Biocontrol introduction
Target pest: Hawkweeds (Pilosella, Hieracium spp.) (Asterales: Asteraceae)
Agent introduced: Cheilosia urbana (Diptera: Syrphidae), hieracium crown hover fly
Imported:
Late-1990's, early-to-mid-2000s
Import source:
Switzerland
Import notes:
Landcare Research (2005d) - releases of C. urbana were made early this year from a new shipment received from Switzerland, from which flies emerged from pupae only in dribs and drabs.
Landcare Research (2006d) - further shipments of both Cheilosia urbana and C. psilophthalma have been received this year by Landcare Research from Commonwealth Agricultural Bureaux International (CABI), Switzerland, but very few adults emerged. Neither CABI nor Landcare Research have been able to establish a breeding population and CABI is only able to send larvae from mated females collected in the field.
Smith (2007a) - several shipments were imported into New Zealand from Switzerland by Landcare Research, in conjunction with the Hieracium Control Trust, in the late 1990s for host range testing. Following permission in 2001 to release the hover flies a further shipment was imported to begin a rearing colony.
Landcare Research (2007a) - specimens of C. urbana from Switzerland, dated 1999, are present in the Biological Control Voucher Collection of the New Zealand Arthropod Collection [indicating an importation from that source in that year].
Released:
2002
Release details:
Landcare Research (2002b) - first release of C. urbana, at one site in Canterbury, South Island.
Landcare Research (2005d) - five new releases of C. urbana were made early this year, from a shipment received from Switzerland. Unfortunately, the flies emerged in dribs and drabs after a prolonged pupation period so only small numbers were available for each release. There have been nine releases of this agent since 2002.
Smith (2007a) - limited number of releases made as difficult to rear (three in 2006-07).
Establishment:
Landcare Research (2005d) - despite nine releases of C. urbana since 2002, there is still no sign of establishment.
Smith (2007a) - establishment is not confirmed.
Landcare Research (2015i) - establishment success unknown.
Landcare Research (2020e) - surveys in 2020 at release sites of hawkweed biocontrol agents - Canterbury and Otago in the South Island (Marlborough release sites were not visited) and on the Central Plateau of the North Island [NB: C. urbana was not necessarily released at all these sites] - did not recover any C. urbana and it is presumed to have failed to establish, which is not surprising given the small numbers released.
Impacts on non-targets:
Hieracium Control Trust (2000) - host range tests [see Syrett et al. (2001) entry below for further details] were completed on 66 test plant species comprising 9 species from the genera Pilosella and Hieracium, 29 species in the family Asteraceae, including the closest relatives to Pilosella and Hieracium among native New Zealand plants, and 28 species from an additional 25 families of plants. Oviposition and larval development tests were carried out in Switzerland, or under insect containment conditions in New Zealand for those plants that could not be grown in Switzerland. No eggs were laid on plants other than Pilosella and Hieracium species, and no larvae survived on any plants other than species in these genera. There are no native plants in the genera Pilosella and Hieracium; they are represented in New Zealand by weedy species introduced from Europe. The host range tests indicate the likelihood that any non-target species will be negatively affected is very low.
Syrett et al. (2001) - host range tests [see Hieracium Control Trust (2000) entry above for further details] were carried out in Switzerland and in containment in New Zealand. Potential hosts tested included all Pilosella and Hieracium species (family Asteraceae, tribe Cichorieae) naturalised in New Zealand (except H. pollichiae), species chosen from other Cichorieae genera (including New Zealand natives), economically important members of other tribes in the family Asteraceae, more distantly related species (important cultivated and native New Zealand plants) from other families, and host plants of close relatives of C. urbana. In no-choice larval development tests, C. urbana was found on all Pilosella and Hieracium species except H. murorum, but plants outside these genera were not attacked. In single-choice oviposition tests eggs were laid on all Pilosella and Hieracium species, but not on any of the other test plants. Very few larvae established in an open field test, and most were on P. aurantiaca (orange hawkweed), P. praealta (king devil hawkweed) and P. officinarum (mouse-ear hawkweed), all weedy in New Zealand.
Smith (2007a) - it is extremely unlikely that C. urbana will attack plants other than mouse-ear hawkweed (Pilosella officinarum), king devil hawkweed (P. praealta), field hawkeed (P. caespitosa), tussock hawkweed (Hieracium lepidulum), and orange hawkweed (P. aurantiaca) [i.e. the four main target weeds plus P. aurantiaca, another introduced weed - see Target species note (17 February 2024) entry in 'General comments' section].
