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Biocontrol introduction

Target pest: Ageratina riparia (Asterales: Asteraceae), mist flower

Agent introduced: Procecidochares alani (Diptera: Tephritidae), mist flower gall fly


1998, 1999, 2000

Import source:

Mexico via Hawai'i

Import notes:

Fröhlich et al. (2000) - following a study on the feasibility of transferring the successful biological control programme for A. riparia in Hawai’i to New Zealand, Landcare Research decided to proceed with plans to import two biological control agents, P. alani and the fungus Entyloma ageratinae, from Hawai’i.

Landcare Research (2007a) - specimens of P. alani from Hawai'i, dated 1998, 1999 and 2000, are present in the Biological Control Voucher Collection of the New Zealand Arthropod Collection [indicating importations from Hawai'i in those years. The 1998 and 1999 importations would have been for host-range testing - see EPA (1998b) entry in 'EPA applications' section; the 2000 importation for releases - see EPA (2000a) entry in 'EPA applications' section.]

Released: 2001

Release details:

Barton et al. (2007) - Procecidochares alani adults were released at 34 sites across the North Island from February 2001 to June 2004. In total, 11,630 flies were released, with the sizes of individual releases varying from 30 to 600 flies.


Barton et al. (2007) - Procecidochares alani was recorded after passing through at least one generation at 26 of the 30 sites that were revisited: an establishment rate of 87%. Successful overwintering occurred at at least 16 sites. Dispersal was not formally assessed but appears to be slow. In October 2001, one gall was recorded 250 m from the nearest release site (eight months previously) and in February 2002 one gall was found about 5 km from the nearest release site (one year previously).

Landcare Research (2015i) - Procecidochares alani is common now at many sites.

Impacts on target:

Barton et al. (2007) - surveys at the Karamatura Valley (Waitakere Ranges, Auckland) release sites showed the number of P. alani galls increasing exponentially to 1.96 galls/stem over the two years following releases, quickly surpassing the mean 0.46 galls/stem reported from Hawai’i (where P. alani is considered to have contributed to the successful suppression of A. riparia). While P. alani has been released too recently for it to show impacts on A. riparia in this study, these figures suggest that the gall fly may yet contribute to the suppression of mist flower in New Zealand, enhancing the impact of the fungus Entyloma ageratinae [see the Entyloma ageratinae introduction entry].

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 P. alani, for which parasitism levels of more than 60% have been measured. These agents are likely being adversely affected by such levels. Procecidochares alani is parasitised by one exotic species: Megastigmus sp. [a chalcid wasp].

Landcare Research (2009a) - in November 2008 a survey was undertaken in the Waitakere Ranges, Auckland (at the same sites last surveyed in 2003) to assess the progress of the biocontrol agents released against A. riparia: the white smut fungus Entyloma argeratinae (released 1998) and P. alani (released 2001). Both agents were found to be still abundant and A. riparia still under excellent control in the Ranges. Procecidochares alani galling was found at a rate of 0.57 galls/stem, similar to the 2003 level of 0.71 galls/stem. In June 2008 another site in the Waitakere Ranges (Karamatura Valley) where P. alani had been released in 2001 was surveyed for the gall fly. The number of galls per stem grew exponentially from 0.26 in 2001 to 1.96 in 2003, and then more slowly up to 2.29 in 2008. This high level of attack was sustained despite a dramatic decrease in the number of A. riparia stems, indicating P. alani is able to seek out and gall the plant, even when it is relatively rare. Based on these 2008 results, concerns that parasites might quickly make inroads into P. alani populations remain unfounded.

Hayes et al. (2013) - a preliminary analysis of financial savings from no longer having to control mist flower by conventional means in the upper North Island suggests a cost reduction of $80,000 to $90,000 per year from the introduction of the fungus Entyloma ageratinae and P. alani in 1998 and 2001 respectively. The net present value for this is more than $3 million with a benefit:cost ratio of 2.5:1; considered very good over a 13 year period.

Landcare Research (2015i) - in conjunction with mist flower fungus (Entyloma ageratinae), P. alani provides excellent control of mist flower.

Paynter et al. (2018) - Procecidochares alani is highly parasitised by the wasp Megastigmus sp. (68% parasitism). The impacts of P. alani on A. riparia are only minor. The fungus Entyloma ageratinae, released as a biocontrol agent in 1998 [see the Entyloma ageratinae introduction entry], controlled A. riparia before P. alani impact could be assessed.

