Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Beating the beetle bug – new biocontrol agent for tradescantia

A long–awaited project that aims to control one of New Zealand’s most widespread and problematic weeds, tradescantia (Tradescantia fluminensis also known as wandering willie), has come to fruition.

Friday 25 Mar 2011

Neolema ogloblini

Neolema ogloblini

A long–awaited project that aims to control one of New Zealand’s most widespread and problematic weeds, tradescantia (Tradescantia fluminensis also known as wandering willie), has come to fruition.

Staff from Landcare Research and the Auckland Council will tomorrow undertake the first release in New Zealand of the tradescantia leaf beetle (Neolema ogloblini), a biocontrol agent, in an effort to control the pest plant. This will also be the first agent released in New Zealand for tradescantia control.

As its name suggests, the tradescantia leaf beetle feeds on the foliage of the weed, which has become widespread in frost-free parts of the North Island and parts of the South Island. Thriving in shaded areas of gardens and bush, tradescantia grows densely on the ground preventing regeneration of desirable plants. Earlier research has shown that this weed is a threat to regeneration, and hence long-term survival, of indigenous forest in northern New Zealand.

The plant is also possibly the most widespread and troublesome weed of gardens throughout New Zealand. Tradescantia is very difficult to control as it breaks into many pieces when pulled, with almost every piece of stem capable of resprouting. The plant is also capable of causing canine allergic dermatitis, an itchy reaction in dogs.

Successful biological control would not only assist native forest regeneration, it would lead to less reliance on use of herbicides in the bush and in gardens.

The release of the beetle marks the end of an eightyear project byLandcare Research scientists to prepare the agent for use in New Zealand. Rigorous testing had to be undertaken to ensure that the beetle would not attack other plants, did not contain any unwanted parasites, or have any unwanted effects whatsoever on the flora and fauna of New Zealand.

The release of biological control agents in New Zealand is subject to stringent procedures imposed by the Environmental Risk Management Authority (ERMA). All prospective agents must be thoroughly tested to prove that they are “host-specific” ie cannot predate other plants; also will not impact on human health, the environment, conservation values, primary production or Maori values.

“Tradescantia is a nasty weed across the Auckland region, including our regional parks, and anything that helps control it is a fantastic step forward,” says Cr Sandra Coney, Chair of the Auckland Council Parks and Heritage Forum.

“I look forward to seeing the results of the release.”

Eighty pupae and adults were moved from Landcare Research’s containment facility at Lincoln to its Auckland site in late December and mass rearing was undertaken.

Auckland Council has recently applied to ERMA for permission to release two further host-specific tradescantia agents that Landcare Research has been studying: the tip-feeding beetle (Neolema abbreviata) and stem-boring (Lema basicostata) beetle, with a decision likely within six months.

Meanwhile, work is continuing in Brazil with a fourth promising agent, the yellow leaf spot fungus (Kordyana brasiliense).

This project is funded by the Department of Conservation, National Biocontrol Collective (including the Auckland Council) and the Ministry of Science and Innovation under the Beating Weeds programme.

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