Management Information
Preventative measures: A Risk Assessment of Hedychium gardnerianum for Hawai‘i and other Pacific islands was prepared by Dr. Curtis Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service. The alien plant screening system is derived from Pheloung et al. (1999) with minor modifications for use in Pacific islands (Daehler et al. 2004). The result is a score of 16 and a recommendation of: "Likely to cause significant ecological or economic harm in Hawai‘i and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘i and/or other parts of the world."Remote sensing techniques and new technologies may help map the potential spread of invasive species such as kahili ginger. Recently, Scientists from Stanford and the Carnegie Institution developed an imaging method based on NASA Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) that detects changes in nitrogen levels and water content (measured from a high altitude sircraft). The detection of the exotic kahili ginger plant (Hedychium gardnerianum) in Hawaii (where the study was conducted) is based on the premise that it has relatively high water content compared with native forest plant species (ie: the native 'ohi'a (Metrosideros polymorpha) trees (Stanford Report March 9 2005). Identifying the actual and potential range of an invasive plant before it dominates a landscape can be an important step in the control of an invasive understory species. Physical: Manual removal is another option for controlling local infestations (ie: in gardens). Small seedlings can be pulled out by hand. Removing the flower heads from Kahili ginger does not kill the plant but does slow down its spread. If the seeds are not fully formed the flowers can be left on the ground. If the seeds have formed, remove the flowers and put them out for disposal in your rubbish bags. Isolated small plants can be grubbed out and the rhizomes should also be removed. Stalks and roots are hard to burn and should not be composted. Take them to your council dump or transfer station or put them out for domestic rubbish collection. Chemical: Common herbicides that are suitable include Escort, Roundup and Amitrole. Use the concentrations as recommended by the manufacturer. Apply from spring to late autumn. Spray lightly on the leaves and roots. Do not remove the leaves or stalks until they have gone brown and dried out. This will take three to four months. In terms of chemical control, it is cost effective to use Escort (metsulfuron-methyl) which is the most effective herbicide for use against kahili ginger (Harris et al. 1996, in Anderson and Gardner 1999). However, when large infestations are the case (such as in Hawaii) chemical control is considered environmentally safe only for small intensively managed areas with a high conservation value (Tunison and Stone 1992, in Anderson and Gardner 1999). This is because of the many side effects of Escort (which include soil leaching, ground water contamination and effects on non-target native plants). In the summer of 1998, kahili ginger was removed from certain parts of Hawaii Volcanoes National Park (HAVO) by the use of Escort with a concentration of 1.5 g/l. The herbicide was applied aerially after epigeal sprouts had been cut down. It is absorbed by the plants through roots and foliage, and inhibits cell division in roots and shoots, which leads to rapid wilting and death. Escort might cause environmental damage, such as soil leaching and ground water contamination and might possibly affect non-target native species (Minden et al 2010) Biological: Biological control is considered the only practical approach for the long-term management of large kahili ginger infestations in native forests. The ability of the bacterium Ralstonia (=Pseudomonas) solanacearum to cause bacterial wilt in kahili ginger H. gardnerianum in the field, together with its lack of virulence in other ginger species, contributes to its potential as a biological control agent (Anderson and Gardner 1999).   
Location Specific Management InformationAuckland Region (North Island)
The flowers can be cut and dropped on the ground prior to the seeds being formed. This will prevent spreading by seed. Small stands of ginger can be cut out but spraying with herbicide is necessary with the more dense stands. Auckland Region (North Island)
Cut stump application: cut above pink “collar” at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Auckland Region (North Island)
H. gardnerianum and H. flavescens has been designated as a Surveillance, Community Initiative and Containment Pest by the Auckland Regional Pest Management Pest Management Strategy 2002-2007. Please see Hierarchy of Plant Designations for an explanation of designation terminology.
