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Biocontrol introduction

Target pest: Onopordum acanthium (Asterales: Asteraceae), cotton thistle

Agent introduced: Trichosirocalus spp. (Coleoptera: Curculionidae) = T. mortadelo and T. briesei, nodding thistle crown weevil


See T. horridus entry.

Import source:

See T. horridus entry.

Import notes:

Groenteman (2007) - it is possible that these species were introduced as T. horridus but it is unclear if this was the case. Their presence in New Zealand should be regarded as unproven.

De Baise et al. (2016) - T. mortadelo is a synonymy of T. horridus, which is the species established in New Zealand (see 'General Comments' below).


See T. horridus entry.

Release details:

See T. horridus entry.


See T. horridus entry.

Impacts on target:

Groenteman (2008b) - plant growth may be suppressed.

Impacts on non-targets:

See T. horridus entry.

General comments:

Alonso-Zarazaga and Sánchez-Ruiz (2002) - what was considered T. horridus is, based on morphological characters, a species complex of three species: T. horridus, T. mortadelo sp. n. and T. briesei sp. n. This may explain the different food preferences observed between the different populations or strains of the supposed single species T. horridus. It is not clear which species were introduced as biocontrol agents to North America, Australia and New Zealand.

De Baise et al. (2016) - molecular and morphological analyses of specimens from three continents, and host plant associations, clearly indicate that there are only two distinct species, T. horridus and T. briesei, and support the synonymy of T. horridus and T. mortadelo. T. horridus has been established in Canada, USA, New Zealand and Australia and T. briesei in Australia. The former species was collected from Carduus, Cirsium and Onopordum spp. in the field, whereas the latter appears to be specific to Onopordum.


Alonso-Zarazaga MA and Sánchez-Ruiz M. (2002). Revision of the Trichosirocalus horridus (Panzer) species complex, with description of two new species infesting thistles (Coleoptera: Curculionidae, Ceutorhynchinae) Australian Journal of Entomology 41, 199-208

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.

De Biase A, Colonnelli E, Belvedere S, La Marca A, Cristofaro M and Smith L. (2016). Genetic and morphological studies of Trichosirocalus species introduced to North America, Australia and New Zealand for the biological control of thistles. Bulletin of Entomological Research 106: 99-113

Groenteman R (2007). Multi-Species Interactions in Weed Biocontrol: Carduus nutans as a case study. PhD Thesis. Unversity of Canterbury, New Zealand

Groenteman R. (2008b). Nodding Thistle Crown Weevil, Trichosirocalus horridus. The Biological Control of Weeds Book (Landcare Research) https://www.landcareresearch.co.nz/discover-our-research/biosecurity/weed-management/using-biocontrol/the-biological-control-of-weeds-book/