicostata (Coleoptera: Chrysomelidae), tradescantia stem beetle
Imported:
2009
Import source:
Brazil
Import notes:
Fowler (2021b) - Lema basicostata is native to south-eastern Brazil and north-eastern Argentina. It was first imported into New Zealand from Brazil into containment for host range testing in 2009. Permission to release this beetle was granted by EPA towards the middle of 2011, but releases did not begin until 2012 because of the need to clear the beetle of a gut parasite.
Released:
2012
Release details:
Fowler et al. (2013) - in 2012, 1,262 L. basicostata were released at 6 sites.
Landcare Research (2013a) - total of 10 releases prior to Aug 2013.
Landcare Research (2014c) - releases are continuing.
Landcare Research (2015j) - 5 releases 2014-15.
Landcare Research (2016c) - Northland and Taranaki Regional Councils are harvesting beetles from initial release sites to spread around their regions. Wellington Botanic Gardens are breeding the beetles to release in Wellington's parks and reserves, with the first release made at Mt Victoria.
Landcare Research (2018h, 2020h) - five releases made in the year Sep 2017 - Aug 2018, four in the year Sep 2019 - Aug 2020.
Establishment:
Landcare Research (2014c) - already well established and numbers appear to be building rapidly.
Impacts on target:
Landcare Research (2015a) - caused significant damage in 3 years to tradescantia at Welcome Bay (near Tauranga), reducing coverage to bare ground in places.
Landcare Research (2016c) - the three beetle species introduced for this weed - Neolema abbreviata, N. ogloblini and Lema basicostata are establishing well and starting to knock back the plant at release sites. Site at Waikakaho (Marlborough) showed L. basicostata alone can have a rapid impact; after only 3 years, 10 square metres of weed had collapsed and disappeared at release site, with heavy damage out for another 20m. A trial has been established in forest remnants at Hikurangi flood plain (Northland) to assess tradescantia control and habitat recovery [see Clarkson et al. (2023) entry below].
Landcare Research (2018f) - the impact of the stem beetle has been monitored at sites in Northland, Auckland and the Bay of Plenty; the damage is encouraging but somewhat patchy. In wetter sites the percentage cover is still quite high, perhaps because tradescantia stems severed by larval feeding are capable of re-establishing, but bare patches are appearing in drier areas.
Landcare Research (2021a) - all three beetle species released against T. fluminensis (L. basicostata, Neolema abbreviata, Neolema ogloblini) have proven effective in controlling tradescantia in multiple regions, most notably Northland and the Waikato.
Fowler (2021b) - early indications suggest that L. basicostata can clear dense patches of tradescantia, particularly in drier sites. This agent should complement attack by the other tradescantia beetles released against T. fluminensis - the leaf beetle, Neolema ogloblini, and the tip beetle, N. abbreviata.
Clarkson et al. (2023) - a restoration field experiment in native forest remnants on the Hikurangi (Northland) floodplain, from 2016 to 2019, compared the effectiveness of biocontrol to manual clearing of T. fluminensis in reducing the weed's abundance and facilitating native plant regeneration. In the biocontrol treatment plots, the three beetle species that have been released against T. fluminensis - Neolema ogloblini, Lema basicostata, and Neolema abbreviata - were released together (the first such combined release of the three agents). After three years, plant species composition and T. fluminensis biomass were not statistically different between the biocontrol treatment and control (no treatment) plots, although mean T. fluminensis biomass was typically lower at biocontrol sites. The lack of significant biocontrol results is likely due to the short time span of the experiment, the large biomass of T. fluminensis present, low beetle population density, and cool, damp conditions (which do not favour these beetles) at most sites. Several more years would probably be required for beetle populations to increase and reduce T. fluminensis biomass sufficiently to facilitate survival of native seedlings.
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 L. basicostata, a stem-boring beetle, have 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 ‘variable’.
Landcare Research (2025h) - pre- and post-release monitoring of T. fluminensis biomass was carried out at selected release sites of the four biocontrol agents - the chrysomelid beetles Neolema ogloblini (leaf beetle), N. abbreviata (tip beetle) and Lema basicostata (stem beetle), and the smut fungus Kordyana brasiliensis. The initial intention was to compare the impacts of individual agents, but this was hard to assess because agent self-dispersal meant most sites where only one species was released had been colonised by one of the other agents. Tradescantia fluminensis dry weight biomass significantly declined at sites where agents successfully established, from an average of approximately 500 g/m2 to slightly above 100 g/m2 (similar to levels observed in the plant’s native range), which is well below the 200 g/m2 threshold other studies have showed is needed for native plant regeneration. In contrast, at the sites where agents had not established there was no significant reduction in biomass. Although the analysis combined biocontrol agents, three agents appear to be capable of reducing tradescantia biomass to below threshold levels (all but the tip beetle, which couldn’t be assessed because of a flood at the only monitoring site at which it established). Biomass declined below threshold at all sites with the leaf beetle only, and we have also observed both the stem beetle and the smut fungus clear tradescantia patches on their own. The beetles seem to prefer warmer, drier sites, and the fungus cooler, damper sites, so the agent impacts appear to complement one another. At some sites the results have been spectacular. A kahikatea [Dacrycarpus dacrydioides] forest remnant site in north Waikato has seen a near complete disappearance of T. fluminensis after the leaf beetle, stem beetle, and smut fungus all established between 2019 and 2021, allowing the recovery of native ferns and tree seedlings.
