Biocontrol introduction
Target pest: Hawkweeds (Pilosella, Hieracium spp.) (Asterales: Asteraceae)
Agent introduced: Oxyptilus pilosellae (Lepidoptera: Pterophoridae), hieracium plume moth
Imported:
1996, 1997, 2001
Import source:
1996 Switzerland, 1997 2001 Germany
Released:
1999
Release details:
Syrett et al. (2001) - the first field release, of 32 adult O. pilosellae, was made on 26 March 1999 at Glenrock Station in the Mackenzie Basin (Canterbury, South Island).
Smith (2007) - due to rearing difficulties O. pilosellae was only released at one site.
Establishment:
Syrett et al. (2001) - no larvae, or new-generation adult O. pilosellae, have yet been recovered from the field.
Smith (2007) - not thought to have established.
Landcare Research (2015i) - did not establish.
Landcare Research (2020e) - surveys in 2020 at release sites of hieracium 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: O. pilosellae was only released in Canterbury] - did not recover any O. pilosellae and it is presumed to have failed to establish, which is not surprising given the small numbers released.
Impacts on non-targets:
Syrett et al. (2001) - host range tests 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 O. pilosellae. Normal O. pilosellae larval feeding was observed only on plants within the genera Pilosella and Hieracium, and Pilosella officinarum (mouse-ear hawkweed) was preferred over other species in these genera. In no-choice feeding tests a small number of late-instar larvae were able to complete development on the New Zealand native plants Sonchus kirkii and Embergeria grandifolia (tribe Cichorieae), but in single-choice feeding tests these plants were less preferred than P. officinarum. Although O. pilosellae has only been found on P. officinarum in its native home range in Europe, host tests indicated that it might attack two of the other weedy hawkweeds, Pilosella caespitosa (field hawkweed) and Hieracium lepidulum (tussock hawkweed), established in New Zealand.
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 O. pilosellae 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].
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
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 (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 (2007). Hieracium Plume Moth. In The Biological Control of Weeds Book (Landcare Research) http://www.landcareresearch.co.nz/research/biocons/weeds/book/documents/Hieracium_Plume_Moth.pdf
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