General comments:
Target species note (17 February 2024) - in the 1990s and 2000s, six biocontrol agents were introduced to New Zealand to control hawkweeds, specifically four weedy species that at the time were considered to be in the genus Hieracium (with three of those in the subgenus Pilosella). Subsequently, Pilosella has been recognised as a distinct genus [see Taxonomic note (17 February 2024) entry below]; the four weed species are now classified as Pilosella officinarum (syn Hieracium pilosella) (mouse-ear hawkweed), P. caespitosa (syn H. caespitosum) (field hawkweed), P. praealta (syn H. praealtum) (king devil hawkweed) and H. lepidulum (tussock hawkweed). Of the biocontrol agents, the rust Puccinia hieracia var. piloselloidarum and the gall wasp Aulacidea subterminalis attack only P. officinarum, the plume moth Oxyptilus pilosellae attacks both P. officinarum and P. caespitosa, the gall fly Macrolabis pilosellae attacks all three Pilosella species, and the hover flies Cheilosia urbana and C. psilophthalma attack all four hawkweed species. (All preceding information from Hieracium Control Trust (2000).) Additionally, Syrett et al. (2001) identify a fifth adventive hawkweed, Pilosella aurantiaca (syn Hieracium aurantiacum) (orange hawkweed), as a problem weed in New Zealand, stating it has only recently been regarded as weedy in this country, although it has been here since 1911. Host range trials indicate it will be attacked at significant levels by A. subterminalis and the two Cheilosia species (Syrett et al. 2001).
Taxonomic note (17 February 2024) - at the time that C. urbana was introduced to New Zealand, the target weeds (hawkweeds) were all considered to be in the genus Hieracium. Bräutigam & Greuter (2007) note that Pilosella was considered by many authors to be a subgenus of Hieracium but that in recent decades generic recognition of Pilosella had gained increased support. Bräutigam & Greuter (2007) recognise Pilosella as a distinct genus from Hieracium and reclassify the Euro-Mediterranean flora accordingly. Under this classification there are introduced hawkweeds present in New Zealand in both genera (Hieracium and Pilosella) [see Target species note (17 February 2024) entry above].
EPA Applications:
EPA (2001) - 17 Nov 2000: application by the Hieracium Control Trust to import for release the insects Macrolabis pilosellae (Binnie 1878), Cheilosia urbana (Meigen 1822) and Cheilosia psilophthalma (Becker 1894) for the purpose of biological control of hawkweeds, Hieracium spp. EPA Application #NOR00001, approved without controls 27 Jun 2001.
References
Bräutigam S, Greuter W (2007). A new treatment of Pilosella for the Euro-Mediterranean flora. Willdenowia 37: 123-137 https://doi.org/10.3372/wi.37.37106
EPA (2001). EPA application NOR00001: to import for release the insects Macrolabis pilosellae (Binnie 1878), Cheilosia urbana Meigen and Cheilosia psilophthalma (Becker 1894) for the purpose of biological control of hawkweeds, Hieracium spp. Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/NOR00001
Hieracium Control Trust (2000). Application to EPA (NOR00001) to import for release the insects Macrolabis pilosellae (Binnie 1878), Cheilosia urbana Meigen and Cheilosia psilophthalma (Becker 1894) for the purpose of biological control of hawkweeds, Hieracium spp. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/NOR00001/6b046d0b38/Application-NOR00001.pdf
Landcare Research (2002b). News flashes: Two more join the fray. Patua Te Otaota - Weed Clippings. Biological Control of Weeds Annual Review 2001/2002. August 2002, 8: 11 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/weedcp02.pdf
Landcare Research (2005d). Hieracium agents settle in for the long haul. What’s New In Biological Control of Weeds? Annual Review. August 2005, 33: 9 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew33.pdf
Landcare Research (2006d). Hieracium heroes and heartbreakers. What’s New In Biological Control of Weeds? August 2006, 38: 8 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew38.pdf
Landcare Research (2007a). New Zealand Arthropod Collection (NZAC) Biological Control Voucher Collection. Landcare Research website [Updated 2020] https://www.landcareresearch.co.nz/tools-and-resources/collections/new-zealand-arthropod-collection-nzac/databases-and-holdings/new-t2-landing-page/
Landcare Research (2015i). Who's who in biological control of weeds? Weed Biocontrol: What's New? 73: 10-11 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-73
Landcare Research (2020e). Hieracium biocontrol – 20 years on. Weed Biocontrol: What's New? 93, Aug 2020 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/hieracium-biocontrol-20-years-on/
Smith L (2007a). Hieracium hover flies: Cheilosia urbana and Cheilosia psilophthalma. 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/hieracium-hover/
Syrett P, Smith L, Grosskopf G, Meurk C (2001). Predicting the likely success of biological control of hawkweeds in New Zealand. Plant Protection Quarterly 16(4): 172-176 https://caws.org.nz/PPQ1617/PPQ%2016-4%20pp172-176%20Syrett.pdf
