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Biocontrol introduction

Target pest: Hypericum perforatum (Malpighiales: Hypericaceae), St John's wort

Agent introduced: Chrysolina hyperici (Coleoptera: Chrysomelidae), lesser St John's wort beetle


1943, 1944

Import source:

England via Australia

Import notes:

Hancox et al. (1986) - in December 1943, 30 000 adults of C. hyperici were imported from Australia for control of St John's wort. This insect was chosen for an entirely pragmatic reason: it was the only species to have reached a sufficiently large population for collection and redistribution.



Release details:

Hancox et al. (1986), Cameron et al. (1989) - the 30,000 adults imported from Australia in 1943 were all released in the Awatere Valley, Marlborough, after one day in quarantine. By December 1946 the Awatere Valley population was sufficiently large for collection and redistribution to Cromwell and Arrowtown in Otago. From 1947 to 1950, C. hyperici was distributed lo a large number of locations throughout New Zealand, although it should be noted that most of the North Island releases were intended for control of a related weed, tutsan (Hypericum androsaemum).


Hancox et al. (1986) - Chrysolina hyperici readily established from the initial release at Awatere Valley.

Syrett (1997) - most common and widespread of 3 agents released against H. perforatum, found throughout distribution of the weed.

Groenteman (2014), Landcare Research (2014c) - rapidly became widely established. Can be found on St Johns Wort throughout the country. Appears to be more common than the Greater St John's wort beetle (C. quadrigemina).

Impacts on target:

Hancox et al. (1986) - by December 1947, four years after the release of C. hyperici over 180 ha of densely infested country in the Awatere Valley had been cleared of St John's wort, and the weed population level here has remained at a low level ever since. However, it should be noted that pasture improvement and rabbit control programmes may have also played a part in reducing St John's wort infestations over this period. From anecdotal reports from other regions it seems that the level of control achieved by C. hyperici has varied considerably both spatially and temporally. In an insecticide exclusion trial near Lake Tekapo, Canterbury, 1983-85, C. hyperici significantly reduced the amount of St John’s wort.

Cameron et al. (1989) - of the two St John's wort beetles introduced (C. hyperici and C. quadrigemina), C.hyperici is the only one to have become successfully established and reached sufficiently high populations to have had an impact on its host plant.

Harman et al. (1996) - has had a significant impact on St John's wort.

Syrett (1997) - occurs in mixed populations with Chrysolina quadrigemina where the latter occurs and occasionally outbreaks of these chrysomelids completely defoliate plants. C. hyperici seems to be the dominant species in NZ - studies indicate its reproductive diapause strategy is more 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 greater St John's wort beetle (C. quadrigemina) extremely effective at controlling St John's wort. Believed to be more significant than C. quadrigemina, C. hyperici nearly always provides excellent control.

Landcare Research (2014d), Groenteman (2014) - recent insecticide exclusion trials have showed that it is St John's wort beetles (C. quadrigemina and C. hyperici) rather than other factors that have reduced the weed's abundance. A recent economic analysis has estimated that the Net Present Value of introducing the beetles is between $140 and $1,490 million over 70 years, a benefit to cost ratio of 10:1 and 100:1 respectively.

Impacts on non-targets:

Hancox et al. (1986) - extensive starvation tests using C. hyperici had been conducted in Britain and Australia prior to release in Australia and 13 years of Australian experience had confirmed its host specificity.

Fowler et al. (2000) - causes (as anticipated pre-release) minor damage to Hypericum androsaemum (tutsan) [a significant weed in New Zealand].

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.

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 the former is a 'full' host (can support breeding populations), and minor 'spillover' feeding on the latter.


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

Groenteman R (2014). St John's wort beetles. In The Biological Control of weeds book (Landcare Research). https://www.landcareresearch.co.nz/discover-our-research/biosecurity/weed-management/using-biocontrol/the-biological-control-of-weeds-book/

Hancox NG, Syrett P, Scott RR (1986). Biological control of St John’s wort (Hypericum perforatum) in New Zealand: a review. Plant Protection Quarterly 1(4): 152-155 https://caws.org.nz/PPQ12/PPQ%2001-4%20pp152-155%20Hancox.pdf

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

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

Miller, D. (1970). Biological control of weeds in New Zealand, 1927-1948. New Zealand Department of Scientific and Industrial Research information series 74. 104 pp.

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 https://doi.org/10.1016/j.biocontrol.2014.10.007

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