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Biocontrol introduction

Target pest: Ulex europaeus (Fabales: Fabaceae), gorse

Agent introduced: Sericothrips staphylinus (Thysanoptera: Thripidae), gorse thrips


1989, 2001

Import source:

Hampshire, England (1989); Portugal via Hawai'i (2001)

Import notes:

Hill et al. (2001) - Sericothrips staphylinus imported to New Zealand originated from Yateley Common, Hampshire, England. Permission to release this species in New Zealand was granted in August 1990, after which laboratory cultures of were established on potted plants to provide release material.

Landcare Research (2001a) - following the slow dispersal of English-sourced S. staphylinus in New Zealand, and the observation that in Hawai'i S. staphylinus from Portugal were outperforming those from England, Portuguese-sourced S. staphylinus from Hawai'i were imported into quarantine in New Zealand in July 2001. Mass-rearing is underway for releases this summer [2001-02].

Gourlay (2007f) - the English strain imported in 1989 was thought to be slow to disperse because winged forms not produced as commonly as non-winged. Consequently, a Portuguese strain, thought to disperse more quickly, was imported in 2001.


1990 (English strain), 2001 (Portuguese strain)

Release details:

Hill et al. (2001) - Sericothrips staphylinus originating from England was released at 129 sites throughout New Zealand from October 1990 until June 1998.

Landcare Research (2002a, 2003b, 2004b, 2005b, 2006a) - the Portuguese strain of S. staphylinus was released in 2001-02 at nine sites, 2002-03 at three sites, 2003-04 at 25 sites, 2004-05 at 10 sites and 2005-06 at 10 sites.

Gourlay (2007f) - the English strain was widely released in the few years after its importation in 1989. The Portuguese strain was imported in 2001 and widely released in subsequent years.


Harman et al. (1996) - seems to be establishing readily throughout the country.

Hill et al. (2001) - Sericothrips staphylinus is known to have established at 59% of release sites to date, although the status at many sites is unknown and some releases are too recent to judge establishment. The thrips has established in all regions of New Zealand, although dispersal has been slow; at most sites, they have moved no more than 10-20 m per year. A high proportion of brachyptery [possessing rudimentary wings] in adults may be a barrier to short-distance dispersal.

Rees & Hill (2001) - Sericothrips staphylinus is now established widely in New Zealand.

Landcare Research (2006c) - recently, S. staphylinus has been found many kilometres away from known release sites.

Gourlay (2007f) - the English strain established at sites throughout New Zealand but has been slow to disperse. The Portuguese strain has also established. The thrips are becoming increasingly common throughout New Zealand.

Impacts on target:

Hill et al. (2000) - although S. staphylinus has established widely in New Zealand, it is too early to assess the long-term impact of this agent on gorse populations. The damage caused by an individual thrips appears insignificant, but in laboratory trials large populations can kill potted plants and significantly reduce the growth rate of seedlings.

Hill et al. (2001) - Sericothrips staphylinus has caused discernible foliar damage (bronzing) at some release sites, but not plant death, and it is not yet clear how much this species will contribute to the biocontrol of gorse.

Rees & Hill (2001) - Sericothrips staphylinus produces large populations in culture, and commonly kills potted plants. Pot trials have demonstrated impacts on seedling growth even at low density but the long-term impact on gorse plants in the field is not yet known. It has not yet caused noticeable mortality of mature gorse plants in the field.

Gourlay (2007f) - the impacts of S. staphylinus are not yet known. While it can now be commonly found on gorse, it is less common to see gorse bushes that appear to be severely affected by them. However, studies in the UK and Australia found that S. staphylinus could reduce the growth and survival of seedlings, even when present in low numbers, and this may be where they have the greatest impact.

Paynter et al. (2018) - while S. staphylinus is abundant, impacts on the target plant are unknown but appear to be minor.

Lam et al. (2021) - laboratory trials investigating the functional responses of a predatory mite found on gorse in New Zealand, Amblyseius herbicolus, to first instar S. staphylinus larvae, indicate that A. herbicolus is likely to be a highly effective predator of S. staphylinus. These results indicate that the presence of A. herbicolus on gorse in New Zealand is a likely explanation for the failure of S. staphylinus as a weed biocontrol agent.

