Biocontrol introduction
Target pest: Cytisus scoparius (Fabales: Fabaceae), Scotch broom, broom
Agent introduced: Arytainilla spartiophila (Hemiptera: Psyllidae), broom psyllid
Imported:
1991, 1992, 1994
Import source:
England
Import notes:
Gourlay (2010c) - Arytainilla spartiophila is native to Europe; it was first imported into New Zealand from England in 1992 and mass-reared for release.
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.
Establishment:
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.
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 A. spartiophila, a piercing/sucking insect, have not been reported in its native range, it does not have a New Zealand native ecological analogue and its impact in New Zealand is assessed as ‘slight’.
Impacts on non-targets:
Landcare Research (2006b) - surveillance this year supports the prediction from host-testing that A. spartiophila would not attack non-target species in the field.
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.
References
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 (2010c). Broom psyllid: Arytainilla spartiophila. 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/broom-psyllid/
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
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 (2006b). Are they behaving themselves? What’s New In Biological Control of Weeds? Annual Review. August 2006, 37: 6-7 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew37.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/
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