Impacts on non-targets:

Fröhlich et al. (1999), Hill (1999), Fröhlich et al. (2000), EPA (2000a) - host range tests had been conducted on 56 plant species prior to the release of P. alani in Hawai’i and Australia. Twenty-six additional plant species of significance in New Zealand were tested, either in Hawai’i or in containment in New Zealand, prior to the release of the gall fly in New Zealand. Representative plants for this additional testing were chosen from New Zealand native plants (15 species), especially in the Asteraceae (daisy) family (12 of those 15 species), ornamental Asteraceae grown in New Zealand and plants known to host insects that are closely related to P. alani. All host range tests have shown P. alani is highly specific to A. riparia. The only non-target plants that the gall fly laid eggs on in these tests were Ageratina adenophora (Mexican devil weed, also an aggressive weed in New Zealand) (in testing prior to release in Hawai’i and Australia) and Eupatorium rugosum (on which a single egg was laid in the testing prior to release in New Zealand), but the resulting larvae did not develop and no galls were formed on either plant. Thus, the risk of P. alani attacking plants other than A. riparia in the field in New Zealand is low, and probably negligible.

Paynter et al. (2004) - surveys record no feeding on Ageratina adenophora, as predicted by laboratory tests.

EPA Applications:

EPA (1998b) - 21 Sep 1998: application by Auckland Regional Council to import into containment mist flower gall fly (Procecidochares alani), for the purpose of host specificity testing to determine its suitability as a biological control agent for mistflower (Ageratina riparia). EPA Application #NOC98002, approved with controls 14 Nov 1998.

EPA (2000a) - 18 Jun 1999: application by Auckland Regional Council to import for release the mist flower gall fly, Procecidochares alani (Steyskal), for the purpose of biological control of mist flower (Ageratina riparia). EPA Application # NOR99004, approved without controls 23 Sep 2000.


Barton J, Fowler SV, Gianotti AF, Winks CJ, de Beurs M, Arnold GC, Forrester G (2007). Successful biological control of mistflower in New Zealand: agent establishment, impact, and benefit to the New Zealand flora. Biological control 40(3): 370-385 https://www.landcareresearch.co.nz/uploads/public/researchpubs/mistflower.pdf

EPA (1998b). Application to EPA (NOC98002) to import into containment a new organism, the mistflower gall fly (Procecidochares alani), for the purpose of host specificity testing to determine its suitability as a biological control agent for mistflower (Ageratina riparia). Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/NOC98002

EPA (2000a). Application to EPA (NOR99004) to release from containment the mist flower gall fly, Procecidochares alani (Steyskal), for the purpose of biological control of mist flower (Argeratina riparia). Environmental Protection Authority website https://www.epa.govt.nz/database-search/hsno-application-register/view/NOR99004

Fröhlich J, Fowler SV, Gianotti AF, Hill RL, Killgore EM, Morin L, Sugiyama LS, Winks C (1999). Biological control of mist flower (Ageratina riparia, Asteraceae) in New Zealand. Proceedings of the New Zealand Plant Protection Conference 52: 6-11 https://journal.nzpps.org/index.php/pnzppc/article/view/11611/11461

Fröhlich J, Fowler SV, Gianotti AF, Hill RL, Killgore EM, Morin L, Sugiyama LS, Winks C (2000). Biological control of mist flower (Ageratina riparia, Asteraceae): transferring a successful program from Hawai’i to New Zealand. Proceedings of the X International Symposium on Biological Control of Weeds 2000, pp. 51-57 https://www.invasive.org/publications/xsymposium/proceed/01pg51.pdf

Hayes L, Fowler SV, Paynter Q, Groenteman R, Peterson P, Dodd S, Bellgard S (2013). Biocontrol of weeds: achievements to date and future outlook. In: Dymond JR (ed) Ecosystem services in New Zealand: conditions and trends. Manaaki Whenua Press, Lincoln, pp 375-385 https://www.landcareresearch.co.nz/__data/assets/pdf_file/0005/77054/2_8_Hayes.pdf

Hill RL (1999). Application to EPA (NOR99004) to import for release, or release from containment, the mist flower gall fly, Procecidochares alani. Environmental Protection Authority website https://www.epa.govt.nz/assets/FileAPI/hsno-ar/NOR99004/10224dd6d2/Application-NOR99004.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 (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 (2009a). Still working after all these years. What’s New in Biological Control of Weeds? February 2009, 47: 7-8 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/wtsnew47.pdf

Landcare Research (2015i). Who's who in biological control of weeds? Weed Biocontrol: What's New? 73: 10-11 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-73

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

Winks C (2007a). Mist Flower Gall Fly. 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/