Application received for biological control of Tradescantia

The Environmental Risk Management Authority (ERMA New Zealand) has received an application to import a Brazilian beetle to control the weed Tradescantia fluminensis, commonly known as wandering willie.

General Manager, New Organisms, Libby Harrison, says the application, which is now open for public consultation, has been made by the Auckland Regional Council on behalf of a consortium of regional councils and the Department of Conservation.

"Tradescantia is a real and growing conservation threat in many parts of the country and a well-known weed in home gardens. Dense mats of it can smother low-growing native plants and it is a threat to forest regrowth," Dr Harrison says.

Herbicide or physical removal can be used to kill tradescantia, but neither approach is feasible over the huge number of sites in the country where this weed is a problem. The use of biological control is a viable option because the beetles seek out the weed and maintain themselves from year to year.

The proposed control agent is Lema obscura, a leaf-eating beetle that comes from the cool, upland regions of south east Brazil – the home range of tradescantia. The larvae of the beetle feed on the plant's leaves and, in large enough numbers, can cause severe damage to the clogging mats.

Landcare Research has carried out laboratory testing to assess the safety of the beetle for release in the New Zealand environment. Risk to native plants is judged to be negligible, as tradescantia is not related to any New Zealand plants.

The application is open for public submissions to ERMA New Zealand until 25 February 2008. If submitters have difficulties meeting this date, they should contact ERMA New Zealand.

For information on the submission process, please refer to the website, www.ermanz.govt.nz