Super weevils set to save native trees

Weevils don't exactly have the greatest reputation but that may be about to change thanks to work being done by scientists in Rotorua.

Usually associated with infestations of grain and other foods and the destruction of various crops, weevils are generally among the undesirables of the insect world.

But a tiny Chinese weevil called Cleopus japonicus, going in to bat for the forestry industry, looks set to prove the tiny insects aren't all bad.

The weevil eats a plant called buddleia, a noxious weed stunting the growth of young pine trees and causing problems in native forest areas where weed control is seldom carried out.

Scientists working for Ensis, the joint venture between the Rotorua crown research institute Scion and its Australian counterpart CSIRO, have reared and released the weevils into the wild, in a bid to control the spread of buddleia.

The use of the insects as a form of "biological control" is far more environmentally friendly than chemical sprays, which is what forestry companies and regional councils have in the past used to rid the land of the noxious weeds.

It is estimated buddleia costs the New Zealand forest industry between $500,000 and $2.9 million annually in control costs and lost production.

The weevils were officially released in a special ceremony in the Whakarewarewa forest, where people attached plants infested with the weevils in the laboratory to plants growing wild.

"It's not like opening a box and they all just fly out," Ensis spokeswoman Jacky James said. "Both the plants and the weevils are from China, so we are just reuniting them in a New Zealand environment."

Scion entomologist Michelle Watson was part of the team that reared and conducted field trials on how the tiny animals adapted to the outdoors environment.

She will also be investigating how far away the insects would be moving from their original release spots in the forest.

"As long as they have lots of food, they will be happy."

Cleopus was approved for release by ERMA (Environmental Risk Management Authority) after the completion of a long and rigorous process to screen the insects' diet, to ensure it did not have an appetite for native or beneficial species.

- DAILY POST (ROTORUA)