B3   >>   BCANZ home   ·   Search database   ·   Browse database

Biocontrol introduction

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

Agent introduced: Zeuxidiplosis giardi (Diptera: Cecidomyiidae), St John's wort gall midge



Import source:


Release details:

Hancox et al. (1986), Cameron et al. (1989) - released in northern and central South Island, as far south as Wanaka (Otago).


Hancox et al. (1986) - has established well and reaches high densities in the stony riverbeds of the northern South Island. It is also present, although only in low numbers, to an altitude of 830 m in North West Nelson where there is considerable winter snowfall.

Landcare Research (2014c) - established in northern South Island.

Impacts on target:

Hancox et al. (1986) - it has been observed that where pockets of maximum galling occur there is no flowering and that seedlings are killed by midge activity. Recently, however, Dimeromicrus sp. [Cameron et al. (1989) reports this as Torymoides sp.], a hymenopteran parasitoid, has been recorded from Z. giardi in the Nelson area. It is not known whether mortality from this parasitoid is significant.

Cameron et al. (1989) - impacts unknown, may stunt plants.

Landcare Research (2014c) - often causes severe stunting.

Paynter et al. (2018) - Z. giardi is localised and ineffective. Heavily parasitised (41% parasitism) to an extent that is likely to significantly influence its efficacy.

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.


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.

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

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

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, 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