Wild ginger application
It is planned to submit an application to EPA in 2021 to release two biological control agents to attack wild ginger (Hedychium gardnerianum).
- Merochlorops dimorphus, a stem-mining fly (Chloropidae)
- Tetratopus sp., ginger weevil (Curculionidae)
These are the first of possibly several biocontrol agents that could work together to help control wild ginger in New Zealand.
Background
This application will be submitted by Auckland Council, acting on behalf of the National Biocontrol Collective, a consortium of regional councils and the Department of Conservation. The Collective funds the development of weed biocontrol programmes in New Zealand. Landcare Research is the science provider for this development. They have contracted Richard Hill & Associates to prepare the application and to manage the application process on behalf of Auckland Council, including pre-application consultation with EPA and with Māori and other stakeholders. Wild ginger is also considered to be a serious weed in Hawaii, and Landcare Research has been collaborating with researchers there to develop control options.
Kahili ginger (Hedychium gardenerianum, although NZ material is thought to be a hybrid with H. coronarium) and yellow ginger (Hedychium flavescens) are both regarded as serious weeds in New Zealand and a major threat to native forests. They are known mostly from the North Island, but also from coastal areas in NW South Island. Both form massive branching surface rhizomes with aerial stems up to 2 m tall. Wild ginger can form dense colonies in native forests, with beds of rhizomes layered up to a metre thick smothering young native plants and preventing seedling establishment. New plants can develop from portions of rhizome, and illegal dumping of garden refuse on roadsides or in the bush is a major source of spread. Tui and blackbirds also disperse Kahili ginger seeds. Wild ginger prefers open, light-filled environments that are warm and moist, but will grow well in partial or full shade beneath the forest canopy.
For more information on wild ginger species see:
The stem-mining fly restricts its damage to stems while the large weevil eats leaves, and the larvae bore into the rhizomes. These are the first of several biological control agents that will be considered for introduction, each attacking a different part of the plant to collectively reduce the pest status of wild ginger.
Identification and assessment of risks, costs and benefits
The potential risks, costs and benefits of the proposed introduction to New Zealand of Merochlorops dimorphus and Tetratopus sp. and the possible reduction in the abundance and vigour of wild ginger are being identified by literature review and by consultation with stakeholders and will be reported here when this is complete. The significant effects identified (highlighted in bold) will be addressed in details in the application:
- Risks, costs and benefits of wild ginger control
It is forbidden to sell, propagate or distribute either ginger. They have no significant economic value. Potential benefits of biological control would be the mitigation of the effects described above. The key possible adverse effects of introducing the control agents will be addressed fully in the application:
- the risk of direct damage to valued garden ornamentals and minor crops
- the risk of direct damage to native plants
- indirect effects on flora and fauna as a result of disruption of ecological relationships
- the removal of kahili ginger as a food source for native birds
Ginger belongs to the family Zingiberaceae and the order Zingiberales. There are no native species within this order. There are a handful of related species with minor ornamental/economic value in New Zealand that belong to the same plant family as Hedychium, including edible ginger, turmeric, and Alpinia spp. The order includes Canna species, banana, and bird of paradise plant which have some ornamental or societal value, but are only distantly related to wild ginger. The application will examine the risk to native plant species and other valued plants.
Testing of the control agents is not yet complete, but results so far indicate that the agents will attack a very narrow range of host plants, and may be specific to Hedychium gingers. Populations capable of interacting significantly with other plants or animals will only be found in close proximity to wild ginger. As a result, no significant disturbance of ecological relationships is expected in New Zealand. The presence of wild ginger itself massively modifies natural interactions between species, and any reduction in the weed will help reverse those impacts. Native birds eat kahili ginger seeds and this issue will be addressed in the application.
Pre-application consultation with Iwi
Applications to introduce control agents against seven weeds will be submitted over the next 18 months. The members of the EPA 's national network Te Herenga will be contacted in August 2014, and invited to enter dialogue on the National Biocontrol Collective's plans to apply to EPA to introduce biological control agents to attack these weeds.
The message to Te Herenga will describe how the applicant intends to assess the risks, costs and benefits associated with the proposed introductions. Members will be invited to identify any issues that they would like to be addressed in the applications.In order of application, the target weeds are privet, Japanese honeysuckle, moth plant, lagarosiphon water weed, old man’s beard, ginger and field horsetail. Three targets (Japanese honeysuckle, moth plant, old man’s beard) have been the subject of previous successful applications, and consultation was completed in each case. The outcome of previous consultations will be presented.
At the request of the applicant, EPA will convene a reference group from Te Herenga to meet and discuss the issues surrounding the proposed applications.
Members of Te Herenga will be informed by EPA when each application is open for public submission, and will be able to comment on how the applicant has addressed issues raised during consultation.
The responses by Te Herenga members specifically related to the proposed introduction of control agents for wild ginger will be summarised here once it is available:
- Summary of Iwi responses
Pre-application consultation with other organisations
Other organisations consulted:
- Nursery and Garden Industry New Zealand
- Regional Councils
- Federated Farmers
- Royal Forest and Bird Protection Society of New Zealand
- Department of Conservation staff
- QEII National Trust
- NZ Landcare Trust
Summary of responses
- A summary of responses will be provided here once it is available
Key documents
Reports on host-range determination
Safety issues are paramount in the minds of biocontrol of weeds researchers. Researchers rigorously test all proposed agents to assess the risk of damage to non-target plants. A set of procedures helps researchers choose a suitable shortlist of test plants, and this methodology is now well-accepted internationally (Wapshere, 1974). The technique is under constant review to update best practice (e.g. Sheppard et al., 2005; Briese, 2005).
The results of host range testing conducted by CABI Biosciences will be fully discussed in the application.
- Host range testing of wild ginger control agents. To come once testing is concluded
The unpublished reports will be peer reviewed and that review will be provided to EPA.
A survey of the invertebrate fauna and fungi associated with wild ginger in New Zealand was carried out by Landcare Research for regional councils and the Department of Conservation.
The feasibility of biological control of wild ginger in New Zealand was investigated for several regional councils.
Cited references
Wapshere AJ (1974) A strategy for evaluating the safety or organisms for biological weed control. Annals of Applied Biology 77: 201–211.
Briese D (2005) Translating host-specificity test results into the real world: The need to harmonize the yin and yang of current testing procedures. Biological Control 35: 208–214.
Sheppard AW, Heard TA, van Klinken RD (2005) Scientific advances in the analysis of direct risks of weed biological control agents to non-target plants. Biological Control 35: 215–226.