The objectives of the management strategy are to prevent the spread of and, where practicable, reduce infestations of H. gardnerianum and H. flavescens over the next five years, from the Waitakere and Hunua Ranges Weed Control Zones, and Great Barrier Island; and to restrict their further spread by humans over the next 10 years. Azores
Wildlife Management International Limited is undertaking trials on a variety of chemical concentrations using Metsulfuron, known locally as Ally (known as Escort in NZ) to control Hedychium gardnerianum (ginger, known locally as conteira), training the local staff in the use of chemical control methods for Hedychium gardnerianum, and beginning the control of conteira within the main Priolo habitat. They have also been advising on rat and feral cat control. These activities are part of the Life Priolo project, a habitat restoration project for the Azores Bullfinch. Bay of Plenty Region (North Island)
Digging is effective for removing small stands, providing all roots are removed intact and disposed of properly. The standard chemical control with herbicide is effective also. Buller District
Cut stump application: cut above pink collar at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Coromandel
The flowers can be cut and dropped on the ground prior to the seeds being formed. This will prevent spreading by seed. Small stands of ginger can be cut out but spraying with herbicide is necessary with the more dense stands. Coromandel
Cut stump application: cut above pink “collar” at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Hawaii
Bacterial wilt caused by the ginger strain of Ralstonia (Pseudomonas) solanacearum systemically infects edible ginger (Zingiber officinale) and ornamental gingers (Hedychium spp.), causing wilt in infected plants.
The suitability of R. solanacearum as a biological control agent for kahili ginger was investigated by inoculating seedlings and rooted cuttings of native forest plants, ornamental ginger, and solanaceous species to confirm host specificity. Inoculation via stem injection or root wounding with a bacterial–water suspension was followed by observation for 8 weeks. All inoculated H. gardnerianum plants developed irreversible chlorosis and severe wilting 3–4 weeks following inoculation. Systemic infection also caused death and decay of rhizomes.
Most plants were completely dead 16–20 weeks following inoculation. The destructiveness of the ginger strain of R. solanacearum to edible ginger has raised questions regarding its use for biological control. However, because locations of kahili ginger infestations are often remote, the risk of contaminating edible ginger plantings is unlikely. The ability of this bacterium to cause severe disease in H. gardnerianum in the field, together with its lack of virulence in other ginger species, contributes to its potential as a biological control agent. Scientists from Stanford and the Carnegie Institution have developed a remote-sensing technique that identifies invasive plant species before they dominate a landscape. Novel measurement techniques from a high-altitude aircraft were used to detect two invasive species found in the rainforest near Kilauea Volcano in Hawaii Volcanoes National Park. The method they used to detect the plants revolved around the recently upgraded NASA Airborne Visible and Infrared Imaging Spectrometer (AVIRIS). AVIRIS is able to detect changes in leaf nitrogen and water content, which are linked (respectively) to the exotic Myrica faya (which has a relatively high nitrogen concentration) and to the exotic Kahili ginger plant (Hedychium gardnerianum) (which has a relatively high water content) (Stanford Report March 9 2005). Jamaica
Wherever Pittosporum is removed the removal of Wild ginger and Redbush should also take place, as these are threatening invasives, and will take advantage of gaps created by Pittosporum removal if they are not simultaneously controlled. Marlborough Region (South Island)
Cut stump application: cut above pink “collar” at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Nelson
H. gardnerianum has been designated as a 'Progressive control pest' by the the Tasman-Nelson Regional Pest Management Strategy. The strategy has its effect over the combined area that lies within the administrative boundaries of the Tasman District Council and Nelson City Council. The objective of the strategy is to reduce the distribution and density of H. gardnerianum in the Golden Bay/Kaiteriteri area during the term of the Strategy. Please see Hierarchy of Plant Designations for an explanation of designation terminology. New Zealand
Dig out or pull seedlings and regrowth. Do not compost roots. Treat with herbicide. Escort 25 gm/100 l water + 0.1% Pulse; Roundup 2% + 0.2% Pulse; Amitrole (Timmins and Mackenzie, 1995. In PIER, 2002)
Hedychium gardnerianum is listed as a pest plant in New Zealand; commercial sale and/or distribution of the plant is not allowed. National Pest Plant Accord, New Zealand.
