Brazilian beetles released to control wandering willie

Brazilian beetles will be released into Wellington's town belt today to help control the wandering willie.

The willie, or pernicious weed tradescantia, is one of the country's "dirty dozen" weeds for 2016, Conservation Minister Maggie Barry said.

"It's an invasive, hard-to-kill weed, originally from South America, which forms a dense, thick carpet on the ground, smothering other plants and preventing native species from establishing themselves," she said.

"It's also an unpleasant species for dogs, who often suffer from allergic reactions after touching it."

The weed is difficult to manage as it breaks into many pieces when pulled, with almost every piece of stem capable of sprouting again.

A team of Landcare Research scientists funded by the National Biocontrol Collective imported three species of beetle from Brazil to investigate their use as a method of control.

Each of the three species of beetle attacks a different part of the plant -- the leaves, stems and tips.

The leaf beetles being released on Mt Victoria today are 4-5mm long, dark bronze in colour and able to fly.

Wellington Botanic Garden has been used as a captive breeding site for the beetles since 2014.

"Using the beetles reduces the need for chemicals and it's to the Wellington City Council's credit that they've seen the potential of this project," Ms Barry said.

"Today is the first time the beetles grown at the Botanic Gardens will be released in the wild, and their progress will be monitored -- it's expected that by damaging the tradescantia there will be more room for native plants to flourish, helping us win our war on weeds."

Tradescantia beetles have already been released in several regions, with some having "impressive" early results.