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Biocontrol introduction

Target pest: Chrysanthemoides monilifera monilifera (Asterales: Asteraceae), boneseed

Agent introduced: Tortrix s.l. sp. "chrysanthemoides" (Lepidoptera: Tortricidae), boneseed leaf roller



Import source:

South Africa

Import notes:

Winks (2008) - a shipment of T. s.l. sp. "chrysanthemoides" was imported from its native South Africa in 2006.



Release details:

Winks (2008) - the first releases were made in 2007 and T. s.l. sp. "chrysanthemoides" has now been released widely throughout New Zealand.

Landcare Research (2022e) - there were widespread releases of T. s.l. sp. "chrysanthemoides" between 2007 and 2008. Most were made in the North Island in Northland and Auckland, although they were also released in Manawatu-Whanganui, the Greater Wellington region, and the Bay of Plenty. In the South Island the leafroller was released in Canterbury as well as further north in the Tasman region.


Winks (2008) - establishment has only been confirmed at some sites in the North Island so far.

Paynter et al. (2012) - during late-summer and autumn 2011 a survey of 20 T. s.l. sp. "chrysanthemoides" release sites from Northland in the North Island to Christchurch in the South Island was conducted, and experiments carried out to investigate why the moth's establishment in New Zealand has been patchy. The survey showed it established at eight of 15 North Island sites and zero of five South Island sites; however, the climate tolerance and predator exclusion experiments indicate climate was not a factor and that establishment failure is associated with predation, mainly by invasive ants of South American (Linepithema humile - Argentine ant), and Australian (Doleromyrma darwiniana, Nylanderia sp.) origin that are attracted to invasive honeydew-secreting scale insects (Parasaissetia nigra and Saissetia oleae [black scale]) found on boneseed. Social wasps (Vesula and Polistes) appear to be more important predators than ants where T. s.l. sp. "chrysanthemoides" is established (largely in the absence of ants), with wasp abundance driven by the moth's abundance and not scale insects.

Landcare Research (2014c) - quite common at some North Island sites.

Paynter (2021a) - establishment has been patchy, with well-established colonies in Northland and the Bay of Plenty. It was recently found to have also established at Christchurch in Canterbury.

Landcare Research (2022e) - in November 2011, four years after the first releases of T. s.l. sp. "chrysanthemoides", it was well established at three release sites in the North Island (in Northland and the Bay of Plenty) but had apparently failed to establish at any of the South Island release sites. It was initially suggested that climate might be responsible for the failure of the South Island releases, but overwintering experiments suggested this was not the cause and a field study indicated that predation was limiting establishment [see Paynter et al. (2012) entry above in this section]. Establishment success was 70% at sites without scale insects, but zero at sites with high densities of scale (which attract honeydew-feeding predatory insects such as wasps and ants). However, in 2022, a population of the boneseed leafroller was discovered on the Port Hills of Christchurch (Canterbury), indicating it had established in the South Island after all.

Impacts on target:

Environment Canterbury (2004) - Tortrix s.l. sp. "chrysanthemoides" was released in Australia in April 2000. Although establishment has been confirmed, populations are still generally low, probably due to parasitism and predation. In particular, where large numbers of ants occur (attracted to scale insects on boneseed) the boneseed leafroller has not established. While the ant fauna of New Zealand is more benign than that of Australia and ants are not expected to be such a problem in this country, the future distribution and abundance of Argentine ants in New Zealand could be very significant for the prospects of the boneseed leafroller.

Winks (2008) - no outbreaks have yet been seen here, and it is too soon to know how effective T. s.l. sp. "chrysanthemoides" will be. Some generalist parasitoids have been found attacking the leafroller here which may restrict population build-up, and establishment is unlikely where Argentine ants are present.

Landcare Research (2014c) - no significant damage yet; appears to be limited by predation and parasitism.

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 T. s.l. sp. "chrysanthemoides", a defoliating moth, have been reported in its native range, it has a New Zealand native ecological analogue and its impact in New Zealand is assessed as ‘slight’. By far the most important predictor of agent impact is evidence the agent is damaging in its native range; if it is capable of damaging outbreaks in the native range, a major impact in the introduced range appears almost guaranteed. T. s.l. sp. "chrysanthemoides" is an exception to this, possibly because of ‘invasion meltdown’. Invasive scale insects that feed on the host plant in New Zealand produce honeydew that attracts invasive Argentine ants, which also prey on T. s.l. sp. “chyrsanthemoides” larvae to the extent that populations failed to establish at many release sites.

