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Biocontrol introduction

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

Agent introduced: Entyloma ageratinae (Tilletiales: Tilletiaceae), mist flower fungus

Imported: 1998

Import source: Jamaica/Mexico via Hawai'i

Released: 1998

Release details: Barton et al. (2007), Fowler (2007) - released at nine sites from Northland to Waikato Nov-Dec 1998.

Establishment: Barton et al. (2007) - established readily and spread throughout the North Island within 5 years. Common.

Impacts on target: Barton et al. (2007) - monitored up to 51 sites 1998-2004: live leaves infected rapidly reached nearly 60%, plant height declined significantly and in heavy infestations mean cover of mist flower declined from 81 to 1.5%. This is now considered to be a successful programme. Fowler (2007) - in 3 years after release mean mist flower ground cover dropped from 90 to 35%. 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 E. ageratinae and the gall fly Procecidochares 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 (2017g) - often causes severe damage, providing excellent control.

Impacts on non-targets: Paynter (2007) - mist flower fungus will only attack mist flower (Ageratina riparia). In lab tests, Mexican devil weed (A. adenophora), also an exotic weed, developed slight disease symptoms but the fungus was unable to complete its life cycle on this host. In the field in Hawai'i and South Africa no disease symptoms have been seen on Mexican devil weed, even when growing beside infected mist flower. Barton et al. ( 2007), Paynter (2007) - as mist flower declined, species richness and cover of native plants increased. While species richness and cover or exotics did not decrease, data to date indicates control of mist flower is benefitting native species more than other weedy exotics.

References

Barton J, Fowler SV, Gianotti AF, Winks CJ, de Beurs M, Arnold GC and Forrester G. (2007). Successful biological control of mistflower in New Zealand: agent establishment, impact, and benefit to the New Zealand flora. Biological control 40:370-385

Fowler S (2007). Mist Flower Fungus. In The Biological Control of Weeds Book (Landcare Research) http://www.landcareresearch.co.nz/research/biocons/weeds/book/documents/Mist_Flower_Fungus.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

Landcare Research (2017g). Who's who in biological control of weeds? Weed Biocontrol: What's New? 81: 10-11 https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-81