Biocontrol introduction
Target pest: Jacobaea vulgaris (Asterales: Asteraceae) = Senecio jacobaea, ragwort
Agent introduced: Tyria jacobaeae (Lepidoptera: Arctiidae), cinnabar moth
Imported:
1926-1931
Import source:
England
Import notes:
Cameron et al. (1989) - consignments of T. jacobaeae pupae were imported into New Zealand from England between 1926 and 1929.
Released:
1929
Release details:
Cameron et al. (1989) - between 1929 and 1932 approximately 3.5 million eggs were distributed on ragwort throughout the country. Main liberation areas were Nelson, Auckland, Taranaki and Southland.
Syrett et al. (1991) - the well-established population of T. jacobaeae in the southern North Island was used as a source of insects for rearing and redistribution throughout New Zealand. Between the summers of 1982/83 and 1990/91, 135 releases were made at 106 sites throughout the country. Releases comprised 1,000+ caterpillars.
Establishment:
Cameron et al. (1989) - initial establishment from the 1929-32 releases was very good in some areas, but populations failed to be maintained for more than two or three years. In 1941 it was reported in particularly large numbers at Horahora along the Waikato River and a few years later there were records from the Wairarapa. To date it persists in abundance only in the southern North Island (Wellington, Wairarapa and Manawatu regions). It appears to have extended its range both northwards and southwards from the Wairarapa area where it has persisted since the early liberations.
Syrett et al. (1991) - T. jacobaeae has established at 35% of the 1982/83 - 1990/91 release sites. After 2-3 years moth adults or larvae were recovered on average only 20 m from the release point, although at one site caterpillars were recovered 1 km away. In 5-6 years they were found 200 m away.
Gourlay (2007g) - most of the original populations died out except in the southern North Island. As a result of rearing and redistribution from this population the moth now occurs patchily throughout most areas of New Zealand where ragwort occurs, and is more common in some years than others.
Landcare Research (2014c) - common in some areas.
Landcare Research (2016h) - over 70 L. jacobaeae (ragwort flea beetle) release sites nationwide revisited 20-30 years post-release and density of ragwort now compared to density at the time of release: cinnabar moth was encountered at 68% of sites at some stage over the course of the study and is well spread throughout New Zealand.
Impacts on target:
Syrett et al. (1991) - at two of six release sites (where appropriate data was collected) where T. jacobaeae had been established in 1987 or earlier (and no other biocontrol agents were present), a decline in ragwort abundance was observed. While T. jacobaeae probably has limited value as a control agent, ragwort abundance decreased at all 3 sites where both T. jacobaeae and Longitarsus jacobaeae (ragwort flea beetle) were established, suggesting these two agents may be complementary in their impact on ragwort populations.
Harman et al. (1996) - Tyria jacobaeae alone is not thought to be effective.
Gourlay (2007g) - Tyria jacobaeae can completely defoliate ragwort plants but these generally recover and there is little impact on plant populations.
Landcare Research (2008d) - a nationwide survey and literature review investigating the toll that parasitism is taking on weed biocontrol agents has found several agents, including T. jacobaeae, for which parasitism levels of more than 60% have been measured. These agents are likely being adversely affected by such levels. Tyria jacobaeae is parasitised by two native species: Phorocera casta [a tachinid fly] and Echthromorpha intricatoria [an ichneumonid wasp].
Landcare Research (2014c) - often causes obvious damage.
Landcare Research (2016h) - in a nationwide study of ragwort sites, damaging levels of cinnabar moth was only ever noted sporadically, and earlier studies have shown it to be limited by natural enemies.
Paynter et al. (2018) - heavily parasitised by tachinid flies (up to 78% parasitism) to an extent that is likely to significantly influence its efficacy. Larvae are also subject to predation by birds.
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 T. jacobaeae, a defoliating moth, have not been reported in its native range (at least on good pasture soils, on which ragwort is predominantly a weed in New Zealand), it does have a New Zealand native ecological analogue and its impact in New Zealand is assessed as ‘slight’.
Impacts on non-targets:
Fowler et al. (2000) - known to cause minor damage to Cineraria sp., Sonchus oleraceus (sow thistle) and native Senecio spp. The attack on Cineraria sp. was anticipated pre-release; the attack on S. oleraceus (sow thistle) and native Senecio spp. was not.
Fowler et al. (2004), Paynter et al. (2004) - surveys record T. jacobaeae eating native fireweeds such as Senecio minimus and S. biserratus. However adults do not oviposit on these and attack is very sporadic 'spill-over' feeding when target weed completely defoliated. Laboratory tests had been performed with native Senecio species, but S. minimus and S. biserratus were not placed in this genus at the time and were not tested.
General comments:
Taxonomic note (29 June 2024) - at the time that T. jacobaeae was introduced into New Zealand, ragwort, the target weed, was classified as Senecio jacobaea. However, molecular studies of the tribe Senecioneae by Pelser et al. (2006) showed that species of Senecio sect. Jacobaea (Mill.) Dumort. formed a well-supported clade that is only distantly related to other species usually attributed to Senecio, and proposed transferring the 27 species of sect. Jacobaea they analysed to the genus Jacobaea Mill. This included Senecio jacobaea, reclassified as Jacobaea vulgaris.
References
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.
Fowler SV, Syrett P, Hill RL. (2000). Success and safety in the biological control of environmental weeds in New Zealand. Austral Ecology 25: 553–562
Fowler, S.V., Gourlay, A.H., Rill, R.H. and Withers, T. (2004). Safety in New Zealand weed biocontrol: a retrospective analysis of host specificity testing and the predictability of impacts on non-target plants. proceedings of the XI International Symposium on Biological Control of Weeds. Cullen, J.M., Briese, D.T., Kriticos, D.J., Lonsdale, W.M., Morin, L. and Scott, J.K. (Eds). Canberra, Australia, CSIRO Entomology, 27 April - 2 May 2003.
Gourlay H (2007g). Ragwort cinnabar moth: Tyria 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-cinnabar-moth/
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 (2008d). Parasitism - a major or minor cause of biocontrol failure? What’s New In Biological Control of Weeds? August 2008, 45: 4-5 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew45.pdf
Landcare Research (2014c). Who's who in biocontrol of weeds? What's new in biological control of weeds? 69: 10-11 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/WhatsNew69.pdf
Landcare Research (2016h). Comparing ragwort then with now: Part One. Weed Biocontrol: What's New? 77: 4-5 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-77
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
Pelser PB, Veldkamp J-F, Van der Meijden R (2006). New combinations in Jacobaea Mill. (Asteraceae – Senecioneae). Compositae Newsletter 44: 1-11 https://www.researchgate.net/publication/247158930_New_combinations_in_Jacobaea_Mill_Asteraceae-Senecioneae
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