Impacts on non-targets:
Auckland Council (2011) - there are no New Zealand native plants in the same order as T. fluminensis, and apart from some ornamental house plants, no closely-related valued exotic plants. Host range testing carried out by Landcare Research included the native nikau palm (Rhopalostylis sapida) because it is the most closely related native plant; there was no semblance of attack on this species. Several host plants (all within the tribe Tradescantineae) supported complete development of L. basicostata. Tradescantia albiflora (naturalised in New Zealand) appears to be as good a host as T. fluminensis. The house plants Callisia repens, Gibasis spp. and Cyanotis somaliensis appear to be adequate hosts. The test results indicate that the physiological host range of L. basicostata lies within the Family Commelinacae, and possibly within the Tribe Tradescantineae. Given the extreme taxonomic distance between this tribe and any valued plant, the risk of significant adverse effects on such plants species in New Zealand (whether native or exotic) is considered to be negligible.
Fowler et al. (2013) - Tradescantia albiflora appears to be a fundamental host. This plant is naturalised in New Zealand and a potential future weed. Potential 'spill-over' attack on other plant species in the Commelinaceae may be beneficial as well as some are already naturalised in New Zealand and are invasive in other countries. New Zealand has no native or commercially significant exotic plants in this family.
Landcare Research (2025h) - pre- and post-release monitoring of T. fluminensis biomass has shown that L. basicotata, along with Neolema ogloblini and Kordyana brasiliensis, can reduce T. fluminensis biomass sufficiently to allow native plant regeneration [see Landcare Research (2025h) entry in ‘Impacts on target’ section above]. At a kahikatea [Dacrycarpus dacrydioides] forest remnant site in north Waikato, the near complete disappearance of T. fluminensis after these three agents all established between 2019 and 2021 has allowed the recovery of native ferns and tree seedlings, an impossible outcome had the tradescantia remained dominant.
EPA Applications:
EPA (2011b) - 11 Mar 2011: application by Auckland Council for the importation and release of two beetles, Lema basicostata and Neolema abbreviata, as biological control agents for the weed tradescantia. EPA Application # ERMA200638, approved without controls 29 Jun 2011.
References
Auckland Council (2011). EPA application [ERMA200683] to release a new organism [Lema basicostata and Neolema abbreviata] without controls. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/ERMA200683/8ee858ce25/ERMA200683-FINAL-Application-ERMA200683-2011-03-11.pdf
Clarkson BR, Cave VM, Bartlam S, Watts CH, Thornburrow D, Paynter Q (2023). Status of forest remnants invaded by tradescantia (Tradescantia fluminensis Vell.) following introduction of biocontrol beetles and manual clearance after three years. New Zealand Journal of Botany (published online 19 Nov 2023) https://doi.org/10.1080/0028825X.2023.2279297
EPA (2011b). EPA application ERMA200683: to import and release two beetles, Lema basicostata and Neolema abbreviata, as biological control agents for the weed tradescantia. Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/ERMA200683
Fowler S (2021b). Tradescantia stem beetle: Lema basicostata. The Biological Control of Weeds Book - Te Whakapau Taru: A New Zealand Guide (Landcare Research) https://www.landcareresearch.co.nz/discover-our-research/biodiversity-biosecurity/weed-biocontrol/projects-agents/biocontrol-agents/tradescantia-stem-beetle/
Fowler SV, Barreto R, Dodd S, Macedo DM, Paynter Q, Pedrosa-Macedo JH, Pereira OL, Peterson P, Smith L, Waipara N, Winks CJ and Forrester G (2013). Tradescantia fluminensis, an exotic weed affecting native forest regeneration in New Zealand: Ecological surveys, safety tests and releases of four biocontrol agents from Brazil. Biological Control 64: 323-329
Landcare Research (2013a). Biocontrol agents released in 2012/13. What's new in biological control of weeds? 65: 7 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-65
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 (2015a). Tradescantia beetles make big impression. What's new in biological control of weeds? 72: 2-3 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-72
Landcare Research (2015j). Biocontrol agents released in 2014/15. Weed Biocontrol: What's New? 73: 2 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-73
Landcare Research (2018f). Tradescantia be gone! Weed Biocontrol: What's New? 84, May 2018 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-84/tradescantia-be-gone
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 (2020h). Further reading and agents released table. Weed Biocontrol: What's New? 93, Aug 2020. https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/further-reading-and-agents-released-table/
Landcare Research (2021a). The more the merrier? Testing efficacy of multiple agents. Weed Biocontrol: What's New? 95, Feb 2021 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/the-more-the-merrier-testing-efficacy-of-multiple-agents
Landcare Research (2025h). More damage, less biomass: monitoring progress of tradescantia biocontrol. Weed Biocontrol: What's New? November 2025, 114: 2-3 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/Issue-114/weed-biocontrol-issue-114.pdf
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
