Target pest: Hypericum perforatum (Malpighiales: Hypericaceae), St Johnís wort
Agent introduced: Chrysolina quadrigemina (Coleoptera: Chrysomelidae), greater St John's wort beetle
Imported: 1965, 1967
Import source: Europe via Australia
Release details: Cameron et al. (1989) - 100,000 beetles released in northern and central South Island
Establishment: Syrett (1997) - after released, not rediscovered until 1984. Groenteman (2014) - initially appeared to have disappeared, but has become common in recent times, and can be found on St John's wort infestations in most places.
Impacts on target: Syrett (1997) - occurs in mixed populations with Chrysolina hyperici and occasionally outbreaks of these chrysomelids completely defoliate plants. Not as widespread or dominant as C. hyperici - studies indicate its reproductive diapause strategy is less successful in areas with colder winters. No longer reports of areas in NZ where St John's wort is a problem weed - it is concluded successful biocontrol is at least partially responsible. Groenteman (2014), Landcare Research (2014c) - with the lesser St John's wort beetle (C. hyperici) extremely effective at controlling St John's wort, though not believed to be as significant as C. hyperici. Landcare Research (2014d), Groenteman (2014) - insecticide exclusion trial showed that St John's wort beetles (C. quadrigemina and C. hyperici) rather than other factors reduced the weed's abundance.
Impacts on non-targets: Paynter et al. (2004) - lab testing predicted severe non-target damage, and potentially underestimated non-target impacts in that Hypericum gramineum and the natives H. perforatum and H. japonicum weren't tested. Surveys on H. gramineum and H. japonicum are on-going and it is too early to assess non-target impacts, but to-date no non-target feeding has been observed, although C. quadrigemina, which is adapted to warmer climates, has been recorded feeding on H. gramineum in Australia. Groenteman (2014) - under artificial conditions in the lab will accept other Hypericum species as hosts, but this has not been replicated in the field. Paynter et al. (2015) - surveys of potential non-target hosts the natives Hypericum involutum and H. pusillum showed minor 'spillover' feeding on both.
Cameron PJ, Hill RL, Bain J and 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.
Groenteman R (2014). St John's Wort Beetles. In The Biological Control of weeds book (Landcare Research) http://www.landcareresearch.co.nz/research/biocons/weeds/book/documents/St_Johns_Wort_Beetles.pdf
Landcare Research (2007). New Zealand Arthropod Collection (NZAC) Biological Control Voucher Collection. http://www.landcareresearch.co.nz/resources/collections/nzac/holdings/biological-control-voucher-collection
Landcare Research (2014c). Who's who in biocontrol of weeds? What's new in biological control of weeds? 69: 10-11 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-69
Landcare Research (2014d). Whodunnit? Solving the case of the disappearing St John's wort. What's new in biological control of weeds? 68: 7 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-68
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
Paynter, Q.E., Fowler, A.H., Gourlay, M.L., Haines, M.L., Harman, H.M., Hona, S.R., Peterson, P.G., Smith, L.A., Wilson-Davey, J.R.A., Winks, C.J. and Withers, T.M. (2004). Safety in New Zealand weed biocontrol: A nationwide survey for impacts on non-target plants New Zealand Plant Protection 57: 102-107
Syrett P (1997). Biological control of St. John's wort in New Zealand. Plant Protection Quarterly 12 (2): 88-90