Hedychium gardnerianum has been included in the Auckland Regional Councils pest plants, Pest Facts New Zealand
The flowers can be cut and dropped on the ground prior to the seeds being formed. This will prevent spreading by seed. Small stands of ginger can be cut out but spraying with herbicide is necessary with the more dense stands. New Zealand
Kahili ginger flowers can be cut and dropped on the ground prior to the seeds being formed. If seeds are present put the flower heads into a bag for disposal with the household rubbish. Flowerhead removal will not kill the plant but it will stop it seeding. Digging is an effective method of removing small stands of wild ginger, providing all the roots are removed intact and disposed of safely at an authorised refuse transfer station.
Wild ginger can also be controlled by killing it with Escort™ herbicide. Be careful not to spray desirable neighbouring plants. Spray the leaves, stems and root system making sure that coverage is complete. Wait until stalks and leaves brown off before removing them. Escort™ should be mixed at 2.5 grams per 5 litres water plus 10 mls of a spreader/sticker like Pulse®.
For larger applications mix Escort™ at 25 grams per 100 litres water, adding 100 mls of spreader/sticker. Escort™ is available in small packs at most garden centres and larger quantities can be bought at farm supply stores. If the wild ginger plants are too tall for convenient spraying they can be chopped down to the rhizomes which should be sprayed immediately. This method means less herbicide is used and there is less chance of drift. The effects of the herbicide (plant death) are noticeable after
3 months, although rhizomes may take 12 to 15 months to rot away. Northland Region (North Island)
The flowers can be cut and dropped on the ground prior to the seeds being formed. This will prevent spreading by seed. Small stands of ginger can be cut out but spraying with herbicide is necessary with the more dense stands. Northland Region (North Island)
Cut stump application: cut above pink “collar” at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Reunion (La Réunion)
Dig out or pull seedlings and regrowth. Do not compost roots. Treat with herbicide. Escort 25 gm/100 l water + 0.1% Pulse; Roundup 2% + 0.2% Pulse; Amitrole (Timmins and Mackenzie, 1995. In PIER, 2002) Reunion (La Réunion)
A research programme funded by the French Environment Ministry made it possible to estimate during a site workshop on the west coast that the eradication of one hectare of Hedychium gardnerianum costs 22000 euros for 230 working days (Lavergne, 2005) . Various management methods have been trialed in Reunion. Chemical methods tested (based on picloram-Tordon 22K ® - or metsulfuron methyl-Ally ® -) do not seem to be effective in containing the invasion in the long term. A method combining cutting stems and grubbing rhizomes would reduce the invasion considerably but at a very high cost and it would possibly cause disruptions to the natural environment and the soil that not necessarily acceptable (Hivert, 2003). South Africa
Dig out or pull seedlings and regrowth. Do not compost roots. Treat with herbicide. Escort 25 gm/100 l water + 0.1% Pulse; Roundup 2% + 0.2% Pulse; Amitrole (Timmins and Mackenzie, 1995. In PIER, 2002) Taranaki Region (North Island)
Cut stump application: cut above pink “collar” at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Taranaki Region (North Island)
H. gardnerianum is classified as a 'Containment pest plant' in the The Pest Management Strategy for Taranaki. 'Containment pest plants' are pest plants that are abundant in suitable habitats in a region or part of a region and for which the long-term goal is to prevent the spread of the plant to new areas or to neighbouring properties.
Each pest plant has a management programme according to its designation. These programmes are summarised in the series of bulletins 'Pest Plant Facts'. Please see kahili ginger: H. gardnerianum for pest plant facts and management programmes. Tasman District
H. gardnerianum has been designated as a 'Progressive control pest' by the the Tasman-Nelson Regional Pest Management Strategy. The strategy has its effect over the combined area that lies within the administrative boundaries of the Tasman District Council and Nelson City Council. The objective of the strategy is to reduce the distribution and density of H. gardnerianum in the Golden Bay/Kaiteriteri area during the term of the Strategy. Please see Hierarchy of Plant Designations for an explanation of designation terminology. Tauranga
Cut stump application: cut above pink “collar” at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Waikato Region (North Island)
Cut stump application: cut above pink “collar” at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Wellington Region (North Island)
Cut stump application: cut above pink “collar” at base, treat fresh stump with Escort (metsulfuron as a methyl ester form), 1 gm/litre. Also check label rates. Wenderholm Regional Park
The techniques outlined in Veitch and MacArthur (1997) have greatly reduced infestations of kahili ginger. It is now kept in check by an annual maintenance programme. Reforestation should be integrated with weed control.
