New insect allies to be conscripted for war on wild ginger

Thrilled biosecurity experts say an almost $465,000 government grant will allow for a potentially world-first attempt to use insects to tackle wild ginger infestations choking Northland bush and forest.

The Northland Regional Council (NRC) applied to the Ministry for Primary Industries' (MPI) Sustainable Farming Fund late last year for $464,470 to research wild ginger biocontrol agents in the Sikkim region of northern India until mid-2021.

Council Biosecurity Manager Don McKenzie says the NRC heard recently that its application had been successful and the three-year, almost $900,000 project would officially kick off in August.

Biosecurity Manager Don McKenzie dwarfed by wild ginger in the Helena Bay area...insects from India may be used in a world-first attempt to tackle wild ginger infestations like this choking Northland's bush and forest.

(Co-funding from the regional council and partner organisations including Hancock Forest Managers, Summit Forests, the Department of Conservation, Northland's three district councils, the Auckland Council, Landcare Research and the National Biocontrol Collective takes the total funding amount to $897,130.

The cash will enable the group and international collaborators to fully research the viability of several potential biocontrol agents identified in India – including a large weevil, a fly and a beetle – as well as covering the cost of their import and distribution if they prove suitable.

News of the funding has thrilled the regional council's Te Hiku constituency representative Mike Finlayson, who says wild ginger has reached plague proportions in Northland.

Councillor Finlayson, a long-time advocate for control of wild ginger, says despite the best efforts of many people over a number of years, the pest plant now occupies more than 5000 hectares beneath state and privately-owned forests around the region.

"It has got to the point where it's now costing the regional economy an estimated $3 million to $5M annually due to the loss of productive land alone," he says.

Councillor Finlayson says ginger is an issue because it forms dense stands which then exclude native/desirable other species.

Mr McKenzie says the best-studied prospective biocontrol agents so far are a shoot-mining fly (Merochlorops cf. dimorphus), whose larvae mine wild ginger stems, and a large weevil (Metaprodioctes cf. trilineatus) that feeds on all parts of the plant, including the rhizomes. However, the project will also provide key information about other insects that could be further developed for biocontrol of wild ginger if needed in future.

Councillor Finlayson says while biocontrol programmes have existed in New Zealand for around 90 years, wild ginger is a novel target for biocontrol internationally.

"This project will develop, never before used, or studied, insects as biocontrol agents for wild ginger."

The import of biocontrol agents to New Zealand could also open up other pathways internationally, with New Zealand possibly supplying successful agents to other areas battling invasive ginger, such as Hawai'i and parts of Queensland.

Mr McKenzie says new project builds on work supported to date by the National Biocontrol Collective (or NBC) which is made up of regional councils nationwide and the Department of Conservation.

"The NBC supports research to develop biocontrol for up to a dozen weeds targets annually so the funds available for each target are extremely modest."

He says both the fly and weevil look highly promising and are likely to be sufficiently host-specific for release in New Zealand, "but further testing needs to be undertaken to confirm this, and to develop mass-rearing and release techniques for them".

Research funded by the NBC has also identified another several insects, again about which little is known, worth further investigating as future wild ginger biocontrols.

The project will be carried out by Landcare Research with help from UK-based collaborator CABI (Centre for Agriculture and Bioscience International) following the usual steps to develop biocontrol for weeds in accordance with international best practice.

The project will support:

• Surveys in India to find, collect and identify prospective biocontrol agents
• Maintaining colonies of promising species, and studies of their life cycles and damage potential
• Determination of the host range (safety) of promising species
• Preparing an application to the Environment Protection Authority to release two suitable agents in this country
• Importing shipments of these agents into a Landcare Research containment facility where they will remain until MPI grants approval to release them.
• Developing mass rearing methods and eventual release of the agents at strategic locations around Northland and elsewhere.
• Assessment of the establishment success and initial impact of the ginger biocontrol agents.

Councillor Finlayson says Northland is already home to a surprising number of biocontrol agents include beetles which feed on tradescantia (formerly known as wandering Jew) as well as fungi and rusts which collectively attack a variety of pest plants and insects including tropical grass webworm, mistflower, gorse, ragwort and woolly nightshade.

"Before any biocontrol can be released in New Zealand, it's subjected to extensive and lengthy research to make sure it's host-specific and won't target other species and any proposed biocontrol for wild ginger will be very well-researched."

People interested to learn more about the regional council's biocontrol programme and its other work in pest control should visit www.nrc.govt.nz/nasties