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Biocontrol introduction

Target pest: Clematis vitalba (Ranunculales: Ranunculaceae), old man's beard

Agent introduced: Phytomyza vitalbae (Diptera: Agromyzidae), old man's beard leaf miner


1994, 1996 (?)

Import source:

Switzerland and Germany



Release details:

Gourlay et al. (2000) - since 1996, 42 releases of P. vitalbae have been made at 33 sites throughout New Zealand.

Gourlay (2007) - released throughout New Zealand in the summer of 1996-97.


Gourlay et al. (2000) - Phytomyza vitalbae is now well established. Monitoring confirms that establishment had occurred at 24 sites and in some areas mined leaves have been found up to 200 km from the release point after just 20 months. Populations are building rapidly, and C. vitalba foliage can contain up to four mines per leaflet in some areas.

Impacts on target:

Gourlay (2007) - some damaging outbreaks have been observed, but the agent seems to be limited by parasitism.

Landcare Research (2016d) - while mining of leaves is now common, six native and two exotic parasitoids generally keep the leaf miner populations too low to impact on growth. However, damaging outbreaks do sometimes occur e.g. heavy mining this autumn at Ashburton and on Banks Peninsula.

Paynter et al. (2018) - impacts have been trivial, with P. vitalbae heavily parasitised and predated by eulophid parasitoids (the adults of which feed on P. vitalbae larvae within leaf mines). Combined parasitism and predation rates average at least 58%.

Impacts on non-targets:

Gourlay et al. (2000) - host specificity of P. vitalbae to 40 species of plants, including eight Clematis species native to New Zealand, ornamental Clematis species and other species within the family Ranunculaceae, was tested in Switzerland. Oviposition occurred on the European species Clematis viticella, C. tangutica, C. montana, C. jackmanii and C. orientalis and on the New Zealand species C. marata, C. cunninghamii and C. foetida. Occasional mines were observed on other European Clematis species in natural populations in Switzerland. From field observations, and further tests in outdoor cages and in containment in New Zealand, it was considered that the risk of damage to New Zealand native Clematis species was low. The 1996 application for release of P. vitalbae into New Zealand made clear the potential for incidental damage to non-target Clematis species; permission to release was granted nonetheless. Since the release of P. vitalbae in New Zealand, ongoing systematic searches for non-target attacks have so far found the leaf miner at one isolated site on non-target, exotic Clematis species.

Paynter et al. (2004), Gourlay (2007), Paynter et al. (2008) - P. vitalbae has been collected from the native species Clematis foetida and can complete it is life cycle on this host but levels of attack are very low. A single specimen has been collected from C. forsteri, also a native species. Non-target attacks shown to be a "spillover" effect, unlikely to have a major detrimental effect on plants. P. vitalbae needs to feed on C. vitalba before it can lay eggs and can probably only persist on C. vitalba. Phytomyza vitalbae mines have been recorded from introduced ornamental species C. connata, C. orientalis, C. rehderiana, C. serratifolia and probably C. montana.


Gourlay AH, Wittenberg R, Hill RL, Spiers AG, Fowler SV (2000). The biological control programme against Clematis vitalba in New Zealand. In Proceedings of the X international symposium on biological control of weeds 2000 (pp. 799-806). Montana State University Bozeman, Montana, USA. https://bugwoodcloud.org/ibiocontrol/proceedings/pdf/10_709-718.pdf

Gourlay H (2007). Old Man's Beard Leaf Miner. In The Biological Control of weeds Book (Landcare Research) http://www.landcareresearch.co.nz/research/biocons/weeds/book/documents/Old_Mans_Beard_Leaf_Miner.pdf

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/

Landcare Research (2016d). What's happening with old man's beard? Weed Biocontrol: What's New? 76: 4-5 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-76

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

Paynter, Q., Martin, N., Berry J., Hona, S., Peterson ,P., Gourlay ,A.H., Wilson-Davey, J., Smith, L., Winks, C. and Fowler, S.V. (2008). Non-target impacts of Phytomyza vitalbae a biological control agent of the European weed Clematis vitalba in New Zealand Biological Control 44: 248-258