Horizons Regional Council released 200 beetles in Totara Reserve on Thursday to tackle the invasive tradescantia weed, also known as wandering willie.

These beetles,(tradescantia stem beetle), were imported from Brazil and bred at Landcare Research’s facility in Auckland.

Horizons environmental management officer Neil Gallagher says the beetles grubs (larvae), damages tradescantia plants by boring into the stems and causing the plants to collapse.

"The tradescantia plant is a problem in our native habitats as it grows rapidly forming thick carpets up to 50cm in depth which obliterates all native ground covering plants. Tradescantia is a difficult weed to control and it is hoped that long term the beetles will reduce the amount of the weed so native trees and shrubs can regenerate." Mr Gallagher says.

This is the second release of tradescantia beetles in Totara Reserve, 300 leaf feeding tradescantia beetles were released by Horizons staff in May 2011.

"The first batch looked great when first placed in the reserve and I was able to see damage from their feeding habits. It’s definitely early days though and we don’t expect to be able to access the long term effects of the beetle for a couple of years," Mr Gallagher says.

The stem feeding beetles are shiny black in colour with a distinct knobby appearance when viewed close up. Adults may be seen feeding or resting on upper leaves during warmer months and are about 4-5 mm long.