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Improving lives by solving problems in agriculture and the environment

Controlling wild ginger

Plants from the Hedychium genus are widely loved and cultivated as ornamentals but a few are threatening delicate ecosystems in Hawaii, New Zealand, the Macaronesian Archipelago (Azores, Madeira and the Canaries), Brazil, Australia and La Réunion. We are researching natural ways to manage the plants where they have become invasive, which involves returning to their original home range in the North eastern Himalayan foothills to try to find damaging and specific insects and/ or pathogens which may prove suitable for release in the invaded range.

Project Overview

So, what's the problem

Many species in the Zingiberaceae family have been widely used throughout history. Root ginger for instance, has been cultivated across Asia both for its medicinal and its culinary properties.

The genus Hedychium however has long been used as an ornamental plant due to its heady perfume and attractive flowers. Three of these ’wild gingers’: Hedychium gardnerianum, H.flavescens and H. coronarium, known as Kahili ginger, yellow ginger and white ginger respectively, have escaped from botanical and public  gardens and are now aggressively invading many forest ecosystems across the world.  

Most of the threatened ecosystems are on islands and these are often unique and delicate. Rare invertebrates in Brazil and the Portuguese Azores bullfinch are threatened by habitat loss, while in New Zealand and Hawaii the smothering of young plants and the prevention of seedlings becoming established threatens whole ecosystem processes and endangers the biodiversity of native, undisturbed forests.

In their native environments of the North eastern slopes of the Indian Himalayas, Nepal and southern China, these wild ginger species grow in harmony with their surroundings. Predators and diseases have co-evolved alongside the ginger and so naturally keep it under control. However due to a lack of predators and diseases in the invaded countries, the plants grow un-checked, spreading with abandon, forming dense thickets and outcompeting native plants. The species are prolific seed producers, have strong vegetative reproductive potential and the vast network of rhizomes (roots) also results in a barrier to native plants and poses a growing threat to the ecosystem as a whole. The sheer density and often the remoteness and inaccessibility of some of the colonized areas mean mechanical control is ineffective.

The use of chemical herbicides also has its problems with concerns of their damaging environmental side-effects. This means that natural control - the use of specific predators and diseases as a means to manage these invasive species - offers the only realistic solution for long-term, sustainable control.

What is this project doing?

CABI has been funded through a consortium of sponsors in Hawaii and New Zealand to look for a biological control for Hedychium gardnerianum since 2008.

The current phase of the project aims to continue testing the most promising agents associated with the plant in its native range against a number of closely related and economically important non target plants. These include: a stem mining fly (Merochlorops cf. dimorphus) and a weevil (Prodioctes sp.) as well as assess the potential of newly exported species of Hispine beetles (Prionispa patra and Gonophora pulchella) to ensure they are specific to the target host, H. gardnerianum. To do this, we need to source and maintain related test plants selected by Hawaii and New Zealand and arrange imports as appropriate.

We also want to and complete the inventory of species on Hedychium hosts from the eastern Himalayas.

In order to conduct the research, collaborations with Indian institutes are essential. CABI has ongoing collaborations with the Indian Council of Agricultural Research (ICAR) through NBAIR (National Bureau of Agricultural and Insect Resources), Sikkim Government’s Department of Forest, Environment and Wildlife Management (DFEWM) and Sikkim University (through funding a PhD student). These links in country are crucial to progress the science and field research as well as negotiate the national legislation requirements and facilitate exporting insect agents to the UK and, ultimately, to New Zealand and Hawaii if they prove specific enough.

CABI will continue to promote the project and seek further stakeholders for the consortium through publications and presentations at high level international conferences.

Results

The project began in 2008 with a feasibility study and exploratory surveys across North East India which has been continued year-on-year thanks to a consortium of stakeholder funders from the US and New Zealand.

Export of natural enemies was approved in 2011 and since then, surveys in the Himalayan foothills (state of Sikkim) have been carried out every year to collect and prioritize natural enemies associated with invasive Hedychium species.

Host range testing in the UK and field testing in India have concentrated on the highly specific Merochlorops fly and the large, conspicuous (Meta) Prodioctes weevil with a view to submitting an application to the New Zealand Environmental Protection Authority when sufficiently robust evidence has been gathered for the specificity and hence safety of these agents. The inventory of species associated with H. gardnerianum, H. flavescens and H. coronarium continues to be consolidated and any new species of interest are also assessed accordingly. 

The team

Project Manager

Staff image of Djamila Djeddour

Djamila Djeddour  Weed Biocontrol Scientist

CABI
Bakeham Lane
Egham
Surrey
TW209TY
United Kingdom
T +44 (0)1491 829055
E d.djeddour@cabi.org

Project team

Staff image of Corin Pratt

Corin Pratt

Invasive Species Management Researcher

Staff image of Suzy Wood

Suzy Wood

Scientific Support

Staff image of Norbert Maczey

Norbert Maczey

Ecologist/ Entomologist - Higher Scientific Officer

Staff image of Nikolai Thom

Nikolai Thom

Plant Production Manager