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Biocontrol introduction

Target pest: Cytisus scoparius (Fabales: Fabaceae), Scotch broom, broom

Agent introduced: Arytainilla spartiophila (Hemiptera: Psyllidae), broom psyllid


1991, 1992, 1994

Import source:


Released: 1993

Release details:

Harman et al. (1996) - first released in the field at Lincoln, Canterbury in 1993. In 1994, some of the early releases of this species were used in a large field experiment in Otago to assess the impact of release size on establishment success.

Gourlay (2009, 2010c) - released throughout New Zealand in the mid-1990s.


Harman et al. (1996) - has established.

Gourlay (2009, 2010c) - well established at sites throughout most of the country.

Impacts on target:

Gourlay (2009, 2010c) - high populations can cause severe damage to new growth; there have been a few outbreaks, especially in Southland but they are still not common. Performance may be affected by predation by mirid bugs (Sejanus spp.). Too early to assess impact.

Paynter et al. (2018) - A. spartiophila is abundant with persistent outbreaks in some regions, but impacts on the target plant appear to be minor.

Impacts on non-targets:

Gourlay (2010c) - will only damage Scotch broom (Cytisus scoparius). Will not even attack other broom species such as Montpellier broom (Genista monspessulana) or white broom (Cytisus multiflorus).

General comments:

Fowler et al. (2021) - the bacterium, ‘Candidatus Liberibacter europaeus’ (Leu) was reported in New Zealand in 2011 in C. scoparius and its biocontrol agent A. spartiophila. There is strong evidence that Leu was accidentally released in New Zealand in A. spartiophila in 1993, at which time Leu was unknown to science. It remains uncertain whether Leu is pathogenic or asymptomatic in Scotch broom. This accidental introduction of Leu via a weed biocontrol agent suggests pre-release safety screening of biocontrol agents that are potential vectors of plant pathogens could become essential.


Fowler SV, Lange C, Beard S, Cheeseman DF, Houliston GJ, Paynter Q, Peterson P, Pitman A, Smith L, Tannières M, Thompson S, Winks C. (2021). Accidental introduction of Candidatus Liberibacter europaeus into New Zealand via a weed biocontrol agent from the UK. Biological Control, Volume 160, September 2021, 104697 https://doi.org/10.1016/j.biocontrol.2021.104697

Gourlay H. (2009). The biological control of broom (Cytisus scoparius). IUFRO International Forest Biosecurity Conference, 16-20 March 2009, Rotorua, New Zealand. Popular Summaries. Compiled by Richardson M, Hodgson C and Forbes A. New Zealand Forest Research Institute Limited. 230-232

Gourlay H. (2010c). Broom Psyllid. In The Biological Control of Weeds Book (Lancare Research). https://www.landcareresearch.co.nz/discover-our-research/biosecurity/weed-management/using-biocontrol/the-biological-control-of-weeds-book/

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

Landcare Research (2007a). New Zealand Arthropod Collection (NZAC) Biological Control Voucher Collection. http://www.landcareresearch.co.nz/resources/collections/nzac/holdings/biological-control-voucher-collection

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