Impacts on non-targets:

Environment Canterbury (2004) - the boneseed leafroller was selected as a potential biocontrol agent for boneseed in New Zealand because it is regarded as being specific to the two species of the genus Chrysanthemoides. There are no New Zealand native plants, and few introduced species of economic importance, in the same tribe (Calenduleae) to which boneseed belongs. Prior to the release of boneseed leafroller in Australia, field searches undertaken by the Australian CSIRO Biological Control Unit in South Africa over a 2-year period on 126 plant species found that the leafroller did not attack any plant species other than Chrysanthemoides monilifera and C. incana. Extensive host-range testing was conducted on the boneseed leafroller for the Australian biological control of boneseed programme, with 96 plant species from 31 families tested, including 50 species from the family Asteraceae to which boneseed belongs. In laboratory tests, feeding occurred on a number of non-target test-plants, necessitating the use of extensive open-field testing in South Africa to determine if these species would be field hosts. The conclusion drawn from these field tests was that the boneseed leafroller is specific to the two species of the genus Chrysanthemoides. Non-target oviposition and very limited survival of larvae may occur on Calendula (marigolds) in the field but only in situations where these plants grow in very close proximity to C. monilifera. Further host range testing, on 10 test-plant species, carried out by Landcare Research in South Africa for the New Zealand biocontrol programme, supported the other evidence already available that the boneseed leafroller is expected to feed only on boneseed in New Zealand.

Paynter et al. (2015) - surveys of potential non-target hosts (based on Australian laboratory host range tests) Acacia mearnsii (black wattle), Daucus carota (wild carrot), Osteospermum fruticosum (trailing African daisy) and Trifolium repens (white clover) record no feeding on these plants.

General comments:

EPA (2005f) - the EPA Committee [assessing the application to import for release Tortrix s.l. sp. "chrysanthemoides"] noted that while the boneseed leafroller has not yet been formally described as a species it is considered a distinct taxon. The tribe to which it belongs is currently under taxonomic revision and its formal description at this time could see the name reduced to a synonym with the revision’s publication. The Committee was satisfied that lack of a formal binomial would not prevent correct identification.

EPA Applications:

EPA (2005e) - 19 August 2004: application by Environment Canterbury to import for release a South African moth, the boneseed leafroller (Tortrix s.l. sp. "chrysanthemoides"), for the purpose of biological control of boneseed (Chrysanthemoides monilifera subsp. monilifera). EPA Application #NOR03001, approved without controls 18 February 2005.


EPA (2005e). Application to EPA (NOR03001) to import for release the boneseed leafroller (Tortrix s.l. sp. "chrysanthemoides") for the purpose of biological control of boneseed (Chrysanthemoides monilifera subsp. monilifera). Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/NOR03001

EPA (2005f). Environmental Protection Authority decision, application #NOR03001. Environmental Protection Authority website https://view.officeapps.live.com/op/view.aspx?src=https%3A%2F%2Fwww.epa.govt.nz%2Fassets%2FFileAPI%2Fhsno-ar%2FNOR03001%2Fd138bdadc6%2FNOR03001.doc&wdOrigin=BROWSELINK

Environment Canterbury (2004). Application to EPA (NOR03001) to import for release, or release from containment, the boneseed leafroller, Tortrix s.l. sp. ”chrysanthemoides”. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/NOR03001/23d8f981a9/NOR03001.pdf

Environment Canterbury (2004). Application to EPA (NOR03001) to import for release, or release from containment, the boneseed leafroller, Tortrix s.l. sp. ”chrysanthemoides”. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/NOR03001/23d8f981a9/NOR03001.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 (2022e). It established after all! Weed Biocontrol: What's New? 101, August 2022 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/it-established-after-all/

Paynter Q (2021a). Boneseed leafroller: Tortrix s.l. sp.“chrysanthemoides”. The Biological Control of Weeds Book - Te Whakapau Taru: A New Zealand Guide (Landcare Research) [Update of Winks (2008)] https://www.landcareresearch.co.nz/discover-our-research/biodiversity-biosecurity/weed-biocontrol/projects-agents/biocontrol-agents/boneseed-leafroller/

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, Forgie SA, Winks CJ, Peterson PG, Ward DF, Nicholson L, Van Zoelen R (2012). Biotic resistance: Facilitation between invasive Homoptera and invasive ants limits the establishment of an introduced weed biocontrol agent in New Zealand. Biological Control 63: 188-194 http://dx.doi.org/10.1016/j.biocontrol.2012.07.010

Paynter QE, Fowler SV, Gourlay AH, Peterson PG, Smith LA and Winks CJ (2015). Relative performance on test and target plants in laboratory tests predicts the risk of non-target attack in the field for arthropod weed biocontrol agents. Biological Control 80: 133-142 https://doi.org/10.1016/j.biocontrol.2014.10.007

Winks C (2008). Boneseed leafroller: Tortrix s.l. sp.“chrysanthemoides”. The Biological Control of Weeds Book - Te Whakapau Taru: A New Zealand Guide (Landcare Research) [Updated 2021 - see Paynter (2021a)] https://www.landcareresearch.co.nz/discover-our-research/biodiversity-biosecurity/weed-biocontrol/projects-agents/biocontrol-agents/boneseed-leafroller/