Natural born killers to deal with invasive weed

Two bugs, a moth and a beetle, may be set to help stamp out tutsan in the Bay.

A moth and beetle could be introduced into the Bay to stamp out the invasive weed tutsan.

The Environmental Protection Authority has approved the moth and beetle to combat tutsan which was a yellow-flowering shrub introduced into New Zealand as a garden plant in the 1800s which thrived in the central North Island, particularly around stream margins and regenerating scrub.

Acting general manager of hazardous substances and new organisms Ray McMillan said the larvae of the moth (Lathronympha strigana) fed on the leaves and stems of tutsan in spring and burrowed into the fruit, consuming its seeds.

The leaf beetle larvae (Chrysolina abchasica), in large enough numbers, were capable of stripping the plant of its leaves, he said.

Livestock would not eat tutsan and removing it was time consuming "even minor infestations required intensive effort and herbicides were usually used to control or reduce larger infestations"

Bay of Plenty Regional Council senior biosecurity officer Shane Grayling said the council would explore options for purchase and release of the tutsan moth and beetle in the near future.

"We hope to be able to establish populations of the biological control agents from local release sites, to help manage tutsan spread over time."

It had provided funding to assist the Tutsan Action Group to develop the moth and beetle as biological control agents, and supported the action group to research and lodge the application.

It was widespread throughout the region, he said.

"Particularly along roadsides and riparian margins, regenerating scrub, in forestry and on some farmland. It forms dense stands and produces a large amount of seed which may be spread by birds, farm machinery, waterways and stock. Roadside mowing can also spread the seed," Mr Grayling said.