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Biocontrol introduction

Target pest: Jacobaea vulgaris (Asterales: Asteraceae) = Senecio jacobaea, ragwort

Agent introduced: Botanophila jacobaeae (Diptera: Anthomyiidae) = Pegohylemyia jacobaeae, ragwort seed fly



Import source:


Import notes:

Cameron et al. (1989) - fourteen consignments of ragwort seed fly puparia (Botanophila seneciella and Botanophila jacobaeae) were imported from England between 1928 and 1939.



Release details:

Cameron et al. (1989) - adults emerging from imported puparia were released between 1936 and 1940. More recently several attempts have been made to transfer B. jacobaeae from the central North Island to other areas (Kaikoura, 1975 - 200 pupae released; Golden Bay, 1982 - 500 pupae, 1983 - 515 pupae; Nelson, 1984 - 1,630 pupae).

Syrett et al. (1991) - released in the central North Island and Nelson.


Syrett et al. (1991) - 50 years after the original introductions B. jacobaeae still has only limited distribution.

Gourlay (2007d) - established on the central volcanic plateau of the North Island, Bay of Plenty and and southern Waikato.

Impacts on target:

Cameron et al. (1989) - the impact of B. jacobaeae on ragwort is negligible. Only 10-20% of seedheads were infested at two field sites and up to 200 seedheadsper square metre escaped attack.

Gourlay (2007d) - does not impact seed production enough to reduce ragwort populations. A high proportion of first seedheads are infested, but this declines throughout the summer when the majority of plants flower. Studies show 80-90% of seeds escape attack.

Paynter et al. (2018) - asynchrony with host plant limits effectiveness.

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 B. jacobaeae, a seed-feeding fly, 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:

Paynter et al. (2004) - surveys record no feeding on Senecio bipinnatisectus and S. vulgaris, consistent with laboratory tests that predicted no non-target feeding.


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.

Gourlay H (2007d). Ragwort seed fly: Botanophila jacobaeae. 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/ragwort-seed-fly/

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

Paynter QE, Fowler AH, Gourlay AH, Haines ML, Harman HM, Hona SR, Peterson PG, Smith LA, Wilson-Davey JRA, Winks CJ, Withers TM (2004). Safety in New Zealand weed biocontrol: A nationwide survey for impacts on non-target plants. New Zealand Plant Protection 57: 102-107 https://journal.nzpps.org/index.php/nzpp/issue/view/vol57

Syrett P, Grindell JM, Hayes LM, Winks CJ (1991). Distribution and establishment of two biological control agents for ragwort in New Zealand. Proceedings of 44th New Zealand Weed and Pest Control Conference 44: 292-293