Management Resources/Links
1. Anderson, R.C. and Gardner, D.E. 1999. An Evaluation of the Wilt-Causing Bacterium Ralstonia solanacearum as a Potential Biological Control Agent for the Alien Kahili Ginger
(Hedychium gardnerianum) in Hawaiian Forests, Biological Control 15: 89–96. 3. Chai, S. Undated. Pittosporum invasion of the Blue Mountains. Jamaica Conservation & Development Trust 4. Daehler, C.C; Denslow, J.S; Ansari, S and Huang-Chi, K., 2004. A Risk-Assessment System for Screening Out Invasive Pest Plants from Hawaii and Other Pacific Islands. Conservation Biology Volume 18 Issue 2 Page 360.
Summary: A study on the use of a screening system to assess proposed plant introductions to Hawaii or other Pacific Islands and to identify high-risk species used in horticulture and forestry which would greatly reduce future pest-plant problems and allow entry of most nonpests. 6. Environment Waikato. 2002. Wild Ginger (Hedychium gardnerianum, H. flavescens) 7. Hivert, J. 2003. Plantes exotiques envahissantes - Etat des méthodes de lutte mise en oeuvre par l'Office National des Forêts à La Réunion. ONF Réunion.
Summary: Synthèse des méthodes de lutte employées par l'ONF à la Réunion contre une vingtaine de plantes exotiques envahissantes. 8. IUCN/SSC Invasive Species Specialist Group (ISSG)., 2010. A Compilation of Information Sources for Conservation Managers.
Summary: This compilation of information sources can be sorted on keywords for example: Baits & Lures, Non Target Species, Eradication, Monitoring, Risk Assessment, Weeds, Herbicides etc. This compilation is at present in Excel format, this will be web-enabled as a searchable database shortly. This version of the database has been developed by the IUCN SSC ISSG as part of an Overseas Territories Environmental Programme funded project XOT603 in partnership with the Cayman Islands Government - Department of Environment. The compilation is a work under progress, the ISSG will manage, maintain and enhance the database with current and newly published information, reports, journal articles etc. 9. Mather, John. Environment BOP. Wild Ginger - Fact Sheet PP02198. Environment Bay of Plenty, NZ. 10. Minden, Vanessa; Klaus Josef Hennenberg; Stefan Porembski & Hans Juergen Boehmer, 2010. Invasion and management of alien Hedychium gardnerianum (kahili ginger, Zingiberaceae) alter plant species composition of a montane rainforest on the island of Hawai’i. Plant Ecol (2010) 206:321–333 11. National Pest Plant Accord, 2001. Biosecurity New Zealand.
Summary: The National Pest Plant Accord is a cooperative agreement between regional councils and government departments with biosecurity responsibilities. Under the accord, regional councils will undertake surveillance to prevent the commercial sale and/or distribution of an agreed list of pest plants.
Available from: http://www.biosecurity.govt.nz/pests-diseases/plants/accord.htm [Accessed 11 August 2005] 12. New Zealand Plant Conservation Network, 2005. Unwanted Organisms. Factsheet Hedychium gardnerianum 14. Plant Pest Control. Undated. (Wild Ginger Fact Sheet PP02/98: Hedychium gardnerianum, Hedychium flavescens). Environment Bay of Plenty. 15. Royal New Zealand Institute of Horticulture (RNZIH), 2005. Kahili ginger Hedychium gardnerianum 17. Swaziland's Alien Plants Database., Undated. Hedychium gardnerianum
Summary: A database of Swaziland's alien plant species. 18. Taranaki Regional Council. 2003. Wild ginger Kahili ginger/yellow ginger (Hedychium gardnerianum, Hedychium flavescens). The Pest Plant Management Section. 19. Tasman District Council (TDC) 2001. Tasman-Nelson Regional Pest Management Strategy Results Page: 1
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