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 S. staphylinus, a piercing/sucking insect, have not been reported in its native range, it has a New Zealand native ecological analogue and its impact in New Zealand is assessed as ‘slight’.

Impacts on non-targets:

Hill et al. (2001) - host range testing was carried out in England, New Zealand and Hawaii (where S. staphylinus was also released as a biocontrol agent). Eighty-three plant species, including many of environmental and economic significance, were tested, largely in the family Fabaceae and concentrating on species closely related to gorse within the tribe Genisteae. At least 17 New Zealand Fabaceae native species were tested. Results indicate that, with the possible exception of Cytisus proliferus [tagasaste/tree lucerne] (on which one individual completed development in the laboratory tests), S. staphylinus cannot reproduce on plants other than Ulex species. However, while C. proliferus could be regarded as a potential alternative host for S. staphylinus, monitoring of C. proliferus plants growing near S. staphylinus-infested gorse in New Zealand has revealed no evidence of colonisation.

Gourlay (2007f) - Sericothrips staphylinus will only damage gorse.

Paynter et al. (2015) - surveys of potential non-target host Cytisus proliferus (tree lucerne, tagasaste) report no feeding.


Gourlay H (2007f). Gorse Thrips: Sericothrips staphylinus. 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/gorse-thrips/

Harman HM, Syrett P, Hill RL, Jessep CT. (1996). Arthropod introductions for biological control of weeds in New Zealand, 1929 - 1995. New Zealand Entomologist, 19(1): 71-80

Hill RL, Gourlay AH, Fowler SV (2000). The biological control program against gorse in New Zealand. In Proceedings of the X international Symposium on Biological Control of Weeds 2000 Jul (Vol. 917, pp. 909-917). Montana State University Bozeman, Montana, USA. https://www.landcareresearch.co.nz/assets/researchpubs/biologial_control_gorse_Hill_2000.pdf

Hill RL, Markin GP, Gourlay AH, Fowler SV, Yoshioka E (2001). Host range, release, and establishment of Sericothrips staphylinus Haliday (Thysanoptera: Thripidae) as a biological control agent for gorse, Ulex europaeus L. (Fabaceae), in New Zealand and Hawaii. Biological Control 21: 63-74

Lam W, Paynter Q, Zhang Z-Q. (2021). Functional response of Amblyseius herbicolus (Acari: Phytoseiidae) on Sericothrips staphylinus (Thysanoptera: Thripidae), an ineffective biocontrol agent of gorse. Biological Control 152, January 2021, art. no. 104468 (first published online Nov 2020) https://doi.org/10.1016/j.biocontrol.2020.104468

Landcare Research (2001a). New thrips in town. What’s New In Biological Control of Weeds? November 2001, 19: 1-2 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew19.pdf

Landcare Research (2002a). Control agents released in 2001/02. Patua Te Otaota - Weed Clippings. Biological Control of Weeds Annual Review 2001/2002. August 2002, 8: 2 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/weedcp02.pdf

Landcare Research (2003b). Control agents released in 2002/03. What’s New In Biological Control of Weeds? Annual Review. August 2003, 25: 2 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew25.pdf

Landcare Research (2004b). Control agents released in 2003/04. What’s New In Biological Control of Weeds? Annual Review. August 2004, 29: 2 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew29.pdf

Landcare Research (2005b). Control agents released in 2004/2005. What's New In Biological Control of Weeds? Annual Review, August 2005, 33: 2 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew33.pdf

Landcare Research (2006a). Control agents released in 2005/06. What’s New In Biological Control of Weeds? Annual Review. August 2006, 37: 11 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew37.pdf

Landcare Research (2006c). Our gaggle of gorse agents. What’s New In Biological Control of Weeds? May 2006, 36: 6-7 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew36.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

Paynter Q, Fowler SV, Groenteman R. (2018). Making weed biological control predictable, safer and more effective: perspectives from New Zealand. BioControl 63: 427-436 (first published online 8 Aug 2017) https://doi.org/10.1007/s10526-017-9837-5 https://link.springer.com/article/10.1007/s10526-017-9837-5

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

Rees M, Hill RL (2001). Large-scale disturbances, biological control and the dynamics of gorse populations. Journal of Applied Ecology 38(2): 364-377 https://doi.org/10.1046/j.1365-2664.2001.00598.x